bundles/org.tukani.xz/src/org/tukaani/xz/lz/LZEncoder.java
private void moveWindow() {
        // Align the move to a multiple of 16 bytes. LZMA2 needs this
        // because it uses the lowest bits from readPos to get the
        // alignment of the uncompressed data.
        int moveOffset = (readPos + 1 - keepSizeBefore) & ~15;
        int moveSize = writePos - moveOffset;
        System.arraycopy(buf, moveOffset, buf, 0, moveSize);

        readPos -= moveOffset;
        readLimit -= moveOffset;
        writePos -= moveOffset;
    }
private void moveWindow() {
        // Align the move to a multiple of 16 bytes. LZMA2 needs this
        // because it uses the lowest bits from readPos to get the
        // alignment of the uncompressed data.
        int moveOffset = (readPos + 1 - keepSizeBefore) & ~15;
        int moveSize = writePos - moveOffset;
        System.arraycopy(buf, moveOffset, buf, 0, moveSize);

        readPos -= moveOffset;
        readLimit -= moveOffset;
        writePos -= moveOffset;
    }
Moves data from the end of the buffer to the beginning, discarding
old data and making space for new input.