static text *
do_like_escape(text *pat, text *esc)
{
text *result;
char *p,
*e,
*r;
int plen,
elen;
bool afterescape;
p = VARDATA_ANY(pat);
plen = VARSIZE_ANY_EXHDR(pat);
e = VARDATA_ANY(esc);
elen = VARSIZE_ANY_EXHDR(esc);
/*
* 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_ANY(esc);
/*
* If specified escape is '\', just copy the pattern as-is.
*/
if (*e == '\\')
{
memcpy(result, pat, VARSIZE_ANY(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;
}
static int
MatchText(unsigned char *t, int tlen, unsigned 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() */
