postgresql/src/fe_utils/mbprint.c

/*-------------------------------------------------------------------------
 *
 * Multibyte character printing support for frontend code
 *
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/fe_utils/mbprint.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"

#include "fe_utils/mbprint.h"

#include "libpq-fe.h"


/*
 * To avoid version-skew problems, this file must not use declarations
 * from pg_wchar.h: the encoding IDs we are dealing with are determined
 * by the libpq.so we are linked with, and that might not match the
 * numbers we see at compile time.  (If this file were inside libpq,
 * the problem would go away...)
 *
 * Hence, we have our own definition of pg_wchar, and we get the values
 * of any needed encoding IDs on-the-fly.
 */

typedef unsigned int pg_wchar;

static int
pg_get_utf8_id(void)
{
	static int	utf8_id = -1;

	if (utf8_id < 0)
		utf8_id = pg_char_to_encoding("utf8");
	return utf8_id;
}

#define PG_UTF8		pg_get_utf8_id()


/*
 * Convert a UTF-8 character to a Unicode code point.
 * This is a one-character version of pg_utf2wchar_with_len.
 *
 * No error checks here, c must point to a long-enough string.
 */
static pg_wchar
utf8_to_unicode(const unsigned char *c)
{
	if ((*c & 0x80) == 0)
		return (pg_wchar) c[0];
	else if ((*c & 0xe0) == 0xc0)
		return (pg_wchar) (((c[0] & 0x1f) << 6) |
						   (c[1] & 0x3f));
	else if ((*c & 0xf0) == 0xe0)
		return (pg_wchar) (((c[0] & 0x0f) << 12) |
						   ((c[1] & 0x3f) << 6) |
						   (c[2] & 0x3f));
	else if ((*c & 0xf8) == 0xf0)
		return (pg_wchar) (((c[0] & 0x07) << 18) |
						   ((c[1] & 0x3f) << 12) |
						   ((c[2] & 0x3f) << 6) |
						   (c[3] & 0x3f));
	else
		/* that is an invalid code on purpose */
		return 0xffffffff;
}


/*
 * Unicode 3.1 compliant validation : for each category, it checks the
 * combination of each byte to make sure it maps to a valid range. It also
 * returns -1 for the following UCS values: ucs > 0x10ffff ucs & 0xfffe =
 * 0xfffe 0xfdd0 < ucs < 0xfdef ucs & 0xdb00 = 0xd800 (surrogates)
 */
static int
utf_charcheck(const unsigned char *c)
{
	if ((*c & 0x80) == 0)
		return 1;
	else if ((*c & 0xe0) == 0xc0)
	{
		/* two-byte char */
		if (((c[1] & 0xc0) == 0x80) && ((c[0] & 0x1f) > 0x01))
			return 2;
		return -1;
	}
	else if ((*c & 0xf0) == 0xe0)
	{
		/* three-byte char */
		if (((c[1] & 0xc0) == 0x80) &&
			(((c[0] & 0x0f) != 0x00) || ((c[1] & 0x20) == 0x20)) &&
			((c[2] & 0xc0) == 0x80))
		{
			int			z = c[0] & 0x0f;
			int			yx = ((c[1] & 0x3f) << 6) | (c[0] & 0x3f);
			int			lx = yx & 0x7f;

			/* check 0xfffe/0xffff, 0xfdd0..0xfedf range, surrogates */
			if (((z == 0x0f) &&
				 (((yx & 0xffe) == 0xffe) ||
				  (((yx & 0xf80) == 0xd80) && (lx >= 0x30) && (lx <= 0x4f)))) ||
				((z == 0x0d) && ((yx & 0xb00) == 0x800)))
				return -1;
			return 3;
		}
		return -1;
	}
	else if ((*c & 0xf8) == 0xf0)
	{
		int			u = ((c[0] & 0x07) << 2) | ((c[1] & 0x30) >> 4);

		/* four-byte char */
		if (((c[1] & 0xc0) == 0x80) &&
			(u > 0x00) && (u <= 0x10) &&
			((c[2] & 0xc0) == 0x80) && ((c[3] & 0xc0) == 0x80))
		{
			/* test for 0xzzzzfffe/0xzzzzfffff */
			if (((c[1] & 0x0f) == 0x0f) && ((c[2] & 0x3f) == 0x3f) &&
				((c[3] & 0x3e) == 0x3e))
				return -1;
			return 4;
		}
		return -1;
	}
	return -1;
}


static void
mb_utf_validate(unsigned char *pwcs)
{
	unsigned char *p = pwcs;

	while (*pwcs)
	{
		int			len;

		if ((len = utf_charcheck(pwcs)) > 0)
		{
			if (p != pwcs)
			{
				int			i;

				for (i = 0; i < len; i++)
					*p++ = *pwcs++;
			}
			else
			{
				pwcs += len;
				p += len;
			}
		}
		else
			/* we skip the char */
			pwcs++;
	}
	if (p != pwcs)
		*p = '\0';
}

