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C語(yǔ)言實(shí)現(xiàn)短字符串壓縮的三種方法詳解

更新時(shí)間：2022年08月10日 16:33:21 作者：T-BARBARIANS

這篇文章主要和大家分享一下smaz，shoco，unisox2三種短字符串壓縮算法，并分別探索它們各自的壓縮率與壓縮和解壓縮性能，需要的可以參考一下

前言

上一篇探索了LZ4的壓縮和解壓性能，以及對(duì)LZ4和ZSTD的壓縮、解壓性能進(jìn)行了橫向?qū)Ρ取Ｎ哪┑淖詈笠步o了一個(gè)彩蛋：任意長(zhǎng)度的字符串都可以被ZSTD、LZ4之類(lèi)的壓縮算壓縮得很好嗎？

本篇我們就來(lái)一探究竟。

一、通用算法的短字符壓縮

開(kāi)門(mén)見(jiàn)山，我們使用一段比較短的文本：Narrator: It is raining today. So, Peppa and George cannot play outside.Peppa: Daddy, it's stopped raining.

使用ZSTD與LZ4分別壓縮一下上面這段短文本。下面分別是它們的壓縮結(jié)果。

ZSTD：

LZ4：

對(duì)短文本的壓縮，zstd的壓縮率很低，lz4壓縮后的文本長(zhǎng)度盡然超過(guò)了原有字符串的長(zhǎng)度。這是為什么？說(shuō)實(shí)話(huà)在這之前我也沒(méi)想到。

引用兩位大佬的名言：

Are you ok?

What's your problem?

二、短字符串壓縮

從上面的結(jié)果可以得知，任何壓縮算法都有它的使用場(chǎng)景，并不是所有長(zhǎng)度的字符串都適合被某種算法壓縮。一般原因是通用壓縮算法維護(hù)了被壓縮字符串的，用于字符串還原的相關(guān)數(shù)據(jù)結(jié)構(gòu)，而這些數(shù)據(jù)結(jié)構(gòu)的長(zhǎng)度超過(guò)了被壓縮短字符串的自身長(zhǎng)度。

那么問(wèn)題來(lái)了，“我真的有壓縮短字符串的需求，我想體驗(yàn)壓縮的極致感，怎么辦？”。

短字符壓縮算法它來(lái)了。這里挑選了3種比較優(yōu)異的短字符壓縮算法，分別是smaz，shoco，以及壓軸的unisox2。跟前兩章一樣，還是從壓縮率，壓縮和解壓縮性能的角度，一起看看他們?cè)诙套址麎嚎s場(chǎng)景的各自表現(xiàn)吧。

（1）Smaz

1、Smaz的壓縮和解壓縮

#include <stdio.h>
#include <string.h>
#include <iostream>
#include "smaz.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 = smaz_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 = smaz_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;
}

執(zhí)行結(jié)果如下：

通過(guò)smaz壓縮后的短字符串長(zhǎng)度為77，和源字符串相比，減少了30Byte。

2、Smaz的壓縮和解壓縮性能

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <sys/time.h>
#include "smaz.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 = 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;
}

結(jié)果如何？

壓縮性能在40w條/S，解壓在百萬(wàn)級(jí)，好像還不錯(cuò)哈！

（2）Shoco

1、Shoco的壓縮和解壓縮

#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;
}

執(zhí)行結(jié)果如下：

通過(guò)shoco壓縮后的短字符串長(zhǎng)度為86，和源字符串相比，減少了21Byte。壓縮率比smaz要低。

2、Shoco的壓縮和解壓縮性能

#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;
}

執(zhí)行結(jié)果如何呢？

holy shit！壓縮和解壓縮居然都達(dá)到了驚人的百萬(wàn)級(jí)。就像算法作者們自己說(shuō)的一樣：“在長(zhǎng)字符串壓縮領(lǐng)域，shoco不想與通用壓縮算法競(jìng)爭(zhēng)，我們的優(yōu)勢(shì)是短字符的快速壓縮，雖然壓縮率很爛！”。這樣說(shuō)，好像也沒(méi)毛病。

（3）Unisox2

我們?cè)賮?lái)看看unisox2呢。

1、Unisox2的壓縮和解壓縮

#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;
}

結(jié)果如下：

通過(guò)Unisox2壓縮后的短字符串長(zhǎng)度為67，和源字符串相比，減少了40Byte，相當(dāng)于是打了6折?。〔诲e(cuò)不錯(cuò)。

2、Unisox2的壓縮和解壓縮性能

Unisox2的壓縮能力目前來(lái)看是三者中最好的，如果他的壓縮和解壓性能也不錯(cuò)的話(huà)，那就真的就比較完美了。再一起看看Unisox2的壓縮和解壓性能吧！

#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;
}

執(zhí)行結(jié)果如下：