62 lines
1.7 KiB
Java
62 lines
1.7 KiB
Java
/**
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*
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*/
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package org.apache.poi.hdgf.streams;
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import java.io.ByteArrayInputStream;
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import java.io.IOException;
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import org.apache.poi.hdgf.LZW4HDGF;
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class CompressedStreamStore extends StreamStore {
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/** The raw, compressed contents */
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private byte[] compressedContents;
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/**
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* We're not sure what this is, but it comes before the
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* real contents in the de-compressed data
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*/
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private byte[] blockHeader = new byte[4];
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protected byte[] _getCompressedContents() { return compressedContents; }
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protected byte[] _getBlockHeader() { return blockHeader; }
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/**
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* Creates a new compressed StreamStore, which will handle
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* the decompression.
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*/
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protected CompressedStreamStore(byte[] data, int offset, int length) throws IOException {
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this(decompress(data,offset,length));
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compressedContents = new byte[length];
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System.arraycopy(data, offset, compressedContents, 0, length);
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}
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/**
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* Handles passing the de-compressed data onto our superclass.
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*/
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private CompressedStreamStore(byte[][] decompressedData) {
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super(decompressedData[1], 0, decompressedData[1].length);
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blockHeader = decompressedData[0];
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}
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/**
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* Decompresses the given data, returning it as header + contents
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*/
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public static byte[][] decompress(byte[] data, int offset, int length) throws IOException {
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ByteArrayInputStream bais = new ByteArrayInputStream(data, offset, length);
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// Decompress
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LZW4HDGF lzw = new LZW4HDGF();
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byte[] decompressed = lzw.decode(bais);
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// Split into header and contents
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byte[][] ret = new byte[2][];
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ret[0] = new byte[4];
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ret[1] = new byte[decompressed.length - 4];
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System.arraycopy(decompressed, 0, ret[0], 0, 4);
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System.arraycopy(decompressed, 4, ret[1], 0, ret[1].length);
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// All done
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return ret;
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}
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} |