src/backend/utils/adt/like_match.c - hawq - Git at Google

 /*-------------------------------------------------------------------------
  *
  * like_match.c
  *	  like expression handling internal code.
  *
  * This file is included by like.c *twice*, to provide an optimization
  * for single-byte encodings.
  *
  * Before the inclusion, we need to define following macros:
  *
  * CHAREQ
  * ICHAREQ
  * NextChar
  * CopyAdvChar
  * MatchText (MBMatchText)
  * MatchTextIC (MBMatchTextIC)
  * do_like_escape (MB_do_like_escape)
  *
  * Copyright (c) 1996-2008, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
  *	$PostgreSQL: pgsql/src/backend/utils/adt/like_match.c,v 1.14 2007/01/05 22:19:41 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */

 /*
 **	Originally written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
 **	Rich $alz is now <rsalz@bbn.com>.
 **	Special thanks to Lars Mathiesen <thorinn@diku.dk> for the LABORT code.
 **
 **	This code was shamelessly stolen from the "pql" code by myself and
 **	slightly modified :)
 **
 **	All references to the word "star" were replaced by "percent"
 **	All references to the word "wild" were replaced by "like"
 **
 **	All the nice shell RE matching stuff was replaced by just "_" and "%"
 **
 **	As I don't have a copy of the SQL standard handy I wasn't sure whether
 **	to leave in the '\' escape character handling.
 **
 **	Keith Parks. <keith@mtcc.demon.co.uk>
 **
 **	SQL92 lets you specify the escape character by saying
 **	LIKE <pattern> ESCAPE <escape character>. We are a small operation
 **	so we force you to use '\'. - ay 7/95
 **
 **	Now we have the like_escape() function that converts patterns with
 **	any specified escape character (or none at all) to the internal
 **	default escape character, which is still '\'. - tgl 9/2000
 **
 ** The code is rewritten to avoid requiring null-terminated strings,
 ** which in turn allows us to leave out some memcpy() operations.
 ** This code should be faster and take less memory, but no promises...
 ** - thomas 2000-08-06
 **
 */


 /*--------------------
  *	Match text and p, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
  *
  *	LIKE_TRUE: they match
  *	LIKE_FALSE: they don't match
  *	LIKE_ABORT: not only don't they match, but the text is too short.
  *
  * If LIKE_ABORT is returned, then no suffix of the text can match the
  * pattern either, so an upper-level % scan can stop scanning now.
  *--------------------
  */

 static int
 MatchText(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 */
 			NextChar(p, plen);
 			if ((plen <= 0) || !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 == '%'))
 				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 (CHAREQ(t, p) || (*p == '\\') || (*p == '_'))
 				{
 					int			matched = MatchText(t, tlen, p, plen);

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

 				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 != '_') && !CHAREQ(t, p))
 		{
 			/*
 			 * Not the single-character wildcard and no explicit match? Then
 			 * time to quit...
 			 */
 			return LIKE_FALSE;
 		}

 		NextChar(t, tlen);
 		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 */
 		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;
 }	/* MatchText() */

 /*
  * Same as above, but ignore case
  */
 static int
 MatchTextIC(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 */
 			NextChar(p, plen);
 			if ((plen <= 0) || !ICHAREQ(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 == '%'))
 				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 (ICHAREQ(t, p) || (*p == '\\') || (*p == '_'))
 				{
 					int			matched = MatchTextIC(t, tlen, p, plen);

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

 				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 != '_') && !ICHAREQ(t, p))
 		{
 			/*
 			 * Not the single-character wildcard and no explicit match? Then
 			 * time to quit...
 			 */
 			return LIKE_FALSE;
 		}

 		NextChar(t, tlen);
 		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 */
 		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;
 }	/* MatchTextIC() */

 /*
  * like_escape() --- given a pattern and an ESCAPE string,
  * convert the pattern to use Postgres' standard backslash escape convention.
  */
 static text *
 do_like_escape(text *pat, text *esc)
 {
 	text	   *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++ = '\\';
 			CopyAdvChar(r, p, plen);
 		}
 	}
 	else
 	{
 		/*
 		 * The specified escape must be only a single character.
 		 */
 		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));
 			return 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 (CHAREQ(p, e) && !afterescape)
 			{
 				*r++ = '\\';
 				NextChar(p, plen);
 				afterescape = true;
 			}
 			else if (*p == '\\')
 			{
 				*r++ = '\\';
 				if (!afterescape)
 					*r++ = '\\';
 				NextChar(p, plen);
 				afterescape = false;
 			}
 			else
 			{
 				CopyAdvChar(r, p, plen);
 				afterescape = false;
 			}
 		}
 	}

