96 lines
4.4 KiB
Java
96 lines
4.4 KiB
Java
/*
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Copyright 2019-2023 Dmitry Isaenko
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This file is part of libKonogonka.
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libKonogonka is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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libKonogonka is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with libKonogonka. If not, see <https://www.gnu.org/licenses/>.
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*/
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package libKonogonka.blz;
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import libKonogonka.Converter;
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public class BlzDecompress {
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public static final byte BLZ_MASK = (byte) 0x80;
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/**
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* Decompress BLZ section. Adapted for NS.
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* @param compressed byte array with compressed data
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* @param decompressed byte array where decompressed data should be saved in
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* */
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public int decompress(byte[] compressed, byte[] decompressed) throws Exception{
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/* NOTE: values must be unsigned int ! */
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int additionalLength = Converter.getLEint(compressed, compressed.length-4);
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int headerSize = Converter.getLEint(compressed, compressed.length-2*4); // 'Footer' aka 'Header'
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int compressedAndHeaderSize = Converter.getLEint(compressed, compressed.length-3*4);
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if (additionalLength == 0)
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throw new Exception("File not compressed");
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else if (additionalLength < 0)
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throw new Exception("File not supported. Please file a bug "+additionalLength);
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int delta = compressed.length - compressedAndHeaderSize;
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int compressedOffset = compressedAndHeaderSize - headerSize + delta;
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int finalOffset = compressedAndHeaderSize + additionalLength + delta;
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int resultingSize = finalOffset;
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/*
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System.out.printf(
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"Additional length : %-21d 0x%-8x %n" +
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"Additional length : %-21d 0x%-8x %n" +
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"Delta : %-21d %n" +
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"Compressed+Header size : %-21d 0x%-8x Incorrect: %-8d 0x%-8x %n" +
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"Compressed offset : %-21d 0x%-8x Incorrect: %-8d 0x%-8x %n" +
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"Resulting Size,Final offset : %-21d 0x%-8x Incorrect: %-8d 0x%-8x %n%n",
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additionalLength, additionalLength,
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headerSize, headerSize,
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delta,
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compressed.length, compressed.length, compressedAndHeaderSize, compressedAndHeaderSize,
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compressedOffset, compressedOffset, compressedAndHeaderSize - headerSize, compressedAndHeaderSize - headerSize,
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finalOffset, finalOffset, compressedAndHeaderSize + additionalLength, compressedAndHeaderSize + additionalLength);
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//*/
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decompress_loop:
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while (true){
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byte control = compressed[--compressedOffset];
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for (int i = 0; i < 8; i++){
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if ((control & BLZ_MASK) == 0) {
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if (compressedOffset < 1)
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throw new Exception("BLZ decompression is out of range");
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decompressed[--finalOffset] = compressed[--compressedOffset];
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}
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else {
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if (compressedOffset < 2)
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throw new Exception("BLZ decompression is out of range");
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compressedOffset -= 2;
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short segmentValue = (short) (( (compressed[compressedOffset+1]) << 8) | (compressed[compressedOffset] & 0xFF));
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int segmentSize = ((segmentValue >> 12) & 0xF) + 3;
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int segmentPosition = (segmentValue & 0xFFF) + 3;
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if (segmentSize > finalOffset)
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segmentSize = finalOffset;
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finalOffset -= segmentSize;
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for (int j = 0; j < segmentSize; j++)
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decompressed[finalOffset + j] = decompressed[finalOffset + j + segmentPosition];
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}
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control <<= 1;
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if (finalOffset == delta)
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break decompress_loop;
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}
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}
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if (delta != 0)
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System.arraycopy(compressed, 0, decompressed, 0, delta);
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return resultingSize;
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}
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}
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