目录

简述

有一个需求是这样的，写的一个程序内置了一个很大的文件（实际就是里面的epsg.io.json），这个文件筛选缩减后还有12MB，如果直接内置到程序中，编译后的程序就很大了。

因为这个程序是一个动态库，而使用upx压缩过的动态库有时候会有一些异常问题出现，所以不考虑使用upx进行压缩。

看到了quicklz后，感觉这是个好东西，于是就用这个来进行压缩，把压缩后的数据写入程序中，使用前进行解压即可。使用这个操作之后，程序大小从12MB缩小为不到1.5MB，效果很明显。

压缩和解压代码

关于quicklz的使用，在网站上有比较详细的说明，各个编程语言的接口也都有封装好。

更多的可以参考

压缩代码

压缩的代码很简单，因为我这里只做字符串的，所以压缩率还比较高，可以达到12%左右。

压缩的代码如下：

// 压缩字符串src，返回qlz编码格式的内容std::string quicklz_compress(const std::string& src){    qlz_state_compress state;    memset(&state, 0, sizeof(qlz_state_compress));    std::string dst;    char buffer[4096 + 1024];    for(size_t pos = 0;pos
    
      4096 ? 4096 : len;        len = qlz_compress(src.data() + pos, buffer, len, &state);        dst.append(buffer,len);    }    return dst;}
    

下面是quiz.c里面进行压缩的代码，可供参考

#include "quicklz.h"#define MAX_BUF_SIZE 1024*1024#define BUF_BUFFER 400#define bool int#define true 1#define false 0int stream_compress(FILE *ifile, FILE *ofile){    char *file_data, *compressed;    size_t d, c, fd_size, compressed_size;    qlz_state_compress *state_compress = (qlz_state_compress *)malloc(sizeof(qlz_state_compress));    fd_size = MAX_BUF_SIZE;    file_data = (char*) malloc(fd_size);    // allocate MAX_BUF_SIZE + BUF_BUFFER bytes for the destination buffer    compressed_size = MAX_BUF_SIZE + BUF_BUFFER;    compressed = (char*) malloc(compressed_size);    // allocate and initially zero out the states. After this, make sure it is    // preserved across calls and never modified manually    memset(state_compress, 0, sizeof(qlz_state_compress));    // compress the file using MAX_BUF_SIZE packets.    while((d = fread(file_data, 1, MAX_BUF_SIZE, ifile)) != 0)    {        c = qlz_compress(file_data, compressed, d, state_compress);        // the buffer "compressed" now contains c bytes which we could have sent directly to a        // decompressing site for decompression        fwrite(compressed, c, 1, ofile);    }    free(state_compress);    free(compressed);    free(file_data);    return 0;}

解压代码

解压的速度很快，对程序运行几乎没有影响，比读取文件快多了。

解压代码如下：

std::string quicklz_decompress(const std::string& qlzdata){    qlz_state_decompress state;    memset(&state, 0, sizeof(qlz_state_decompress));    std::string dst;    for(size_t pos = 0;ops < qlzdata.size(); ){        // 获取压缩数据段大小        size_t co_size = qlz_size_compressed(qlzdata.data() + pos);        // 获取该压缩段解压后的大小        size_t de_size = qlz_size_decompressed(qlzdata.data() + pos);        std::string buffer(de_size,0);        qlz_decompress(qlzdata.data()+pos, (char*)buffer.data(),&state);        pos += co_size;        dst.append(buffer);    }    return dst;}

下面是quiz.c里面进行解压的代码，可供参考

int stream_decompress(FILE *ifile, FILE *ofile){    char *file_data, *decompressed;    size_t d, c, dc, fd_size, d_size;    qlz_state_decompress *state_decompress = (qlz_state_decompress *)malloc(sizeof(qlz_state_decompress));    // a compressed packet can be at most MAX_BUF_SIZE + BUF_BUFFER bytes if it    // was compressed with this program.    fd_size = MAX_BUF_SIZE + BUF_BUFFER;    file_data = (char*) malloc(fd_size);    // allocate decompression buffer    d_size = fd_size - BUF_BUFFER;    decompressed = (char*) malloc(d_size);    // allocate and initially zero out the scratch buffer. After this, make sure it is    // preserved across calls and never modified manually    memset(state_decompress, 0, sizeof(qlz_state_decompress));    // read 9-byte header to find the size of the entire compressed packet, and    // then read remaining packet    while((c = fread(file_data, 1, 9, ifile)) != 0)    {        // Do we need a bigger decompressed buffer? If the file was compressed        // with segments larger than the default in this program.        dc = qlz_size_decompressed(file_data);        if (dc > (fd_size - BUF_BUFFER)) {            free(file_data);            fd_size = dc + BUF_BUFFER;            file_data = (char*)malloc(fd_size);        }        // Do we need a bigger compressed buffer?        c = qlz_size_compressed(file_data);        if (c > d_size) {            free (decompressed);            d_size = c;            decompressed = (char*)malloc(d_size);        }        fread(file_data + 9, 1, c - 9, ifile);        d = qlz_decompress(file_data, decompressed, state_decompress);        fwrite(decompressed, d, 1, ofile);    }    free(decompressed);    free(state_decompress);    free(file_data);    return 0;}

将二进制文件生成C数组程序代码

上面的代码用于压缩和解压qlz数据，但是这些数据还需要生成C风格的数组，于是就写了一个小程序来做转换，代码如下：

#include 
    
     #include 
     
      #include 
      
       int main(int c,char** v){    if(c != 3){        printf("Usage:%s infile outfile\n",v[0]);        return 0;    }    FILE* fin = fopen(v[1],"rb");    if(!fin){        printf("Error:%s Open Failed\n",v[1]);        return 1;    }    FILE* fout = fopen(v[2],"wb");    if(fout){        size_t len = 0;        unsigned char buffer[16];        char strbuffer[1024] = "const unsigned char carr_xxx[] = {";                fwrite(strbuffer,1,strlen(strbuffer),fout);        while((len = fread(buffer,1 ,sizeof buffer,fin)) != 0){            strbuffer[0] = '\n';            strbuffer[1] = '\t';            for(size_t i = 0, offset = 2; i < len; ++i) {                offset += sprintf(&strbuffer[offset],"%hhu,",buffer[i]);            }            fwrite(strbuffer,1,strlen(strbuffer),fout);        }        if(strbuffer[0] != 'c'){            fseek(fout,-1, SEEK_CUR);        }        strcpy(strbuffer,"\n};\n");        fwrite(strbuffer,1,strlen(strbuffer),fout);        fclose(fout);    }    fclose(fin);    return 0;}