postgresql/src/backend/utils/adt/varlena.c

/*-------------------------------------------------------------------------
 *
 * varlena.c
 *	  Functions for the variable-length built-in types.
 *
 * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.180 2010/08/24 06:30:43 itagaki Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>

#include "access/tuptoaster.h"
#include "catalog/pg_type.h"
#include "libpq/md5.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "parser/scansup.h"
#include "regex/regex.h"
#include "utils/builtins.h"
#include "utils/bytea.h"
#include "utils/lsyscache.h"
#include "utils/pg_locale.h"


/* GUC variable */
int			bytea_output = BYTEA_OUTPUT_HEX;

typedef struct varlena unknown;

typedef struct
{
	bool		use_wchar;		/* T if multibyte encoding */
	char	   *str1;			/* use these if not use_wchar */
	char	   *str2;			/* note: these point to original texts */
	pg_wchar   *wstr1;			/* use these if use_wchar */
	pg_wchar   *wstr2;			/* note: these are palloc'd */
	int			len1;			/* string lengths in logical characters */
	int			len2;
	/* Skip table for Boyer-Moore-Horspool search algorithm: */
	int			skiptablemask;	/* mask for ANDing with skiptable subscripts */
	int			skiptable[256]; /* skip distance for given mismatched char */
} TextPositionState;

#define DatumGetUnknownP(X)			((unknown *) PG_DETOAST_DATUM(X))
#define DatumGetUnknownPCopy(X)		((unknown *) PG_DETOAST_DATUM_COPY(X))
#define PG_GETARG_UNKNOWN_P(n)		DatumGetUnknownP(PG_GETARG_DATUM(n))
#define PG_GETARG_UNKNOWN_P_COPY(n) DatumGetUnknownPCopy(PG_GETARG_DATUM(n))
#define PG_RETURN_UNKNOWN_P(x)		PG_RETURN_POINTER(x)

static int	text_cmp(text *arg1, text *arg2);
static int32 text_length(Datum str);
static int	text_position(text *t1, text *t2);
static void text_position_setup(text *t1, text *t2, TextPositionState *state);
static int	text_position_next(int start_pos, TextPositionState *state);
static void text_position_cleanup(TextPositionState *state);
static text *text_catenate(text *t1, text *t2);
static text *text_substring(Datum str,
			   int32 start,
			   int32 length,
			   bool length_not_specified);
static text *text_overlay(text *t1, text *t2, int sp, int sl);
static void appendStringInfoText(StringInfo str, const text *t);
static bytea *bytea_catenate(bytea *t1, bytea *t2);
static bytea *bytea_substring(Datum str,
				int S,
				int L,
				bool length_not_specified);
static bytea *bytea_overlay(bytea *t1, bytea *t2, int sp, int sl);
static StringInfo makeStringAggState(FunctionCallInfo fcinfo);

static Datum text_to_array_internal(PG_FUNCTION_ARGS);
static text *array_to_text_internal(FunctionCallInfo fcinfo, ArrayType *v,
									char *fldsep, char *null_string);


/*****************************************************************************
 *	 CONVERSION ROUTINES EXPORTED FOR USE BY C CODE							 *
 *****************************************************************************/

/*
 * cstring_to_text
 *
 * Create a text value from a null-terminated C string.
 *
 * The new text value is freshly palloc'd with a full-size VARHDR.
 */
text *
cstring_to_text(const char *s)
{
	return cstring_to_text_with_len(s, strlen(s));
}

/*
 * cstring_to_text_with_len
 *
 * Same as cstring_to_text except the caller specifies the string length;
 * the string need not be null_terminated.
 */
text *
cstring_to_text_with_len(const char *s, int len)
{
	text	   *result = (text *) palloc(len + VARHDRSZ);

	SET_VARSIZE(result, len + VARHDRSZ);
	memcpy(VARDATA(result), s, len);

	return result;
}

/*
 * text_to_cstring
 *
 * Create a palloc'd, null-terminated C string from a text value.
 *
 * We support being passed a compressed or toasted text value.
 * This is a bit bogus since such values shouldn't really be referred to as
 * "text *", but it seems useful for robustness.  If we didn't handle that
 * case here, we'd need another routine that did, anyway.
 */
char *
text_to_cstring(const text *t)
{
	/* must cast away the const, unfortunately */
	text	   *tunpacked = pg_detoast_datum_packed((struct varlena *) t);
	int			len = VARSIZE_ANY_EXHDR(tunpacked);
	char	   *result;

	result = (char *) palloc(len + 1);
	memcpy(result, VARDATA_ANY(tunpacked), len);
	result[len] = '\0';

	if (tunpacked != t)
		pfree(tunpacked);

	return result;
}

/*
 * text_to_cstring_buffer
 *
 * Copy a text value into a caller-supplied buffer of size dst_len.
 *
 * The text string is truncated if necessary to fit.  The result is
 * guaranteed null-terminated (unless dst_len == 0).
 *
 * We support being passed a compressed or toasted text value.
 * This is a bit bogus since such values shouldn't really be referred to as
 * "text *", but it seems useful for robustness.  If we didn't handle that
 * case here, we'd need another routine that did, anyway.
 */
void
text_to_cstring_buffer(const text *src, char *dst, size_t dst_len)
{
	/* must cast away the const, unfortunately */
	text	   *srcunpacked = pg_detoast_datum_packed((struct varlena *) src);
	size_t		src_len = VARSIZE_ANY_EXHDR(srcunpacked);

	if (dst_len > 0)
	{
		dst_len--;
		if (dst_len >= src_len)
			dst_len = src_len;
		else	/* ensure truncation is encoding-safe */
			dst_len = pg_mbcliplen(VARDATA_ANY(srcunpacked), src_len, dst_len);
		memcpy(dst, VARDATA_ANY(srcunpacked), dst_len);
		dst[dst_len] = '\0';
	}

	if (srcunpacked != src)
		pfree(srcunpacked);
}


/*****************************************************************************
 *	 USER I/O ROUTINES														 *
 *****************************************************************************/


#define VAL(CH)			((CH) - '0')
#define DIG(VAL)		((VAL) + '0')

/*
 *		byteain			- converts from printable representation of byte array
 *
 *		Non-printable characters must be passed as '\nnn' (octal) and are
 *		converted to internal form.  '\' must be passed as '\\'.
 *		ereport(ERROR, ...) if bad form.
 *
 *		BUGS:
 *				The input is scanned twice.
 *				The error checking of input is minimal.
 */
Datum
byteain(PG_FUNCTION_ARGS)
{
	char	   *inputText = PG_GETARG_CSTRING(0);
	char	   *tp;
	char	   *rp;
	int			bc;
	bytea	   *result;

	/* Recognize hex input */
	if (inputText[0] == '\\' && inputText[1] == 'x')
	{
		size_t		len = strlen(inputText);

		bc = (len - 2) / 2 + VARHDRSZ;	/* maximum possible length */
		result = palloc(bc);
		bc = hex_decode(inputText + 2, len - 2, VARDATA(result));
		SET_VARSIZE(result, bc + VARHDRSZ);		/* actual length */

		PG_RETURN_BYTEA_P(result);
	}

	/* Else, it's the traditional escaped style */
	for (bc = 0, tp = inputText; *tp != '\0'; bc++)
	{
		if (tp[0] != '\\')
			tp++;
		else if ((tp[0] == '\\') &&
				 (tp[1] >= '0' && tp[1] <= '3') &&
				 (tp[2] >= '0' && tp[2] <= '7') &&
				 (tp[3] >= '0' && tp[3] <= '7'))
			tp += 4;
		else if ((tp[0] == '\\') &&
				 (tp[1] == '\\'))
			tp += 2;
		else
		{
			/*
			 * one backslash, not followed by another or ### valid octal
			 */
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					 errmsg("invalid input syntax for type bytea")));
		}
	}

	bc += VARHDRSZ;

	result = (bytea *) palloc(bc);
	SET_VARSIZE(result, bc);

	tp = inputText;
	rp = VARDATA(result);
	while (*tp != '\0')
	{
		if (tp[0] != '\\')
			*rp++ = *tp++;
		else if ((tp[0] == '\\') &&
				 (tp[1] >= '0' && tp[1] <= '3') &&
				 (tp[2] >= '0' && tp[2] <= '7') &&
				 (tp[3] >= '0' && tp[3] <= '7'))
		{
			bc = VAL(tp[1]);
			bc <<= 3;
			bc += VAL(tp[2]);
			bc <<= 3;
			*rp++ = bc + VAL(tp[3]);

			tp += 4;
		}
		else if ((tp[0] == '\\') &&
				 (tp[1] == '\\'))
		{
			*rp++ = '\\';
			tp += 2;
		}
		else
		{
			/*
			 * We should never get here. The first pass should not allow it.
			 */
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					 errmsg("invalid input syntax for type bytea")));
		}
	}

	PG_RETURN_BYTEA_P(result);
}

/*
 *		byteaout		- converts to printable representation of byte array
 *
 *		In the traditional escaped format, non-printable characters are
 *		printed as '\nnn' (octal) and '\' as '\\'.
 */
Datum
byteaout(PG_FUNCTION_ARGS)
{
	bytea	   *vlena = PG_GETARG_BYTEA_PP(0);
	char	   *result;
	char	   *rp;

	if (bytea_output == BYTEA_OUTPUT_HEX)
	{
		/* Print hex format */
		rp = result = palloc(VARSIZE_ANY_EXHDR(vlena) * 2 + 2 + 1);
		*rp++ = '\\';
		*rp++ = 'x';
		rp += hex_encode(VARDATA_ANY(vlena), VARSIZE_ANY_EXHDR(vlena), rp);
	}
	else if (bytea_output == BYTEA_OUTPUT_ESCAPE)
	{
		/* Print traditional escaped format */
		char	   *vp;
		int			len;
		int			i;

		len = 1;				/* empty string has 1 char */
		vp = VARDATA_ANY(vlena);
		for (i = VARSIZE_ANY_EXHDR(vlena); i != 0; i--, vp++)
		{
			if (*vp == '\\')
				len += 2;
			else if ((unsigned char) *vp < 0x20 || (unsigned char) *vp > 0x7e)
				len += 4;
			else
				len++;
		}
		rp = result = (char *) palloc(len);
		vp = VARDATA_ANY(vlena);
		for (i = VARSIZE_ANY_EXHDR(vlena); i != 0; i--, vp++)
		{
			if (*vp == '\\')
			{
				*rp++ = '\\';
				*rp++ = '\\';
			}
			else if ((unsigned char) *vp < 0x20 || (unsigned char) *vp > 0x7e)
			{
				int			val;	/* holds unprintable chars */

				val = *vp;
				rp[0] = '\\';
				rp[3] = DIG(val & 07);
				val >>= 3;
				rp[2] = DIG(val & 07);
				val >>= 3;
				rp[1] = DIG(val & 03);
				rp += 4;
			}
			else
				*rp++ = *vp;
		}
	}
	else
	{
		elog(ERROR, "unrecognized bytea_output setting: %d",
			 bytea_output);
		rp = result = NULL;		/* keep compiler quiet */
	}
	*rp = '\0';
	PG_RETURN_CSTRING(result);
}

/*
 *		bytearecv			- converts external binary format to bytea
 */
Datum
bytearecv(PG_FUNCTION_ARGS)
{
	StringInfo	buf = (StringInfo) PG_GETARG_POINTER(0);
	bytea	   *result;
	int			nbytes;

	nbytes = buf->len - buf->cursor;
	result = (bytea *) palloc(nbytes + VARHDRSZ);
	SET_VARSIZE(result, nbytes + VARHDRSZ);
	pq_copymsgbytes(buf, VARDATA(result), nbytes);
	PG_RETURN_BYTEA_P(result);
}

/*
 *		byteasend			- converts bytea to binary format
 *
 * This is a special case: just copy the input...
 */
Datum
byteasend(PG_FUNCTION_ARGS)
{
	bytea	   *vlena = PG_GETARG_BYTEA_P_COPY(0);

	PG_RETURN_BYTEA_P(vlena);
}


/*
 *		textin			- converts "..." to internal representation
 */
Datum
textin(PG_FUNCTION_ARGS)
{
	char	   *inputText = PG_GETARG_CSTRING(0);

