问包装byte[]的ImageInputStreamImpl实现

EN

public static class MyMemoryCacheImageInputStream extends ImageInputStreamImpl {

        private SimpleByteArrayInputStream stream;

        public MyMemoryCacheImageInputStream(SimpleByteArrayInputStream stream) {
            if (stream == null) {
                throw new IllegalArgumentException("stream == null!");
            }
            this.stream = stream;
        }

        @Override
        public int read() throws IOException {
            bitOffset = 0;
            return stream.read();
        }

        @Override
        public void seek(long pos) throws IOException {
            super.seek(pos);
            stream.seek(pos);
        }

        @Override
        public int read(byte[] b, int off, int len) throws IOException {
            if (b == null) {
                throw new NullPointerException("b == null!");
            }
            if (off < 0 || len < 0 || off + len > b.length || off + len < 0) {
                throw new IndexOutOfBoundsException("off < 0 || len < 0 || off+len > b.length || off+len < 0!");
            }

            bitOffset = 0;

            if (len == 0) {
                return 0;
            }

            return stream.read(b, off, len);
        }

        @Override
        public boolean isCached() {
            return false;
        }

        @Override
        public boolean isCachedFile() {
            return false;
        }

        @Override
        public boolean isCachedMemory() {
            return false;
        }

        @Override
        public void close() throws IOException {
            super.close();
            stream = null;
        }
    }