/*===========================================================================
 Copyright (c) 1998-2000, The Santa Cruz Operation 
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 and/or other materials provided with the distribution.

 *Neither name of The Santa Cruz Operation nor the names of its contributors
 may be used to endorse or promote products derived from this software
 without specific prior written permission. 

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 IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 =========================================================================*/

/*	cscope - interactive C symbol cross-reference
 *
 *	keyword look-up routine for the C symbol scanner
 */

#include "global.h"
#include "lookup.h"

static char const rcsid[] = "$Id: lookup.c,v 1.1.1.2 2002/01/09 18:50:33 umeshv Exp $";

/* keyword text for fast testing of keywords in the scanner */
char	enumtext[] = "enum";
char	externtext[] = "extern";
char	structtext[] = "struct";
char	typedeftext[] = "typedef";
char	uniontext[] = "union";

/* This keyword table is also used for keyword text compression.  Keywords
 * with an index less than the numeric value of a space are replaced with the
 * control character corresponding to the index, so they cannot be moved
 * without changing the database file version and adding compatibility code
 * for old databases.
 */
struct	keystruct keyword[] = {
	{"",		'\0',	NULL},	/* dummy entry */
	{"#define",	' ',	NULL},	/* must be table entry 1 */
	{"#include",	' ',	NULL},	/* must be table entry 2 */
	{"break",	'\0',	NULL},	/* rarely in cross-reference */
	{"case",	' ',	NULL},
	{"char",	' ',	NULL},
	{"continue",	'\0',	NULL},	/* rarely in cross-reference */
	{"default",	'\0',	NULL},	/* rarely in cross-reference */
	{"double",	' ',	NULL},
	{"\t",		'\0',	NULL},	/* must be the table entry 9 */
	{"\n",		'\0',	NULL},	/* must be the table entry 10 */
	{"else",	' ',	NULL},
	{enumtext,	' ',	NULL},
	{externtext,	' ',	NULL},
	{"float",	' ',	NULL},
	{"for",		'(',	NULL},
	{"goto",	' ',	NULL},
	{"if",		'(',	NULL},
	{"int",		' ',	NULL},
	{"long",	' ',	NULL},
	{"register",	' ',	NULL},
	{"return",	'\0',	NULL},
	{"short",	' ',	NULL},
	{"sizeof",	'\0',	NULL},
	{"static",	' ',	NULL},
	{structtext,	' ',	NULL},
	{"switch",	'(',	NULL},
	{typedeftext,	' ',	NULL},
	{uniontext,	' ',	NULL},
	{"unsigned",	' ',	NULL},
	{"void",	' ',	NULL},
	{"while",	'(',	NULL},
	
	/* these keywords are not compressed */
	{"do",		'\0',	NULL},
	{"auto",	' ',	NULL},
	{"fortran",	' ',	NULL},
	{"const",	' ',	NULL},
	{"signed",	' ',	NULL},
	{"volatile",	' ',	NULL},
};
#define KEYWORDS	(sizeof(keyword) / sizeof(struct keystruct))

#define HASHMOD	(KEYWORDS * 2 + 1)

static	struct	keystruct *hashtab[HASHMOD]; /* pointer table */

/* put the keywords into the symbol table */

void
initsymtab(void)
{
	int	i, j;
	struct	keystruct *p;
	
	for (i = 1; i < KEYWORDS; ++i) {
		p = &keyword[i];
		j = hash(p->text) % HASHMOD;
		p->next = hashtab[j];
		hashtab[j] = p;
	}
}

/* see if this identifier is a keyword */

char *
lookup(char *ident)
{
	struct	keystruct *p;
	int	c;
	
	/* look up the identifier in the keyword table */
	for (p = hashtab[hash(ident) % HASHMOD]; p != NULL; p = p->next) {
		if (strequal(ident, p->text)) {
			if (compress == YES && (c = p - keyword) < ' ') {
				ident[0] = c;	/* compress the keyword */
			}
			return(p->text);
		}
	}
	/* this is an identifier */
	return(NULL);
}

/* form hash value for string */
int
hash(char *ss)
{
	int	i;
	unsigned char 	*s = (unsigned char *)ss;
	
	for (i = 0; *s != '\0'; )
		i += *s++;	/* += is faster than <<= for cscope */
	return(i);
}