	PG_RETURN_TEXT_P(cstring_to_text(inputText));
}

/*
 *		textout			- converts internal representation to "..."
 */
Datum
textout(PG_FUNCTION_ARGS)
{
	Datum		txt = PG_GETARG_DATUM(0);

	PG_RETURN_CSTRING(TextDatumGetCString(txt));
}

/*
 *		textrecv			- converts external binary format to text
 */
Datum
textrecv(PG_FUNCTION_ARGS)
{
	StringInfo	buf = (StringInfo) PG_GETARG_POINTER(0);
	text	   *result;
	char	   *str;
	int			nbytes;

	str = pq_getmsgtext(buf, buf->len - buf->cursor, &nbytes);

	result = cstring_to_text_with_len(str, nbytes);
	pfree(str);
	PG_RETURN_TEXT_P(result);
}

/*
 *		textsend			- converts text to binary format
 */
Datum
textsend(PG_FUNCTION_ARGS)
{
	text	   *t = PG_GETARG_TEXT_PP(0);
	StringInfoData buf;

	pq_begintypsend(&buf);
	pq_sendtext(&buf, VARDATA_ANY(t), VARSIZE_ANY_EXHDR(t));
	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}


/*
 *		unknownin			- converts "..." to internal representation
 */
Datum
unknownin(PG_FUNCTION_ARGS)
{
	char	   *str = PG_GETARG_CSTRING(0);

	/* representation is same as cstring */
	PG_RETURN_CSTRING(pstrdup(str));
}

/*
 *		unknownout			- converts internal representation to "..."
 */
Datum
unknownout(PG_FUNCTION_ARGS)
{
	/* representation is same as cstring */
	char	   *str = PG_GETARG_CSTRING(0);

	PG_RETURN_CSTRING(pstrdup(str));
}

/*
 *		unknownrecv			- converts external binary format to unknown
 */
Datum
unknownrecv(PG_FUNCTION_ARGS)
{
	StringInfo	buf = (StringInfo) PG_GETARG_POINTER(0);
	char	   *str;
	int			nbytes;

	str = pq_getmsgtext(buf, buf->len - buf->cursor, &nbytes);
	/* representation is same as cstring */
	PG_RETURN_CSTRING(str);
}

/*
 *		unknownsend			- converts unknown to binary format
 */
Datum
unknownsend(PG_FUNCTION_ARGS)
{
	/* representation is same as cstring */
	char	   *str = PG_GETARG_CSTRING(0);
	StringInfoData buf;

	pq_begintypsend(&buf);
	pq_sendtext(&buf, str, strlen(str));
	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}


/* ========== PUBLIC ROUTINES ========== */

/*
 * textlen -
 *	  returns the logical length of a text*
 *	   (which is less than the VARSIZE of the text*)
 */
Datum
textlen(PG_FUNCTION_ARGS)
{
	Datum		str = PG_GETARG_DATUM(0);

	/* try to avoid decompressing argument */
	PG_RETURN_INT32(text_length(str));
}

/*
 * text_length -
 *	Does the real work for textlen()
 *
 *	This is broken out so it can be called directly by other string processing
 *	functions.	Note that the argument is passed as a Datum, to indicate that
 *	it may still be in compressed form.  We can avoid decompressing it at all
 *	in some cases.
 */
static int32
text_length(Datum str)
{
	/* fastpath when max encoding length is one */
	if (pg_database_encoding_max_length() == 1)
		PG_RETURN_INT32(toast_raw_datum_size(str) - VARHDRSZ);
	else
	{
		text	   *t = DatumGetTextPP(str);

		PG_RETURN_INT32(pg_mbstrlen_with_len(VARDATA_ANY(t),
											 VARSIZE_ANY_EXHDR(t)));
	}
}

/*
 * textoctetlen -
 *	  returns the physical length of a text*
 *	   (which is less than the VARSIZE of the text*)
 */
Datum
textoctetlen(PG_FUNCTION_ARGS)
{
	Datum		str = PG_GETARG_DATUM(0);

	/* We need not detoast the input at all */
	PG_RETURN_INT32(toast_raw_datum_size(str) - VARHDRSZ);
}

/*
 * textcat -
 *	  takes two text* and returns a text* that is the concatenation of
 *	  the two.
 *
 * Rewritten by Sapa, sapa@hq.icb.chel.su. 8-Jul-96.
 * Updated by Thomas, Thomas.Lockhart@jpl.nasa.gov 1997-07-10.
 * Allocate space for output in all cases.
 * XXX - thomas 1997-07-10
 */
Datum
textcat(PG_FUNCTION_ARGS)
{
	text	   *t1 = PG_GETARG_TEXT_PP(0);
	text	   *t2 = PG_GETARG_TEXT_PP(1);

	PG_RETURN_TEXT_P(text_catenate(t1, t2));
}

/*
 * text_catenate
 *	Guts of textcat(), broken out so it can be used by other functions
 *
 * Arguments can be in short-header form, but not compressed or out-of-line
 */
static text *
text_catenate(text *t1, text *t2)
{
	text	   *result;
	int			len1,
				len2,
				len;
	char	   *ptr;

	len1 = VARSIZE_ANY_EXHDR(t1);
	len2 = VARSIZE_ANY_EXHDR(t2);

	/* paranoia ... probably should throw error instead? */
	if (len1 < 0)
		len1 = 0;
	if (len2 < 0)
		len2 = 0;

	len = len1 + len2 + VARHDRSZ;
	result = (text *) palloc(len);

	/* Set size of result string... */
	SET_VARSIZE(result, len);

	/* Fill data field of result string... */
	ptr = VARDATA(result);
	if (len1 > 0)
		memcpy(ptr, VARDATA_ANY(t1), len1);
	if (len2 > 0)
		memcpy(ptr + len1, VARDATA_ANY(t2), len2);

	return result;
}

/*
 * charlen_to_bytelen()
 *	Compute the number of bytes occupied by n characters starting at *p
 *
 * It is caller's responsibility that there actually are n characters;
 * the string need not be null-terminated.
 */
static int
charlen_to_bytelen(const char *p, int n)
{
	if (pg_database_encoding_max_length() == 1)
	{
		/* Optimization for single-byte encodings */
		return n;
	}
	else
	{
		const char *s;

		for (s = p; n > 0; n--)
			s += pg_mblen(s);

		return s - p;
	}
}

/*
 * text_substr()
 * Return a substring starting at the specified position.
 * - thomas 1997-12-31
 *
 * Input:
 *	- string
 *	- starting position (is one-based)
 *	- string length
 *
 * If the starting position is zero or less, then return from the start of the string
 *	adjusting the length to be consistent with the "negative start" per SQL92.
 * If the length is less than zero, return the remaining string.
 *
 * Added multibyte support.
 * - Tatsuo Ishii 1998-4-21
 * Changed behavior if starting position is less than one to conform to SQL92 behavior.
 * Formerly returned the entire string; now returns a portion.
 * - Thomas Lockhart 1998-12-10
 * Now uses faster TOAST-slicing interface
 * - John Gray 2002-02-22
 * Remove "#ifdef MULTIBYTE" and test for encoding_max_length instead. Change
 * behaviors conflicting with SQL92 to meet SQL92 (if E = S + L < S throw
 * error; if E < 1, return '', not entire string). Fixed MB related bug when
 * S > LC and < LC + 4 sometimes garbage characters are returned.
 * - Joe Conway 2002-08-10
 */
Datum
text_substr(PG_FUNCTION_ARGS)
{
	PG_RETURN_TEXT_P(text_substring(PG_GETARG_DATUM(0),
									PG_GETARG_INT32(1),
									PG_GETARG_INT32(2),
									false));
}

/*
 * text_substr_no_len -
 *	  Wrapper to avoid opr_sanity failure due to
 *	  one function accepting a different number of args.
 */
Datum
text_substr_no_len(PG_FUNCTION_ARGS)
{
	PG_RETURN_TEXT_P(text_substring(PG_GETARG_DATUM(0),
									PG_GETARG_INT32(1),
									-1, true));
}

/*
 * text_substring -
 *	Does the real work for text_substr() and text_substr_no_len()
 *
 *	This is broken out so it can be called directly by other string processing
 *	functions.	Note that the argument is passed as a Datum, to indicate that
 *	it may still be in compressed/toasted form.  We can avoid detoasting all
 *	of it in some cases.
 *
 *	The result is always a freshly palloc'd datum.
 */
static text *
text_substring(Datum str, int32 start, int32 length, bool length_not_specified)
{
	int32		eml = pg_database_encoding_max_length();
	int32		S = start;		/* start position */
	int32		S1;				/* adjusted start position */
	int32		L1;				/* adjusted substring length */

	/* life is easy if the encoding max length is 1 */
	if (eml == 1)
	{
		S1 = Max(S, 1);

		if (length_not_specified)		/* special case - get length to end of
										 * string */
			L1 = -1;
		else
		{
			/* end position */
			int			E = S + length;

			/*
			 * A negative value for L is the only way for the end position to
			 * be before the start. SQL99 says to throw an error.
			 */
			if (E < S)
				ereport(ERROR,
						(errcode(ERRCODE_SUBSTRING_ERROR),
						 errmsg("negative substring length not allowed")));

			/*
			 * A zero or negative value for the end position can happen if the
			 * start was negative or one. SQL99 says to return a zero-length
			 * string.
			 */
			if (E < 1)
				return cstring_to_text("");

			L1 = E - S1;
		}

		/*
		 * If the start position is past the end of the string, SQL99 says to
		 * return a zero-length string -- PG_GETARG_TEXT_P_SLICE() will do
		 * that for us. Convert to zero-based starting position
		 */
		return DatumGetTextPSlice(str, S1 - 1, L1);
	}
	else if (eml > 1)
	{
		/*
		 * When encoding max length is > 1, we can't get LC without
		 * detoasting, so we'll grab a conservatively large slice now and go
		 * back later to do the right thing
		 */
		int32		slice_start;
		int32		slice_size;
		int32		slice_strlen;
		text	   *slice;
		int32		E1;
		int32		i;
		char	   *p;
		char	   *s;
		text	   *ret;

		/*
		 * if S is past the end of the string, the tuple toaster will return a
		 * zero-length string to us
		 */
		S1 = Max(S, 1);

		/*
		 * We need to start at position zero because there is no way to know
		 * in advance which byte offset corresponds to the supplied start
		 * position.
		 */
		slice_start = 0;

		if (length_not_specified)		/* special case - get length to end of
										 * string */
			slice_size = L1 = -1;
		else
		{
			int			E = S + length;

			/*
			 * A negative value for L is the only way for the end position to
			 * be before the start. SQL99 says to throw an error.
			 */
			if (E < S)
				ereport(ERROR,
						(errcode(ERRCODE_SUBSTRING_ERROR),
						 errmsg("negative substring length not allowed")));

			/*
			 * A zero or negative value for the end position can happen if the
			 * start was negative or one. SQL99 says to return a zero-length
			 * string.
			 */
			if (E < 1)
				return cstring_to_text("");

			/*
			 * if E is past the end of the string, the tuple toaster will
			 * truncate the length for us
			 */
			L1 = E - S1;

			/*
			 * Total slice size in bytes can't be any longer than the start
			 * position plus substring length times the encoding max length.
			 */
			slice_size = (S1 + L1) * eml;
		}

		/*
		 * If we're working with an untoasted source, no need to do an extra
		 * copying step.
		 */
		if (VARATT_IS_COMPRESSED(DatumGetPointer(str)) ||
			VARATT_IS_EXTERNAL(DatumGetPointer(str)))
			slice = DatumGetTextPSlice(str, slice_start, slice_size);
		else
			slice = (text *) DatumGetPointer(str);

		/* see if we got back an empty string */
		if (VARSIZE_ANY_EXHDR(slice) == 0)
		{
			if (slice != (text *) DatumGetPointer(str))
				pfree(slice);
			return cstring_to_text("");
		}

		/* Now we can get the actual length of the slice in MB characters */
		slice_strlen = pg_mbstrlen_with_len(VARDATA_ANY(slice),
											VARSIZE_ANY_EXHDR(slice));

