readGZIPHeader() — netty Function Reference

Source Code

codec-compression/src/main/java/io/netty/handler/codec/compression/JdkZlibDecoder.java lines 343–433

    private boolean readGZIPHeader(ByteBuf in) {
        switch (gzipState) {
            case HEADER_START:
                if (in.readableBytes() < 10) {
                    return false;
                }
                // read magic numbers
                int magic0 = in.readByte();
                int magic1 = in.readByte();

                if (magic0 != 31) {
                    throw new DecompressionException("Input is not in the GZIP format");
                }
                crc.update(magic0);
                crc.update(magic1);

                int method = in.readUnsignedByte();
                if (method != Deflater.DEFLATED) {
                    throw new DecompressionException("Unsupported compression method "
                            + method + " in the GZIP header");
                }
                crc.update(method);

                flags = in.readUnsignedByte();
                crc.update(flags);

                if ((flags & FRESERVED) != 0) {
                    throw new DecompressionException(
                            "Reserved flags are set in the GZIP header");
                }

                // mtime (int)
                crc.update(in, in.readerIndex(), 4);
                in.skipBytes(4);

                crc.update(in.readUnsignedByte()); // extra flags
                crc.update(in.readUnsignedByte()); // operating system

                gzipState = GzipState.FLG_READ;
                // fall through
            case FLG_READ:
                if ((flags & FEXTRA) != 0) {
                    if (in.readableBytes() < 2) {
                        return false;
                    }
                    int xlen1 = in.readUnsignedByte();
                    int xlen2 = in.readUnsignedByte();
                    crc.update(xlen1);
                    crc.update(xlen2);

                    xlen |= xlen1 << 8 | xlen2;
                }
                gzipState = GzipState.XLEN_READ;
                // fall through
            case XLEN_READ:
                if (xlen != -1) {
                    if (in.readableBytes() < xlen) {
                        return false;
                    }
                    crc.update(in, in.readerIndex(), xlen);
                    in.skipBytes(xlen);
                }
                gzipState = GzipState.SKIP_FNAME;
                // fall through
            case SKIP_FNAME:
                if (!skipIfNeeded(in, FNAME)) {
                    return false;
                }
                gzipState = GzipState.SKIP_COMMENT;
                // fall through
            case SKIP_COMMENT:
                if (!skipIfNeeded(in, FCOMMENT)) {
                    return false;
                }
                gzipState = GzipState.PROCESS_FHCRC;
                // fall through
            case PROCESS_FHCRC:
                if ((flags & FHCRC) != 0) {
                    if (!verifyCrc16(in)) {
                        return false;
                    }