Minimal set of string functions.

easy-string.c

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define str_assert(condition) \
	{ \
		if (!(condition)) { \
			fprintf(stderr, "Expression: '%s' failed at %s:%i\n", \
				#condition, file, line); \
			return 0; \
		} \
	}

int indexOf(char *source, char *key, int pos, char *file, int line) {
	int i, j;
	size_t length;
	
	str_assert(source != NULL);
	str_assert(key != NULL);
	str_assert(pos > -1);
	
	length = strlen(source);
	
	for (i=0,j=0; i<length; i++) {
		(source[i] == key[j]) ? (j++) : (j=0);
		
		if (j == strlen(key)) {
			j = 0;
			if (pos == 0) return i - strlen(key) + 1;
			pos--;
		}
	}
	
	return -1;
}
#define indexOf(source, key, pos) indexOf(source, key, pos, __FILE__, __LINE__)

char *substring(char *source, int start, int end, char *file, int line) {
	
	str_assert(source != NULL);
	str_assert(start > -1);
	str_assert(end > -1);
	str_assert(start < end);
	
	strcpy(source, source + start);
	source[end - start] = 0;
	
	return source;
}
#define substring(source, start, end) substring(source, start, end, __FILE__, __LINE__)

char *replace(char *source, char *older, char *newer, char *file, int line) {
	int older_index;
	
	str_assert(source != NULL);
	str_assert(older != NULL);
	str_assert(newer != NULL);
	
	older_index = indexOf(source, older, 0);
	str_assert(older_index != -1);
	
	memmove(source + older_index + strlen(newer), source + older_index + strlen(older),
		strlen(source + older_index) - strlen(older));
	
	memcpy(source + older_index, newer, strlen(newer));
	
	return source;
}
#define replace(source, older, newer) replace(source, older, newer, __FILE__, __LINE__)

char *getNumbers(char *source, char *file, int line) {
	int i, j;
	size_t length;
	
	str_assert(source != NULL);
	
	length = strlen(source);
	
	for (i=0,j=0; i<length; i++) {
		if (source[i] > 47 && source[i] < 58) source[j++] = source[i];
	}
	source[j] = 0;
	
	return source;
}
#define getNumbers(source) getNumbers(source, __FILE__, __LINE__)

char *toUpper(char *source, char *file, int line) {
	int i;
	size_t length;
	
	str_assert(source != NULL);
	
	length = strlen(source);
	
	for (i=0; i<length; i++) {
		if (source[i] > 96 && source[i] < 123) source[i] = toupper(source[i]);
	}
	source[i] = 0;
	
	return source;
}
#define toUpper(source) toUpper(source, __FILE__, __LINE__)

char *toLower(char *source, char *file, int line) {
	int i;
	size_t length;
	
	str_assert(source != NULL);
	
	length = strlen(source);
	
	for (i=0; i<length; i++) {
		if (source[i] > 64 && source[i] < 90) source[i] = tolower(source[i]);
	}
	source[i] = 0;
	
	return source;
}
#define toLower(source) toLower(source, __FILE__, __LINE__)

char *trim(char *source, char *file, int line) {
	int i, j, whitespace;
	size_t length;
	
	str_assert(source != NULL);
	
	length = strlen(source);
	
	for (i=0,j=0,whitespace=0; i<length; i++) {
		
		(source[i] == ' ') ? (whitespace = 1) : (whitespace = 0);
		if (!whitespace) source[j++] = source[i];
	}
	source[j] = 0;
	
	return source;
}
#define trim(source) trim(source, __FILE__, __LINE__)

/*///////////////////////////////////
	
		Testing:
		
///////////////////////////////////*/

int main() {
	char str[100] = "FOO bar 123";
	
	printf("substring\t%s\n", 	substring(str, 0, 9));
	printf("toLower\t\t%s\n", 	toLower(str));
	printf("toUpper\t\t%s\n", 	toUpper(str));
	printf("trim\t\t%s\n", 		trim(str));
	printf("getNumbers\t%s\n", 	getNumbers(str));
	printf("replace\t\t%s\n", 	replace(str, "1", "Hello, world!"));
}