		/*
		 * Check that the start position wasn't > slice_strlen. If so, SQL99
		 * says to return a zero-length string.
		 */
		if (S1 > slice_strlen)
		{
			if (slice != (text *) DatumGetPointer(str))
				pfree(slice);
			return cstring_to_text("");
		}

		/*
		 * Adjust L1 and E1 now that we know the slice string length. Again
		 * remember that S1 is one based, and slice_start is zero based.
		 */
		if (L1 > -1)
			E1 = Min(S1 + L1, slice_start + 1 + slice_strlen);
		else
			E1 = slice_start + 1 + slice_strlen;

		/*
		 * Find the start position in the slice; remember S1 is not zero based
		 */
		p = VARDATA_ANY(slice);
		for (i = 0; i < S1 - 1; i++)
			p += pg_mblen(p);

		/* hang onto a pointer to our start position */
		s = p;

		/*
		 * Count the actual bytes used by the substring of the requested
		 * length.
		 */
		for (i = S1; i < E1; i++)
			p += pg_mblen(p);

		ret = (text *) palloc(VARHDRSZ + (p - s));
		SET_VARSIZE(ret, VARHDRSZ + (p - s));
		memcpy(VARDATA(ret), s, (p - s));

		if (slice != (text *) DatumGetPointer(str))
			pfree(slice);

		return ret;
	}
	else
		elog(ERROR, "invalid backend encoding: encoding max length < 1");

	/* not reached: suppress compiler warning */
	return NULL;
}

/*
 * textoverlay
 *	Replace specified substring of first string with second
 *
 * The SQL standard defines OVERLAY() in terms of substring and concatenation.
 * This code is a direct implementation of what the standard says.
 */
Datum
textoverlay(PG_FUNCTION_ARGS)
{
	text	   *t1 = PG_GETARG_TEXT_PP(0);
	text	   *t2 = PG_GETARG_TEXT_PP(1);
	int			sp = PG_GETARG_INT32(2);		/* substring start position */
	int			sl = PG_GETARG_INT32(3);		/* substring length */

	PG_RETURN_TEXT_P(text_overlay(t1, t2, sp, sl));
}

Datum
textoverlay_no_len(PG_FUNCTION_ARGS)
{
	text	   *t1 = PG_GETARG_TEXT_PP(0);
	text	   *t2 = PG_GETARG_TEXT_PP(1);
	int			sp = PG_GETARG_INT32(2);		/* substring start position */
	int			sl;

	sl = text_length(PointerGetDatum(t2));		/* defaults to length(t2) */
	PG_RETURN_TEXT_P(text_overlay(t1, t2, sp, sl));
}

static text *
text_overlay(text *t1, text *t2, int sp, int sl)
{
	text	   *result;
	text	   *s1;
	text	   *s2;
	int			sp_pl_sl;

	/*
	 * Check for possible integer-overflow cases.  For negative sp, throw a
	 * "substring length" error because that's what should be expected
	 * according to the spec's definition of OVERLAY().
	 */
	if (sp <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_SUBSTRING_ERROR),
				 errmsg("negative substring length not allowed")));
	sp_pl_sl = sp + sl;
	if (sp_pl_sl <= sl)
		ereport(ERROR,
				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
				 errmsg("integer out of range")));

	s1 = text_substring(PointerGetDatum(t1), 1, sp - 1, false);
	s2 = text_substring(PointerGetDatum(t1), sp_pl_sl, -1, true);
	result = text_catenate(s1, t2);
	result = text_catenate(result, s2);

	return result;
}

/*
 * textpos -
 *	  Return the position of the specified substring.
 *	  Implements the SQL92 POSITION() function.
 *	  Ref: A Guide To The SQL Standard, Date & Darwen, 1997
 * - thomas 1997-07-27
 */
Datum
textpos(PG_FUNCTION_ARGS)
{
	text	   *str = PG_GETARG_TEXT_PP(0);
	text	   *search_str = PG_GETARG_TEXT_PP(1);

	PG_RETURN_INT32((int32) text_position(str, search_str));
}

/*
 * text_position -
 *	Does the real work for textpos()
 *
 * Inputs:
 *		t1 - string to be searched
 *		t2 - pattern to match within t1
 * Result:
 *		Character index of the first matched char, starting from 1,
 *		or 0 if no match.
 *
 *	This is broken out so it can be called directly by other string processing
 *	functions.
 */
static int
text_position(text *t1, text *t2)
{
	TextPositionState state;
	int			result;

	text_position_setup(t1, t2, &state);
	result = text_position_next(1, &state);
	text_position_cleanup(&state);
	return result;
}


/*
 * text_position_setup, text_position_next, text_position_cleanup -
 *	Component steps of text_position()
 *
 * These are broken out so that a string can be efficiently searched for
 * multiple occurrences of the same pattern.  text_position_next may be
 * called multiple times with increasing values of start_pos, which is
 * the 1-based character position to start the search from.  The "state"
 * variable is normally just a local variable in the caller.
 */

static void
text_position_setup(text *t1, text *t2, TextPositionState *state)
{
	int			len1 = VARSIZE_ANY_EXHDR(t1);
	int			len2 = VARSIZE_ANY_EXHDR(t2);

	if (pg_database_encoding_max_length() == 1)
	{
		/* simple case - single byte encoding */
		state->use_wchar = false;
		state->str1 = VARDATA_ANY(t1);
		state->str2 = VARDATA_ANY(t2);
		state->len1 = len1;
		state->len2 = len2;
	}
	else
	{
		/* not as simple - multibyte encoding */
		pg_wchar   *p1,
				   *p2;

		p1 = (pg_wchar *) palloc((len1 + 1) * sizeof(pg_wchar));
		len1 = pg_mb2wchar_with_len(VARDATA_ANY(t1), p1, len1);
		p2 = (pg_wchar *) palloc((len2 + 1) * sizeof(pg_wchar));
		len2 = pg_mb2wchar_with_len(VARDATA_ANY(t2), p2, len2);

		state->use_wchar = true;
		state->wstr1 = p1;
		state->wstr2 = p2;
		state->len1 = len1;
		state->len2 = len2;
	}

	/*
	 * Prepare the skip table for Boyer-Moore-Horspool searching.  In these
	 * notes we use the terminology that the "haystack" is the string to be
	 * searched (t1) and the "needle" is the pattern being sought (t2).
	 *
	 * If the needle is empty or bigger than the haystack then there is no
	 * point in wasting cycles initializing the table.	We also choose not to
	 * use B-M-H for needles of length 1, since the skip table can't possibly
	 * save anything in that case.
	 */
	if (len1 >= len2 && len2 > 1)
	{
		int			searchlength = len1 - len2;
		int			skiptablemask;
		int			last;
		int			i;

		/*
		 * First we must determine how much of the skip table to use.  The
		 * declaration of TextPositionState allows up to 256 elements, but for
		 * short search problems we don't really want to have to initialize so
		 * many elements --- it would take too long in comparison to the
		 * actual search time.	So we choose a useful skip table size based on
		 * the haystack length minus the needle length.  The closer the needle
		 * length is to the haystack length the less useful skipping becomes.
		 *
		 * Note: since we use bit-masking to select table elements, the skip
		 * table size MUST be a power of 2, and so the mask must be 2^N-1.
		 */
		if (searchlength < 16)
			skiptablemask = 3;
		else if (searchlength < 64)
			skiptablemask = 7;
		else if (searchlength < 128)
			skiptablemask = 15;
		else if (searchlength < 512)
			skiptablemask = 31;
		else if (searchlength < 2048)
			skiptablemask = 63;
		else if (searchlength < 4096)
			skiptablemask = 127;
		else
			skiptablemask = 255;
		state->skiptablemask = skiptablemask;

		/*
		 * Initialize the skip table.  We set all elements to the needle
		 * length, since this is the correct skip distance for any character
		 * not found in the needle.
		 */
		for (i = 0; i <= skiptablemask; i++)
			state->skiptable[i] = len2;

		/*
		 * Now examine the needle.	For each character except the last one,
		 * set the corresponding table element to the appropriate skip
		 * distance.  Note that when two characters share the same skip table
		 * entry, the one later in the needle must determine the skip
		 * distance.
		 */
		last = len2 - 1;

		if (!state->use_wchar)
		{
			const char *str2 = state->str2;

			for (i = 0; i < last; i++)
				state->skiptable[(unsigned char) str2[i] & skiptablemask] = last - i;
		}
		else
		{
			const pg_wchar *wstr2 = state->wstr2;

			for (i = 0; i < last; i++)
				state->skiptable[wstr2[i] & skiptablemask] = last - i;
		}
	}
}

static int
text_position_next(int start_pos, TextPositionState *state)
{
	int			haystack_len = state->len1;
	int			needle_len = state->len2;
	int			skiptablemask = state->skiptablemask;

	Assert(start_pos > 0);		/* else caller error */

	if (needle_len <= 0)
		return start_pos;		/* result for empty pattern */

	start_pos--;				/* adjust for zero based arrays */

	/* Done if the needle can't possibly fit */
	if (haystack_len < start_pos + needle_len)
		return 0;

	if (!state->use_wchar)
	{
		/* simple case - single byte encoding */
		const char *haystack = state->str1;
		const char *needle = state->str2;
		const char *haystack_end = &haystack[haystack_len];
		const char *hptr;

		if (needle_len == 1)
		{
			/* No point in using B-M-H for a one-character needle */
			char		nchar = *needle;

			hptr = &haystack[start_pos];
			while (hptr < haystack_end)
			{
				if (*hptr == nchar)
					return hptr - haystack + 1;
				hptr++;
			}
		}
		else
		{
			const char *needle_last = &needle[needle_len - 1];

			/* Start at startpos plus the length of the needle */
			hptr = &haystack[start_pos + needle_len - 1];
			while (hptr < haystack_end)
			{
				/* Match the needle scanning *backward* */
				const char *nptr;
				const char *p;

				nptr = needle_last;
				p = hptr;
				while (*nptr == *p)
				{
					/* Matched it all?	If so, return 1-based position */
					if (nptr == needle)
						return p - haystack + 1;
					nptr--, p--;
				}

				/*
				 * No match, so use the haystack char at hptr to decide how
				 * far to advance.	If the needle had any occurrence of that
				 * character (or more precisely, one sharing the same
				 * skiptable entry) before its last character, then we advance
				 * far enough to align the last such needle character with
				 * that haystack position.	Otherwise we can advance by the
				 * whole needle length.
				 */
				hptr += state->skiptable[(unsigned char) *hptr & skiptablemask];
			}
		}
	}
	else
	{
		/* The multibyte char version. This works exactly the same way. */
		const pg_wchar *haystack = state->wstr1;
		const pg_wchar *needle = state->wstr2;
		const pg_wchar *haystack_end = &haystack[haystack_len];
		const pg_wchar *hptr;

		if (needle_len == 1)
		{
			/* No point in using B-M-H for a one-character needle */
			pg_wchar	nchar = *needle;

			hptr = &haystack[start_pos];
			while (hptr < haystack_end)
			{
				if (*hptr == nchar)
					return hptr - haystack + 1;
				hptr++;
			}
		}
		else
		{
			const pg_wchar *needle_last = &needle[needle_len - 1];

			/* Start at startpos plus the length of the needle */
			hptr = &haystack[start_pos + needle_len - 1];
			while (hptr < haystack_end)
			{
				/* Match the needle scanning *backward* */
				const pg_wchar *nptr;
				const pg_wchar *p;

				nptr = needle_last;
				p = hptr;
				while (*nptr == *p)
				{
					/* Matched it all?	If so, return 1-based position */
					if (nptr == needle)
						return p - haystack + 1;
					nptr--, p--;
				}

				/*
				 * No match, so use the haystack char at hptr to decide how
				 * far to advance.	If the needle had any occurrence of that
				 * character (or more precisely, one sharing the same
				 * skiptable entry) before its last character, then we advance
				 * far enough to align the last such needle character with
				 * that haystack position.	Otherwise we can advance by the
				 * whole needle length.
				 */
				hptr += state->skiptable[*hptr & skiptablemask];
			}
		}
	}

	return 0;					/* not found */
}

static void
text_position_cleanup(TextPositionState *state)
{
	if (state->use_wchar)
	{
		pfree(state->wstr1);
		pfree(state->wstr2);
	}
}

