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這篇文章主要講解了“C語言如何實現短字符串壓縮”，文中的講解內容簡單清晰，易于學習與理解，下面請大家跟著小編的思路慢慢深入，一起來研究和學習“C語言如何實現短字符串壓縮”吧！
開門見山，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果。
ZSTD：
LZ4：
對短文本的壓縮，zstd的壓縮率很低，lz4壓縮后的文本長度盡然超過了原有字符串的長度。這是為什么？說實話在這之前我也沒想到。
引用兩位大佬的名言：
Are you ok?
What's your problem?
從上面的結果可以得知，任何壓縮算法都有它的使用場景，并不是所有長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了被壓縮字符串的，用于字符串還原的相關數據結構，而這些數據結構的長度超過了被壓縮短字符串的自身長度。
那么問題來了，“我真的有壓縮短字符串的需求，我想體驗壓縮的極致感，怎么辦？”。
短字符壓縮算法它來了。這里挑選了3種比較優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，一起看看他們在短字符壓縮場景的各自表現吧。
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;
}執行結果如下：
通過smaz壓縮后的短字符串長度為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;
}結果如何？
壓縮性能在40w條/S，解壓在百萬級，好像還不錯哈！
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;
}執行結果如下：
通過shoco壓縮后的短字符串長度為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;
}執行結果如何呢？
holy shit！壓縮和解壓縮居然都達到了驚人的百萬級。就像算法作者們自己說的一樣：“在長字符串壓縮領域，shoco不想與通用壓縮算法競爭，我們的優勢是短字符的快速壓縮，雖然壓縮率很爛！”。這樣說，好像也沒毛病。
我們再來看看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;
}結果如下：
通過Unisox2壓縮后的短字符串長度為67，和源字符串相比，減少了40Byte，相當于是打了6折啊！不錯不錯。
2、Unisox2的壓縮和解壓縮性能
Unisox2的壓縮能力目前來看是三者中最好的，如果他的壓縮和解壓性能也不錯的話，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;
}執行結果如下：
事與愿違，Unisox2雖然有三個算法中最好的壓縮率，可是卻也擁有最差的壓縮和解壓性能。
感謝各位的閱讀，以上就是“C語言如何實現短字符串壓縮”的內容了，經過本文的學習后，相信大家對C語言如何實現短字符串壓縮這一問題有了更深刻的體會，具體使用情況還需要大家實踐驗證。這里是億速云，小編將為大家推送更多相關知識點的文章，歡迎關注！
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