Function gmt_strrep

src/script2verbatim.c:80–145

  */

 char *gmt_strrep(const char *s1, const char *s2, const char *s3) {
	 size_t s1_len, s2_len, s3_len, count, s1_without_s2_len, newstr_len, i, substr_len, remains;
	 const char *p, *start_substr, *end_substr;
	 char *newstr, *dst;
	 if (!s1 || !s2 || !s3)
		 return 0;
	 s1_len = strlen(s1);
	 if (!s1_len)
		 return (char *)s1;
	 s2_len = strlen(s2);
	 if (!s2_len)
		 return (char *)s1;

	 /*
	  * Two-pass approach: figure out how much space to allocate for
	  * the new string, pre-allocate it, then perform replacement(s).
	  */
	 count = 0;
	 p = s1;
	 assert(s2_len); /* otherwise, strstr(s1,s2) will return s1. */
	 do {
		 p = strstr(p, s2);
		 if (p) {
			 p += s2_len;
			 count++;
		 }
	 } while (p);

	 if (!count)
		 return (char *)s1;

	 /*
	  * The following size arithmetic is extremely cautious, to guard against size_t overflows.
	  */
	 assert(s1_len >= count * s2_len);
	 assert(count);
	 s1_without_s2_len = s1_len - count * s2_len;
	 s3_len = strlen(s3);
	 newstr_len = s1_without_s2_len + count * s3_len;
	 if (s3_len && ((newstr_len <= s1_without_s2_len) || (newstr_len + 1 == 0))) /* Overflow. */
		 return 0;

	 newstr = (char *)calloc(newstr_len + 1, sizeof(char)); /* w/ terminator */
	 if (!newstr)		/* ENOMEM, but no good way to signal it. */
		 return 0;

	 dst = newstr;
	 start_substr = s1;
	 for (i = 0; i != count; ++i) {
		 end_substr = strstr(start_substr, s2);
		 assert(end_substr);
		 substr_len = end_substr - start_substr;
		 memcpy(dst, start_substr, substr_len);
		 dst += substr_len;
		 memcpy(dst, s3, s3_len);
		 dst += s3_len;
		 start_substr = end_substr + s2_len;
	 }