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。