C正则库做DNS域名验证时的性能对比

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 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
", pattern);


    re = pcre_compile(pattern, 0, &error, &erroffset, NULL);
    if (re == NULL) {
        printf("PCRE compilation failed at offset %d: %s
", erroffset, error);
        return 1;
    }

    if ((fd = fopen(argv[1], "r")) == NULL) {
        printf("open file error
");
        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
", 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
", pattern);

    if(regcomp(&re, pattern, REG_EXTENDED | REG_NEWLINE)) {
        len = regerror(err, &re, errbuf, sizeof(errbuf));
        printf("error: regcomp: %s
", errbuf);
        return 1;
    }

    if ((fd = fopen(argv[1], "r")) == NULL) {
        printf("open file error
");
        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
", 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。