Component Class — netty Architecture

Source Code

buffer/src/main/java/io/netty/buffer/CompositeByteBuf.java lines 1913–1985

    private static final class Component {
        final ByteBuf srcBuf; // the originally added buffer
        final ByteBuf buf; // srcBuf unwrapped zero or more times

        int srcAdjustment; // index of the start of this CompositeByteBuf relative to srcBuf
        int adjustment; // index of the start of this CompositeByteBuf relative to buf

        int offset; // offset of this component within this CompositeByteBuf
        int endOffset; // end offset of this component within this CompositeByteBuf

        private ByteBuf slice; // cached slice, may be null

        Component(ByteBuf srcBuf, int srcOffset, ByteBuf buf, int bufOffset,
                int offset, int len, ByteBuf slice) {
            this.srcBuf = srcBuf;
            this.srcAdjustment = srcOffset - offset;
            this.buf = buf;
            this.adjustment = bufOffset - offset;
            this.offset = offset;
            this.endOffset = offset + len;
            this.slice = slice;
        }

        int srcIdx(int index) {
            return index + srcAdjustment;
        }

        int idx(int index) {
            return index + adjustment;
        }

        int length() {
            return endOffset - offset;
        }

        void reposition(int newOffset) {
            int move = newOffset - offset;
            endOffset += move;
            srcAdjustment -= move;
            adjustment -= move;
            offset = newOffset;
        }

        // copy then release
        void transferTo(ByteBuf dst) {
            dst.writeBytes(buf, idx(offset), length());
            free();
        }

        ByteBuf slice() {
            ByteBuf s = slice;
            if (s == null) {
                slice = s = srcBuf.slice(srcIdx(offset), length());
            }
            return s;
        }

        ByteBuf duplicate() {
            return srcBuf.duplicate();
        }

        ByteBuffer internalNioBuffer(int index, int length) {
            // Some buffers override this so we must use srcBuf
            return srcBuf.internalNioBuffer(srcIdx(index), length);
        }

        void free() {
            slice = null;
            // Release the original buffer since it may have a different
            // refcount to the unwrapped buf (e.g. if PooledSlicedByteBuf)
            srcBuf.release();
        }
    }