C正则库做DNS域名验证时的性能对比 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\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。