decodeULE128() — netty Function Reference

Source Code

microbench/src/main/java/io/netty/handler/codec/http2/HpackDecoderULE128Benchmark.java lines 103–128

    static long decodeULE128(ByteBuf in, long result) throws Http2Exception {
        assert result <= 0x7f && result >= 0;
        final boolean resultStartedAtZero = result == 0;
        final int writerIndex = in.writerIndex();
        for (int readerIndex = in.readerIndex(), shift = 0; readerIndex < writerIndex; ++readerIndex, shift += 7) {
            byte b = in.getByte(readerIndex);
            if (shift == 56 && ((b & 0x80) != 0 || b == 0x7F && !resultStartedAtZero)) {
                // the maximum value that can be represented by a signed 64 bit number is:
                // [0x01L, 0x7fL] + 0x7fL + (0x7fL << 7) + (0x7fL << 14) + (0x7fL << 21) + (0x7fL << 28) + (0x7fL << 35)
                // + (0x7fL << 42) + (0x7fL << 49) + (0x7eL << 56)
                // OR
                // 0x0L + 0x7fL + (0x7fL << 7) + (0x7fL << 14) + (0x7fL << 21) + (0x7fL << 28) + (0x7fL << 35) +
                // (0x7fL << 42) + (0x7fL << 49) + (0x7fL << 56)
                // this means any more shifts will result longMaxBuf overflow so we should break out and throw an error.
                throw DECODE_ULE_128_TO_LONG_DECOMPRESSION_EXCEPTION;
            }

            if ((b & 0x80) == 0) {
                in.readerIndex(readerIndex + 1);
                return result + ((b & 0x7FL) << shift);
            }
            result += (b & 0x7FL) << shift;
        }

        throw DECODE_ULE_128_DECOMPRESSION_EXCEPTION;
    }