int aws_huffman_decode()

in source/huffman.c [213:285]

• 47 lines of code
• 9 McCabe index (conditional complexity)

int aws_huffman_decode(
    struct aws_huffman_decoder *decoder,
    struct aws_byte_cursor *to_decode,
    struct aws_byte_buf *output) {

    AWS_ASSERT(decoder);
    AWS_ASSERT(decoder->coder);
    AWS_ASSERT(to_decode);
    AWS_ASSERT(output);

    struct decoder_state state;
    state.decoder = decoder;
    state.input_cursor = to_decode;

    /* Measures how much of the input was read */
    size_t bits_left = decoder->num_bits + to_decode->len * 8;

    while (1) {

        decode_fill_working_bits(&state);

        uint8_t symbol;
        uint8_t bits_read = decoder->coder->decode(
            (uint32_t)(decoder->working_bits >> (BITSIZEOF(decoder->working_bits) - MAX_PATTERN_BITS)),
            &symbol,
            decoder->coder->userdata);

        if (bits_read == 0) {
            if (bits_left < MAX_PATTERN_BITS) {
                /* More input is needed to continue */
                return AWS_OP_SUCCESS;
            }
            /* Unknown symbol found */
            return aws_raise_error(AWS_ERROR_COMPRESSION_UNKNOWN_SYMBOL);
        }
        if (bits_read > bits_left) {
            /* Check if the buffer has been overrun.
            Note: because of the check in decode_fill_working_bits,
            the buffer won't actually overrun, instead there will
            be 0's in the bottom of working_bits. */

            return AWS_OP_SUCCESS;
        }

        if (output->len == output->capacity) {
            /* Check if we've hit the end of the output buffer.
             * Grow buffer, or raise error, depending on settings */
            if (decoder->allow_growth) {
                /* Double the capacity */
                if (aws_byte_buf_reserve_relative(output, output->capacity)) {
                    return AWS_OP_ERR;
                }
            } else {
                return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
            }
        }

        bits_left -= bits_read;
        decoder->working_bits <<= bits_read;
        decoder->num_bits -= bits_read;

        /* Store the found symbol */
        aws_byte_buf_write_u8(output, symbol);

        /* Successfully decoded whole buffer */
        if (bits_left == 0) {
            return AWS_OP_SUCCESS;
        }
    }

    /* This case is unreachable */
    AWS_ASSERT(0);
}