Snappy-Java Source Code
Snappy-Java is a Java port of the "snappy", a fast C++ compresser/decompresser developed by Google.
Snappy-Java Source Code files are provided in the source packge (snappy-java-1.1.8.4-sources.jar). You can download it at Snappy Maven Website.
You can also browse Snappy-Java Source Code below:
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⏎ org/xerial/snappy/pure/SnappyRawDecompressor.java
/*
* 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.xerial.snappy.pure;
import java.nio.ByteOrder;
import org.xerial.snappy.SnappyError;
import org.xerial.snappy.SnappyErrorCode;
import static org.xerial.snappy.pure.SnappyConstants.LITERAL;
import static org.xerial.snappy.pure.SnappyConstants.SIZE_OF_INT;
import static org.xerial.snappy.pure.SnappyConstants.SIZE_OF_LONG;
import static org.xerial.snappy.pure.UnsafeUtil.UNSAFE;
import static java.lang.Integer.reverseBytes;
public final class SnappyRawDecompressor
{
private static final int[] DEC_32_TABLE = {4, 1, 2, 1, 4, 4, 4, 4};
private static final int[] DEC_64_TABLE = {0, 0, 0, -1, 0, 1, 2, 3};
private SnappyRawDecompressor() {}
private static final ByteOrder byteOrder = ByteOrder.nativeOrder();
private static int littleEndian(int i) {
return (byteOrder == ByteOrder.LITTLE_ENDIAN) ? i : reverseBytes(i);
}
public static int getUncompressedLength(Object compressed, long compressedAddress, long compressedLimit)
{
return readUncompressedLength(compressed, compressedAddress, compressedLimit)[0];
}
public static int decompress(
final Object inputBase,
final long inputAddress,
final long inputLimit,
final Object outputBase,
final long outputAddress,
final long outputLimit)
{
// Read the uncompressed length from the front of the input
long input = inputAddress;
int[] varInt = readUncompressedLength(inputBase, input, inputLimit);
int expectedLength = varInt[0];
input += varInt[1];
if(!(expectedLength <= (outputLimit - outputAddress))) {
throw new SnappyError(SnappyErrorCode.INVALID_CHUNK_SIZE, String.format("Uncompressed length %s must be less than %s", expectedLength, (outputLimit - outputAddress)));
}
// Process the entire input
int uncompressedSize = uncompressAll(
inputBase,
input,
inputLimit,
outputBase,
outputAddress,
outputLimit);
if (!(expectedLength == uncompressedSize)) {
throw new SnappyError(SnappyErrorCode.INVALID_CHUNK_SIZE, String.format("Recorded length is %s bytes but actual length after decompression is %s bytes ",
expectedLength,
uncompressedSize));
}
return expectedLength;
}
private static int uncompressAll(
final Object inputBase,
final long inputAddress,
final long inputLimit,
final Object outputBase,
final long outputAddress,
final long outputLimit)
{
final long fastOutputLimit = outputLimit - SIZE_OF_LONG; // maximum offset in output buffer to which it's safe to write long-at-a-time
long output = outputAddress;
long input = inputAddress;
while (input < inputLimit) {
int opCode = UNSAFE.getByte(inputBase, input++) & 0xFF;
int entry = opLookupTable[opCode] & 0xFFFF;
int trailerBytes = entry >>> 11;
int trailer = 0;
if (input + SIZE_OF_INT < inputLimit) {
trailer = littleEndian(UNSAFE.getInt(inputBase, input)) & wordmask[trailerBytes];
}
else {
if (input + trailerBytes > inputLimit) {
throw new SnappyError(SnappyErrorCode.PARSING_ERROR, String.format("position: %d", input - inputAddress));
}
switch (trailerBytes) {
case 4:
trailer = (UNSAFE.getByte(inputBase, input + 3) & 0xff) << 24;
case 3:
trailer |= (UNSAFE.getByte(inputBase, input + 2) & 0xff) << 16;
case 2:
trailer |= (UNSAFE.getByte(inputBase, input + 1) & 0xff) << 8;
case 1:
trailer |= (UNSAFE.getByte(inputBase, input) & 0xff);
}
}
if (trailer < 0) {
throw new SnappyError(SnappyErrorCode.PARSING_ERROR, String.format("position: %d", input - inputAddress));
}
input += trailerBytes;
int length = entry & 0xff;
if (length == 0) {
continue;
}
if ((opCode & 0x3) == LITERAL) {
int literalLength = length + trailer;
// copy literal
long literalOutputLimit = output + literalLength;
if (literalOutputLimit > fastOutputLimit || input + literalLength > inputLimit - SIZE_OF_LONG) {
if (literalOutputLimit > outputLimit) {
throw new SnappyError(SnappyErrorCode.PARSING_ERROR, String.format("position: %d", input - inputAddress));
}
// slow, precise copy
UNSAFE.copyMemory(inputBase, input, outputBase, output, literalLength);
input += literalLength;
output += literalLength;
}
else {
// fast copy. We may over-copy but there's enough room in input and output to not overrun them
do {
UNSAFE.putLong(outputBase, output, UNSAFE.getLong(inputBase, input));
input += SIZE_OF_LONG;
output += SIZE_OF_LONG;
}
while (output < literalOutputLimit);
input -= (output - literalOutputLimit); // adjust index if we over-copied
output = literalOutputLimit;
}
}
else {
// matchOffset/256 is encoded in bits 8..10. By just fetching
// those bits, we get matchOffset (since the bit-field starts at
// bit 8).
