src/backend/utils/adt/like.c

/*-------------------------------------------------------------------------
 *
 * like.c
 *	  like expression handling code.
 *
 *	 NOTES
 *		A big hack of the regexp.c code!! Contributed by
 *		Keith Parks <emkxp01@mtcc.demon.co.uk> (7/95).
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	$PostgreSQL: pgsql/src/backend/utils/adt/like.c,v 1.67 2007/01/05 22:19:41 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>

#include "mb/pg_wchar.h"
#include "utils/builtins.h"


#define LIKE_TRUE						1
#define LIKE_FALSE						0
#define LIKE_ABORT						(-1)


static int	MatchText(char *t, int tlen, char *p, int plen);
static int	MatchTextIC(char *t, int tlen, char *p, int plen);
static int	MatchBytea(char *t, int tlen, char *p, int plen);
static text *do_like_escape(text *, text *);

static int	MBMatchText(char *t, int tlen, char *p, int plen);
static int	MBMatchTextIC(char *t, int tlen, char *p, int plen);
static text *MB_do_like_escape(text *, text *);

/*--------------------
 * Support routine for MatchText. Compares given multibyte streams
 * as wide characters. If they match, returns 1 otherwise returns 0.
 *--------------------
 */
static int
wchareq(char *p1, char *p2)
{
	int			p1_len;

	/* Optimization:  quickly compare the first byte. */
	if (*p1 != *p2)
		return 0;

	p1_len = pg_mblen(p1);
	if (pg_mblen(p2) != p1_len)
		return 0;

	/* They are the same length */
	while (p1_len--)
	{
		if (*p1++ != *p2++)
			return 0;
	}
	return 1;
}

/*
 * Formerly we had a routine iwchareq() here that tried to do case-insensitive
 * comparison of multibyte characters.	It did not work at all, however,
 * because it relied on tolower() which has a single-byte API ... and
 * towlower() wouldn't be much better since we have no suitably cheap way
 * of getting a single character transformed to the system's wchar_t format.
 * So now, we just downcase the strings using lower() and apply regular LIKE
 * comparison.	This should be revisited when we install better locale support.
 *
 * Note that MBMatchText and MBMatchTextIC do exactly the same thing now.
 * Is it worth refactoring to avoid duplicated code?  They might become
 * different again in the future.
 */

/* Set up to compile like_match.c for multibyte characters */
#define CHAREQ(p1, p2) wchareq(p1, p2)
#define ICHAREQ(p1, p2) wchareq(p1, p2)
#define NextChar(p, plen) \
	do { int __l = pg_mblen(p); (p) +=__l; (plen) -=__l; } while (0)
#define CopyAdvChar(dst, src, srclen) \
	do { int __l = pg_mblen(src); \
		 (srclen) -= __l; \
		 while (__l-- > 0) \
			 *(dst)++ = *(src)++; \
	   } while (0)

#define MatchText	MBMatchText
#define MatchTextIC MBMatchTextIC
#define do_like_escape	MB_do_like_escape

#include "like_match.c"

#undef CHAREQ
#undef ICHAREQ
#undef NextChar
#undef CopyAdvChar
#undef MatchText
#undef MatchTextIC
#undef do_like_escape

/* Set up to compile like_match.c for single-byte characters */
#define CHAREQ(p1, p2) (*(p1) == *(p2))
#define ICHAREQ(p1, p2) (tolower((unsigned char) *(p1)) == tolower((unsigned char) *(p2)))
#define NextChar(p, plen) ((p)++, (plen)--)
#define CopyAdvChar(dst, src, srclen) (*(dst)++ = *(src)++, (srclen)--)

#include "like_match.c"

/* And some support for BYTEA */
#define BYTEA_CHAREQ(p1, p2) (*(p1) == *(p2))
#define BYTEA_NextChar(p, plen) ((p)++, (plen)--)
#define BYTEA_CopyAdvChar(dst, src, srclen) (*(dst)++ = *(src)++, (srclen)--)


/*
 *	interface routines called by the function manager
 */

Datum
namelike(PG_FUNCTION_ARGS)
{
	Name		str = PG_GETARG_NAME(0);
	text	   *pat = PG_GETARG_TEXT_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	s = NameStr(*str);
	slen = strlen(s);
	p = VARDATA(pat);
	plen = (VARSIZE(pat) - VARHDRSZ);

	if (pg_database_encoding_max_length() == 1)
		result = (MatchText(s, slen, p, plen) == LIKE_TRUE);
	else
		result = (MBMatchText(s, slen, p, plen) == LIKE_TRUE);