/* varstr_cmp()
 * Comparison function for text strings with given lengths.
 * Includes locale support, but must copy strings to temporary memory
 *	to allow null-termination for inputs to strcoll().
 * Returns an integer less than, equal to, or greater than zero, indicating
 * whether arg1 is less than, equal to, or greater than arg2.
 */
int
varstr_cmp(char *arg1, int len1, char *arg2, int len2)
{
	int			result;

	/*
	 * Unfortunately, there is no strncoll(), so in the non-C locale case we
	 * have to do some memory copying.	This turns out to be significantly
	 * slower, so we optimize the case where LC_COLLATE is C.  We also try to
	 * optimize relatively-short strings by avoiding palloc/pfree overhead.
	 */
	if (lc_collate_is_c())
	{
		result = strncmp(arg1, arg2, Min(len1, len2));
		if ((result == 0) && (len1 != len2))
			result = (len1 < len2) ? -1 : 1;
	}
	else
	{
#define STACKBUFLEN		1024

		char		a1buf[STACKBUFLEN];
		char		a2buf[STACKBUFLEN];
		char	   *a1p,
				   *a2p;

#ifdef WIN32
		/* Win32 does not have UTF-8, so we need to map to UTF-16 */
		if (GetDatabaseEncoding() == PG_UTF8)
		{
			int			a1len;
			int			a2len;
			int			r;

			if (len1 >= STACKBUFLEN / 2)
			{
				a1len = len1 * 2 + 2;
				a1p = palloc(a1len);
			}
			else
			{
				a1len = STACKBUFLEN;
				a1p = a1buf;
			}
			if (len2 >= STACKBUFLEN / 2)
			{
				a2len = len2 * 2 + 2;
				a2p = palloc(a2len);
			}
			else
			{
				a2len = STACKBUFLEN;
				a2p = a2buf;
			}

			/* stupid Microsloth API does not work for zero-length input */
			if (len1 == 0)
				r = 0;
			else
			{
				r = MultiByteToWideChar(CP_UTF8, 0, arg1, len1,
										(LPWSTR) a1p, a1len / 2);
				if (!r)
					ereport(ERROR,
					 (errmsg("could not convert string to UTF-16: error %lu",
							 GetLastError())));
			}
			((LPWSTR) a1p)[r] = 0;

			if (len2 == 0)
				r = 0;
			else
			{
				r = MultiByteToWideChar(CP_UTF8, 0, arg2, len2,
										(LPWSTR) a2p, a2len / 2);
				if (!r)
					ereport(ERROR,
					 (errmsg("could not convert string to UTF-16: error %lu",
							 GetLastError())));
			}
			((LPWSTR) a2p)[r] = 0;

			errno = 0;
			result = wcscoll((LPWSTR) a1p, (LPWSTR) a2p);
			if (result == 2147483647)	/* _NLSCMPERROR; missing from mingw
										 * headers */
				ereport(ERROR,
						(errmsg("could not compare Unicode strings: %m")));

			/*
			 * In some locales wcscoll() can claim that nonidentical strings
			 * are equal.  Believing that would be bad news for a number of
			 * reasons, so we follow Perl's lead and sort "equal" strings
			 * according to strcmp (on the UTF-8 representation).
			 */
			if (result == 0)
			{
				result = strncmp(arg1, arg2, Min(len1, len2));
				if ((result == 0) && (len1 != len2))
					result = (len1 < len2) ? -1 : 1;
			}

			if (a1p != a1buf)
				pfree(a1p);
			if (a2p != a2buf)
				pfree(a2p);

			return result;
		}
#endif   /* WIN32 */

		if (len1 >= STACKBUFLEN)
			a1p = (char *) palloc(len1 + 1);
		else
			a1p = a1buf;
		if (len2 >= STACKBUFLEN)
			a2p = (char *) palloc(len2 + 1);
		else
			a2p = a2buf;

		memcpy(a1p, arg1, len1);
		a1p[len1] = '\0';
		memcpy(a2p, arg2, len2);
		a2p[len2] = '\0';

		result = strcoll(a1p, a2p);

		/*
		 * In some locales strcoll() can claim that nonidentical strings are
		 * equal.  Believing that would be bad news for a number of reasons,
		 * so we follow Perl's lead and sort "equal" strings according to
		 * strcmp().
		 */
		if (result == 0)
			result = strcmp(a1p, a2p);

		if (a1p != a1buf)
			pfree(a1p);
		if (a2p != a2buf)
			pfree(a2p);
	}

	return result;
}


/* text_cmp()
 * Internal comparison function for text strings.
 * Returns -1, 0 or 1
 */
static int
text_cmp(text *arg1, text *arg2)
{
	char	   *a1p,
			   *a2p;
	int			len1,
				len2;

	a1p = VARDATA_ANY(arg1);
	a2p = VARDATA_ANY(arg2);

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	return varstr_cmp(a1p, len1, a2p, len2);
}

/*
 * Comparison functions for text strings.
 *
 * Note: btree indexes need these routines not to leak memory; therefore,
 * be careful to free working copies of toasted datums.  Most places don't
 * need to be so careful.
 */

Datum
texteq(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	bool		result;

	/*
	 * Since we only care about equality or not-equality, we can avoid all the
	 * expense of strcoll() here, and just do bitwise comparison.
	 */
	if (VARSIZE_ANY_EXHDR(arg1) != VARSIZE_ANY_EXHDR(arg2))
		result = false;
	else
		result = (strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2),
						  VARSIZE_ANY_EXHDR(arg1)) == 0);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result);
}

Datum
textne(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	bool		result;

	/*
	 * Since we only care about equality or not-equality, we can avoid all the
	 * expense of strcoll() here, and just do bitwise comparison.
	 */
	if (VARSIZE_ANY_EXHDR(arg1) != VARSIZE_ANY_EXHDR(arg2))
		result = true;
	else
		result = (strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2),
						  VARSIZE_ANY_EXHDR(arg1)) != 0);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result);
}

Datum
text_lt(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	bool		result;

	result = (text_cmp(arg1, arg2) < 0);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result);
}

Datum
text_le(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	bool		result;

	result = (text_cmp(arg1, arg2) <= 0);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result);
}

Datum
text_gt(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	bool		result;

	result = (text_cmp(arg1, arg2) > 0);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result);
}

Datum
text_ge(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	bool		result;

	result = (text_cmp(arg1, arg2) >= 0);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result);
}

Datum
bttextcmp(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	int32		result;

	result = text_cmp(arg1, arg2);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_INT32(result);
}


Datum
text_larger(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	text	   *result;

	result = ((text_cmp(arg1, arg2) > 0) ? arg1 : arg2);

	PG_RETURN_TEXT_P(result);
}

Datum
text_smaller(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	text	   *result;

	result = ((text_cmp(arg1, arg2) < 0) ? arg1 : arg2);

	PG_RETURN_TEXT_P(result);
}


/*
 * The following operators support character-by-character comparison
 * of text datums, to allow building indexes suitable for LIKE clauses.
 * Note that the regular texteq/textne comparison operators are assumed
 * to be compatible with these!
 */

static int
internal_text_pattern_compare(text *arg1, text *arg2)
{
	int			result;
	int			len1,
				len2;

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	result = strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));
	if (result != 0)
		return result;
	else if (len1 < len2)
		return -1;
	else if (len1 > len2)
		return 1;
	else
		return 0;
}


Datum
text_pattern_lt(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	int			result;

	result = internal_text_pattern_compare(arg1, arg2);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result < 0);
}


Datum
text_pattern_le(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	int			result;

	result = internal_text_pattern_compare(arg1, arg2);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result <= 0);
}


Datum
text_pattern_ge(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	int			result;

	result = internal_text_pattern_compare(arg1, arg2);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result >= 0);
}


Datum
text_pattern_gt(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	int			result;

	result = internal_text_pattern_compare(arg1, arg2);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result > 0);
}


Datum
bttext_pattern_cmp(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	int			result;

	result = internal_text_pattern_compare(arg1, arg2);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_INT32(result);
}


/*-------------------------------------------------------------
 * byteaoctetlen
 *
 * get the number of bytes contained in an instance of type 'bytea'
 *-------------------------------------------------------------
 */
Datum
byteaoctetlen(PG_FUNCTION_ARGS)
{
	Datum		str = PG_GETARG_DATUM(0);

	/* We need not detoast the input at all */
	PG_RETURN_INT32(toast_raw_datum_size(str) - VARHDRSZ);
}

/*
 * byteacat -
 *	  takes two bytea* and returns a bytea* that is the concatenation of
 *	  the two.
 *
 * Cloned from textcat and modified as required.
 */
Datum
byteacat(PG_FUNCTION_ARGS)
{
	bytea	   *t1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *t2 = PG_GETARG_BYTEA_PP(1);

	PG_RETURN_BYTEA_P(bytea_catenate(t1, t2));
}

/*
 * bytea_catenate
 *	Guts of byteacat(), broken out so it can be used by other functions
 *
 * Arguments can be in short-header form, but not compressed or out-of-line
 */
static bytea *
bytea_catenate(bytea *t1, bytea *t2)
{
	bytea	   *result;
	int			len1,
				len2,
				len;
	char	   *ptr;

	len1 = VARSIZE_ANY_EXHDR(t1);
	len2 = VARSIZE_ANY_EXHDR(t2);

	/* paranoia ... probably should throw error instead? */
	if (len1 < 0)
		len1 = 0;
	if (len2 < 0)
		len2 = 0;

	len = len1 + len2 + VARHDRSZ;
	result = (bytea *) palloc(len);

	/* Set size of result string... */
	SET_VARSIZE(result, len);

	/* Fill data field of result string... */
	ptr = VARDATA(result);
	if (len1 > 0)
		memcpy(ptr, VARDATA_ANY(t1), len1);
	if (len2 > 0)
		memcpy(ptr + len1, VARDATA_ANY(t2), len2);

	return result;
}

#define PG_STR_GET_BYTEA(str_) \
	DatumGetByteaP(DirectFunctionCall1(byteain, CStringGetDatum(str_)))

/*
 * bytea_substr()
 * Return a substring starting at the specified position.
 * Cloned from text_substr and modified as required.
 *
 * Input:
 *	- string
 *	- starting position (is one-based)
 *	- string length (optional)
 *
 * If the starting position is zero or less, then return from the start of the string
 * adjusting the length to be consistent with the "negative start" per SQL92.
 * If the length is less than zero, an ERROR is thrown. If no third argument
 * (length) is provided, the length to the end of the string is assumed.
 */
Datum
bytea_substr(PG_FUNCTION_ARGS)
{
	PG_RETURN_BYTEA_P(bytea_substring(PG_GETARG_DATUM(0),
									  PG_GETARG_INT32(1),
									  PG_GETARG_INT32(2),
									  false));
}

/*
 * bytea_substr_no_len -
 *	  Wrapper to avoid opr_sanity failure due to
 *	  one function accepting a different number of args.
 */
Datum
bytea_substr_no_len(PG_FUNCTION_ARGS)
{
	PG_RETURN_BYTEA_P(bytea_substring(PG_GETARG_DATUM(0),
									  PG_GETARG_INT32(1),
									  -1,
									  true));
}

static bytea *
bytea_substring(Datum str,
				int S,
				int L,
				bool length_not_specified)
{
	int			S1;				/* adjusted start position */
	int			L1;				/* adjusted substring length */

	S1 = Max(S, 1);

	if (length_not_specified)
	{
		/*
		 * Not passed a length - DatumGetByteaPSlice() grabs everything to the
		 * end of the string if we pass it a negative value for length.
		 */
		L1 = -1;
	}
	else
	{
		/* end position */
		int			E = S + L;

		/*
		 * A negative value for L is the only way for the end position to be
		 * before the start. SQL99 says to throw an error.
		 */
		if (E < S)
			ereport(ERROR,
					(errcode(ERRCODE_SUBSTRING_ERROR),
					 errmsg("negative substring length not allowed")));

		/*
		 * A zero or negative value for the end position can happen if the
		 * start was negative or one. SQL99 says to return a zero-length
		 * string.
		 */
		if (E < 1)
			return PG_STR_GET_BYTEA("");