int matchOffset = entry & 0x700;
matchOffset += trailer;
long matchAddress = output - matchOffset;
if (matchAddress < outputAddress || output + length > outputLimit) {
throw new SnappyError(SnappyErrorCode.PARSING_ERROR, String.format("position: %d", input - inputAddress));
}
long matchOutputLimit = output + length;
if (output > fastOutputLimit) {
// slow match copy
while (output < matchOutputLimit) {
UNSAFE.putByte(outputBase, output++, UNSAFE.getByte(outputBase, matchAddress++));
}
}
else {
// copy repeated sequence
if (matchOffset < SIZE_OF_LONG) {
// 8 bytes apart so that we can copy long-at-a-time below
int increment32 = DEC_32_TABLE[matchOffset];
int decrement64 = DEC_64_TABLE[matchOffset];
UNSAFE.putByte(outputBase, output, UNSAFE.getByte(outputBase, matchAddress));
UNSAFE.putByte(outputBase, output + 1, UNSAFE.getByte(outputBase, matchAddress + 1));
UNSAFE.putByte(outputBase, output + 2, UNSAFE.getByte(outputBase, matchAddress + 2));
UNSAFE.putByte(outputBase, output + 3, UNSAFE.getByte(outputBase, matchAddress + 3));
output += SIZE_OF_INT;
matchAddress += increment32;
UNSAFE.putInt(outputBase, output, UNSAFE.getInt(outputBase, matchAddress));
output += SIZE_OF_INT;
matchAddress -= decrement64;
}
else {
UNSAFE.putLong(outputBase, output, UNSAFE.getLong(outputBase, matchAddress));
matchAddress += SIZE_OF_LONG;
output += SIZE_OF_LONG;
}
if (matchOutputLimit > fastOutputLimit) {
if (matchOutputLimit > outputLimit) {
throw new SnappyError(SnappyErrorCode.PARSING_ERROR, String.format("position: %d", input - inputAddress));
}
while (output < fastOutputLimit) {
UNSAFE.putLong(outputBase, output, UNSAFE.getLong(outputBase, matchAddress));
matchAddress += SIZE_OF_LONG;
output += SIZE_OF_LONG;
}
while (output < matchOutputLimit) {
UNSAFE.putByte(outputBase, output++, UNSAFE.getByte(outputBase, matchAddress++));
}
}
else {
while (output < matchOutputLimit) {
UNSAFE.putLong(outputBase, output, UNSAFE.getLong(outputBase, matchAddress));
matchAddress += SIZE_OF_LONG;
output += SIZE_OF_LONG;
}
}
}
output = matchOutputLimit; // correction in case we over-copied
}
}
return (int) (output - outputAddress);
}
// Mapping from i in range [0,4] to a mask to extract the bottom 8*i bits
private static final int[] wordmask = new int[] {
0, 0xff, 0xffff, 0xffffff, 0xffffffff
};
// Data stored per entry in lookup table:
// Range Bits-used Description
// ------------------------------------
// 1..64 0..7 Literal/copy length encoded in opcode byte
// 0..7 8..10 Copy offset encoded in opcode byte / 256
// 0..4 11..13 Extra bytes after opcode
//
// We use eight bits for the length even though 7 would have sufficed
// because of efficiency reasons:
// (1) Extracting a byte is faster than a bit-field
// (2) It properly aligns copy offset so we do not need a <<8
private static final short[] opLookupTable = new short[] {
0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,
0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,
0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,
0x0007, 0x080a, 0x1007, 0x2007, 0x0008, 0x080b, 0x1008, 0x2008,
0x0009, 0x0904, 0x1009, 0x2009, 0x000a, 0x0905, 0x100a, 0x200a,
0x000b, 0x0906, 0x100b, 0x200b, 0x000c, 0x0907, 0x100c, 0x200c,
0x000d, 0x0908, 0x100d, 0x200d, 0x000e, 0x0909, 0x100e, 0x200e,
