压缩示例代码libarchive,zlib

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文章目录

前言
一、zlib库
- - 在内存中对数据进行压缩，defalteInit函数默认压缩为zlib格式
  - 在内存中将数据压缩为gzip格式
二、libarchive库
- - 压缩为tar.gz文件
总结

前言

记录用C/C++实现数据压缩的代码

一、zlib库

home page: https://zlib.net/

manual: https://zlib.net/manual.html

use example: https://zlib.net/zlib_how.html

在内存中对数据进行压缩，defalteInit函数默认压缩为zlib格式

zpip.c

/* zpipe.c: example of proper use of zlib's inflate() and deflate()Not copyrighted -- provided to the public domainVersion 1.4  11 December 2005  Mark Adler *//* Version history:1.0  30 Oct 2004  First version1.1   8 Nov 2004  Add void casting for unused return valuesUse switch statement for inflate() return values1.2   9 Nov 2004  Add assertions to document zlib guarantees1.3   6 Apr 2005  Remove incorrect assertion in inf()1.4  11 Dec 2005  Add hack to avoid MSDOS end-of-line conversionsAvoid some compiler warnings for input and output buffers*/#include <stdio.h>
#include <string.h>
#include <assert.h>
#include "zlib.h"#if defined(MSDOS) || defined(OS2) || defined(WIN32) || defined(__CYGWIN__)
#  include <fcntl.h>
#  include <io.h>
#  define SET_BINARY_MODE(file) setmode(fileno(file), O_BINARY)
#else
#  define SET_BINARY_MODE(file)
#endif#define CHUNK 16384/* Compress from file source to file dest until EOF on source.def() returns Z_OK on success, Z_MEM_ERROR if memory could not beallocated for processing, Z_STREAM_ERROR if an invalid compressionlevel is supplied, Z_VERSION_ERROR if the version of zlib.h and theversion of the library linked do not match, or Z_ERRNO if there isan error reading or writing the files. */
int def(FILE *source, FILE *dest, int level)
{int ret, flush;unsigned have;z_stream strm;unsigned char in[CHUNK];unsigned 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 = in;/* run deflate() on input until output buffer not full, finishcompression if all of source has been read in */do {strm.avail_out = CHUNK;strm.next_out = 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 beallocated for processing, Z_DATA_ERROR if the deflate data isinvalid or incomplete, Z_VERSION_ERROR if the version of zlib.h andthe version of the library linked do not match, or Z_ERRNO if thereis an error reading or writing the files. */
int inf(FILE *source, FILE *dest)
{int ret;unsigned have;z_stream strm;unsigned char in[CHUNK];unsigned 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 = in;/* run inflate() on input until output buffer not full */do {strm.avail_out = CHUNK;strm.next_out = 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);}
}/* compress or decompress from stdin to stdout */
int main(int argc, char **argv)
{int ret;/* avoid end-of-line conversions */SET_BINARY_MODE(stdin);SET_BINARY_MODE(stdout);/* do compression if no arguments */if (argc == 1) {ret = def(stdin, stdout, Z_DEFAULT_COMPRESSION);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;}
}

在内存中将数据压缩为gzip格式

int def(unsigned char **in, uint32_t *len, int level)
{int ret, flush;z_stream strm;strm.zalloc = Z_NULL;strm.zfree = Z_NULL;strm.opaque = Z_NULL;// gzip格式ret = deflateInit2(&strm, level, Z_DEFLATED, 15 | 16, 8, Z_DEFAULT_STRATEGY);if (ret != Z_OK){return ret;}do{strm.avail_in = *len;flush = Z_FINISH;strm.next_in = *in;do{strm.avail_out = *len;strm.next_out = out;ret = deflate(&strm, flush);if (ret == Z_STREAM_ERROR){(void)deflateEnd(&strm);free(out);return Z_STREAM_ERROR;}} while (0);if (strm.avail_in != 0){free(out);(void)deflateEnd(&strm);return Z_STREAM_ERROR;}} while (0);if (ret != Z_STREAM_END){free(out);(void)deflateEnd(&strm);return Z_STREAM_ERROR;}*len = *len - strm.avail_out;*in = out;(void)deflateEnd(&strm);return Z_OK;
}

二、libarchive库

压缩为tar.gz文件

#include <stdio.h>
#include <archive.h>
#include <archive_entry.h>#define CHUNK 16384void write_archive(const char* outname, char** filename)
{struct archive *a;struct archive_entry *entry;struct stat st;char buf[BUFSIZ];int len;int fd;a = archive_write_new();archive_write_add_filter_gzip(a);archive_write_set_format_pax_restricted(a);archive_write_open_filename(a, outname);while (*filename){stat(*filename, &st);entry = archive_entry_new();archive_entry_set_pathname(entry, *filename);archive_entry_set_size(entry, st.st_size);archive_entry_set_filetype(entry, AE_IFREG);archive_entry_set_perm(entry, 0644);archive_write_header(a, entry);fd = open(*filename, O_RDONLY);len = read(fd, buf, BUFSIZ);while (len > 0){archive_write_data(a, buf, len);len = read(fd, buf, BUFSIZ);}close(fd);archive_entry_free(entry);filename++;}archive_write_close(a);archive_write_free(a);
}