正则表达式在C++中的实现-POSIX库

＃i nclude <stdio.h>
＃i nclude <sys/types.h>
＃i nclude <regex.h>

char *get_regerror (int errcode, regex_t *compiled)
{
 size_t length = regerror (errcode, compiled, NULL, 0);
 char *buffer = malloc(length);
 if (!buffer) return NULL;
 (void) regerror (errcode, compiled, buffer, length);
 return buffer;
}

int regtest(const char*pattern, const char* string)
{
 regex_t reg;
 regmatch_t *subexprs = NULL;
 int ret;
 int i;

 if (0 != (ret=regcomp(?, pattern, REG_EXTENDED))) {
  char *buffer = get_regerror(ret, ?);
  if (buffer) {
   fprintf(stderr, "regcomp:[%d]%s\n", ret, buffer);
   free(buffer);
  }

  return -1;
 }

 subexprs = malloc((reg.re_nsub+1)*sizeof(regmatch_t));
 if (!subexprs) {
  fprintf(stderr, "error malloc subexprs\n");
  regfree(?);
  return -1;
 }

 if (0 != (ret=regexec(?, string, reg.re_nsub+1, subexprs, 0))) {
  char *buffer = get_regerror(ret, ?);
  if (buffer) {
   fprintf(stderr, "regexec:[%d]%s\n", ret, buffer);
   free(buffer);
  }
  
  regfree(?);
  return -1;
 }

 for (i = 0; i <= reg.re_nsub; i++)  {
  printf("[%d]:", i);
  
  if (subexprs[i].rm_so == subexprs[i].rm_eo) {
   printf("[EMPTY SUBEXPR]\n");
  }
  else if (subexprs[i].rm_so == -1 ||
   subexprs[i].rm_eo == -1) {
   printf("[NO SUBEXPR]\n");
  }
  else  {
   fwrite(string+subexprs[i].rm_so, 1,
    subexprs[i].rm_eo-subexprs[i].rm_so, stdout);
   printf("\n");
  }
 }

 regfree(?);
 if (subexprs) free(subexprs);
 return 0;
}

int main(int argc, char *argv[])
{
 if (argc != 3) {
  fprintf(stderr, "Usage: regtest pattern string\n");
  return -1;
 }

 fprintf(stderr, "pattern:%s\n", argv[1]);
 fprintf(stderr, "string:%s\n", argv[2]);

 return regtest(argv[1], argv[2]);
}