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simple LZMA SDK compression/decompression example
// note: -D_7ZIP_ST is required when compiling on non-Windows platforms
// g++ -o lzma_sample -std=c++14 -D_7ZIP_ST lzma_sample.cpp LzmaDec.c LzmaEnc.c LzFind.c
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <memory>
#include "LzmaEnc.h"
#include "LzmaDec.h"
static void *_lzmaAlloc(ISzAllocPtr, size_t size) {
return new uint8_t[size];
}
static void _lzmaFree(ISzAllocPtr, void *addr) {
if (!addr)
return;
delete[] reinterpret_cast<uint8_t *>(addr);
}
static ISzAlloc _allocFuncs = {
_lzmaAlloc, _lzmaFree
};
std::unique_ptr<uint8_t[]> lzmaCompress(const uint8_t *input, uint32_t inputSize, uint32_t *outputSize) {
std::unique_ptr<uint8_t[]> result;
// set up properties
CLzmaEncProps props;
LzmaEncProps_Init(&props);
if (inputSize >= (1 << 20))
props.dictSize = 1 << 20; // 1mb dictionary
else
props.dictSize = inputSize; // smaller dictionary = faster!
props.fb = 40;
// prepare space for the encoded properties
SizeT propsSize = 5;
uint8_t propsEncoded[5];
// allocate some space for the compression output
// this is way more than necessary in most cases...
// but better safe than sorry
// (a smarter implementation would use a growing buffer,
// but this requires a bunch of fuckery that is out of
/// scope for this simple example)
SizeT outputSize64 = inputSize * 1.5;
if (outputSize64 < 1024)
outputSize64 = 1024;
auto output = std::make_unique<uint8_t[]>(outputSize64);
int lzmaStatus = LzmaEncode(
output.get(), &outputSize64, input, inputSize,
&props, propsEncoded, &propsSize, 0,
NULL,
&_allocFuncs, &_allocFuncs);
*outputSize = outputSize64 + 13;
if (lzmaStatus == SZ_OK) {
// tricky: we have to generate the LZMA header
// 5 bytes properties + 8 byte uncompressed size
result = std::make_unique<uint8_t[]>(outputSize64 + 13);
uint8_t *resultData = result.get();
memcpy(resultData, propsEncoded, 5);
for (int i = 0; i < 8; i++)
resultData[5 + i] = (inputSize >> (i * 8)) & 0xFF;
memcpy(resultData + 13, output.get(), outputSize64);
}
return result;
}
std::unique_ptr<uint8_t[]> lzmaDecompress(const uint8_t *input, uint32_t inputSize, uint32_t *outputSize) {
if (inputSize < 13)
return NULL; // invalid header!
// extract the size from the header
UInt64 size = 0;
for (int i = 0; i < 8; i++)
size |= (input[5 + i] << (i * 8));
if (size <= (256 * 1024 * 1024)) {
auto blob = std::make_unique<uint8_t[]>(size);
ELzmaStatus lzmaStatus;
SizeT procOutSize = size, procInSize = inputSize - 13;
int status = LzmaDecode(blob.get(), &procOutSize, &input[13], &procInSize, input, 5, LZMA_FINISH_END, &lzmaStatus, &_allocFuncs);
if (status == SZ_OK && procOutSize == size) {
*outputSize = size;
return blob;
}
}
return NULL;
}
void hexdump(const uint8_t *buf, int size) {
int lines = (size + 15) / 16;
for (int i = 0; i < lines; i++) {
printf("%08x | ", i * 16);
int lineMin = i * 16;
int lineMax = lineMin + 16;
int lineCappedMax = (lineMax > size) ? size : lineMax;
for (int j = lineMin; j < lineCappedMax; j++)
printf("%02x ", buf[j]);
for (int j = lineCappedMax; j < lineMax; j++)
printf(" ");
printf("| ");
for (int j = lineMin; j < lineCappedMax; j++) {
if (buf[j] >= 32 && buf[j] <= 127)
printf("%c", buf[j]);
else
printf(".");
}
printf("\n");
}
}
void testIt(const uint8_t *input, int size) {
printf("Test Input:\n");
hexdump(input, size);
uint32_t compressedSize;
auto compressedBlob = lzmaCompress(input, size, &compressedSize);
if (compressedBlob) {
printf("Compressed:\n");
hexdump(compressedBlob.get(), compressedSize);
} else {
printf("Nope, we screwed it\n");
return;
}
// let's try decompressing it now
uint32_t decompressedSize;
auto decompressedBlob = lzmaDecompress(compressedBlob.get(), compressedSize, &decompressedSize);
if (decompressedBlob) {
printf("Decompressed:\n");
hexdump(decompressedBlob.get(), decompressedSize);
} else {
printf("Nope, we screwed it (part 2)\n");
return;
}
printf("----------\n");
}
void testIt(const char *string) {
testIt((const uint8_t *)string, strlen(string));
}
int main(int argc, char **argv) {
testIt("a");
testIt("here is a cool string");
testIt("here's something that should compress pretty well: abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef");
return 0;
}
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