/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.commons.compress.compressors.snappy;
import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import java.util.Arrays;
import org.apache.commons.compress.compressors.CompressorInputStream;
import org.apache.commons.compress.utils.BoundedInputStream;
import org.apache.commons.compress.utils.IOUtils;
/**
* CompressorInputStream for the framing Snappy format.
*
* <p>Based on the "spec" in the version "Last revised: 2013-10-25"</p>
*
* @see <a href="http://code.google.com/p/snappy/source/browse/trunk/framing_format.txt">Snappy framing format description</a>
* @since 1.7
*/
public class FramedSnappyCompressorInputStream extends CompressorInputStream {
/**
* package private for tests only.
*/
static final long MASK_OFFSET = 0xa282ead8L;
private static final int STREAM_IDENTIFIER_TYPE = 0xff;
private static final int COMPRESSED_CHUNK_TYPE = 0;
private static final int UNCOMPRESSED_CHUNK_TYPE = 1;
private static final int PADDING_CHUNK_TYPE = 0xfe;
private static final int MIN_UNSKIPPABLE_TYPE = 2;
private static final int MAX_UNSKIPPABLE_TYPE = 0x7f;
private static final int MAX_SKIPPABLE_TYPE = 0xfd;
private static final byte[] SZ_SIGNATURE = new byte[] {
(byte) STREAM_IDENTIFIER_TYPE, // tag
6, 0, 0, // length
's', 'N', 'a', 'P', 'p', 'Y'
};
/** The underlying stream to read compressed data from */
private final PushbackInputStream in;
private SnappyCompressorInputStream currentCompressedChunk;
// used in no-arg read method
private final byte[] oneByte = new byte[1];
private boolean endReached, inUncompressedChunk;
private int uncompressedBytesRemaining;
private long expectedChecksum = -1;
private final PureJavaCrc32C checksum = new PureJavaCrc32C();
/**
* Constructs a new input stream that decompresses snappy-framed-compressed data
* from the specified input stream.
* @param in the InputStream from which to read the compressed data
*/
public FramedSnappyCompressorInputStream(InputStream in) throws IOException {
this.in = new PushbackInputStream(in, 1);
readStreamIdentifier();
}
/** {@inheritDoc} */
@Override
public int read() throws IOException {
return read(oneByte, 0, 1) == -1 ? -1 : oneByte[0] & 0xFF;
}
/** {@inheritDoc} */
@Override
public void close() throws IOException {
if (currentCompressedChunk != null) {
currentCompressedChunk.close();
currentCompressedChunk = null;
}
in.close();
}
/** {@inheritDoc} */
@Override
public int read(byte[] b, int off, int len) throws IOException {
int read = readOnce(b, off, len);
if (read == -1) {
readNextBlock();
if (endReached) {
return -1;
}
read = readOnce(b, off, len);
}
return read;
}
/** {@inheritDoc} */
@Override
public int available() throws IOException {
if (inUncompressedChunk) {
return Math.min(uncompressedBytesRemaining,
in.available());
} else if (currentCompressedChunk != null) {
return currentCompressedChunk.available();
}
return 0;
}
/**
* Read from the current chunk into the given array.
*
* @return -1 if there is no current chunk or the number of bytes
* read from the current chunk (which may be -1 if the end of the
* chunk is reached).