/*
 * public functions : wcswidth and mbvalidate
 */

/*
 * pg_wcswidth is the dumb display-width function.
 * It assumes that everything will appear on one line.
 * OTOH it is easier to use than pg_wcssize if this applies to you.
 */
int
pg_wcswidth(const char *pwcs, size_t len, int encoding)
{
	int			width = 0;

	while (len > 0)
	{
		int			chlen,
					chwidth;

		chlen = PQmblen(pwcs, encoding);
		if (len < (size_t) chlen)
			break;				/* Invalid string */

		chwidth = PQdsplen(pwcs, encoding);
		if (chwidth > 0)
			width += chwidth;

		pwcs += chlen;
		len -= chlen;
	}
	return width;
}

/*
 * pg_wcssize takes the given string in the given encoding and returns three
 * values:
 *	  result_width: Width in display characters of the longest line in string
 *	  result_height: Number of lines in display output
 *	  result_format_size: Number of bytes required to store formatted
 *		representation of string
 *
 * This MUST be kept in sync with pg_wcsformat!
 */
void
pg_wcssize(const unsigned char *pwcs, size_t len, int encoding,
		   int *result_width, int *result_height, int *result_format_size)
{
	int			w,
				chlen = 0,
				linewidth = 0;
	int			width = 0;
	int			height = 1;
	int			format_size = 0;

	for (; *pwcs && len > 0; pwcs += chlen)
	{
		chlen = PQmblen((const char *) pwcs, encoding);
		if (len < (size_t) chlen)
			break;
		w = PQdsplen((const char *) pwcs, encoding);

		if (chlen == 1)			/* single-byte char */
		{
			if (*pwcs == '\n')	/* Newline */
			{
				if (linewidth > width)
					width = linewidth;
				linewidth = 0;
				height += 1;
				format_size += 1;	/* For NUL char */
			}
			else if (*pwcs == '\r') /* Linefeed */
			{
				linewidth += 2;
				format_size += 2;
			}
			else if (*pwcs == '\t') /* Tab */
			{
				do
				{
					linewidth++;
					format_size++;
				} while (linewidth % 8 != 0);
			}
			else if (w < 0)		/* Other control char */
			{
				linewidth += 4;
				format_size += 4;
			}
			else				/* Output it as-is */
			{
				linewidth += w;
				format_size += 1;
			}
		}
		else if (w < 0)			/* Non-ascii control char */
		{
			linewidth += 6;		/* \u0000 */
			format_size += 6;
		}
		else					/* All other chars */
		{
			linewidth += w;
			format_size += chlen;
		}
		len -= chlen;
	}
	if (linewidth > width)
		width = linewidth;
	format_size += 1;			/* For NUL char */

	/* Set results */
	if (result_width)
		*result_width = width;
	if (result_height)
		*result_height = height;
	if (result_format_size)
		*result_format_size = format_size;
}

/*
 *	Format a string into one or more "struct lineptr" lines.
 *	lines[i].ptr == NULL indicates the end of the array.
 *
 * This MUST be kept in sync with pg_wcssize!
 */
void
pg_wcsformat(const unsigned char *pwcs, size_t len, int encoding,
			 struct lineptr *lines, int count)
{
	int			w,
				chlen = 0;
	int			linewidth = 0;
	unsigned char *ptr = lines->ptr;	/* Pointer to data area */

	for (; *pwcs && len > 0; pwcs += chlen)
	{
		chlen = PQmblen((const char *) pwcs, encoding);
		if (len < (size_t) chlen)
			break;
		w = PQdsplen((const char *) pwcs, encoding);

		if (chlen == 1)			/* single-byte char */
		{
			if (*pwcs == '\n')	/* Newline */
			{
				*ptr++ = '\0';
				lines->width = linewidth;
				linewidth = 0;
				lines++;
				count--;
				if (count <= 0)
					exit(1);	/* Screwup */

				/* make next line point to remaining memory */
				lines->ptr = ptr;
			}
			else if (*pwcs == '\r') /* Linefeed */
			{
				strcpy((char *) ptr, "\\r");
				linewidth += 2;
				ptr += 2;
			}
			else if (*pwcs == '\t') /* Tab */
			{
				do
				{
					*ptr++ = ' ';
					linewidth++;
				} while (linewidth % 8 != 0);
			}
			else if (w < 0)		/* Other control char */
			{
				sprintf((char *) ptr, "\\x%02X", *pwcs);
				linewidth += 4;
				ptr += 4;
			}
			else				/* Output it as-is */
			{
				linewidth += w;
				*ptr++ = *pwcs;
			}
		}
		else if (w < 0)			/* Non-ascii control char */
		{
			if (encoding == PG_UTF8)
				sprintf((char *) ptr, "\\u%04X", utf8_to_unicode(pwcs));
			else
			{
				/*
				 * This case cannot happen in the current code because only
				 * UTF-8 signals multibyte control characters. But we may need
				 * to support it at some stage
				 */
				sprintf((char *) ptr, "\\u????");
			}
			ptr += 6;
			linewidth += 6;
		}
		else					/* All other chars */
		{
			int			i;

			for (i = 0; i < chlen; i++)
				*ptr++ = pwcs[i];
			linewidth += w;
		}
		len -= chlen;
	}
	lines->width = linewidth;
	*ptr++ = '\0';				/* Terminate formatted string */

	if (count <= 0)
		exit(1);				/* Screwup */

	(lines + 1)->ptr = NULL;	/* terminate line array */
}


/*
 * Encoding validation: delete any unvalidatable characters from the string
 *
 * This seems redundant with existing functionality elsewhere?
 */
unsigned char *
mbvalidate(unsigned char *pwcs, int encoding)
{
	if (encoding == PG_UTF8)
		mb_utf_validate(pwcs);
	else
	{
		/*
		 * other encodings needing validation should add their own routines
		 * here
		 */
	}

	return pwcs;
}