str2upper.c

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

unsigned char upper(unsigned char ch) {
	if (ch >= 'a' && ch <= 'z') {
		ch ^= 0x20;
	}
	return ch;
}

unsigned char lower(unsigned char ch) {
	if (ch >= 'A' && ch <= 'Z') {
		ch ^= 0x20;
	}
	return ch;
}

unsigned char* str2upper(unsigned char* str, int length) {
	unsigned char* dst = (unsigned char*) malloc(length + 1);
	for (int i = 0; i < length; i++ ){ dst[i] = upper(str[i]); }
	dst[length] = 0;
	return dst;
}

unsigned char* str2lower(unsigned char* str, int length) {
	unsigned char* dst = (unsigned char*) malloc(length + 1);
	for (int i = 0; i < length; i++ ){ dst[i] = lower(str[i]); }
	dst[length] = 0;
	return dst;
}

void str2upper_test() {
	unsigned char* x = "hello wolrd!";
	unsigned char* y = str2upper(x, strlen(x));
	printf("str2upper('%s') = '%s'\n", x, y);
	free(y);
}

void str2lower_test() {
	unsigned char* x = "HellO wOlRD!";
	unsigned char* y = str2lower(x, strlen(x));
	printf("str2lower('%s') = '%s'\n", x, y);
	free(y);
}


int main(){
	str2upper_test();
	str2lower_test();
}