zlib-解压缩数据

为什么80%的码农都做不了架构师？>>>   

压缩数据

• 压缩

<pre><code> 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); // 要处理的数量 if (ferror(source)) { (void)deflateEnd(&strm); return Z_ERRNO; } flush = feof(source) ? Z_FINISH : Z_NO_FLUSH; // strm.next_in = in; // 要处理缓冲区的地址 /* run deflate() on input until output buffer not full, finish compression if all of source has been read in */ do { strm.avail_out = CHUNK; // 存放处理后的数据的剩余空间 strm.next_out = out; // 处理完存放的缓冲区地址 ret = deflate(&strm, flush); /* no bad return value */ assert(ret != Z_STREAM_ERROR); /* state not clobbered */ have = CHUNK - strm.avail_out; // 处理后数据的大小-这里是压缩后数据的大小（总大小-剩余空间） if (fwrite(out, 1, have, dest) != have || ferror(dest)) { (void)deflateEnd(&strm); return Z_ERRNO; } } while (strm.avail_out == 0); // 如果剩余空间为0 说明压缩完的数据还没有完全取得，所以，重新给buff和avail——out，继续取 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; </code></pre>

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解压数据

• 解压数据

<pre><code> 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 */ //<b> 错误处理很重要 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; } </b> 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); // 解压缩，数据往往会膨胀，相同大小的压缩数据往往需要多次inflate才能得到完整原始数据 /* 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; } </code></pre>

转载于:https://my.oschina.net/lyr/blog/90789