		L1 = E - S1;
	}

	/*
	 * If the start position is past the end of the string, SQL99 says to
	 * return a zero-length string -- DatumGetByteaPSlice() will do that for
	 * us. Convert to zero-based starting position
	 */
	return DatumGetByteaPSlice(str, S1 - 1, L1);
}

/*
 * byteaoverlay
 *	Replace specified substring of first string with second
 *
 * The SQL standard defines OVERLAY() in terms of substring and concatenation.
 * This code is a direct implementation of what the standard says.
 */
Datum
byteaoverlay(PG_FUNCTION_ARGS)
{
	bytea	   *t1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *t2 = PG_GETARG_BYTEA_PP(1);
	int			sp = PG_GETARG_INT32(2);		/* substring start position */
	int			sl = PG_GETARG_INT32(3);		/* substring length */

	PG_RETURN_BYTEA_P(bytea_overlay(t1, t2, sp, sl));
}

Datum
byteaoverlay_no_len(PG_FUNCTION_ARGS)
{
	bytea	   *t1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *t2 = PG_GETARG_BYTEA_PP(1);
	int			sp = PG_GETARG_INT32(2);		/* substring start position */
	int			sl;

	sl = VARSIZE_ANY_EXHDR(t2); /* defaults to length(t2) */
	PG_RETURN_BYTEA_P(bytea_overlay(t1, t2, sp, sl));
}

static bytea *
bytea_overlay(bytea *t1, bytea *t2, int sp, int sl)
{
	bytea	   *result;
	bytea	   *s1;
	bytea	   *s2;
	int			sp_pl_sl;

	/*
	 * Check for possible integer-overflow cases.  For negative sp, throw a
	 * "substring length" error because that's what should be expected
	 * according to the spec's definition of OVERLAY().
	 */
	if (sp <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_SUBSTRING_ERROR),
				 errmsg("negative substring length not allowed")));
	sp_pl_sl = sp + sl;
	if (sp_pl_sl <= sl)
		ereport(ERROR,
				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
				 errmsg("integer out of range")));

	s1 = bytea_substring(PointerGetDatum(t1), 1, sp - 1, false);
	s2 = bytea_substring(PointerGetDatum(t1), sp_pl_sl, -1, true);
	result = bytea_catenate(s1, t2);
	result = bytea_catenate(result, s2);

	return result;
}

/*
 * byteapos -
 *	  Return the position of the specified substring.
 *	  Implements the SQL92 POSITION() function.
 * Cloned from textpos and modified as required.
 */
Datum
byteapos(PG_FUNCTION_ARGS)
{
	bytea	   *t1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *t2 = PG_GETARG_BYTEA_PP(1);
	int			pos;
	int			px,
				p;
	int			len1,
				len2;
	char	   *p1,
			   *p2;

	len1 = VARSIZE_ANY_EXHDR(t1);
	len2 = VARSIZE_ANY_EXHDR(t2);

	if (len2 <= 0)
		PG_RETURN_INT32(1);		/* result for empty pattern */

	p1 = VARDATA_ANY(t1);
	p2 = VARDATA_ANY(t2);

	pos = 0;
	px = (len1 - len2);
	for (p = 0; p <= px; p++)
	{
		if ((*p2 == *p1) && (memcmp(p1, p2, len2) == 0))
		{
			pos = p + 1;
			break;
		};
		p1++;
	};

	PG_RETURN_INT32(pos);
}

/*-------------------------------------------------------------
 * byteaGetByte
 *
 * this routine treats "bytea" as an array of bytes.
 * It returns the Nth byte (a number between 0 and 255).
 *-------------------------------------------------------------
 */
Datum
byteaGetByte(PG_FUNCTION_ARGS)
{
	bytea	   *v = PG_GETARG_BYTEA_PP(0);
	int32		n = PG_GETARG_INT32(1);
	int			len;
	int byte;

	len = VARSIZE_ANY_EXHDR(v);

	if (n < 0 || n >= len)
		ereport(ERROR,
				(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
				 errmsg("index %d out of valid range, 0..%d",
						n, len - 1)));

	byte = ((unsigned char *) VARDATA_ANY(v))[n];

	PG_RETURN_INT32(byte);
}

/*-------------------------------------------------------------
 * byteaGetBit
 *
 * This routine treats a "bytea" type like an array of bits.
 * It returns the value of the Nth bit (0 or 1).
 *
 *-------------------------------------------------------------
 */
Datum
byteaGetBit(PG_FUNCTION_ARGS)
{
	bytea	   *v = PG_GETARG_BYTEA_PP(0);
	int32		n = PG_GETARG_INT32(1);
	int			byteNo,
				bitNo;
	int			len;
	int byte;

	len = VARSIZE_ANY_EXHDR(v);

	if (n < 0 || n >= len * 8)
		ereport(ERROR,
				(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
				 errmsg("index %d out of valid range, 0..%d",
						n, len * 8 - 1)));

	byteNo = n / 8;
	bitNo = n % 8;

	byte = ((unsigned char *) VARDATA_ANY(v))[byteNo];

	if (byte &(1 << bitNo))
		PG_RETURN_INT32(1);
	else
		PG_RETURN_INT32(0);
}

/*-------------------------------------------------------------
 * byteaSetByte
 *
 * Given an instance of type 'bytea' creates a new one with
 * the Nth byte set to the given value.
 *
 *-------------------------------------------------------------
 */
Datum
byteaSetByte(PG_FUNCTION_ARGS)
{
	bytea	   *v = PG_GETARG_BYTEA_P(0);
	int32		n = PG_GETARG_INT32(1);
	int32		newByte = PG_GETARG_INT32(2);
	int			len;
	bytea	   *res;

	len = VARSIZE(v) - VARHDRSZ;

	if (n < 0 || n >= len)
		ereport(ERROR,
				(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
				 errmsg("index %d out of valid range, 0..%d",
						n, len - 1)));

	/*
	 * Make a copy of the original varlena.
	 */
	res = (bytea *) palloc(VARSIZE(v));
	memcpy((char *) res, (char *) v, VARSIZE(v));

	/*
	 * Now set the byte.
	 */
	((unsigned char *) VARDATA(res))[n] = newByte;

	PG_RETURN_BYTEA_P(res);
}

/*-------------------------------------------------------------
 * byteaSetBit
 *
 * Given an instance of type 'bytea' creates a new one with
 * the Nth bit set to the given value.
 *
 *-------------------------------------------------------------
 */
Datum
byteaSetBit(PG_FUNCTION_ARGS)
{
	bytea	   *v = PG_GETARG_BYTEA_P(0);
	int32		n = PG_GETARG_INT32(1);
	int32		newBit = PG_GETARG_INT32(2);
	bytea	   *res;
	int			len;
	int			oldByte,
				newByte;
	int			byteNo,
				bitNo;

	len = VARSIZE(v) - VARHDRSZ;

	if (n < 0 || n >= len * 8)
		ereport(ERROR,
				(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
				 errmsg("index %d out of valid range, 0..%d",
						n, len * 8 - 1)));

	byteNo = n / 8;
	bitNo = n % 8;

	/*
	 * sanity check!
	 */
	if (newBit != 0 && newBit != 1)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("new bit must be 0 or 1")));

	/*
	 * Make a copy of the original varlena.
	 */
	res = (bytea *) palloc(VARSIZE(v));
	memcpy((char *) res, (char *) v, VARSIZE(v));

	/*
	 * Update the byte.
	 */
	oldByte = ((unsigned char *) VARDATA(res))[byteNo];

	if (newBit == 0)
		newByte = oldByte & (~(1 << bitNo));
	else
		newByte = oldByte | (1 << bitNo);

	((unsigned char *) VARDATA(res))[byteNo] = newByte;

	PG_RETURN_BYTEA_P(res);
}


/* text_name()
 * Converts a text type to a Name type.
 */
Datum
text_name(PG_FUNCTION_ARGS)
{
	text	   *s = PG_GETARG_TEXT_PP(0);
	Name		result;
	int			len;

	len = VARSIZE_ANY_EXHDR(s);

	/* Truncate oversize input */
	if (len >= NAMEDATALEN)
		len = NAMEDATALEN - 1;

	result = (Name) palloc(NAMEDATALEN);
	memcpy(NameStr(*result), VARDATA_ANY(s), len);

	/* now null pad to full length... */
	while (len < NAMEDATALEN)
	{
		*(NameStr(*result) + len) = '\0';
		len++;
	}

	PG_RETURN_NAME(result);
}

/* name_text()
 * Converts a Name type to a text type.
 */
Datum
name_text(PG_FUNCTION_ARGS)
{
	Name		s = PG_GETARG_NAME(0);

	PG_RETURN_TEXT_P(cstring_to_text(NameStr(*s)));
}


/*
 * textToQualifiedNameList - convert a text object to list of names
 *
 * This implements the input parsing needed by nextval() and other
 * functions that take a text parameter representing a qualified name.
 * We split the name at dots, downcase if not double-quoted, and
 * truncate names if they're too long.
 */
List *
textToQualifiedNameList(text *textval)
{
	char	   *rawname;
	List	   *result = NIL;
	List	   *namelist;
	ListCell   *l;

	/* Convert to C string (handles possible detoasting). */
	/* Note we rely on being able to modify rawname below. */
	rawname = text_to_cstring(textval);

	if (!SplitIdentifierString(rawname, '.', &namelist))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_NAME),
				 errmsg("invalid name syntax")));

	if (namelist == NIL)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_NAME),
				 errmsg("invalid name syntax")));

	foreach(l, namelist)
	{
		char	   *curname = (char *) lfirst(l);

		result = lappend(result, makeString(pstrdup(curname)));
	}

	pfree(rawname);
	list_free(namelist);

	return result;
}

/*
 * SplitIdentifierString --- parse a string containing identifiers
 *
 * This is the guts of textToQualifiedNameList, and is exported for use in
 * other situations such as parsing GUC variables.	In the GUC case, it's
 * important to avoid memory leaks, so the API is designed to minimize the
 * amount of stuff that needs to be allocated and freed.
 *
 * Inputs:
 *	rawstring: the input string; must be overwritable!	On return, it's
 *			   been modified to contain the separated identifiers.
 *	separator: the separator punctuation expected between identifiers
 *			   (typically '.' or ',').	Whitespace may also appear around
 *			   identifiers.
 * Outputs:
 *	namelist: filled with a palloc'd list of pointers to identifiers within
 *			  rawstring.  Caller should list_free() this even on error return.
 *
 * Returns TRUE if okay, FALSE if there is a syntax error in the string.
 *
 * Note that an empty string is considered okay here, though not in
 * textToQualifiedNameList.
 */
bool
SplitIdentifierString(char *rawstring, char separator,
					  List **namelist)
{
	char	   *nextp = rawstring;
	bool		done = false;

	*namelist = NIL;

	while (isspace((unsigned char) *nextp))
		nextp++;				/* skip leading whitespace */

	if (*nextp == '\0')
		return true;			/* allow empty string */

	/* At the top of the loop, we are at start of a new identifier. */
	do
	{
		char	   *curname;
		char	   *endp;

		if (*nextp == '\"')
		{
			/* Quoted name --- collapse quote-quote pairs, no downcasing */
			curname = nextp + 1;
			for (;;)
			{
				endp = strchr(nextp + 1, '\"');
				if (endp == NULL)
					return false;		/* mismatched quotes */
				if (endp[1] != '\"')
					break;		/* found end of quoted name */
				/* Collapse adjacent quotes into one quote, and look again */
				memmove(endp, endp + 1, strlen(endp));
				nextp = endp;
			}
			/* endp now points at the terminating quote */
			nextp = endp + 1;
		}
		else
		{
			/* Unquoted name --- extends to separator or whitespace */
			char	   *downname;
			int			len;

			curname = nextp;
			while (*nextp && *nextp != separator &&
				   !isspace((unsigned char) *nextp))
				nextp++;
			endp = nextp;
			if (curname == nextp)
				return false;	/* empty unquoted name not allowed */

