/*
* Copyright (C) 2014 Jörg Prante
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.xbib.io.compress.lzf;
import java.io.IOException;
import java.io.InputStream;
/**
* Safe {@link ChunkDecoder} implementation that can be used on any platform.
*/
public class VanillaChunkDecoder extends ChunkDecoder {
public VanillaChunkDecoder() {
}
@Override
public final int decodeChunk(final InputStream is, final byte[] inputBuffer, final byte[] outputBuffer)
throws IOException {
int bytesInOutput;
/* note: we do NOT read more than 5 bytes because otherwise might need to shuffle bytes
* for output buffer (could perhaps optimize in future?)
*/
int bytesRead = readHeader(is, inputBuffer);
if ((bytesRead < HEADER_BYTES)
|| inputBuffer[0] != LZFChunk.BYTE_Z || inputBuffer[1] != LZFChunk.BYTE_V) {
if (bytesRead == 0) { // probably fine, clean EOF
return -1;
}
throw new IOException("Corrupt input data, block did not start with 2 byte signature ('ZV') followed by type byte, 2-byte length)");
}
int type = inputBuffer[2];
int compLen = uint16(inputBuffer, 3);
if (type == LZFChunk.BLOCK_TYPE_NON_COMPRESSED) { // uncompressed
readFully(is, false, outputBuffer, 0, compLen);
bytesInOutput = compLen;
} else { // compressed
readFully(is, true, inputBuffer, 0, 2 + compLen); // first 2 bytes are uncompressed length
int uncompLen = uint16(inputBuffer, 0);
decodeChunk(inputBuffer, 2, outputBuffer, 0, uncompLen);
bytesInOutput = uncompLen;
}
return bytesInOutput;
}
@Override
public final void decodeChunk(byte[] in, int inPos, byte[] out, int outPos, int outEnd)
throws IOException {
do {
int ctrl = in[inPos++] & 255;
if (ctrl < LZFChunk.MAX_LITERAL) { // literal run
switch (ctrl) {
case 31:
out[outPos++] = in[inPos++];
case 30:
out[outPos++] = in[inPos++];
case 29:
out[outPos++] = in[inPos++];
case 28:
out[outPos++] = in[inPos++];
case 27:
out[outPos++] = in[inPos++];
case 26:
out[outPos++] = in[inPos++];
case 25:
out[outPos++] = in[inPos++];
case 24:
out[outPos++] = in[inPos++];
case 23:
out[outPos++] = in[inPos++];
case 22:
out[outPos++] = in[inPos++];
case 21:
out[outPos++] = in[inPos++];
case 20:
out[outPos++] = in[inPos++];
case 19:
out[outPos++] = in[inPos++];
case 18:
out[outPos++] = in[inPos++];
case 17:
out[outPos++] = in[inPos++];
case 16:
out[outPos++] = in[inPos++];
case 15:
out[outPos++] = in[inPos++];
case 14:
out[outPos++] = in[inPos++];
case 13:
out[outPos++] = in[inPos++];
case 12:
out[outPos++] = in[inPos++];
case 11:
out[outPos++] = in[inPos++];
case 10:
out[outPos++] = in[inPos++];
case 9:
out[outPos++] = in[inPos++];
case 8:
out[outPos++] = in[inPos++];
case 7:
out[outPos++] = in[inPos++];
case 6:
out[outPos++] = in[inPos++];
case 5:
out[outPos++] = in[inPos++];
case 4:
out[outPos++] = in[inPos++];
case 3:
out[outPos++] = in[inPos++];
case 2:
out[outPos++] = in[inPos++];
case 1:
out[outPos++] = in[inPos++];
case 0:
out[outPos++] = in[inPos++];
}
continue;
}
// back reference
int len = ctrl >> 5;
ctrl = -((ctrl & 0x1f) << 8) - 1;
if (len < 7) { // 2 bytes; length of 3 - 8 bytes
ctrl -= in[inPos++] & 255;
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
switch (len) {
case 6:
out[outPos] = out[outPos++ + ctrl];
case 5:
out[outPos] = out[outPos++ + ctrl];
case 4:
out[outPos] = out[outPos++ + ctrl];
case 3:
out[outPos] = out[outPos++ + ctrl];
case 2:
out[outPos] = out[outPos++ + ctrl];
case 1:
out[outPos] = out[outPos++ + ctrl];
}
continue;
}
// long version (3 bytes, length of up to 264 bytes)
len = in[inPos++] & 255;
ctrl -= in[inPos++] & 255;
// First: if there is no overlap, can just use arraycopy:
if ((ctrl + len) < -9) {
len += 9;
if (len <= 32) {
copyUpTo32WithSwitch(out, outPos + ctrl, out, outPos, len - 1);
} else {
System.arraycopy(out, outPos + ctrl, out, outPos, len);
}
outPos += len;
continue;
}
// otherwise manual copy: so first just copy 9 bytes we know are needed
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
// then loop
// Odd: after extensive profiling, looks like magic number
// for unrolling is 4: with 8 performance is worse (even
// bit less than with no unrolling).
len += outPos;
final int end = len - 3;
while (outPos < end) {
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
out[outPos] = out[outPos++ + ctrl];
}
switch (len - outPos) {
case 3:
out[outPos] = out[outPos++ + ctrl];
case 2:
out[outPos] = out[outPos++ + ctrl];
case 1:
out[outPos] = out[outPos++ + ctrl];
}
} while (outPos < outEnd);
// sanity check to guard against corrupt data:
if (outPos != outEnd) {
throw new IOException("Corrupt data: overrun in decompress, input offset " + inPos + ", output offset " + outPos);
}
}
protected static void copyUpTo32WithSwitch(byte[] in, int inPos, byte[] out, int outPos,
int lengthMinusOne) {
switch (lengthMinusOne) {
case 31:
out[outPos++] = in[inPos++];
case 30:
out[outPos++] = in[inPos++];
case 29:
out[outPos++] = in[inPos++];
case 28:
out[outPos++] = in[inPos++];
case 27:
out[outPos++] = in[inPos++];
case 26:
out[outPos++] = in[inPos++];
case 25:
out[outPos++] = in[inPos++];
case 24:
out[outPos++] = in[inPos++];
case 23:
out[outPos++] = in[inPos++];
case 22:
out[outPos++] = in[inPos++];
case 21:
out[outPos++] = in[inPos++];
case 20:
out[outPos++] = in[inPos++];
case 19:
out[outPos++] = in[inPos++];
case 18:
out[outPos++] = in[inPos++];
case 17:
out[outPos++] = in[inPos++];
case 16:
out[outPos++] = in[inPos++];
case 15:
out[outPos++] = in[inPos++];
case 14:
out[outPos++] = in[inPos++];
case 13:
out[outPos++] = in[inPos++];
case 12:
out[outPos++] = in[inPos++];
case 11:
out[outPos++] = in[inPos++];
case 10:
out[outPos++] = in[inPos++];
case 9:
out[outPos++] = in[inPos++];
case 8:
out[outPos++] = in[inPos++];
case 7:
out[outPos++] = in[inPos++];
case 6:
out[outPos++] = in[inPos++];
case 5:
out[outPos++] = in[inPos++];
case 4:
out[outPos++] = in[inPos++];
case 3:
out[outPos++] = in[inPos++];
case 2:
out[outPos++] = in[inPos++];
case 1:
out[outPos++] = in[inPos++];
case 0:
out[outPos++] = in[inPos++];
}
}
}