	PG_RETURN_BOOL(result);
}

Datum
namenlike(PG_FUNCTION_ARGS)
{
	Name		str = PG_GETARG_NAME(0);
	text	   *pat = PG_GETARG_TEXT_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	s = NameStr(*str);
	slen = strlen(s);
	p = VARDATA(pat);
	plen = (VARSIZE(pat) - VARHDRSZ);

	if (pg_database_encoding_max_length() == 1)
		result = (MatchText(s, slen, p, plen) != LIKE_TRUE);
	else
		result = (MBMatchText(s, slen, p, plen) != LIKE_TRUE);

	PG_RETURN_BOOL(result);
}

Datum
textlike(PG_FUNCTION_ARGS)
{
	text	   *str = PG_GETARG_TEXT_P(0);
	text	   *pat = PG_GETARG_TEXT_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	s = VARDATA(str);
	slen = (VARSIZE(str) - VARHDRSZ);
	p = VARDATA(pat);
	plen = (VARSIZE(pat) - VARHDRSZ);

	if (pg_database_encoding_max_length() == 1)
		result = (MatchText(s, slen, p, plen) == LIKE_TRUE);
	else
		result = (MBMatchText(s, slen, p, plen) == LIKE_TRUE);

	PG_RETURN_BOOL(result);
}

Datum
textnlike(PG_FUNCTION_ARGS)
{
	text	   *str = PG_GETARG_TEXT_P(0);
	text	   *pat = PG_GETARG_TEXT_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	s = VARDATA(str);
	slen = (VARSIZE(str) - VARHDRSZ);
	p = VARDATA(pat);
	plen = (VARSIZE(pat) - VARHDRSZ);

	if (pg_database_encoding_max_length() == 1)
		result = (MatchText(s, slen, p, plen) != LIKE_TRUE);
	else
		result = (MBMatchText(s, slen, p, plen) != LIKE_TRUE);

	PG_RETURN_BOOL(result);
}

Datum
bytealike(PG_FUNCTION_ARGS)
{
	bytea	   *str = PG_GETARG_BYTEA_P(0);
	bytea	   *pat = PG_GETARG_BYTEA_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	s = VARDATA(str);
	slen = (VARSIZE(str) - VARHDRSZ);
	p = VARDATA(pat);
	plen = (VARSIZE(pat) - VARHDRSZ);

	result = (MatchBytea(s, slen, p, plen) == LIKE_TRUE);

	PG_RETURN_BOOL(result);
}

Datum
byteanlike(PG_FUNCTION_ARGS)
{
	bytea	   *str = PG_GETARG_BYTEA_P(0);
	bytea	   *pat = PG_GETARG_BYTEA_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	s = VARDATA(str);
	slen = (VARSIZE(str) - VARHDRSZ);
	p = VARDATA(pat);
	plen = (VARSIZE(pat) - VARHDRSZ);

	result = (MatchBytea(s, slen, p, plen) != LIKE_TRUE);

	PG_RETURN_BOOL(result);
}

/*
 * Case-insensitive versions
 */

Datum
nameiclike(PG_FUNCTION_ARGS)
{
	Name		str = PG_GETARG_NAME(0);
	text	   *pat = PG_GETARG_TEXT_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	if (pg_database_encoding_max_length() == 1)
	{
		s = NameStr(*str);
		slen = strlen(s);
		p = VARDATA(pat);
		plen = (VARSIZE(pat) - VARHDRSZ);
		result = (MatchTextIC(s, slen, p, plen) == LIKE_TRUE);
	}
	else
	{
		/* Force inputs to lower case to achieve case insensitivity */
		text	   *strtext;

		strtext = DatumGetTextP(DirectFunctionCall1(name_text,
													NameGetDatum(str)));
		strtext = DatumGetTextP(DirectFunctionCall1(lower,
												  PointerGetDatum(strtext)));
		pat = DatumGetTextP(DirectFunctionCall1(lower,
												PointerGetDatum(pat)));

		s = VARDATA(strtext);
		slen = (VARSIZE(strtext) - VARHDRSZ);
		p = VARDATA(pat);
		plen = (VARSIZE(pat) - VARHDRSZ);
		result = (MBMatchTextIC(s, slen, p, plen) == LIKE_TRUE);
	}