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

 	return result;
 }
	/*-------------------------------------------------------------------------
	*
	* like_match.c
	* like expression handling internal code.
	*
	* This file is included by like.c twice, to provide an optimization
	* for single-byte encodings.
	*
	* Before the inclusion, we need to define following macros:
	*
	* CHAREQ
	* ICHAREQ
	* NextChar
	* CopyAdvChar
	* MatchText (MBMatchText)
	* MatchTextIC (MBMatchTextIC)
	* do_like_escape (MB_do_like_escape)
	*
	* Copyright (c) 1996-2008, PostgreSQL Global Development Group
	*
	* IDENTIFICATION
	* $PostgreSQL: pgsql/src/backend/utils/adt/like_match.c,v 1.14 2007/01/05 22:19:41 momjian Exp $
	*
	*-------------------------------------------------------------------------
	*/

	/*
	** Originally written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
	** Rich $alz is now <rsalz@bbn.com>.
	** Special thanks to Lars Mathiesen <thorinn@diku.dk> for the LABORT code.
	**
	** This code was shamelessly stolen from the "pql" code by myself and
	** slightly modified :)
	**
	** All references to the word "star" were replaced by "percent"
	** All references to the word "wild" were replaced by "like"
	**
	** All the nice shell RE matching stuff was replaced by just "_" and "%"
	**
	** As I don't have a copy of the SQL standard handy I wasn't sure whether
	** to leave in the '\' escape character handling.
	**
	** Keith Parks. <keith@mtcc.demon.co.uk>
	**
	** SQL92 lets you specify the escape character by saying
	** LIKE <pattern> ESCAPE <escape character>. We are a small operation
	** so we force you to use '\'. - ay 7/95
	**
	** Now we have the like_escape() function that converts patterns with
	** any specified escape character (or none at all) to the internal
	** default escape character, which is still '\'. - tgl 9/2000
	**
	** The code is rewritten to avoid requiring null-terminated strings,
	** which in turn allows us to leave out some memcpy() operations.
	** This code should be faster and take less memory, but no promises...
	** - thomas 2000-08-06
	**
	*/


	/*--------------------
	* Match text and p, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
	*
	* LIKE_TRUE: they match
	* LIKE_FALSE: they don't match
	* LIKE_ABORT: not only don't they match, but the text is too short.
	*
	* If LIKE_ABORT is returned, then no suffix of the text can match the
	* pattern either, so an upper-level % scan can stop scanning now.
	*--------------------
	*/

	static int
	MatchText(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 */
	NextChar(p, plen);
	if ((plen <= 0) \|\| !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 == '%'))
	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 (CHAREQ(t, p) \|\| (p == '\\') \|\| (p == '_'))
	{
	int matched = MatchText(t, tlen, p, plen);

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

	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 != '_') && !CHAREQ(t, p))
	{
	/*
	* Not the single-character wildcard and no explicit match? Then
	* time to quit...
	*/
	return LIKE_FALSE;
	}

	NextChar(t, tlen);
	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 */
	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;
	} /* MatchText() */

	/*
	* Same as above, but ignore case
	*/
	static int
	MatchTextIC(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 */
	NextChar(p, plen);
	if ((plen <= 0) \|\| !ICHAREQ(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 == '%'))
	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 (ICHAREQ(t, p) \|\| (p == '\\') \|\| (p == '_'))
	{
	int matched = MatchTextIC(t, tlen, p, plen);

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

	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 != '_') && !ICHAREQ(t, p))
	{
	/*
	* Not the single-character wildcard and no explicit match? Then
	* time to quit...
	*/
	return LIKE_FALSE;
	}

	NextChar(t, tlen);
	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 */
	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;
	} /* MatchTextIC() */

	/*
	* like_escape() --- given a pattern and an ESCAPE string,
	* convert the pattern to use Postgres' standard backslash escape convention.
	*/
	static text *
	do_like_escape(text pat, text esc)
	{
	text *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++ = '\\';
	CopyAdvChar(r, p, plen);
	}
	}
	else
	{
	/*
	* The specified escape must be only a single character.
	*/
	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));
	return 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 (CHAREQ(p, e) && !afterescape)
	{
	*r++ = '\\';
	NextChar(p, plen);
	afterescape = true;
	}
	else if (*p == '\\')
	{
	*r++ = '\\';
	if (!afterescape)
	*r++ = '\\';
	NextChar(p, plen);
	afterescape = false;
	}
	else
	{
	CopyAdvChar(r, p, plen);
	afterescape = false;
	}
	}
	}

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

	return result;
	}