Function ReadStringInternal

tensorflow/core/lib/strings/ordered_code.cc:215–268

Parse the encoding of a previously encoded string. If parse succeeds, return true, consume encoding from "*src", and if result != NULL append the decoded string to "*result". Otherwise, return false and leave both undefined.

// "*src", and if result != NULL append the decoded string to "*result".
// Otherwise, return false and leave both undefined.
inline static bool ReadStringInternal(StringPiece* src, string* result) {
  const char* start = src->data();
  const char* string_limit = src->data() + src->size();

  // We only scan up to "limit-2" since a valid string must end with
  // a two character terminator: 'kEscape1 kSeparator'
  const char* limit = string_limit - 1;
  const char* copy_start = start;
  while (true) {
    start = SkipToNextSpecialByte(start, limit);
    if (start >= limit) break;  // No terminator sequence found
    const char c = *(start++);
    // If inversion is required, instead of inverting 'c', we invert the
    // character constants to which 'c' is compared.  We get the same
    // behavior but save the runtime cost of inverting 'c'.
    DCHECK(IsSpecialByte(c));
    if (c == kEscape1) {
      if (result) {
        AppendBytes(result, copy_start, start - copy_start - 1);
      }
      // kEscape1 kSeparator ends component
      // kEscape1 kNullCharacter represents '\0'
      const char next = *(start++);
      if (next == kSeparator) {
        src->remove_prefix(start - src->data());
        return true;
      } else if (next == kNullCharacter) {
        if (result) {
          *result += '\0';
        }
      } else {
        return false;
      }
      copy_start = start;
    } else {
      assert(c == kEscape2);
      if (result) {
        AppendBytes(result, copy_start, start - copy_start - 1);
      }
      // kEscape2 kFFCharacter represents '\xff'
      // kEscape2 kInfinity is an error
      const char next = *(start++);
      if (next == kFFCharacter) {
        if (result) {
          *result += '\xff';
        }
      } else {
        return false;
      }
      copy_start = start;
    }
  }
  return false;
}

bool OrderedCode::ReadString(StringPiece* src, string* result) {
  return ReadStringInternal(src, result);