C Regular Library Performance comparison for DNS domain name verification

In this paper, the regular library of C regex and Pcre in the domain validation of the scene to do the evaluation.

The regular expression that validates the DNS domain name is:

"^[0-9a-za-z_-]+ (\\.[ 0-9a-za-z_-]+) * (\\.[ A-za-z]{2,}\\.) $"

Regular validation processing is done for 6,177,578 logs in the normal DNS request log.

1,pcre

The version number of the pcre used for the evaluation is: 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 intmain(intargc, char*argv[]){    pcre            *re;    constchar*error;    interroffset;    FILE*fd;    intovector[OVECCOUNT];    intrc, i;    intsucc = 0, fail = 0;    charsrc[1024];    charpattern[] = "^[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);        return1;    }    if((fd = fopen(argv[1], "r")) == NULL) {        printf("open file error\n");        return1;    }        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);    return0;}

　　

The time it takes to process all the data is:

$time./pcre_t Query_domains
Pattern: ^[0-9a-za-z_-]+ (\.[ 0-9a-za-z_-]+) * (\.[ A-za-z]{2,}\.) $
success:6177443 fail:135

real0m8.257s
user0m8.194s
sys0m0.058s

2,regex

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#include <stdio.h>#include <string.h>#include <regex.h>#define SUBSLEN 100#define EBUFLEN 1280 #define BUFLEN 1024intmain(intargc, char*argv[]){    size_tlen;    regex_t         re;    regmatch_t      subs[SUBSLEN];    charmatched[BUFLEN];    charerrbuf[EBUFLEN];    int err, i, succ=0, fail=0;    FILE*fd;    char*src;    charline[1024];    charpattern[] = "^[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);        return1;    }     if((fd = fopen(argv[1], "r")) == NULL) {        printf("open file error\n");        return1;    }        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);}

Processing all data takes time:

$time./regex_t Query_domains
Pattern: ^[0-9a-za-z_-]+ (\.[ 0-9a-za-z_-]+) * (\.[ A-za-z]+\.) $
success:6177443, fails:135

real0m50.876s
user0m50.783s
sys0m0.058s

3, conclusion.

As you can see, for domain name validation scenarios. The pcre is significantly better than the POSIX regex library. When the rules have been compiled, the pcre processes about 74.8w domain names per second, while the regex processes approximately 121,000 per second.

C Regular Library Performance comparison for DNS domain name verification