private int readBlock() {
        blockSize = read();
        int n = 0;
        if (blockSize > 0) {
            int count = 0;
            try {
                while (n < blockSize) {
                    count = blockSize - n;
                    rawData.get(block, n, count);

                    n += count;
                }
            } catch (Exception e) {
                if (Log.isLoggable(TAG, Log.DEBUG)) {
                    Log.d(TAG, "Error Reading Block n: " + n + " count: " + count + " blockSize: " + blockSize, e);
                }
                header.status = STATUS_FORMAT_ERROR;
            }
        }
        return n;
    }
Reads next variable length block from input.

@return number of bytes stored in "buffer"
core/src/main/java/com/bumptech/glide/gifdecoder/GifHeaderParser.java