	PG_RETURN_BOOL(result);
}

Datum
nameicnlike(PG_FUNCTION_ARGS)
{
	Name		str = PG_GETARG_NAME(0);
	text	   *pat = PG_GETARG_TEXT_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	if (pg_database_encoding_max_length() == 1)
	{
		s = NameStr(*str);
		slen = strlen(s);
		p = VARDATA(pat);
		plen = (VARSIZE(pat) - VARHDRSZ);
		result = (MatchTextIC(s, slen, p, plen) != LIKE_TRUE);
	}
	else
	{
		/* Force inputs to lower case to achieve case insensitivity */
		text	   *strtext;

		strtext = DatumGetTextP(DirectFunctionCall1(name_text,
													NameGetDatum(str)));
		strtext = DatumGetTextP(DirectFunctionCall1(lower,
												  PointerGetDatum(strtext)));
		pat = DatumGetTextP(DirectFunctionCall1(lower,
												PointerGetDatum(pat)));

		s = VARDATA(strtext);
		slen = (VARSIZE(strtext) - VARHDRSZ);
		p = VARDATA(pat);
		plen = (VARSIZE(pat) - VARHDRSZ);
		result = (MBMatchTextIC(s, slen, p, plen) != LIKE_TRUE);
	}

	PG_RETURN_BOOL(result);
}

Datum
texticlike(PG_FUNCTION_ARGS)
{
	text	   *str = PG_GETARG_TEXT_P(0);
	text	   *pat = PG_GETARG_TEXT_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	if (pg_database_encoding_max_length() == 1)
	{
		s = VARDATA(str);
		slen = (VARSIZE(str) - VARHDRSZ);
		p = VARDATA(pat);
		plen = (VARSIZE(pat) - VARHDRSZ);
		result = (MatchTextIC(s, slen, p, plen) == LIKE_TRUE);
	}
	else
	{
		/* Force inputs to lower case to achieve case insensitivity */
		str = DatumGetTextP(DirectFunctionCall1(lower,
												PointerGetDatum(str)));
		pat = DatumGetTextP(DirectFunctionCall1(lower,
												PointerGetDatum(pat)));
		s = VARDATA(str);
		slen = (VARSIZE(str) - VARHDRSZ);
		p = VARDATA(pat);
		plen = (VARSIZE(pat) - VARHDRSZ);
		result = (MBMatchTextIC(s, slen, p, plen) == LIKE_TRUE);
	}

	PG_RETURN_BOOL(result);
}

Datum
texticnlike(PG_FUNCTION_ARGS)
{
	text	   *str = PG_GETARG_TEXT_P(0);
	text	   *pat = PG_GETARG_TEXT_P(1);
	bool		result;
	char	   *s,
			   *p;
	int			slen,
				plen;

	if (pg_database_encoding_max_length() == 1)
	{
		s = VARDATA(str);
		slen = (VARSIZE(str) - VARHDRSZ);
		p = VARDATA(pat);
		plen = (VARSIZE(pat) - VARHDRSZ);
		result = (MatchTextIC(s, slen, p, plen) != LIKE_TRUE);
	}
	else
	{
		/* Force inputs to lower case to achieve case insensitivity */
		str = DatumGetTextP(DirectFunctionCall1(lower,
												PointerGetDatum(str)));
		pat = DatumGetTextP(DirectFunctionCall1(lower,
												PointerGetDatum(pat)));
		s = VARDATA(str);
		slen = (VARSIZE(str) - VARHDRSZ);
		p = VARDATA(pat);
		plen = (VARSIZE(pat) - VARHDRSZ);
		result = (MBMatchTextIC(s, slen, p, plen) != LIKE_TRUE);
	}

	PG_RETURN_BOOL(result);
}

/*
 * like_escape() --- given a pattern and an ESCAPE string,
 * convert the pattern to use Postgres' standard backslash escape convention.
 */
Datum
like_escape(PG_FUNCTION_ARGS)
{
	text	   *pat = PG_GETARG_TEXT_P(0);
	text	   *esc = PG_GETARG_TEXT_P(1);
	text	   *result;

	if (pg_database_encoding_max_length() == 1)
		result = do_like_escape(pat, esc);
	else
		result = MB_do_like_escape(pat, esc);

	PG_RETURN_TEXT_P(result);
}

/*
 * like_escape_bytea() --- given a pattern and an ESCAPE string,
 * convert the pattern to use Postgres' standard backslash escape convention.
 */
Datum
like_escape_bytea(PG_FUNCTION_ARGS)
{
	bytea	   *pat = PG_GETARG_BYTEA_P(0);
	bytea	   *esc = PG_GETARG_BYTEA_P(1);
	bytea	   *result;
	char	   *p,
			   *e,
			   *r;
	int			plen,
				elen;
	bool		afterescape;

	p = VARDATA(pat);
	plen = (VARSIZE(pat) - VARHDRSZ);
	e = VARDATA(esc);
	elen = (VARSIZE(esc) - VARHDRSZ);

