UTF8 codec in C

unicode.c

void utf8_encode(int codepoint, unsigned char encoded[5]) {
	
	if (codepoint < 0x80) {
		encoded[1] = 0;
		
		encoded[0] = codepoint;
		encoded[0] &= ~(1 << 7);
		return;
	}
	
	if (codepoint < 0x800) {
		encoded[2] = 0;
		
		encoded[1] = codepoint;
		encoded[1] &= ~(1 << 6);
		encoded[1] |= 1 << 7;
		
		
		encoded[0] = codepoint >> 6;
		encoded[0] &= ~(1 << 5);
		encoded[0] |= 1 << 6;
		encoded[0] |= 1 << 7;
		return;
	}
	
	if (codepoint < 0x10000) {
		encoded[3] = 0;
		
		encoded[2] = codepoint;
		encoded[2] &= ~(1 << 6);
		encoded[2] |= 1 << 7;
		
		encoded[1] = codepoint >> 6;
		encoded[1] &= ~(1 << 6);
		encoded[1] |= 1 << 7;
		
		encoded[0] = codepoint >> 12;
		encoded[0] &= ~(1 << 4);
		encoded[0] |= 1 << 5;
		encoded[0] |= 1 << 6;
		encoded[0] |= 1 << 7;
		return;
	}
	
	if (codepoint < 0x200000) {
		encoded[4] = 0;
		
		encoded[3] = codepoint;
		encoded[3] &= ~(1 << 6);
		encoded[3] |= 1 << 7;
		
		encoded[2] = codepoint >> 6;
		encoded[2] &= ~(1 << 6);
		encoded[2] |= 1 << 7;
		
		encoded[1] = codepoint >> 12;
		encoded[1] &= ~(1 << 6);
		encoded[1] |= 1 << 7;
		
		encoded[0] = codepoint >> 18;
		encoded[0] &= ~(1 << 3);
		encoded[0] |= 1 << 4;
		encoded[0] |= 1 << 5;
		encoded[0] |= 1 << 6;
		encoded[0] |= 1 << 7;
		return;
	}
}

unsigned int utf8_decode(unsigned char encoded[5]) {
	unsigned int header = (unsigned int)encoded[0];
	unsigned int decoded = 0;
	
	if (header <= 0x7F)
		decoded = encoded[0] & 127;
	
	else if (header <= 0xDF)
		decoded = ((header & 31) << 6) | ((encoded[1] & 63) << 0);
	
	else if (header <= 0xEF)
		decoded = ((header & 15) << 12) | ((encoded[1] & 63) << 6) | ((encoded[2] & 63) << 0);
	
	else if (header <= 0xF7)
		decoded = ((header & 7) << 18) | ((encoded[1] & 63) << 12) | ((encoded[2] & 63) << 6) | ((encoded[3] & 63) << 0);
	
	return decoded;
}

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

#include <stdio.h>

int main(void) {
	int i;
	char encoded[5] = {0};
	FILE *fp;
	
	if ((fp = fopen("unicode_test.txt", "w")) == NULL) return 1;
	
	for (i=0x1F300; i<0x1F300+1000; i++) {
		utf8_encode(i, encoded);
	
		fprintf(fp, "%s", encoded);
		printf("0x%x == 0x%x\n", utf8_decode(encoded), i);
		
		if ((i+1) % 100 == 0) fprintf(fp, "\n");
	}
	
	fclose(fp);
	
	return 0;
}