*/
private int readOnce(byte[] b, int off, int len) throws IOException {
int read = -1;
if (inUncompressedChunk) {
int amount = Math.min(uncompressedBytesRemaining, len);
if (amount == 0) {
return -1;
}
read = in.read(b, off, amount);
if (read != -1) {
uncompressedBytesRemaining -= read;
count(read);
}
} else if (currentCompressedChunk != null) {
long before = currentCompressedChunk.getBytesRead();
read = currentCompressedChunk.read(b, off, len);
if (read == -1) {
currentCompressedChunk.close();
currentCompressedChunk = null;
} else {
count(currentCompressedChunk.getBytesRead() - before);
}
}
if (read > 0) {
checksum.update(b, off, read);
}
return read;
}
private void readNextBlock() throws IOException {
verifyLastChecksumAndReset();
inUncompressedChunk = false;
int type = readOneByte();
if (type == -1) {
endReached = true;
} else if (type == STREAM_IDENTIFIER_TYPE) {
in.unread(type);
pushedBackBytes(1);
readStreamIdentifier();
readNextBlock();
} else if (type == PADDING_CHUNK_TYPE
|| (type > MAX_UNSKIPPABLE_TYPE && type <= MAX_SKIPPABLE_TYPE)) {
skipBlock();
readNextBlock();
} else if (type >= MIN_UNSKIPPABLE_TYPE && type <= MAX_UNSKIPPABLE_TYPE) {
throw new IOException("unskippable chunk with type " + type
+ " (hex " + Integer.toHexString(type) + ")"
+ " detected.");
} else if (type == UNCOMPRESSED_CHUNK_TYPE) {
inUncompressedChunk = true;
uncompressedBytesRemaining = readSize() - 4 /* CRC */;
expectedChecksum = unmask(readCrc());
} else if (type == COMPRESSED_CHUNK_TYPE) {
long size = readSize() - 4 /* CRC */;
expectedChecksum = unmask(readCrc());
currentCompressedChunk =
new SnappyCompressorInputStream(new BoundedInputStream(in, size));
// constructor reads uncompressed size
count(currentCompressedChunk.getBytesRead());
} else {
// impossible as all potential byte values have been covered
throw new IOException("unknown chunk type " + type
+ " detected.");
}
}
private long readCrc() throws IOException {
byte[] b = new byte[4];
int read = IOUtils.readFully(in, b);
count(read);
if (read != 4) {
throw new IOException("premature end of stream");
}
long crc = 0;
for (int i = 0; i < 4; i++) {
crc |= (b[i] & 0xFFL) << (8 * i);
}
return crc;
}
static long unmask(long x) {
// ugly, maybe we should just have used ints and deal with the
// overflow
x -= MASK_OFFSET;
x &= 0xffffFFFFL;
return ((x >> 17) | (x << 15)) & 0xffffFFFFL;
}
private int readSize() throws IOException {
int b = 0;
int sz = 0;
for (int i = 0; i < 3; i++) {
b = readOneByte();
if (b == -1) {
throw new IOException("premature end of stream");
}
sz |= (b << (i * 8));
}
return sz;
}
private void skipBlock() throws IOException {
int size = readSize();
long read = IOUtils.skip(in, size);
count(read);
if (read != size) {
throw new IOException("premature end of stream");
}
}
private void readStreamIdentifier() throws IOException {
byte[] b = new byte[10];
int read = IOUtils.readFully(in, b);
count(read);
if (10 != read || !matches(b, 10)) {
throw new IOException("Not a framed Snappy stream");
}
}
private int readOneByte() throws IOException {
int b = in.read();
if (b != -1) {
count(1);
return b & 0xFF;
}
return -1;
}
private void verifyLastChecksumAndReset() throws IOException {
if (expectedChecksum >= 0 && expectedChecksum != checksum.getValue()) {
throw new IOException("Checksum verification failed");
}
expectedChecksum = -1;
checksum.reset();
}
/**
* Checks if the signature matches what is expected for a .sz file.
*
* <p>.sz files start with a chunk with tag 0xff and content sNaPpY.</p>
*
* @param signature the bytes to check
* @param length the number of bytes to check
* @return true if this is a .sz stream, false otherwise
*/
public static boolean matches(byte[] signature, int length) {
if (length < SZ_SIGNATURE.length) {
return false;
}
byte[] shortenedSig = signature;
if (signature.length > SZ_SIGNATURE.length) {
shortenedSig = new byte[SZ_SIGNATURE.length];
System.arraycopy(signature, 0, shortenedSig, 0, SZ_SIGNATURE.length);
}
return Arrays.equals(shortenedSig, SZ_SIGNATURE);
}
}