postgresql/src/backend/nodes/read.c

/*-------------------------------------------------------------------------
 *
 * read.c--
 *    routines to convert a string (legal ascii representation of node) back
 *    to nodes
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/nodes/read.c,v 1.3 1997/08/12 22:53:04 momjian Exp $
 *
 * HISTORY
 *    AUTHOR		DATE		MAJOR EVENT
 *    Andrew Yu		Nov 2, 1994	file creation
 *
 *-------------------------------------------------------------------------
 */
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include "postgres.h"
#include "nodes/pg_list.h"
#include "nodes/readfuncs.h"
#include "utils/elog.h"

/*
 * stringToNode -
 *    returns a Node with a given legal ascii representation
 */
void *
stringToNode(char *str)
{
    void *retval;

    lsptok(str, NULL);	/* set the string used in lsptok */
    retval = nodeRead(true);	/* start reading */

    return retval;
}

/*****************************************************************************
 *
 * the lisp token parser
 *
 *****************************************************************************/

#define RIGHT_PAREN (1000000 + 1)
#define LEFT_PAREN  (1000000 + 2)
#define PLAN_SYM    (1000000 + 3)
#define AT_SYMBOL   (1000000 + 4)
#define ATOM_TOKEN  (1000000 + 5)

/*
 * nodeTokenType -
 *    returns the type of the node token contained in token.
 *    It returns one of the following valid NodeTags:
 *	T_Integer, T_Float, T_String
 *    and some of its own:
 * 	RIGHT_PAREN, LEFT_PAREN, PLAN_SYM, AT_SYMBOL, ATOM_TOKEN
 *
 *    Assumption: the ascii representation is legal
 */
static NodeTag
nodeTokenType(char *token, int length)
{
    NodeTag retval = 0;
    
    /*
     * Check if the token is a number (decimal or integer,
     * positive or negative
     */
    if (isdigit(*token) ||
	(length>=2 && *token=='-' && isdigit(*(token+1)) ))
	{
	    /*
	     * skip the optional '-' (i.e. negative number)
	     */
	    if (*token == '-') {
		token++;
	    }
	    
	    /*
	     * See if there is a decimal point
	     */
	    
	    for (; length && *token != '.'; token++, length--);
	    
	    /*
	     * if there isn't, token's an int, otherwise it's a float.
	     */
	    
	    retval = (*token != '.') ? T_Integer : T_Float;
	}
    else if (isalpha(*token))
	retval = ATOM_TOKEN;
    else if (*token == '(')
	retval = LEFT_PAREN;
    else if (*token == ')')
	retval = RIGHT_PAREN;
    else if (*token == '@')
	retval = AT_SYMBOL;
    else if (*token == '\"')
	retval = T_String;
    else if (*token == '{')
	retval = PLAN_SYM;
    return(retval);
}

/*
 * Works kinda like strtok, except it doesn't put nulls into string.
 * 
 * Returns the length in length instead.  The string can be set without
 * returning a token by calling lsptok with length == NULL.
 *
 */
char *
lsptok(char *string, int *length)
{
    static char *local_str;
    char *ret_string;
    
    if (string != NULL) {
	local_str = string;
	if (length == NULL) {
	    return(NULL);
	}
    }
    
    for (; *local_str == ' '
	 || *local_str == '\n'
	 || *local_str == '\t'; local_str++);
    
    /*
     * Now pointing at next token.
     */
    ret_string = local_str;
    if (*local_str == '\0') return(NULL);
    *length = 1;
    
    if (*local_str == '\"') {
	for (local_str++; *local_str != '\"'; (*length)++, local_str++);
	(*length)++; local_str++;
    }else if (*local_str == ')' || *local_str == '(' ||
	      *local_str == '}' || *local_str == '{') {
	local_str++;
    }else {
	for (; *local_str != ' '
	     && *local_str != '\n'
	     && *local_str != '\t'
	     && *local_str != '{'
	     && *local_str != '}'
	     && *local_str != '('
	     && *local_str != ')'; local_str++, (*length)++);
	(*length)--;
    }
    return(ret_string);
}

/*
 * This guy does all the reading.
 *
 * Secrets:  He assumes that lsptok already has the string (see below).
 * Any callers should set read_car_only to true.
 */
void *
nodeRead(bool read_car_only)
{
    char *token;
    NodeTag type;
    Node *this_value = NULL, *return_value = NULL;
    int tok_len;
    char tmp;
    bool make_dotted_pair_cell = false;
    
    token = lsptok(NULL, &tok_len);
    
    if (token == NULL) return(NULL);
    
    type = nodeTokenType(token, tok_len);
    
    switch(type) {
    case PLAN_SYM:
	this_value = parsePlanString();
	token = lsptok(NULL, &tok_len);
	if (token[0] != '}') return(NULL);

	if (!read_car_only)
	    make_dotted_pair_cell = true;
	else
	    make_dotted_pair_cell = false;
	break;
    case LEFT_PAREN:
	if (!read_car_only) {
	    List *l = makeNode(List);

	    lfirst(l) = nodeRead(false);
	    lnext(l) = nodeRead(false);
	    this_value = (Node*)l;
	}else {
	    this_value = nodeRead(false);
	}
	break;
    case RIGHT_PAREN:
	this_value = NULL;
	break;
    case AT_SYMBOL:
	break;
    case ATOM_TOKEN:
	if (!strncmp(token, "nil", 3)) {
	    this_value = NULL;
	    /*
	     * It might be "nil" but it is an atom!
	     */
	    if (read_car_only) {
		make_dotted_pair_cell = false;
	    } else {
		make_dotted_pair_cell = true;
	    }
	}else {
	    tmp = token[tok_len];
	    token[tok_len] = '\0';
	    this_value = (Node*)pstrdup(token);	/* !attention! not a Node.
						   use with caution */
	    token[tok_len] = tmp;
	    make_dotted_pair_cell = true;
	}
	break;
    case T_Float:
	tmp = token[tok_len];
	token[tok_len] = '\0';
	this_value = (Node*)makeFloat(atof(token));
	token[tok_len] = tmp;
	make_dotted_pair_cell = true;
	break;
    case T_Integer:
	tmp = token[tok_len];
	token[tok_len] = '\0';
	this_value = (Node*)makeInteger(atoi(token));
	token[tok_len] = tmp;
	make_dotted_pair_cell = true;
	break;
    case T_String:
	tmp = token[tok_len - 1];
	token[tok_len - 1] = '\0';
	token++;
	this_value = (Node*)makeString(token);		/* !! not strdup'd */
	token[tok_len - 2] = tmp;
	make_dotted_pair_cell = true;
	break;
    default:
	elog(WARN, "nodeRead: Bad type %d", type);
	break;
    }
    if (make_dotted_pair_cell) {
	List *l = makeNode(List);

	lfirst(l) = this_value;
	if (!read_car_only) {
	    lnext(l) = nodeRead(false);
	}else {
	    lnext(l) = NULL;
	}
	return_value = (Node*)l;
    }else {
	return_value = this_value;
    }
    return(return_value);
}