Method replace

plugins/cachekey/pattern.cc:271–328

* @brief Replaces all replacements found in the replacement string with what matched in the PCRE capturing groups. * @param subject PCRE subject string * @param result reference to A string where the result of the replacement will be stored * @return true - success, false - nothing matched or failure. */

 * @return true - success, false - nothing matched or failure.
 */
bool
Pattern::replace(const String &subject, String &result)
{
  int matchCount;
  int ovector[OVECOUNT];

  CacheKeyDebug("replacing:'%s' in pattern:'%s', subject:'%s'", _replacement.c_str(), _pattern.c_str(), subject.c_str());

  if (!_re || !_replace) {
    CacheKeyError("regular expression not initialized or not configured to replace");
    return false;
  }

  matchCount = pcre_exec(_re, nullptr, subject.c_str(), subject.length(), 0, PCRE_NOTEMPTY, ovector, OVECOUNT);
  if (matchCount < 0) {
    if (matchCount != PCRE_ERROR_NOMATCH) {
      CacheKeyError("matching error %d", matchCount);
    }
    return false;
  }

  /* Verify the replacement has the right number of matching groups */
  for (int i = 0; i < _tokenCount; i++) {
    if (_tokens[i] >= matchCount) {
      CacheKeyError("invalid reference in replacement string: $%d", _tokens[i]);
      return false;
    }
  }

  int previous = 0;
  for (int i = 0; i < _tokenCount; i++) {
    int replIndex = _tokens[i];
    int start     = ovector[2 * replIndex];
    int length    = ovector[2 * replIndex + 1] - ovector[2 * replIndex];

    /* Handle the case when no match / a group capture result in an empty string */
    if (start < 0) {
      start  = 0;
      length = 0;
    }

    String src(_replacement, _tokenOffset[i], 2);
    String dst(subject, start, length);

    CacheKeyDebug("replacing '%s' with '%s'", src.c_str(), dst.c_str());

    result.append(_replacement, previous, _tokenOffset[i] - previous);
    result.append(dst);

    previous = _tokenOffset[i] + 2; /* 2 is the size of $0 or $1 or $2, ... or $9 */
  }

  result.append(_replacement, previous, _replacement.length() - previous);

  CacheKeyDebug("replacing '%s' resulted in '%s'", _replacement.c_str(), result.c_str());

  return true;
}