C/C++ 用zlib解压gzip文件

见示例：

其中调用inflate()后，zlib会保存解压进程，avail_in,next_in会更新，保存解压进程的断点。avail_out == 0说明这次输出内存用完，数据可能还没解压完，需要继续调用inflate(), 会从上次的位置继续解压。

#include <stdio.h>
/* For "exit". */
#include <stdlib.h>
/* For "strerror". */
#include <string.h>
/* For "errno". */
#include <errno.h>
#include <zlib.h>/* CHUNK is the size of the memory chunk used by the zlib routines. */#define CHUNK 0x4000/* The following macro calls a zlib routine and checks the returnvalue. If the return value ("status") is not OK, it prints an errormessage and exits the program. Zlib's error statuses are all lessthan zero. */#define CALL_ZLIB( x )                                                                             \{                                                                                              \int status;                                                                                \status = x;                                                                                \if( status < 0 )                                                                           \{                                                                                          \fprintf( stderr,                                                                       \"%s:%d: %s returned a bad status of %d.\n",                                   \__FILE__,                                                                     \__LINE__,                                                                     \#x,                                                                           \status );                                                                     \exit( EXIT_FAILURE );                                                                  \}                                                                                          \}/* if "test" is true, print an error message and halt execution. */#define FAIL( test, message )                                                                      \{                                                                                              \if( test )                                                                                 \{                                                                                          \inflateEnd( &strm );                                                                   \fprintf( stderr,                                                                       \"%s:%d: " message " file '%s' failed: %s\n",                                  \__FILE__,                                                                     \__LINE__,                                                                     \file_name,                                                                    \strerror( errno ) );                                                          \exit( EXIT_FAILURE );                                                                  \}                                                                                          \}/* These are parameters to inflateInit2. Seehttp://zlib.net/manual.html for the exact meanings. */#define windowBits 15
#define ENABLE_ZLIB_GZIP 32int main()
{const char*   file_name = "test.gz";FILE*         file;z_stream      strm = {0};unsigned char in[CHUNK];unsigned char out[CHUNK];strm.zalloc = Z_NULL;strm.zfree = Z_NULL;strm.opaque = Z_NULL;strm.next_in = in;strm.avail_in = 0;CALL_ZLIB( inflateInit2( &strm, windowBits | ENABLE_ZLIB_GZIP ) );/* Open the file. */file = fopen( file_name, "rb" );FAIL( !file, "open" );while( 1 ){int bytes_read;int zlib_status;bytes_read = fread( in, sizeof( char ), sizeof( in ), file );FAIL( ferror( file ), "read" );strm.avail_in = bytes_read;strm.next_in = in;do{unsigned have;strm.avail_out = CHUNK;strm.next_out = out;zlib_status = inflate( &strm, Z_NO_FLUSH );switch( zlib_status ){case Z_OK:case Z_STREAM_END:case Z_BUF_ERROR:break;default:inflateEnd( &strm );fprintf( stderr, "Gzip error %d in '%s'.\n", zlib_status, file_name );return -1;}have = CHUNK - strm.avail_out;fwrite( out, sizeof( unsigned char ), have, stdout );} while( strm.avail_out == 0 );if( feof( file ) ){inflateEnd( &strm );break;}}FAIL( fclose( file ), "close" );return 0;
}

Ref:

https://www.lemoda.net/c/zlib-open-read/

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

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