C语言实现短字符串压缩的三种方法详解-C/C++开发

目录前言一、通用算法的短字符压缩二、短字符串压缩（1）Smaz（2）Shoco（3）Unisox2三、总结前言上一篇探索了LZ4的压缩和解压性能，以及对LZ4和ZSTD的压缩、解压性能进行了横向对比。...

前言

上一篇探索了LZ4的压缩和解压性能，以及对LZ4和ZSTD的压缩、解压性能进行了横向对比。文末的最后也给了一个彩蛋：任意长度的字符串都可以被ZSTD、LZ4之类的压缩算压缩得很好吗？

本篇我们就来一探究竟。

一、通用算法的短字符压缩

开门见山，我们使用一段比较短的文本：

使用ZSTD与LZ4分别压缩一下上面这段短文本。下面分别是它们的压缩结果。

t cnt = 0; int buf_len; int com_size; int decom_size; timeval st, et; char *com_ptr = NULL; char* decom_ptr = NULL; char str_buf[1024] = "Narrator: It is raining today. So, Peppa and George cannot play outside.Peppa: Daddy, it's stopped raining."; buf_len = strlen(str_buf); gettimeofday(&st, NULL); while(1) { com_ptr = (char *)malloc(buf_len); com_size = smaz_compress(str_buf, buf_len, com_ptr, buf_len); free(com_ptr); cnt++; gettimeofday(&et, NULL); if(et.tv_sec - st.tv_sec >= 10) { break; } } cout << endl <<"compress per second:" << cnt/10 << " times" << endl; cnt = 0; com_ptr = (char *)malloc(buf_len); com_size = smaz_compress(str_buf, buf_len, com_ptr, buf_len); gettimeofday(&st, NULL); while(1) { // decompress length not more than origin buf length decom_ptr = (char *)malloc(buf_len + 1); decom_size = smaz_decompress(com_ptr, com_size, decom_ptr, buf_len + 1); // check decompress length if(buf_len != decom_size) { cout << "decom error" << endl; } free(decom_ptr); cnt++; gettimeofday(&et, NULL); if(et.tv_sec - st.tv_sec >= 10) { break; } } cout << "decompress per second:" << cnt/10 << " times" << endl << endl; free(com_ptr); return 0; }

结果如何？

压缩性能在40w条/S，解压在百万级，好像还不错哈！

（2）Shoco

#include <stdio.h>
#include <string.h>
#include <iostream>
#include "shoco.h"

using namespace std;

int main()
{
    int buf_len;
    int com_size;
    int decom_size;

    char com_buf[4096] = {0};
    char decom_buf[4096] = {0};

    char str_buf[1024] = "Narrator: It is raining today. So, Peppa and George cannot play outside.Peppa: Daddy, it's stopped raining.";

    buf_len = strlen(str_buf);
    com_size = shoco_compress(str_buf, buf_len, com_buf, 4096);

    cout << "text size:" << buf_len << endl;
    cout << "compress text size:" << com_size << endl;
    cout << "compress ratio:" << (float)buf_len / (float)com_size << endl << endl;

    decom_size = shoco_decompress(com_buf, com_size, decom_buf, 4096);
    cout << "decompress text size:" << decom_size << endl;

    if(strncmp(str_buf, decom_buf, buf_len)) {
        cout << "decompress text is not equal to source text" << endl;
    }

    return 0;
}

执行结果如下：

通过shoco压缩后的短字符串长度为86，和源字符串相比，减少了21Byte。压缩率比smaz要低。

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <sys/time.h>
#include "shoco.h"

using namespace std;

int main()
{
    int cnt = 0;
    int buf_len;
    int com_size;
    int decom_size;

    timeval st, et;

    char *com_ptr = NULL;
    char* decom_ptr = NULL;

    char str_buf[1024] = "Narrator: It is raining today. So, Peppa and George cannot play outside.Peppa: Daddy, it's stopped raining.";

    buf_len = strlen(str_buf);
    gettimeofday(&st, NULL);
    while(1) {

        com_ptr = (char *)malloc(buf_len);
        com_size = shoco_compress(str_buf, buf_len, com_ptr, buf_len);

        free(com_ptr);
        cnt++;

        gettimeofday(&et, NULL);
        if(et.tv_sec - st.tv_sec >= 10) {
            break;
        }
    }

    cout << endl <<"compress per second:" << cnt/10 << " times" << endl;

    cnt = 0;
    com_ptr = (char *)malloc(buf_len);
    com_size = shoco_compress(str_buf, buf_len, com_ptr, buf_len);

    gettimeofday(&st, NULL);
    while(1) {

        // decompress length not more than origin buf length
        decom_ptr = (char *)malloc(buf_len + 1);
        decom_size = shoco_decompress(com_ptr, com_size, decom_ptr, buf_len + 1);