	/*
	 * Worst-case pattern growth is 2x --- unlikely, but it's hardly worth
	 * trying to calculate the size more accurately than that.
	 */
	result = (text *) palloc(plen * 2 + VARHDRSZ);
	r = VARDATA(result);

	if (elen == 0)
	{
		/*
		 * No escape character is wanted.  Double any backslashes in the
		 * pattern to make them act like ordinary characters.
		 */
		while (plen > 0)
		{
			if (*p == '\\')
				*r++ = '\\';
			BYTEA_CopyAdvChar(r, p, plen);
		}
	}
	else
	{
		/*
		 * The specified escape must be only a single character.
		 */
		BYTEA_NextChar(e, elen);
		if (elen != 0)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
					 errmsg("invalid escape string"),
				  errhint("Escape string must be empty or one character.")));

		e = VARDATA(esc);

		/*
		 * If specified escape is '\', just copy the pattern as-is.
		 */
		if (*e == '\\')
		{
			memcpy(result, pat, VARSIZE(pat));
			PG_RETURN_BYTEA_P(result);
		}

		/*
		 * Otherwise, convert occurrences of the specified escape character to
		 * '\', and double occurrences of '\' --- unless they immediately
		 * follow an escape character!
		 */
		afterescape = false;
		while (plen > 0)
		{
			if (BYTEA_CHAREQ(p, e) && !afterescape)
			{
				*r++ = '\\';
				BYTEA_NextChar(p, plen);
				afterescape = true;
			}
			else if (*p == '\\')
			{
				*r++ = '\\';
				if (!afterescape)
					*r++ = '\\';
				BYTEA_NextChar(p, plen);
				afterescape = false;
			}
			else
			{
				BYTEA_CopyAdvChar(r, p, plen);
				afterescape = false;
			}
		}
	}

	SET_VARSIZE(result, r - ((char *) result));

	PG_RETURN_BYTEA_P(result);
}

/*
 * Same as above, but specifically for bytea (binary) datatype
 */
static int
MatchBytea(char *t, int tlen, char *p, int plen)
{
	/* Fast path for match-everything pattern */
	if ((plen == 1) && (*p == '%'))
		return LIKE_TRUE;

	while ((tlen > 0) && (plen > 0))
	{
		if (*p == '\\')
		{
			/* Next pattern char must match literally, whatever it is */
			BYTEA_NextChar(p, plen);
			if ((plen <= 0) || !BYTEA_CHAREQ(t, p))
				return LIKE_FALSE;
		}
		else if (*p == '%')
		{
			/* %% is the same as % according to the SQL standard */
			/* Advance past all %'s */
			while ((plen > 0) && (*p == '%'))
				BYTEA_NextChar(p, plen);
			/* Trailing percent matches everything. */
			if (plen <= 0)
				return LIKE_TRUE;

			/*
			 * Otherwise, scan for a text position at which we can match the
			 * rest of the pattern.
			 */
			while (tlen > 0)
			{
				/*
				 * Optimization to prevent most recursion: don't recurse
				 * unless first pattern char might match this text char.
				 */
				if (BYTEA_CHAREQ(t, p) || (*p == '\\') || (*p == '_'))
				{
					int			matched = MatchBytea(t, tlen, p, plen);

					if (matched != LIKE_FALSE)
						return matched; /* TRUE or ABORT */
				}

				BYTEA_NextChar(t, tlen);
			}

			/*
			 * End of text with no match, so no point in trying later places
			 * to start matching this pattern.
			 */
			return LIKE_ABORT;
		}
		else if ((*p != '_') && !BYTEA_CHAREQ(t, p))
		{
			/*
			 * Not the single-character wildcard and no explicit match? Then
			 * time to quit...
			 */
			return LIKE_FALSE;
		}

		BYTEA_NextChar(t, tlen);
		BYTEA_NextChar(p, plen);
	}

	if (tlen > 0)
		return LIKE_FALSE;		/* end of pattern, but not of text */

	/* End of input string.  Do we have matching pattern remaining? */
	while ((plen > 0) && (*p == '%'))	/* allow multiple %'s at end of
										 * pattern */
		BYTEA_NextChar(p, plen);
	if (plen <= 0)
		return LIKE_TRUE;

	/*
	 * End of text with no match, so no point in trying later places to start
	 * matching this pattern.
	 */
	return LIKE_ABORT;
}	/* MatchBytea() */