0x000f, 0x090a, 0x100f, 0x200f, 0x0010, 0x090b, 0x1010, 0x2010,
0x0011, 0x0a04, 0x1011, 0x2011, 0x0012, 0x0a05, 0x1012, 0x2012,
0x0013, 0x0a06, 0x1013, 0x2013, 0x0014, 0x0a07, 0x1014, 0x2014,
0x0015, 0x0a08, 0x1015, 0x2015, 0x0016, 0x0a09, 0x1016, 0x2016,
0x0017, 0x0a0a, 0x1017, 0x2017, 0x0018, 0x0a0b, 0x1018, 0x2018,
0x0019, 0x0b04, 0x1019, 0x2019, 0x001a, 0x0b05, 0x101a, 0x201a,
0x001b, 0x0b06, 0x101b, 0x201b, 0x001c, 0x0b07, 0x101c, 0x201c,
0x001d, 0x0b08, 0x101d, 0x201d, 0x001e, 0x0b09, 0x101e, 0x201e,
0x001f, 0x0b0a, 0x101f, 0x201f, 0x0020, 0x0b0b, 0x1020, 0x2020,
0x0021, 0x0c04, 0x1021, 0x2021, 0x0022, 0x0c05, 0x1022, 0x2022,
0x0023, 0x0c06, 0x1023, 0x2023, 0x0024, 0x0c07, 0x1024, 0x2024,
0x0025, 0x0c08, 0x1025, 0x2025, 0x0026, 0x0c09, 0x1026, 0x2026,
0x0027, 0x0c0a, 0x1027, 0x2027, 0x0028, 0x0c0b, 0x1028, 0x2028,
0x0029, 0x0d04, 0x1029, 0x2029, 0x002a, 0x0d05, 0x102a, 0x202a,
0x002b, 0x0d06, 0x102b, 0x202b, 0x002c, 0x0d07, 0x102c, 0x202c,
0x002d, 0x0d08, 0x102d, 0x202d, 0x002e, 0x0d09, 0x102e, 0x202e,
0x002f, 0x0d0a, 0x102f, 0x202f, 0x0030, 0x0d0b, 0x1030, 0x2030,
0x0031, 0x0e04, 0x1031, 0x2031, 0x0032, 0x0e05, 0x1032, 0x2032,
0x0033, 0x0e06, 0x1033, 0x2033, 0x0034, 0x0e07, 0x1034, 0x2034,
0x0035, 0x0e08, 0x1035, 0x2035, 0x0036, 0x0e09, 0x1036, 0x2036,
0x0037, 0x0e0a, 0x1037, 0x2037, 0x0038, 0x0e0b, 0x1038, 0x2038,
0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,
0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,
0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,
0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040
};
/**
* Reads the variable length integer encoded a the specified offset, and
* returns this length with the number of bytes read.
*/
static int[] readUncompressedLength(Object compressed, long compressedAddress, long compressedLimit)
{
int result;
int bytesRead = 0;
{
int b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
bytesRead++;
result = b & 0x7f;
if ((b & 0x80) != 0) {
b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
bytesRead++;
result |= (b & 0x7f) << 7;
if ((b & 0x80) != 0) {
b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
bytesRead++;
result |= (b & 0x7f) << 14;
if ((b & 0x80) != 0) {
b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
bytesRead++;
result |= (b & 0x7f) << 21;
if ((b & 0x80) != 0) {
b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
bytesRead++;
result |= (b & 0x7f) << 28;
if ((b & 0x80) != 0) {
throw new SnappyError(SnappyErrorCode.PARSING_ERROR, String.format("position: %d, error: %s", compressedAddress + bytesRead, "last byte of compressed length int has high bit set"));
}
}
}
}
}
}
return new int[] {result, bytesRead};
}
private static int getUnsignedByteSafe(Object base, long address, long limit)
{
if (address >= limit) {
throw new SnappyError(SnappyErrorCode.PARSING_ERROR, String.format("position: %d, error: %s", limit - address, "Input is truncated"));
}
return UNSAFE.getByte(base, address) & 0xFF;
}
}
⏎ org/xerial/snappy/pure/SnappyRawDecompressor.java
Or download all of them as a single archive file:
File name: snappy-java-1.1.8.4-sources.jar File size: 1962098 bytes Release date: 2021-01-25 Download
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