			/*
			 * Downcase the identifier, using same code as main lexer does.
			 *
			 * XXX because we want to overwrite the input in-place, we cannot
			 * support a downcasing transformation that increases the string
			 * length.	This is not a problem given the current implementation
			 * of downcase_truncate_identifier, but we'll probably have to do
			 * something about this someday.
			 */
			len = endp - curname;
			downname = downcase_truncate_identifier(curname, len, false);
			Assert(strlen(downname) <= len);
			strncpy(curname, downname, len);
			pfree(downname);
		}

		while (isspace((unsigned char) *nextp))
			nextp++;			/* skip trailing whitespace */

		if (*nextp == separator)
		{
			nextp++;
			while (isspace((unsigned char) *nextp))
				nextp++;		/* skip leading whitespace for next */
			/* we expect another name, so done remains false */
		}
		else if (*nextp == '\0')
			done = true;
		else
			return false;		/* invalid syntax */

		/* Now safe to overwrite separator with a null */
		*endp = '\0';

		/* Truncate name if it's overlength */
		truncate_identifier(curname, strlen(curname), false);

		/*
		 * Finished isolating current name --- add it to list
		 */
		*namelist = lappend(*namelist, curname);

		/* Loop back if we didn't reach end of string */
	} while (!done);

	return true;
}


/*****************************************************************************
 *	Comparison Functions used for bytea
 *
 * Note: btree indexes need these routines not to leak memory; therefore,
 * be careful to free working copies of toasted datums.  Most places don't
 * need to be so careful.
 *****************************************************************************/

Datum
byteaeq(PG_FUNCTION_ARGS)
{
	bytea	   *arg1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *arg2 = PG_GETARG_BYTEA_PP(1);
	int			len1,
				len2;
	bool		result;

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	/* fast path for different-length inputs */
	if (len1 != len2)
		result = false;
	else
		result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), len1) == 0);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result);
}

Datum
byteane(PG_FUNCTION_ARGS)
{
	bytea	   *arg1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *arg2 = PG_GETARG_BYTEA_PP(1);
	int			len1,
				len2;
	bool		result;

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	/* fast path for different-length inputs */
	if (len1 != len2)
		result = true;
	else
		result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), len1) != 0);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL(result);
}

Datum
bytealt(PG_FUNCTION_ARGS)
{
	bytea	   *arg1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *arg2 = PG_GETARG_BYTEA_PP(1);
	int			len1,
				len2;
	int			cmp;

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL((cmp < 0) || ((cmp == 0) && (len1 < len2)));
}

Datum
byteale(PG_FUNCTION_ARGS)
{
	bytea	   *arg1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *arg2 = PG_GETARG_BYTEA_PP(1);
	int			len1,
				len2;
	int			cmp;

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL((cmp < 0) || ((cmp == 0) && (len1 <= len2)));
}

Datum
byteagt(PG_FUNCTION_ARGS)
{
	bytea	   *arg1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *arg2 = PG_GETARG_BYTEA_PP(1);
	int			len1,
				len2;
	int			cmp;

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL((cmp > 0) || ((cmp == 0) && (len1 > len2)));
}

Datum
byteage(PG_FUNCTION_ARGS)
{
	bytea	   *arg1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *arg2 = PG_GETARG_BYTEA_PP(1);
	int			len1,
				len2;
	int			cmp;

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_BOOL((cmp > 0) || ((cmp == 0) && (len1 >= len2)));
}

Datum
byteacmp(PG_FUNCTION_ARGS)
{
	bytea	   *arg1 = PG_GETARG_BYTEA_PP(0);
	bytea	   *arg2 = PG_GETARG_BYTEA_PP(1);
	int			len1,
				len2;
	int			cmp;

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	cmp = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));
	if ((cmp == 0) && (len1 != len2))
		cmp = (len1 < len2) ? -1 : 1;

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_INT32(cmp);
}

/*
 * appendStringInfoText
 *
 * Append a text to str.
 * Like appendStringInfoString(str, text_to_cstring(t)) but faster.
 */
static void
appendStringInfoText(StringInfo str, const text *t)
{
	appendBinaryStringInfo(str, VARDATA_ANY(t), VARSIZE_ANY_EXHDR(t));
}

/*
 * replace_text
 * replace all occurrences of 'old_sub_str' in 'orig_str'
 * with 'new_sub_str' to form 'new_str'
 *
 * returns 'orig_str' if 'old_sub_str' == '' or 'orig_str' == ''
 * otherwise returns 'new_str'
 */
Datum
replace_text(PG_FUNCTION_ARGS)
{
	text	   *src_text = PG_GETARG_TEXT_PP(0);
	text	   *from_sub_text = PG_GETARG_TEXT_PP(1);
	text	   *to_sub_text = PG_GETARG_TEXT_PP(2);
	int			src_text_len;
	int			from_sub_text_len;
	TextPositionState state;
	text	   *ret_text;
	int			start_posn;
	int			curr_posn;
	int			chunk_len;
	char	   *start_ptr;
	StringInfoData str;

	text_position_setup(src_text, from_sub_text, &state);

	/*
	 * Note: we check the converted string length, not the original, because
	 * they could be different if the input contained invalid encoding.
	 */
	src_text_len = state.len1;
	from_sub_text_len = state.len2;

	/* Return unmodified source string if empty source or pattern */
	if (src_text_len < 1 || from_sub_text_len < 1)
	{
		text_position_cleanup(&state);
		PG_RETURN_TEXT_P(src_text);
	}

	start_posn = 1;
	curr_posn = text_position_next(1, &state);

	/* When the from_sub_text is not found, there is nothing to do. */
	if (curr_posn == 0)
	{
		text_position_cleanup(&state);
		PG_RETURN_TEXT_P(src_text);
	}

	/* start_ptr points to the start_posn'th character of src_text */
	start_ptr = VARDATA_ANY(src_text);

	initStringInfo(&str);

	do
	{
		CHECK_FOR_INTERRUPTS();

		/* copy the data skipped over by last text_position_next() */
		chunk_len = charlen_to_bytelen(start_ptr, curr_posn - start_posn);
		appendBinaryStringInfo(&str, start_ptr, chunk_len);

		appendStringInfoText(&str, to_sub_text);

		start_posn = curr_posn;
		start_ptr += chunk_len;
		start_posn += from_sub_text_len;
		start_ptr += charlen_to_bytelen(start_ptr, from_sub_text_len);

		curr_posn = text_position_next(start_posn, &state);
	}
	while (curr_posn > 0);

	/* copy trailing data */
	chunk_len = ((char *) src_text + VARSIZE_ANY(src_text)) - start_ptr;
	appendBinaryStringInfo(&str, start_ptr, chunk_len);

	text_position_cleanup(&state);

	ret_text = cstring_to_text_with_len(str.data, str.len);
	pfree(str.data);

	PG_RETURN_TEXT_P(ret_text);
}

/*
 * check_replace_text_has_escape_char
 *
 * check whether replace_text contains escape char.
 */
static bool
check_replace_text_has_escape_char(const text *replace_text)
{
	const char *p = VARDATA_ANY(replace_text);
	const char *p_end = p + VARSIZE_ANY_EXHDR(replace_text);

	if (pg_database_encoding_max_length() == 1)
	{
		for (; p < p_end; p++)
		{
			if (*p == '\\')
				return true;
		}
	}
	else
	{
		for (; p < p_end; p += pg_mblen(p))
		{
			if (*p == '\\')
				return true;
		}
	}

	return false;
}

/*
 * appendStringInfoRegexpSubstr
 *
 * Append replace_text to str, substituting regexp back references for
 * \n escapes.	start_ptr is the start of the match in the source string,
 * at logical character position data_pos.
 */
static void
appendStringInfoRegexpSubstr(StringInfo str, text *replace_text,
							 regmatch_t *pmatch,
							 char *start_ptr, int data_pos)
{
	const char *p = VARDATA_ANY(replace_text);
	const char *p_end = p + VARSIZE_ANY_EXHDR(replace_text);
	int			eml = pg_database_encoding_max_length();

	for (;;)
	{
		const char *chunk_start = p;
		int			so;
		int			eo;

		/* Find next escape char. */
		if (eml == 1)
		{
			for (; p < p_end && *p != '\\'; p++)
				 /* nothing */ ;
		}
		else
		{
			for (; p < p_end && *p != '\\'; p += pg_mblen(p))
				 /* nothing */ ;
		}

		/* Copy the text we just scanned over, if any. */
		if (p > chunk_start)
			appendBinaryStringInfo(str, chunk_start, p - chunk_start);

		/* Done if at end of string, else advance over escape char. */
		if (p >= p_end)
			break;
		p++;

		if (p >= p_end)
		{
			/* Escape at very end of input.  Treat same as unexpected char */
			appendStringInfoChar(str, '\\');
			break;
		}

		if (*p >= '1' && *p <= '9')
		{
			/* Use the back reference of regexp. */
			int			idx = *p - '0';

			so = pmatch[idx].rm_so;
			eo = pmatch[idx].rm_eo;
			p++;
		}
		else if (*p == '&')
		{
			/* Use the entire matched string. */
			so = pmatch[0].rm_so;
			eo = pmatch[0].rm_eo;
			p++;
		}
		else if (*p == '\\')
		{
			/* \\ means transfer one \ to output. */
			appendStringInfoChar(str, '\\');
			p++;
			continue;
		}
		else
		{
			/*
			 * If escape char is not followed by any expected char, just treat
			 * it as ordinary data to copy.  (XXX would it be better to throw
			 * an error?)
			 */
			appendStringInfoChar(str, '\\');
			continue;
		}

		if (so != -1 && eo != -1)
		{
			/*
			 * Copy the text that is back reference of regexp.	Note so and eo
			 * are counted in characters not bytes.
			 */
			char	   *chunk_start;
			int			chunk_len;

			Assert(so >= data_pos);
			chunk_start = start_ptr;
			chunk_start += charlen_to_bytelen(chunk_start, so - data_pos);
			chunk_len = charlen_to_bytelen(chunk_start, eo - so);
			appendBinaryStringInfo(str, chunk_start, chunk_len);
		}
	}
}

#define REGEXP_REPLACE_BACKREF_CNT		10

/*
 * replace_text_regexp
 *
 * replace text that matches to regexp in src_text to replace_text.
 *
 * Note: to avoid having to include regex.h in builtins.h, we declare
 * the regexp argument as void *, but really it's regex_t *.
 */
text *
replace_text_regexp(text *src_text, void *regexp,
					text *replace_text, bool glob)
{
	text	   *ret_text;
	regex_t    *re = (regex_t *) regexp;
	int			src_text_len = VARSIZE_ANY_EXHDR(src_text);
	StringInfoData buf;
	regmatch_t	pmatch[REGEXP_REPLACE_BACKREF_CNT];
	pg_wchar   *data;
	size_t		data_len;
	int			search_start;
	int			data_pos;
	char	   *start_ptr;
	bool		have_escape;

	initStringInfo(&buf);

	/* Convert data string to wide characters. */
	data = (pg_wchar *) palloc((src_text_len + 1) * sizeof(pg_wchar));
	data_len = pg_mb2wchar_with_len(VARDATA_ANY(src_text), data, src_text_len);

	/* Check whether replace_text has escape char. */
	have_escape = check_replace_text_has_escape_char(replace_text);

	/* start_ptr points to the data_pos'th character of src_text */
	start_ptr = (char *) VARDATA_ANY(src_text);
	data_pos = 0;

	search_start = 0;
	while (search_start <= data_len)
	{
		int			regexec_result;

		CHECK_FOR_INTERRUPTS();

		regexec_result = pg_regexec(re,
									data,
									data_len,
									search_start,
									NULL,		/* no details */
									REGEXP_REPLACE_BACKREF_CNT,
									pmatch,
									0);

		if (regexec_result == REG_NOMATCH)
			break;

		if (regexec_result != REG_OKAY)
		{
			char		errMsg[100];

			pg_regerror(regexec_result, re, errMsg, sizeof(errMsg));
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_REGULAR_EXPRESSION),
					 errmsg("regular expression failed: %s", errMsg)));
		}

		/*
		 * Copy the text to the left of the match position.  Note we are given
		 * character not byte indexes.
		 */
		if (pmatch[0].rm_so - data_pos > 0)
		{
			int			chunk_len;

			chunk_len = charlen_to_bytelen(start_ptr,
										   pmatch[0].rm_so - data_pos);
			appendBinaryStringInfo(&buf, start_ptr, chunk_len);

