Status ParseHeader()

in tensorflow_compression/cc/kernels/y4m_dataset_kernels.cc [295:394]
93 lines of code
25 McCabe index (conditional complexity)

      Status ParseHeader(string_view header, const size_t file_index,
                         int64_t& width, int64_t& height,
                         ChromaFormat& chroma_format) {
        const string_view digits = "0123456789";

        width = 0;
        height = 0;
        chroma_format = ChromaFormat::undefined;

        // Last character is guaranteed to be newline because ReadHeader uses
        // it to find the end of the header.
        header.remove_suffix(1);

        if (!absl::ConsumePrefix(&header, "YUV4MPEG2")) {
          return errors::InvalidArgument(
              "Input file '", dataset()->filenames_[file_index],
              "' does not have a YUV4MPEG2 marker.");
        }

        while (!header.empty()) {
          size_t pos;
          if (header.size() < 2 || header[0] != ' ') {
            return errors::InvalidArgument(
                "Input file '", dataset()->filenames_[file_index],
                "' has an invalid Y4M header. Remaining header: '", header,
                "'.");
          }
          const char key = header[1];
          header.remove_prefix(2);
          switch (key) {
            case 'W':
              pos = header.find_first_not_of(digits);
              if (!absl::SimpleAtoi(header.substr(0, pos), &width) ||
                  width <= 0) {
                return errors::InvalidArgument(
                    "Input file '", dataset()->filenames_[file_index],
                    "' has an invalid width specifier '", header.substr(0, pos),
                    "'.");
              }
              header.remove_prefix(pos == header.npos ? header.size() : pos);
              break;
            case 'H':
              pos = header.find_first_not_of(digits);
              if (!absl::SimpleAtoi(header.substr(0, pos), &height) ||
                  height <= 0) {
                return errors::InvalidArgument(
                    "Input file '", dataset()->filenames_[file_index],
                    "' has an invalid height specifier '",
                    header.substr(0, pos), "'.");
              }
              header.remove_prefix(pos == header.npos ? header.size() : pos);
              break;
            case 'C':
              if (absl::ConsumePrefix(&header, "420jpeg")) {
                chroma_format = ChromaFormat::I420;
              } else if (absl::ConsumePrefix(&header, "444")) {
                chroma_format = ChromaFormat::I444;
              } else {
                return errors::InvalidArgument(
                    "Input file '", dataset()->filenames_[file_index],
                    "' has an unsupported chroma format '",
                    header.substr(0, header.find(' ')), "'.");
              }
              break;
            case 'I':
              if (!absl::ConsumePrefix(&header, "p")) {
                return errors::InvalidArgument(
                    "Input file '", dataset()->filenames_[file_index],
                    "' is not in progressive format.");
              }
              break;
            default:
              pos = header.find(' ');
              header.remove_prefix(pos == header.npos ? header.size() : pos);
              break;
          }
        }

        if (!width) {
          return errors::InvalidArgument(
              "Input file '", dataset()->filenames_[file_index],
              "' has no width specifier.");
        }
        if (!height) {
          return errors::InvalidArgument(
              "Input file '", dataset()->filenames_[file_index],
              "' has no height specifier.");
        }
        if (chroma_format == ChromaFormat::undefined) {
          return errors::InvalidArgument(
              "Input file '", dataset()->filenames_[file_index],
              "' has no chroma format specifier.");
        }
        if (chroma_format == ChromaFormat::I420 && (width & 1 || height & 1)) {
          return errors::InvalidArgument(
              "Input file '", dataset()->filenames_[file_index],
              "' has 4:2:0 chroma format, but odd width or height.");
        }
        return Status::OK();
      }