String Functions source code

This snippet submitted by Dominic Vonk on 2013-05-08. It has been viewed 110795 times.
Rating of 7.4 with 585 votes
 
 #include <stdio.h>
#include <stdlib.h>

/* String Length */
int str_len(char *string)
{
    char *count = string;
 	while(*count) {count++;}
	return count - string;
}
/* String Append */
char* str_append(char* string, char* append) {
	char* newstring = NULL;
	size_t needed = snprintf(NULL, 0, "%s%s", string, append);
	newstring = malloc(needed);
	sprintf(newstring, "%s%s", string, append);
	return newstring;
}
/* String Append Char */
char* str_append_chr(char* string, char append) {
	char* newstring = NULL;
	size_t needed = snprintf(NULL, 0, "%s%c", string, append);
	newstring = malloc(needed);
	sprintf(newstring, "%s%c", string, append);
	return newstring;
}
/* String Equals */
int str_equals(char *equal1, char *eqaul2)
{
   while(*equal1==*eqaul2)
   {
      if ( *equal1 == '\0' || *eqaul2 == '\0' ){break;}
      equal1++;
      eqaul2++;
   }
   if(*eqaul1 == '\0' && *eqaul2 == '\0' ){return 0;}
   else {return -1};
}
/* String Replace */
char* str_replace(char* search, char* replace, char* subject) {
	char* newstring = "";
	int i = 0;
	for(i = 0; i < str_len(subject); i++) {
		if (subject[i] == search[0]) {
			int e = 0;
			char* calc = "";
			for(e = 0; e < str_len(search); e++) {
				if(subject[i+e] == search[e]) {
					calc = str_append_chr(calc, search[e]);
				}
			}
			if (str_equals(search, calc) == 0) {
				newstring = str_append(newstring, replace);
				i = i + str_len (search)-1;
			}
			else {
				newstring = str_append_chr(newstring, subject[i]);
			}
		}
		else {
			newstring = str_append_chr(newstring, subject[i]);
		}
	}
	return newstring;
}
/* String Replace Maximal */
char* str_replace_max(char* search, char* replace, char* subject, int count) {
	char* newstring = "";
	int i = 0;
	for(i = 0; i < str_len(subject); i++) {
		if (subject[i] == search[0]) {
			int e = 0;
			char* calc = "";
			for(e = 0; e < str_len(search); e++) {
				if(subject[i+e] == search[e]) {
					calc = str_append_chr(calc, search[e]);
				}
			}
			if (str_equals(search, calc) == 0) {
				if(count > 0) {
					newstring = str_append(newstring, replace);
					i = i + str_len (search)-1;
					count = count - 1;
				}
				else {
					newstring = str_append_chr(newstring, subject[i]);
				}
				
			}
			else {
				newstring = str_append_chr(newstring, subject[i]);
			}
		}
		else {
			newstring = str_append_chr(newstring, subject[i]);
		}
	}
	return newstring;
}
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