C正则库做DNS域名验证时的性能对比

Posted 2020-06-11

本文对C的正则库regex和pcre在做域名验证的场景下做评测。

验证DNS域名的正则表达式为：

"^[0-9a-zA-Z_-]+(\\.[0-9a-zA-Z_-]+)*(\\.[a-zA-Z]{2,}\\.)$"

对于正常DNS请求日志中的6177578条日志做正则验证处理。

1，pcre

评测所用的pcre的版本号是：7.8.3

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#include <stdio.h> #include <string.h> #include <pcre.h>   #define OVECCOUNT 30    /* should be a multiple of 3 */ #define EBUFLEN 128 #define BUFLEN 1024   int main(int argc, char *argv[]) {     pcre            *re;     const char      *error;     int             erroffset;     FILE           *fd;     int             ovector[OVECCOUNT];     int             rc, i;     int             succ = 0, fail = 0;       char            src[1024];     char            pattern[] = "^[0-9a-zA-Z_-]+(\\.[0-9a-zA-Z_-]+)*(\\.[a-zA-Z]{2,}\\.)$";       printf("Pattern: %s\n", pattern);         re = pcre_compile(pattern, 0, &error, &erroffset, NULL);     if (re == NULL) {         printf("PCRE compilation failed at offset %d: %s\n", erroffset, error);         return 1;     }       if ((fd = fopen(argv[1], "r")) == NULL) {         printf("open file error\n");         return 1;     }             while(fgets(src, 1024, fd)) {         rc = pcre_exec(re, NULL, src, strlen(src), 0, 0, ovector, OVECCOUNT);         if (rc < 0) {         fail++;         } else {        succ++;         }     }       printf("success:%d fail:%d\n", succ, fail);       fclose(fd);     free(re);     return 0; }

　　

处理完所有数据的耗时是：

$time ./pcre_t query_domains 
Pattern: ^[0-9a-zA-Z_-]+(\.[0-9a-zA-Z_-]+)*(\.[a-zA-Z]{2,}\.)$
success:6177443 fail:135

real 0m8.257s
user 0m8.194s
sys 0m0.058s

 

2，regex

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#include <stdio.h> #include <string.h> #include <regex.h>   #define SUBSLEN 100 #define EBUFLEN 1280  #define BUFLEN 1024   int main(int argc, char *argv[]) {     size_t          len;     regex_t         re;     regmatch_t      subs[SUBSLEN];     char            matched[BUFLEN];     char            errbuf[EBUFLEN];     int             err, i, succ=0, fail=0;     FILE           *fd;       char            *src;     char            line[1024];     char            pattern[] = "^[0-9a-zA-Z_-]+(\\.[0-9a-zA-Z_-]+)*(\\.[a-zA-Z]+\\.)$";       printf("Pattern: %s\n", pattern);       if(regcomp(&re, pattern, REG_EXTENDED | REG_NEWLINE)) {         len = regerror(err, &re, errbuf, sizeof(errbuf));         printf("error: regcomp: %s\n", errbuf);         return 1;     }       if ((fd = fopen(argv[1], "r")) == NULL) {         printf("open file error\n");         return 1;     }             while(fgets(line, 1024, fd)) {         err = regexec(&re, line, (size_t) SUBSLEN, subs, 0);         if (err == REG_NOMATCH) {         fail++;         }  else {         succ++;         }     }       printf("success:%d, fails:%d\n", succ, fail);     fclose(fd);     regfree(&re);     return (0); }

处理完所有数据耗时：

$time ./regex_t query_domains 
Pattern: ^[0-9a-zA-Z_-]+(\.[0-9a-zA-Z_-]+)*(\.[a-zA-Z]+\.)$
success:6177443, fails:135

real 0m50.876s
user 0m50.783s
sys 0m0.058s

 

3，结论。

可以看到，对于域名验证的场景。pcre明显优于POSIX regex库。在规则已经编译好的情况下，pcre每秒大约处理74.8w条域名，而regex每秒大约处理12.1万条。