c语言zlib压缩解压示例

在C语言中使用zlib库进行文件的压缩和解压，zlib是一个流行的开源数据压缩库，它提供了一系列强大的压缩算法。以下是一个简单的压缩和解压示例：

**压缩示例**:

#include <stdio.h>
#include <zlib.h>

void compress_file(const char *input_filename, const char *output_filename) {
    FILE *in = fopen(input_filename, "rb");
    if (!in) {
        perror("Failed to open input file");
        return;
    }

    FILE *out = fopen(output_filename, "wb");
    if (!out) {
        perror("Failed to create output file");
        fclose(in);
        return;
    }

    uLongf ret;
    z_stream strm;
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -15, 8, Z_DEFAULT_STRATEGY);

    if (ret != Z_OK) {
        perror("Deflate initialization failed");
        fclose(out);
        fclose(in);
        return;
    }

    size_t bytes_read;
    unsigned char buffer[4096];
    while ((bytes_read = fread(buffer, 1, sizeof(buffer), in)) > 0) {
        strm.next_in = buffer;
        strm.avail_in = bytes_read;
        strm.total_out = 0;

        ret = deflate(&strm, Z_FINISH); // 或者 Z_NO_FLUSH for streaming
        if (ret == Z_STREAM_END) break; // 如果已经压缩完成

        if (ret != Z_OK) {
            perror("Deflating data failed");
            deflateEnd(&strm);
            fclose(out);
            fclose(in);
            return;
        }
        
        size_t bytes_written = strm.total_out;
        fwrite(strm.output_buffer, 1, bytes_written, out);
    }

    deflateEnd(&strm);
    fclose(in);
    fclose(out);
}