			/*
			 * Advance start_ptr over that text, to avoid multiple rescans of
			 * it if the replace_text contains multiple back-references.
			 */
			start_ptr += chunk_len;
			data_pos = pmatch[0].rm_so;
		}

		/*
		 * Copy the replace_text. Process back references when the
		 * replace_text has escape characters.
		 */
		if (have_escape)
			appendStringInfoRegexpSubstr(&buf, replace_text, pmatch,
										 start_ptr, data_pos);
		else
			appendStringInfoText(&buf, replace_text);

		/* Advance start_ptr and data_pos over the matched text. */
		start_ptr += charlen_to_bytelen(start_ptr,
										pmatch[0].rm_eo - data_pos);
		data_pos = pmatch[0].rm_eo;

		/*
		 * When global option is off, replace the first instance only.
		 */
		if (!glob)
			break;

		/*
		 * Search from next character when the matching text is zero width.
		 */
		search_start = data_pos;
		if (pmatch[0].rm_so == pmatch[0].rm_eo)
			search_start++;
	}

	/*
	 * Copy the text to the right of the last match.
	 */
	if (data_pos < data_len)
	{
		int			chunk_len;

		chunk_len = ((char *) src_text + VARSIZE_ANY(src_text)) - start_ptr;
		appendBinaryStringInfo(&buf, start_ptr, chunk_len);
	}

	ret_text = cstring_to_text_with_len(buf.data, buf.len);
	pfree(buf.data);
	pfree(data);

	return ret_text;
}

/*
 * split_text
 * parse input string
 * return ord item (1 based)
 * based on provided field separator
 */
Datum
split_text(PG_FUNCTION_ARGS)
{
	text	   *inputstring = PG_GETARG_TEXT_PP(0);
	text	   *fldsep = PG_GETARG_TEXT_PP(1);
	int			fldnum = PG_GETARG_INT32(2);
	int			inputstring_len;
	int			fldsep_len;
	TextPositionState state;
	int			start_posn;
	int			end_posn;
	text	   *result_text;

	/* field number is 1 based */
	if (fldnum < 1)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("field position must be greater than zero")));

	text_position_setup(inputstring, fldsep, &state);

	/*
	 * Note: we check the converted string length, not the original, because
	 * they could be different if the input contained invalid encoding.
	 */
	inputstring_len = state.len1;
	fldsep_len = state.len2;

	/* return empty string for empty input string */
	if (inputstring_len < 1)
	{
		text_position_cleanup(&state);
		PG_RETURN_TEXT_P(cstring_to_text(""));
	}

	/* empty field separator */
	if (fldsep_len < 1)
	{
		text_position_cleanup(&state);
		/* if first field, return input string, else empty string */
		if (fldnum == 1)
			PG_RETURN_TEXT_P(inputstring);
		else
			PG_RETURN_TEXT_P(cstring_to_text(""));
	}

	/* identify bounds of first field */
	start_posn = 1;
	end_posn = text_position_next(1, &state);

	/* special case if fldsep not found at all */
	if (end_posn == 0)
	{
		text_position_cleanup(&state);
		/* if field 1 requested, return input string, else empty string */
		if (fldnum == 1)
			PG_RETURN_TEXT_P(inputstring);
		else
			PG_RETURN_TEXT_P(cstring_to_text(""));
	}

	while (end_posn > 0 && --fldnum > 0)
	{
		/* identify bounds of next field */
		start_posn = end_posn + fldsep_len;
		end_posn = text_position_next(start_posn, &state);
	}

	text_position_cleanup(&state);

	if (fldnum > 0)
	{
		/* N'th field separator not found */
		/* if last field requested, return it, else empty string */
		if (fldnum == 1)
			result_text = text_substring(PointerGetDatum(inputstring),
										 start_posn,
										 -1,
										 true);
		else
			result_text = cstring_to_text("");
	}
	else
	{
		/* non-last field requested */
		result_text = text_substring(PointerGetDatum(inputstring),
									 start_posn,
									 end_posn - start_posn,
									 false);
	}

	PG_RETURN_TEXT_P(result_text);
}

/*
 * Convenience function to return true when two text params are equal.
 */
static bool
text_isequal(text *txt1, text *txt2)
{
	return DatumGetBool(DirectFunctionCall2(texteq,
											PointerGetDatum(txt1),
											PointerGetDatum(txt2)));
}

/*
 * text_to_array
 * parse input string and return text array of elements,
 * based on provided field separator
 */
Datum
text_to_array(PG_FUNCTION_ARGS)
{
	return text_to_array_internal(fcinfo);
}

/*
 * text_to_array_null
 * parse input string and return text array of elements,
 * based on provided field separator and null string
 *
 * This is a separate entry point only to prevent the regression tests from
 * complaining about different argument sets for the same internal function.
 */
Datum
text_to_array_null(PG_FUNCTION_ARGS)
{
	return text_to_array_internal(fcinfo);
}

/*
 * common code for text_to_array and text_to_array_null functions
 *
 * These are not strict so we have to test for null inputs explicitly.
 */
static Datum
text_to_array_internal(PG_FUNCTION_ARGS)
{
	text	   *inputstring;
	text	   *fldsep;
	text	   *null_string;
	int			inputstring_len;
	int			fldsep_len;
	char	   *start_ptr;
	text	   *result_text;
	bool		is_null;
	ArrayBuildState *astate = NULL;

	/* when input string is NULL, then result is NULL too */
	if (PG_ARGISNULL(0))
		PG_RETURN_NULL();

	inputstring = PG_GETARG_TEXT_PP(0);

	/* fldsep can be NULL */
	if (!PG_ARGISNULL(1))
		fldsep = PG_GETARG_TEXT_PP(1);
	else
		fldsep = NULL;

	/* null_string can be NULL or omitted */
	if (PG_NARGS() > 2 && !PG_ARGISNULL(2))
		null_string = PG_GETARG_TEXT_PP(2);
	else
		null_string = NULL;

	if (fldsep != NULL)
	{
		/*
		 * Normal case with non-null fldsep.  Use the text_position machinery
		 * to search for occurrences of fldsep.
		 */
		TextPositionState state;
		int			fldnum;
		int			start_posn;
		int			end_posn;
		int			chunk_len;
		
		text_position_setup(inputstring, fldsep, &state);

		/*
		 * Note: we check the converted string length, not the original,
		 * because they could be different if the input contained invalid
		 * encoding.
		 */
		inputstring_len = state.len1;
		fldsep_len = state.len2;

		/* return empty array for empty input string */
		if (inputstring_len < 1)
		{
			text_position_cleanup(&state);
			PG_RETURN_ARRAYTYPE_P(construct_empty_array(TEXTOID));
		}

		/*
		 * empty field separator: return the input string as a one-element
		 * array
		 */
		if (fldsep_len < 1)
		{
			text_position_cleanup(&state);
			/* single element can be a NULL too */
			is_null = null_string ? text_isequal(inputstring, null_string) : false;
			PG_RETURN_ARRAYTYPE_P(create_singleton_array(fcinfo, TEXTOID,
														 PointerGetDatum(inputstring),
														 is_null, 1));
		}
		
		start_posn = 1;
		/* start_ptr points to the start_posn'th character of inputstring */
		start_ptr = VARDATA_ANY(inputstring);

		for (fldnum = 1;; fldnum++) /* field number is 1 based */
		{
			CHECK_FOR_INTERRUPTS();

			end_posn = text_position_next(start_posn, &state);

			if (end_posn == 0)
			{
				/* fetch last field */
				chunk_len = ((char *) inputstring + VARSIZE_ANY(inputstring)) - start_ptr;
			}
			else
			{
				/* fetch non-last field */
				chunk_len = charlen_to_bytelen(start_ptr, end_posn - start_posn);
			}

			/* must build a temp text datum to pass to accumArrayResult */
			result_text = cstring_to_text_with_len(start_ptr, chunk_len);
			is_null = null_string ? text_isequal(result_text, null_string) : false;
		
			/* stash away this field */
			astate = accumArrayResult(astate,
									  PointerGetDatum(result_text),
									  is_null,
									  TEXTOID,
									  CurrentMemoryContext);

			pfree(result_text);

			if (end_posn == 0)
				break;

			start_posn = end_posn;
			start_ptr += chunk_len;
			start_posn += fldsep_len;
			start_ptr += charlen_to_bytelen(start_ptr, fldsep_len);
		}

		text_position_cleanup(&state);
	}
	else
	{
		/* 
		 * When fldsep is NULL, each character in the inputstring becomes an
		 * element in the result array.  The separator is effectively the space
		 * between characters.
		 */
		inputstring_len = VARSIZE_ANY_EXHDR(inputstring);
		
		/* return empty array for empty input string */
		if (inputstring_len < 1)
			PG_RETURN_ARRAYTYPE_P(construct_empty_array(TEXTOID));
		
		start_ptr = VARDATA_ANY(inputstring);
		
		while (inputstring_len > 0)
		{
			int		chunk_len = pg_mblen(start_ptr);

			CHECK_FOR_INTERRUPTS();

			/* must build a temp text datum to pass to accumArrayResult */
			result_text = cstring_to_text_with_len(start_ptr, chunk_len);
			is_null = null_string ? text_isequal(result_text, null_string) : false;
		
			/* stash away this field */
			astate = accumArrayResult(astate,
									  PointerGetDatum(result_text),
									  is_null,
									  TEXTOID,
									  CurrentMemoryContext);

			pfree(result_text);

			start_ptr += chunk_len;
			inputstring_len -= chunk_len;
		}
	}

	PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate,
										  CurrentMemoryContext));
}

/*
 * array_to_text
 * concatenate Cstring representation of input array elements
 * using provided field separator
 */
Datum
array_to_text(PG_FUNCTION_ARGS)
{
	ArrayType  *v = PG_GETARG_ARRAYTYPE_P(0);
	char	   *fldsep = text_to_cstring(PG_GETARG_TEXT_PP(1));

	PG_RETURN_TEXT_P(array_to_text_internal(fcinfo, v, fldsep, NULL));
}

/*
 * array_to_text_null
 * concatenate Cstring representation of input array elements
 * using provided field separator and null string
 *
 * This version is not strict so we have to test for null inputs explicitly.
 */
Datum
array_to_text_null(PG_FUNCTION_ARGS)
{
	ArrayType  *v;
	char	   *fldsep;
	char	   *null_string;

	/* returns NULL when first or second parameter is NULL */
	if (PG_ARGISNULL(0) || PG_ARGISNULL(1))
		PG_RETURN_NULL();
	
	v = PG_GETARG_ARRAYTYPE_P(0);
	fldsep = text_to_cstring(PG_GETARG_TEXT_PP(1));

	/* NULL null string is passed through as a null pointer */
	if (!PG_ARGISNULL(2))
		null_string = text_to_cstring(PG_GETARG_TEXT_PP(2));
	else
		null_string = NULL;

	PG_RETURN_TEXT_P(array_to_text_internal(fcinfo, v, fldsep, null_string));
}

/*
 * common code for array_to_text and array_to_text_null functions
 */
static text *
array_to_text_internal(FunctionCallInfo fcinfo, ArrayType *v,
					   char *fldsep, char *null_string)
{
	text	   *result;
	int			nitems,
			   *dims,
				ndims;
	Oid			element_type;
	int			typlen;
	bool		typbyval;
	char		typalign;
	StringInfoData buf;
	bool		printed = false;
	char	   *p;
	bits8	   *bitmap;
	int			bitmask;
	int			i;
	ArrayMetaState *my_extra;

	ndims = ARR_NDIM(v);
	dims = ARR_DIMS(v);
	nitems = ArrayGetNItems(ndims, dims);

	/* if there are no elements, return an empty string */
	if (nitems == 0)
		return cstring_to_text_with_len("", 0);

	element_type = ARR_ELEMTYPE(v);
	initStringInfo(&buf);

