add utils for utf8 manipulation

Makefile

@@ -1,7 +1,7 @@
 .PHONY: all clean
 
 all:
-	$(CC) main.c syllable.c -o main
+	$(CC) main.c syllable.c utf8.c -o main
 	./main
 
 clean:

utf8.c

@@ -0,0 +1,76 @@
+#include <stdlib.h>
+#include "utf8.h"
+
+unsigned long utf8_unpack_char(char *src)
+{
+	unsigned long c = 0;
+
+	if ((src[0] & 0x80) == 0x00) {
+		c  = ((src[0] & 0x7f) <<  0);
+	} else if ((src[0] & 0xe0) == 0xc0) {
+		c  = ((src[0] & 0x1f) <<  6);
+		c |= ((src[1] & 0x3f) <<  0);
+	} else if ((src[0] & 0xf0) == 0xe0) {
+		c  = ((src[0] & 0x0f) << 12);
+		c |= ((src[1] & 0x3f) <<  6);
+		c |= ((src[2] & 0x3f) <<  0);
+	} else if ((src[0] & 0xf8) == 0xf0) {
+		c  = ((src[0] & 0x07) << 18);
+		c |= ((src[1] & 0x3f) << 12);
+		c |= ((src[2] & 0x3f) <<  6);
+		c |= ((src[3] & 0x3f) <<  0);
+	}
+
+	return c;
+}
+
+void utf8_pack_char(char *dest, unsigned long c)
+{
+	if (c <= 0x00007f) {
+		dest[0] = c;
+	} else if (c <= 0x0007ff) {
+		dest[0] = (0xc0 | ((c >>  6) & 0xff));
+		dest[1] = (0x80 | ((c >>  0) & 0x3f));
+	} else if (c <= 0x00ffff) {
+		dest[0] = (0xe0 | ((c >> 12) & 0xff));
+		dest[1] = (0x80 | ((c >>  6) & 0x3f));
+		dest[2] = (0x80 | ((c >>  0) & 0x3f));
+	} else if (c <= 0x10ffff) {
+		dest[0] = (0xf0 | ((c >> 18) & 0xff));
+		dest[1] = (0x80 | ((c >> 12) & 0x3f));
+		dest[2] = (0x80 | ((c >>  6) & 0x3f));
+		dest[3] = (0x80 | ((c >>  0) & 0x3f));
+	} else {
+		dest[0] = '?'; // should not happen
+	}
+}
+
+unsigned int utf8_char_length(unsigned long c)
+{
+	if (c <= 0x00007f) {
+		return 1;
+	} else if (c <= 0x0007ff) {
+		return 2;
+	} else if (c <= 0x00ffff) {
+		return 3;
+	} else if (c <= 0x10ffff) {
+		return 4;
+	}
+
+	return 0; // should not happen
+}
+
+char *utf8_code_to_string(unsigned long c)
+{
+	unsigned int length = utf8_char_length(c) + 1;
+	char *buffer;
+
+	buffer = malloc(length);
+	if (buffer == NULL)
+		return NULL;
+
+	utf8_pack_char(buffer, c);
+	buffer[length] = 0;
+
+	return buffer;
+}

utf8.h

@@ -0,0 +1,10 @@
+#ifndef __UTF8_H
+#define __UTF8_H
+
+unsigned long utf8_unpack_char(char *src);
+void utf8_pack_char(char *dest, unsigned long c);
+
+unsigned int utf8_char_length(unsigned long c);
+char *utf8_code_to_string(unsigned long c);
+
+#endif /* __UTF8_H */