QuickLZ －－ 一个号称世界压缩速度最快的压缩库
QuickLZ 是一个号称世界压缩速度最快的压缩库，并且也是个开源的压缩库，其遵守 GPL 1, 2 或 3协议。
在QuickLZ的官网上有个关于QuickLZ的测试：
| Library | Level | Compressed size | Compression Mbyte/s | Decompression Mbyte/s |
| QuickLZ C 1.5.0 | 1 | 47.9% | 308 | 358 |
| QuickLZ C 1.4.0 | 1 | 47.9% | 272 | 332 |
| QuickLZ C 1.4.0 | 2 | 42.3% | 131 | 309 |
| QuickLZ C 1.4.0 | 3 | 40.0% | 31 | 516 |
| QuickLZ C# 1.4.0 | 1 | 47.9% | 133 | 132 |
| QuickLZ Java 1.4.0 | 1 | 47.9% | 127 | 95 |
| LZF 3.1 | UF | 54.9% | 204 | 396 |
| LZF 3.1 | VF | 51.9% | 193 | 384 |
| FastLZ 0.1.0 | 1 | 53.0% | 173 | 442 |
| FastLZ 0.1.0 | 2 | 50.7% | 167 | 406 |
| LZO 1X 2.02 | 1 | 48.3% | 169 | 434 |
| zlib 1.22 | 1 | 37.6% | 55 | 234 |
在这里，我也对QuickLZ和zlib进行一个对比的测试，看看是不是真的那么快那么好。
QuickLZ有个前端程序叫qpress，可以在QuickLZ的官网上下载下来进行测试。而zlib没有前端程序，所以要自己写一个。
zlib 的测试程序可以根据zlib 的源码中的一个例子进行改写，如下：
#include <zlib.h> #include <stdio.h> #include <string.h> #include <assert.h> #include <zconf.h> #define CHUNK 16384 int def(FILE *source, FILE *dest, int level) { int ret, flush; unsigned have; z_stream strm; char in[CHUNK]; char out[CHUNK]; /* allocate deflate state */ strm.zalloc = Z_NULL; strm.zfree = Z_NULL; strm.opaque = Z_NULL; ret = deflateInit(&strm, level); if (ret != Z_OK) return ret; /* compress until end of file */ do { strm.avail_in = fread(in, 1, CHUNK, source); if (ferror(source)) { (void)deflateEnd(&strm); return Z_ERRNO; } flush = feof(source) ? Z_FINISH : Z_NO_FLUSH; strm.next_in = (Bytef*)in; /* run deflate() on input until output buffer not full, finish compression if all of source has been read in */ do { strm.avail_out = CHUNK; strm.next_out = (Bytef*)out; ret = deflate(&strm, flush); /* no bad return value */ assert(ret != Z_STREAM_ERROR); /* state not clobbered */ have = CHUNK - strm.avail_out; if (fwrite(out, 1, have, dest) != have || ferror(dest)) { (void)deflateEnd(&strm); return Z_ERRNO; } } while (strm.avail_out == 0); assert(strm.avail_in == 0); /* all input will be used */ /* done when last data in file processed */ } while (flush != Z_FINISH); assert(ret == Z_STREAM_END); /* stream will be complete */ /* clean up and return */ (void)deflateEnd(&strm); return Z_OK; } /* Decompress from file source to file dest until stream ends or EOF. inf() returns Z_OK on success, Z_MEM_ERROR if memory could not be allocated for processing, Z_DATA_ERROR if the deflate data is invalid or incomplete, Z_VERSION_ERROR if the version of zlib.h and the version of the library linked do not match, or Z_ERRNO if there is an error reading or writing the files. */ int inf(FILE *source, FILE *dest) { int ret; unsigned have; z_stream strm; char in[CHUNK]; char out[CHUNK]; /* allocate inflate state */ strm.zalloc = Z_NULL; strm.zfree = Z_NULL; strm.opaque = Z_NULL; strm.avail_in = 0; strm.next_in = Z_NULL; ret = inflateInit(&strm); if (ret != Z_OK) return ret; /* decompress until deflate stream ends or end of file */ do { strm.avail_in = fread(in, 1, CHUNK, source); if (ferror(source)) { (void)inflateEnd(&strm); return Z_ERRNO; } if (strm.avail_in == 0) break; strm.next_in = (Bytef*)in; /* run inflate() on input until output buffer not full */ do { strm.avail_out = CHUNK; strm.next_out = (Bytef*)out; ret = inflate(&strm, Z_NO_FLUSH); assert(ret != Z_STREAM_ERROR); /* state not clobbered */ switch (ret) { case Z_NEED_DICT: ret = Z_DATA_ERROR; /* and fall through */ case Z_DATA_ERROR: case Z_MEM_ERROR: (void)inflateEnd(&strm); return ret; } have = CHUNK - strm.avail_out; if (fwrite(out, 1, have, dest) != have || ferror(dest)) { (void)inflateEnd(&strm); return Z_ERRNO; } } while (strm.avail_out == 0); /* done when inflate() says it's done */ } while (ret != Z_STREAM_END); /* clean up and return */ (void)inflateEnd(&strm); return ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR; } /* report a zlib or i/o error */ void zerr(int ret) { fputs("zpipe: ", stderr); switch (ret) { case Z_ERRNO: if (ferror(stdin)) fputs("error reading stdin/n", stderr); if (ferror(stdout)) fputs("error writing stdout/n", stderr); break; case Z_STREAM_ERROR: fputs("invalid compression level/n", stderr); break; case Z_DATA_ERROR: fputs("invalid or incomplete deflate data/n", stderr); break; case Z_MEM_ERROR: fputs("out of memory/n", stderr); break; case Z_VERSION_ERROR: fputs("zlib version mismatch!/n", stderr); } } int main(int argc, char **argv) { int ret; /* do compression if no arguments */ if (argc == 1) { //ret = def(stdin, stdout, Z_DEFAULT_COMPRESSION); ret = def(stdin, stdout, Z_BEST_SPEED); if (ret != Z_OK) zerr(ret); return ret; } /* do decompression if -d specified */ else if (argc == 2 && strcmp(argv[1], "-d") == 0) { ret = inf(stdin, stdout); if (ret != Z_OK) zerr(ret); return ret; } /* otherwise, report usage */ else { fputs("zpipe usage: zpipe [-d] < source > dest/n", stderr); return 1; } }
在测试zilib是采用了两个压缩方式，一个是最快的压缩（Z_BEST_SPEED）和一个是默认的压缩（Z_DEFAULT_COMPRESSION），在main函数中可以看到。
下面是我在linux下的ntfs分区中，对一个1G的有着fat32文件系统的文件（这个1G的文件是我在windows下用winhex对一个1G的fat32的分区进行拷贝得到的文件）进行压缩后的测试的结果：
QuickLZ采用了稳定的1.4.1版，zlib采用了稳定的1.2.3版。
quickLZ (最低压缩 zlib(默认压缩 zlib (最低压缩率)
率)version 1.4.1 率)version 1.2.3
time Compressed real 2m5.507s real 1m23.828s
1,075,838,976 bytes user 1m44.079s user 1m2.476s
in 1 file(s) into sys 0m3.164s sys 0m2.948s
598,244,013 bytes
real 0m29.478s
user 0m10.209s
sys 0m2.484s
压缩后大小 598244013(571M ) 484103258(462M ) 510911735(488M )
在上面的测试中，我们可以看到，quickLZ的压缩率要比zlib 的低，但压缩率还是可以的，而压缩的速度确实比zlib 的快了很多。quickLZ在最低压缩率的情况下压缩1G的文件，用了29.478秒，压缩到571M，而zlib在默认的压缩率下使用了2分5.507秒，压缩到462M，在zlib在最低压缩率下，也使用了1分23.828秒，压缩到488M。
看来QuickLZ的压缩速度确实并非浪得虚名。
QuickLZ的官网：http://www.quicklz.com/
zlib的官网： http://www.zlib.net/