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這篇文章主要講解了“C語(yǔ)言如何實(shí)現(xiàn)短字符串壓縮”,文中的講解內(nèi)容簡(jiǎn)單清晰,易于學(xué)習(xí)與理解,下面請(qǐng)大家跟著小編的思路慢慢深入,一起來(lái)研究和學(xué)習(xí)“C語(yǔ)言如何實(shí)現(xiàn)短字符串壓縮”吧!
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?
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!
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。
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折啊!不錯(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,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:
事與愿違,Unisox2雖然有三個(gè)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(yǔ)言如何實(shí)現(xiàn)短字符串壓縮”的內(nèi)容了,經(jīng)過(guò)本文的學(xué)習(xí)后,相信大家對(duì)C語(yǔ)言如何實(shí)現(xiàn)短字符串壓縮這一問(wèn)題有了更深刻的體會(huì),具體使用情況還需要大家實(shí)踐驗(yàn)證。這里是億速云,小編將為大家推送更多相關(guān)知識(shí)點(diǎn)的文章,歡迎關(guān)注!
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