decode() — netty Function Reference

Architecture documentation for the decode() function in Lz4FrameDecoder.java from the netty codebase.

Function java Buffer Allocators

Entity Profile

Buffer→ Allocators→ decode() — netty Function Reference

Dependency Diagram

graph TD
  6c7e5e02_2ee9_ba37_521d_ac588546a856["decode()"]
  2d460c23_2951_e424_21c2_a4587a5e314f["Lz4FrameDecoder"]
  6c7e5e02_2ee9_ba37_521d_ac588546a856 -->|defined in| 2d460c23_2951_e424_21c2_a4587a5e314f
  style 6c7e5e02_2ee9_ba37_521d_ac588546a856 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

codec-compression/src/main/java/io/netty/handler/codec/compression/Lz4FrameDecoder.java lines 150–268

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        try {
            switch (currentState) {
            case INIT_BLOCK:
                if (in.readableBytes() < HEADER_LENGTH) {
                    break;
                }
                final long magic = in.readLong();
                if (magic != MAGIC_NUMBER) {
                    throw new DecompressionException("unexpected block identifier");
                }

                final int token = in.readByte();
                final int compressionLevel = (token & 0x0F) + COMPRESSION_LEVEL_BASE;
                int blockType = token & 0xF0;

                int compressedLength = Integer.reverseBytes(in.readInt());
                if (compressedLength < 0 || compressedLength > MAX_BLOCK_SIZE) {
                    throw new DecompressionException(String.format(
                            "invalid compressedLength: %d (expected: 0-%d)",
                            compressedLength, MAX_BLOCK_SIZE));
                }

                int decompressedLength = Integer.reverseBytes(in.readInt());
                final int maxDecompressedLength = 1 << compressionLevel;
                if (decompressedLength < 0 || decompressedLength > maxDecompressedLength) {
                    throw new DecompressionException(String.format(
                            "invalid decompressedLength: %d (expected: 0-%d)",
                            decompressedLength, maxDecompressedLength));
                }
                if (decompressedLength == 0 && compressedLength != 0
                        || decompressedLength != 0 && compressedLength == 0
                        || blockType == BLOCK_TYPE_NON_COMPRESSED && decompressedLength != compressedLength) {
                    throw new DecompressionException(String.format(
                            "stream corrupted: compressedLength(%d) and decompressedLength(%d) mismatch",
                            compressedLength, decompressedLength));
                }

                int currentChecksum = Integer.reverseBytes(in.readInt());
                if (decompressedLength == 0 && compressedLength == 0) {
                    if (currentChecksum != 0) {
                        throw new DecompressionException("stream corrupted: checksum error");
                    }
                    currentState = State.FINISHED;
                    decompressor = null;
                    checksum = null;
                    break;
                }

                this.blockType = blockType;
                this.compressedLength = compressedLength;
                this.decompressedLength = decompressedLength;
                this.currentChecksum = currentChecksum;

                currentState = State.DECOMPRESS_DATA;
                // fall through
            case DECOMPRESS_DATA:
                blockType = this.blockType;
                compressedLength = this.compressedLength;
                decompressedLength = this.decompressedLength;
                currentChecksum = this.currentChecksum;

                if (in.readableBytes() < compressedLength) {
                    break;
                }

                final ByteBufChecksum checksum = this.checksum;
                ByteBuf uncompressed = null;

                try {
                    switch (blockType) {
                        case BLOCK_TYPE_NON_COMPRESSED:
                            // Just pass through, we not update the readerIndex yet as we do this outside of the
                            // switch statement.
                            uncompressed = in.retainedSlice(in.readerIndex(), decompressedLength);
                            break;
                        case BLOCK_TYPE_COMPRESSED:
                            uncompressed = ctx.alloc().buffer(decompressedLength, decompressedLength);

                            decompressor.decompress(CompressionUtil.safeReadableNioBuffer(in),