        // check decompress length
        if(buf_len != decom_size) {
            cout << "decom error" << endl;
        }

        free(decom_ptr);
        cnt++;

        gettimeofday(&et, NULL);
        if(et.tv_sec - st.tv_sec >= 10) {
            break;
        }
    }

    cout << "decompress per second:" << cnt/10 << " times" << endl << endl;

    free(com_ptr);
    return 0;
}

执行结果如何呢？

holy shit！压缩和解压缩居然都达到了惊人的百万级。就像算法作者们自己说的一样：“在长字符串压缩领域，shoco不想与通用压缩算法竞争，我们的优势是短字符的快速压缩，虽然压缩率很烂！”。这样说，好像也没毛病。

（3）Unisox2

我们再来看看unisox2呢。

#include <stdio.h>
#include <string.h>
#include "unishox2.h"

int main()
{
    int buf_len;
    int com_size;
    int decom_size;

    char com_buf[4096] = {0};
    char decom_buf[4096] = {0};

    char str_buf[1024] = "Narrator: It is raining today. So, Peppa and George cannot play outside.Peppa: Daddy, it's stopped raining.";

    buf_len = strlen(str_buf);
    com_size = unishox2_compress_simple(str_buf, buf_len, com_buf);

    printf("text size:%d\n", buf_len);
    printf("compress text size:%d\n", com_size);
    printf("compress ratio:%f\n\n", (float)buf_len / (float)com_size);

    decom_size = unishox2_decompress_simple(com_buf, com_size, decom_buf);

    printf("decompress text size:%d\n", decom_size);

    if(strncmp(str_buf, decom_buf, buf_len)) {
        printf("decompress text is not equal to source text\n");
    }

    return 0;
}

结果如下：

通过Unisox2压缩后的短字符串长度为67，和源字符串相比，减少了40Byte，相当于是打了6折啊！不错不错。

的压缩和解压缩性能

Unisox2的压缩能力目前来看是三者中最好的，如果他的压缩和解压性能也不错的话，那就真的就比较完美了。再一起看看Unisox2的压缩和解压性能吧！

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <sys/time.h>
#include "unishox2.h"

int main()
{
    int cnt = 0;
    int buf_len;
    int com_size;
    int decom_size;

    struct timeval st, et;

    char *com_ptr = NULL;
    char* decom_ptr = NULL;

    char str_buf[1024] = "Narrator: It is raining today. So, Peppa and George cannot play outside.Peppa: Daddy, it's stopped raining.";

    buf_len = strlen(str_buf);
    gettimeofday(&st, NULL);
    while(1) {

        com_ptr = (char *)malloc(buf_len);
        com_size = unishox2_compress_simple(str_buf, buf_len, com_ptr);

        free(com_ptr);
        cnt++;

        gettimeofday(&et, NULL);
        if(et.tv_sec - st.tv_sec >= 10) {
            break;
        }
    }

    printf("\ncompress per second:%d times\n", cnt/10);

    cnt = 0;
    com_ptr = (char *)malloc(buf_len);
    com_size = unishox2_compress_simple(str_buf, buf_len, com_ptr);

    gettimeofday(&st, NULL);
    while(1) {

        // decompress length not more than origin buf length
        decom_ptr = (char *)malloc(buf_len + 1);
        decom_size = unishox2_decompress_simple(com_ptr, com_size, decom_ptr);

        // check decompress length
        if(buf_len != decom_size) {
            printf("decom error\n");
        }

        free(decom_ptr);
        cnt++;

        gettimeofday(&et, NULL);
        if(et.tv_sec - st.tv_sec >= 10) {
            break;
        }
    }

    printf("decompress per second:%d times\n\n", cnt/10);

    free(com_ptr);
    return 0;
}

执行结果如下：