com.ning.compress.lzf.ChunkDecoder Maven / Gradle / Ivy
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package com.ning.compress.lzf;
import java.io.IOException;
import java.io.InputStream;
/**
* Decoder that handles decoding of sequence of encoded LZF chunks,
* combining them into a single contiguous result byte array.
*
* Note that instances have no state, so they are
* fully thread-safe and reusable.
*
* @author Tatu Saloranta ([email protected])
*/
public abstract class ChunkDecoder
{
protected final static byte BYTE_NULL = 0;
protected final static int HEADER_BYTES = 5;
public ChunkDecoder() { }
/*
///////////////////////////////////////////////////////////////////////
// Public API
///////////////////////////////////////////////////////////////////////
*/
/**
* Method for decompressing a block of input data encoded in LZF
* block structure (compatible with lzf command line utility),
* and can consist of any number of blocks.
* Note that input MUST consists of a sequence of one or more complete
* chunks; partial chunks can not be handled.
*/
public final byte[] decode(final byte[] inputBuffer) throws LZFException
{
byte[] result = new byte[calculateUncompressedSize(inputBuffer, 0, inputBuffer.length)];
decode(inputBuffer, 0, inputBuffer.length, result);
return result;
}
/**
* Method for decompressing a block of input data encoded in LZF
* block structure (compatible with lzf command line utility),
* and can consist of any number of blocks.
* Note that input MUST consists of a sequence of one or more complete
* chunks; partial chunks can not be handled.
*/
public final byte[] decode(final byte[] inputBuffer, int inputPtr, int inputLen) throws LZFException
{
byte[] result = new byte[calculateUncompressedSize(inputBuffer, inputPtr, inputLen)];
decode(inputBuffer, inputPtr, inputLen, result);
return result;
}
/**
* Method for decompressing a block of input data encoded in LZF
* block structure (compatible with lzf command line utility),
* and can consist of any number of blocks.
* Note that input MUST consists of a sequence of one or more complete
* chunks; partial chunks can not be handled.
*/
public final int decode(final byte[] inputBuffer, final byte[] targetBuffer) throws LZFException
{
return decode(inputBuffer, 0, inputBuffer.length, targetBuffer);
}
/**
* Method for decompressing a block of input data encoded in LZF
* block structure (compatible with LZF command line utility),
* and can consist of any number of blocks.
* Note that input MUST consists of a sequence of one or more complete
* chunks; partial chunks can not be handled.
*/
public int decode(final byte[] sourceBuffer, int inPtr, int inLength,
final byte[] targetBuffer) throws LZFException
{
int outPtr = 0;
int blockNr = 0;
final int end = inPtr + inLength - 1; // -1 to offset possible end marker
while (inPtr < end) {
// let's do basic sanity checks; no point in skimping with these checks
if (sourceBuffer[inPtr] != LZFChunk.BYTE_Z || sourceBuffer[inPtr+1] != LZFChunk.BYTE_V) {
throw new LZFException("Corrupt input data, block #"+blockNr+" (at offset "+inPtr+"): did not start with 'ZV' signature bytes");
}
inPtr += 2;
int type = sourceBuffer[inPtr++];
int len = uint16(sourceBuffer, inPtr);
inPtr += 2;
if (type == LZFChunk.BLOCK_TYPE_NON_COMPRESSED) { // uncompressed
if ((outPtr + len) > targetBuffer.length) {
_reportArrayOverflow(targetBuffer, outPtr, len);
}
System.arraycopy(sourceBuffer, inPtr, targetBuffer, outPtr, len);
outPtr += len;
} else { // compressed
int uncompLen = uint16(sourceBuffer, inPtr);
if ((outPtr + uncompLen) > targetBuffer.length) {
_reportArrayOverflow(targetBuffer, outPtr, uncompLen);
}
inPtr += 2;
decodeChunk(sourceBuffer, inPtr, targetBuffer, outPtr, outPtr+uncompLen);
outPtr += uncompLen;
}
inPtr += len;
++blockNr;
}
return outPtr;
}
/**
* Main decode from a stream. Decompressed bytes are placed in the outputBuffer, inputBuffer
* is a "scratch-area".
*
* @param is An input stream of LZF compressed bytes
* @param inputBuffer A byte array used as a scratch area.
* @param outputBuffer A byte array in which the result is returned
*
* @return The number of bytes placed in the outputBuffer.
*/
public abstract int decodeChunk(final InputStream is, final byte[] inputBuffer, final byte[] outputBuffer)
throws IOException;
/**
* Main decode method for individual chunks.
