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C正则库做DNS域名验证时的性能对比

2024-07-18 18:00:11   210人阅读

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

#include <stdio.h>#include <string.h>#include <pcre.h>#define OVECCOUNT 30    /* should be a multiple of 3 */#define EBUFLEN 128#define BUFLEN 1024int 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

#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。


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