/*-------------------------------------------------------------------------

 *

 * like_match.c

 *    LIKE pattern matching internal code.

 *

 * This file is included by like.c four times, to provide matching code for

 * (1) single-byte encodings, (2) UTF8, (3) other multi-byte encodings,

 * and (4) case insensitive matches in single-byte encodings.

 * (UTF8 is a special case because we can use a much more efficient version

 * of NextChar than can be used for general multi-byte encodings.)

 *

 * Before the inclusion, we need to define the following macros:

 *

 * NextChar

 * MatchText - to name of function wanted

 * do_like_escape - name of function if wanted - needs CHAREQ and CopyAdvChar

 * MATCH_LOWER - define for case (4) to specify case folding for 1-byte chars

 *

 * Copyright (c) 1996-2025, PostgreSQL Global Development Group

 *

 * IDENTIFICATION

 *  src/backend/utils/adt/like_match.c

 *

 *-------------------------------------------------------------------------

 */

/*

 *  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

 *  LIKE_ABORT 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>

 *

 *  SQL 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 pattern, 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.

 *--------------------

 */

#ifdef MATCH_LOWER

#define GETCHAR(t, locale) MATCH_LOWER(t, locale)

#else

#define GETCHAR(t, locale) (t)

#endif

static int

MatchText(const char *t, int tlen, const char *p, int plen, pg_locale_t locale)

{

  /* Fast path for match-everything pattern */

  if (plen == 1 && *p == '%')

    return LIKE_TRUE;

  /* Since this function recurses, it could be driven to stack overflow */

  check_stack_depth();

  /*

   * In this loop, we advance by char when matching wildcards (and thus on

   * recursive entry to this function we are properly char-synced). On other

   * occasions it is safe to advance by byte, as the text and pattern will

   * be in lockstep. This allows us to perform all comparisons between the

   * text and pattern on a byte by byte basis, even for multi-byte

   * encodings.

   */

  while (tlen > 0 && plen > 0)

  {

    if (*p == '\\')

    {

      /* Next pattern byte must match literally, whatever it is */

      NextByte(p, plen);

      /* ... and there had better be one, per SQL standard */

      if (plen <= 0)

        ereport(ERROR,

            (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),

             errmsg("LIKE pattern must not end with escape character")));

      if (GETCHAR(*p, locale) != GETCHAR(*t, locale))

        return LIKE_FALSE;

    }

    else if (*p == '%')

    {

      char    firstpat;

      /*

       * % processing is essentially a search for a text position at

       * which the remainder of the text matches the remainder of the

       * pattern, using a recursive call to check each potential match.

       *

       * If there are wildcards immediately following the %, we can skip

       * over them first, using the idea that any sequence of N _'s and

       * one or more %'s is equivalent to N _'s and one % (ie, it will

       * match any sequence of at least N text characters).  In this way

       * we will always run the recursive search loop using a pattern

       * fragment that begins with a literal character-to-match, thereby

       * not recursing more than we have to.

       */

      NextByte(p, plen);

      while (plen > 0)

      {

        if (*p == '%')

          NextByte(p, plen);

        else if (*p == '_')

        {

          /* If not enough text left to match the pattern, ABORT */

          if (tlen <= 0)

            return LIKE_ABORT;

          NextChar(t, tlen);

          NextByte(p, plen);

        }

        else

          break;   /* Reached a non-wildcard pattern char */

      }

      /*

       * If we're at end of pattern, match: we have a trailing % which

       * matches any remaining text string.

       */

      if (plen <= 0)

        return LIKE_TRUE;

      /*

       * Otherwise, scan for a text position at which we can match the

       * rest of the pattern.  The first remaining pattern char is known

       * to be a regular or escaped literal character, so we can compare

       * the first pattern byte to each text byte to avoid recursing

       * more than we have to.  This fact also guarantees that we don't

       * have to consider a match to the zero-length substring at the

       * end of the text.  With a nondeterministic collation, we can't

       * rely on the first bytes being equal, so we have to recurse in

       * any case.

       */

      if (*p == '\\')

      {

        if (plen < 2)

          ereport(ERROR,

              (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),

               errmsg("LIKE pattern must not end with escape character")));

        firstpat = GETCHAR(p[1], locale);

      }

      else

        firstpat = GETCHAR(*p, locale);

      while (tlen > 0)

      {

        if (GETCHAR(*t, locale) == firstpat || (locale && !locale->deterministic))

        {

          int     matched = MatchText(t, tlen, p, plen, locale);

          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 == '_')

    {

      /* _ matches any single character, and we know there is one */

      NextChar(t, tlen);

      NextByte(p, plen);

      continue;

    }

    else if (locale && !locale->deterministic)

    {

      /*

       * For nondeterministic locales, we find the next substring of the

       * pattern that does not contain wildcards and try to find a

       * matching substring in the text.  Crucially, we cannot do this

       * character by character, as in the normal case, but must do it

       * substring by substring, partitioned by the wildcard characters.

       * (This is per SQL standard.)