*/
public abstract void decodeChunk(byte[] in, int inPos, byte[] out, int outPos, int outEnd)
throws LZFException;
/**
* @return If positive number, number of bytes skipped; if -1, end-of-stream was
* reached; otherwise, amount of content
* decoded (using formula of returnValue = -(decodedAmount + 2))
*/
public abstract int skipOrDecodeChunk(final InputStream is, final byte[] inputBuffer,
final byte[] outputBuffer, final long maxToSkip)
throws IOException;
/*
///////////////////////////////////////////////////////////////////////
// Public static methods
///////////////////////////////////////////////////////////////////////
*/
/**
* Helper method that will calculate total uncompressed size, for sequence of
* one or more LZF blocks stored in given byte array.
* Will do basic sanity checking, so that this method can be called to
* verify against some types of corruption.
*/
public static int calculateUncompressedSize(byte[] data, int ptr, int length) throws LZFException
{
int uncompressedSize = 0;
int blockNr = 0;
final int end = ptr + length;
while (ptr < end) {
// can use optional end marker
if (ptr == (data.length + 1) && data[ptr] == BYTE_NULL) {
++ptr; // so that we'll be at end
break;
}
// simpler to handle bounds checks by catching exception here...
try {
if (data[ptr] != LZFChunk.BYTE_Z || data[ptr+1] != LZFChunk.BYTE_V) {
throw new LZFException("Corrupt input data, block #"+blockNr+" (at offset "+ptr+"): did not start with 'ZV' signature bytes");
}
int type = (int) data[ptr+2];
int blockLen = uint16(data, ptr+3);
if (type == LZFChunk.BLOCK_TYPE_NON_COMPRESSED) { // uncompressed
ptr += 5;
uncompressedSize += blockLen;
} else if (type == LZFChunk.BLOCK_TYPE_COMPRESSED) { // compressed
uncompressedSize += uint16(data, ptr+5);
ptr += 7;
} else { // unknown... CRC-32 would be 2, but that's not implemented by cli tool
throw new LZFException("Corrupt input data, block #"+blockNr+" (at offset "+ptr+"): unrecognized block type "+(type & 0xFF));
}
ptr += blockLen;
} catch (ArrayIndexOutOfBoundsException e) {
throw new LZFException("Corrupt input data, block #"+blockNr+" (at offset "+ptr+"): truncated block header");
}
++blockNr;
}
// one more sanity check:
if (ptr != end) {
throw new LZFException("Corrupt input data: block #"+blockNr+" extends "+(data.length - ptr)+" beyond end of input");
}
return uncompressedSize;
}
/*
///////////////////////////////////////////////////////////////////////
// Internal methods
///////////////////////////////////////////////////////////////////////
*/
protected final static int uint16(byte[] data, int ptr) {
return ((data[ptr] & 0xFF) << 8) + (data[ptr+1] & 0xFF);
}
/**
* Helper method to forcibly load header bytes that must be read before
* chunk can be handled.
*/
protected final static int readHeader(final InputStream is, final byte[] inputBuffer)
throws IOException
{
// Ok: simple case first, where we just get all data we need
int needed = HEADER_BYTES;
int count = is.read(inputBuffer, 0, needed);
if (count == needed) {
return count;
}
if (count <= 0) {
return 0;
}
// if not, a source that trickles data (network etc); must loop
int offset = count;
needed -= count;
do {
count = is.read(inputBuffer, offset, needed);
if (count <= 0) {
break;
}
offset += count;
needed -= count;
} while (needed > 0);
return offset;
}
protected final static void readFully(InputStream is, boolean compressed,
byte[] outputBuffer, int offset, int len) throws IOException
{
int left = len;
while (left > 0) {
int count = is.read(outputBuffer, offset, left);
if (count < 0) { // EOF not allowed here
throw new LZFException("EOF in "+len+" byte ("
+(compressed ? "" : "un")+"compressed) block: could only read "
+(len-left)+" bytes");
}
offset += count;
left -= count;
}
}
protected final static void skipFully(final InputStream is, int amount) throws IOException
{
final int orig = amount;
while (amount > 0) {
long skipped = is.skip(amount);
if (skipped <= 0) {
throw new LZFException("Input problem: failed to skip "+orig+" bytes in input stream, only skipped "
+(orig-amount));
}
amount -= (int) skipped;
}
}
protected void _reportCorruptHeader() throws LZFException {
throw new LZFException("Corrupt input data, block did not start with 2 byte signature ('ZV') followed by type byte, 2-byte length)");
}
/**
* Helper method called when it is determined that the target buffer can not
* hold all data to copy or uncompress
*/
protected void _reportArrayOverflow(byte[] targetBuffer, int outPtr, int dataLen)
throws LZFException
{
throw new LZFException("Target buffer too small ("+targetBuffer.length+"): can not copy/uncompress "
+dataLen+" bytes to offset "+outPtr);
}
}