	/*
	 * We arrange to look up info about element type, including its output
	 * conversion proc, only once per series of calls, assuming the element
	 * type doesn't change underneath us.
	 */
	my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
	if (my_extra == NULL)
	{
		fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
													  sizeof(ArrayMetaState));
		my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
		my_extra->element_type = ~element_type;
	}

	if (my_extra->element_type != element_type)
	{
		/*
		 * Get info about element type, including its output conversion proc
		 */
		get_type_io_data(element_type, IOFunc_output,
						 &my_extra->typlen, &my_extra->typbyval,
						 &my_extra->typalign, &my_extra->typdelim,
						 &my_extra->typioparam, &my_extra->typiofunc);
		fmgr_info_cxt(my_extra->typiofunc, &my_extra->proc,
					  fcinfo->flinfo->fn_mcxt);
		my_extra->element_type = element_type;
	}
	typlen = my_extra->typlen;
	typbyval = my_extra->typbyval;
	typalign = my_extra->typalign;

	p = ARR_DATA_PTR(v);
	bitmap = ARR_NULLBITMAP(v);
	bitmask = 1;

	for (i = 0; i < nitems; i++)
	{
		Datum		itemvalue;
		char	   *value;

		/* Get source element, checking for NULL */
		if (bitmap && (*bitmap & bitmask) == 0)
		{
			/* if null_string is NULL, we just ignore null elements */
			if (null_string != NULL)
			{
				if (printed)
					appendStringInfo(&buf, "%s%s", fldsep, null_string);
				else
					appendStringInfoString(&buf, null_string);
				printed = true;
			}
		}
		else
		{
			itemvalue = fetch_att(p, typbyval, typlen);

			value = OutputFunctionCall(&my_extra->proc, itemvalue);

			if (printed)
				appendStringInfo(&buf, "%s%s", fldsep, value);
			else
				appendStringInfoString(&buf, value);
			printed = true;

			p = att_addlength_pointer(p, typlen, p);
			p = (char *) att_align_nominal(p, typalign);
		}

		/* advance bitmap pointer if any */
		if (bitmap)
		{
			bitmask <<= 1;
			if (bitmask == 0x100)
			{
				bitmap++;
				bitmask = 1;
			}
		}
	}
	
	result = cstring_to_text_with_len(buf.data, buf.len);
	pfree(buf.data);

	return result;
}

#define HEXBASE 16
/*
 * Convert a int32 to a string containing a base 16 (hex) representation of
 * the number.
 */
Datum
to_hex32(PG_FUNCTION_ARGS)
{
	uint32		value = (uint32) PG_GETARG_INT32(0);
	char	   *ptr;
	const char *digits = "0123456789abcdef";
	char		buf[32];		/* bigger than needed, but reasonable */

	ptr = buf + sizeof(buf) - 1;
	*ptr = '\0';

	do
	{
		*--ptr = digits[value % HEXBASE];
		value /= HEXBASE;
	} while (ptr > buf && value);

	PG_RETURN_TEXT_P(cstring_to_text(ptr));
}

/*
 * Convert a int64 to a string containing a base 16 (hex) representation of
 * the number.
 */
Datum
to_hex64(PG_FUNCTION_ARGS)
{
	uint64		value = (uint64) PG_GETARG_INT64(0);
	char	   *ptr;
	const char *digits = "0123456789abcdef";
	char		buf[32];		/* bigger than needed, but reasonable */

	ptr = buf + sizeof(buf) - 1;
	*ptr = '\0';

	do
	{
		*--ptr = digits[value % HEXBASE];
		value /= HEXBASE;
	} while (ptr > buf && value);

	PG_RETURN_TEXT_P(cstring_to_text(ptr));
}

/*
 * Create an md5 hash of a text string and return it as hex
 *
 * md5 produces a 16 byte (128 bit) hash; double it for hex
 */
#define MD5_HASH_LEN  32

Datum
md5_text(PG_FUNCTION_ARGS)
{
	text	   *in_text = PG_GETARG_TEXT_PP(0);
	size_t		len;
	char		hexsum[MD5_HASH_LEN + 1];

	/* Calculate the length of the buffer using varlena metadata */
	len = VARSIZE_ANY_EXHDR(in_text);

	/* get the hash result */
	if (pg_md5_hash(VARDATA_ANY(in_text), len, hexsum) == false)
		ereport(ERROR,
				(errcode(ERRCODE_OUT_OF_MEMORY),
				 errmsg("out of memory")));

	/* convert to text and return it */
	PG_RETURN_TEXT_P(cstring_to_text(hexsum));
}

/*
 * Create an md5 hash of a bytea field and return it as a hex string:
 * 16-byte md5 digest is represented in 32 hex characters.
 */
Datum
md5_bytea(PG_FUNCTION_ARGS)
{
	bytea	   *in = PG_GETARG_BYTEA_PP(0);
	size_t		len;
	char		hexsum[MD5_HASH_LEN + 1];

	len = VARSIZE_ANY_EXHDR(in);
	if (pg_md5_hash(VARDATA_ANY(in), len, hexsum) == false)
		ereport(ERROR,
				(errcode(ERRCODE_OUT_OF_MEMORY),
				 errmsg("out of memory")));

	PG_RETURN_TEXT_P(cstring_to_text(hexsum));
}

/*
 * Return the size of a datum, possibly compressed
 *
 * Works on any data type
 */
Datum
pg_column_size(PG_FUNCTION_ARGS)
{
	Datum		value = PG_GETARG_DATUM(0);
	int32		result;
	int			typlen;

	/* On first call, get the input type's typlen, and save at *fn_extra */
	if (fcinfo->flinfo->fn_extra == NULL)
	{
		/* Lookup the datatype of the supplied argument */
		Oid			argtypeid = get_fn_expr_argtype(fcinfo->flinfo, 0);

		typlen = get_typlen(argtypeid);
		if (typlen == 0)		/* should not happen */
			elog(ERROR, "cache lookup failed for type %u", argtypeid);

		fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
													  sizeof(int));
		*((int *) fcinfo->flinfo->fn_extra) = typlen;
	}
	else
		typlen = *((int *) fcinfo->flinfo->fn_extra);

	if (typlen == -1)
	{
		/* varlena type, possibly toasted */
		result = toast_datum_size(value);
	}
	else if (typlen == -2)
	{
		/* cstring */
		result = strlen(DatumGetCString(value)) + 1;
	}
	else
	{
		/* ordinary fixed-width type */
		result = typlen;
	}

	PG_RETURN_INT32(result);
}

/*
 * string_agg - Concatenates values and returns string.
 *
 * Syntax: string_agg(value text, delimiter text) RETURNS text
 *
 * Note: Any NULL values are ignored. The first-call delimiter isn't
 * actually used at all, and on subsequent calls the delimiter precedes
 * the associated value.
 */

/* subroutine to initialize state */
static StringInfo
makeStringAggState(FunctionCallInfo fcinfo)
{
	StringInfo	state;
	MemoryContext aggcontext;
	MemoryContext oldcontext;

	if (!AggCheckCallContext(fcinfo, &aggcontext))
	{
		/* cannot be called directly because of internal-type argument */
		elog(ERROR, "string_agg_transfn called in non-aggregate context");
	}

	/*
	 * Create state in aggregate context.  It'll stay there across subsequent
	 * calls.
	 */
	oldcontext = MemoryContextSwitchTo(aggcontext);
	state = makeStringInfo();
	MemoryContextSwitchTo(oldcontext);

	return state;
}

Datum
string_agg_transfn(PG_FUNCTION_ARGS)
{
	StringInfo	state;

	state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);

	/* Append the value unless null. */
	if (!PG_ARGISNULL(1))
	{
		/* On the first time through, we ignore the delimiter. */
		if (state == NULL)
			state = makeStringAggState(fcinfo);
		else if (!PG_ARGISNULL(2))
			appendStringInfoText(state, PG_GETARG_TEXT_PP(2));	/* delimiter */

		appendStringInfoText(state, PG_GETARG_TEXT_PP(1));		/* value */
	}

	/*
	 * The transition type for string_agg() is declared to be "internal",
	 * which is a pass-by-value type the same size as a pointer.
	 */
	PG_RETURN_POINTER(state);
}

Datum
string_agg_finalfn(PG_FUNCTION_ARGS)
{
	StringInfo	state;

	/* cannot be called directly because of internal-type argument */
	Assert(AggCheckCallContext(fcinfo, NULL));

	state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);

	if (state != NULL)
		PG_RETURN_TEXT_P(cstring_to_text(state->data));
	else
		PG_RETURN_NULL();
}

static text *
concat_internal(const char *sepstr, int seplen, int argidx, FunctionCallInfo fcinfo)
{
	StringInfoData	str;
	text		   *result;
	int				i;

	initStringInfo(&str);

	for (i = argidx; i < PG_NARGS(); i++)
	{
		if (!PG_ARGISNULL(i))
		{
			Oid		valtype;
			Datum	value;
			Oid		typOutput;
			bool	typIsVarlena;

			if (i > argidx)
				appendBinaryStringInfo(&str, sepstr, seplen);

			/* append n-th value */
			value = PG_GETARG_DATUM(i);
			valtype = get_fn_expr_argtype(fcinfo->flinfo, i);
			getTypeOutputInfo(valtype, &typOutput, &typIsVarlena);
			appendStringInfoString(&str,
				OidOutputFunctionCall(typOutput, value));
		}
	}

	result = cstring_to_text_with_len(str.data, str.len);
	pfree(str.data);

	return result;
}

/*
 * Concatenate all arguments. NULL arguments are ignored.
 */
Datum
text_concat(PG_FUNCTION_ARGS)
{
	PG_RETURN_TEXT_P(concat_internal(NULL, 0, 0, fcinfo));
}

/*
 * Concatenate all but first argument values with separators. The first
 * parameter is used as a separator. NULL arguments are ignored.
 */
Datum
text_concat_ws(PG_FUNCTION_ARGS)
{
	text		   *sep;

	/* return NULL when separator is NULL */
	if (PG_ARGISNULL(0))
		PG_RETURN_NULL();

	sep = PG_GETARG_TEXT_PP(0);

	PG_RETURN_TEXT_P(concat_internal(
		VARDATA_ANY(sep), VARSIZE_ANY_EXHDR(sep), 1, fcinfo));
}

/*
 * Return first n characters in the string. When n is negative,
 * return all but last |n| characters.
 */
Datum
text_left(PG_FUNCTION_ARGS)
{
	text	   *str = PG_GETARG_TEXT_PP(0);
	const char *p = VARDATA_ANY(str);
	int			len = VARSIZE_ANY_EXHDR(str);
	int			n = PG_GETARG_INT32(1);
	int			rlen;

	if (n < 0)
		n = pg_mbstrlen_with_len(p, len) + n;
	rlen = pg_mbcharcliplen(p, len, n);

	PG_RETURN_TEXT_P(cstring_to_text_with_len(p, rlen));
}

/*
 * Return last n characters in the string. When n is negative,
 * return all but first |n| characters.
 */
Datum
text_right(PG_FUNCTION_ARGS)
{
	text	   *str = PG_GETARG_TEXT_PP(0);
	const char *p = VARDATA_ANY(str);
	int			len = VARSIZE_ANY_EXHDR(str);
	int			n = PG_GETARG_INT32(1);
	int			off;

	if (n < 0)
		n = -n;
	else
		n = pg_mbstrlen_with_len(p, len) - n;
	off = pg_mbcharcliplen(p, len, n);

	PG_RETURN_TEXT_P(cstring_to_text_with_len(p + off, len - off));
}

/*
 * Return reversed string
 */
Datum
text_reverse(PG_FUNCTION_ARGS)
{
	text		   *str = PG_GETARG_TEXT_PP(0);
	const char	   *p = VARDATA_ANY(str);
	int				len = VARSIZE_ANY_EXHDR(str);
	const char	   *endp = p + len;
	text		   *result;
	char		   *dst;

	result = palloc(len + VARHDRSZ);
	dst = (char*) VARDATA(result) + len;
	SET_VARSIZE(result, len + VARHDRSZ);

	if (pg_database_encoding_max_length() > 1)
	{
		/* multibyte version */
		while (p < endp)
		{
			int		sz;

			sz = pg_mblen(p);
			dst -= sz;
			memcpy(dst, p, sz);
			p += sz;
		}
	}
	else
	{
		/* single byte version */
		while (p < endp)
			*(--dst) = *p++;
	}

	PG_RETURN_TEXT_P(result);
}