       */

      const char *p1;

      size_t    p1len;

      const char *t1;

      size_t    t1len;

      bool    found_escape;

      const char *subpat;

      size_t    subpatlen;

      char     *buf = NULL;

      /*

       * Determine next substring of pattern without wildcards.  p is

       * the start of the subpattern, p1 is one past the last byte. Also

       * track if we found an escape character.

       */

      p1 = p;

      p1len = plen;

      found_escape = false;

      while (p1len > 0)

      {

        if (*p1 == '\\')

        {

          found_escape = true;

          NextByte(p1, p1len);

          if (p1len == 0)

            ereport(ERROR,

                (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),

                 errmsg("LIKE pattern must not end with escape character")));

        }

        else if (*p1 == '_' || *p1 == '%')

          break;

        NextByte(p1, p1len);

      }

      /*

       * If we found an escape character, then make an unescaped copy of

       * the subpattern.

       */

      if (found_escape)

      {

        char     *b;

        b = buf = palloc(p1 - p);

        for (const char *c = p; c < p1; c++)

        {

          if (*c == '\\')

            ;

          else

            *(b++) = *c;

        }

        subpat = buf;

        subpatlen = b - buf;

      }

      else

      {

        subpat = p;

        subpatlen = p1 - p;

      }

      /*

       * Shortcut: If this is the end of the pattern, then the rest of

       * the text has to match the rest of the pattern.

       */

      if (p1len == 0)

      {

        int     cmp;

        cmp = pg_strncoll(subpat, subpatlen, t, tlen, locale);

        if (buf)

          pfree(buf);

        if (cmp == 0)

          return LIKE_TRUE;

        else

          return LIKE_FALSE;

      }

      /*

       * Now build a substring of the text and try to match it against

       * the subpattern.  t is the start of the text, t1 is one past the

       * last byte.  We start with a zero-length string.

       */

      t1 = t;

      t1len = tlen;

      for (;;)

      {

        int     cmp;

        CHECK_FOR_INTERRUPTS();

        cmp = pg_strncoll(subpat, subpatlen, t, (t1 - t), locale);

        /*

         * If we found a match, we have to test if the rest of pattern

         * can match against the rest of the string.  Otherwise we

         * have to continue here try matching with a longer substring.

         * (This is similar to the recursion for the '%' wildcard

         * above.)

         *

         * Note that we can't just wind forward p and t and continue

         * with the main loop.  This would fail for example with

         *

         * U&'\0061\0308bc' LIKE U&'\00E4_c' COLLATE ignore_accents

         *

         * You'd find that t=\0061 matches p=\00E4, but then the rest

         * won't match; but t=\0061\0308 also matches p=\00E4, and

         * then the rest will match.

         */

        if (cmp == 0)

        {

          int     matched = MatchText(t1, t1len, p1, p1len, locale);

          if (matched == LIKE_TRUE)

          {

            if (buf)

              pfree(buf);

            return matched;

          }

        }

        /*

         * Didn't match.  If we used up the whole text, then the match

         * fails.  Otherwise, try again with a longer substring.

         */

        if (t1len == 0)

        {

          if (buf)

            pfree(buf);

          return LIKE_FALSE;

        }

        else

          NextChar(t1, t1len);

      }

    }

    else if (GETCHAR(*p, locale) != GETCHAR(*t, locale))

    {

      /* non-wildcard pattern char fails to match text char */

      return LIKE_FALSE;

    }

    /*

     * Pattern and text match, so advance.

     *

     * It is safe to use NextByte instead of NextChar here, even for

     * multi-byte character sets, because we are not following immediately

     * after a wildcard character. If we are in the middle of a multibyte

     * character, we must already have matched at least one byte of the

     * character from both text and pattern; so we cannot get out-of-sync

     * on character boundaries.  And we know that no backend-legal

     * encoding allows ASCII characters such as '%' to appear as non-first

     * bytes of characters, so we won't mistakenly detect a new wildcard.

     */

    NextByte(t, tlen);

    NextByte(p, plen);

  }

  if (tlen > 0)

    return LIKE_FALSE;   /* end of pattern, but not of text */

  /*

   * End of text, but perhaps not of pattern.  Match iff the remaining

   * pattern can match a zero-length string, ie, it's zero or more %'s.

   */

  while (plen > 0 && *p == '%')

    NextByte(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() */

Unexecuted instantiation: like.c:UTF8_MatchText

Unexecuted instantiation: like.c:MB_MatchText

Unexecuted instantiation: like.c:SB_MatchText

Unexecuted instantiation: like.c:SB_IMatchText

/*

 * like_escape() --- given a pattern and an ESCAPE string,

 * convert the pattern to use Postgres' standard backslash escape convention.

 */

#ifdef do_like_escape

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;

}

Unexecuted instantiation: like.c:SB_do_like_escape

Unexecuted instantiation: like.c:MB_do_like_escape

#endif              /* do_like_escape */

#ifdef CHAREQ

#undef CHAREQ

#endif

#undef NextChar

#undef CopyAdvChar

#undef MatchText

#ifdef do_like_escape

#undef do_like_escape

#endif

#undef GETCHAR

#ifdef MATCH_LOWER

#undef MATCH_LOWER

#endif