add unicode->utf8 converter

include/cherry/unicode.h

@@ -33,6 +33,8 @@ int             org_cherry_unicode_isgraph(cy_unicode_t ch);
 int             org_cherry_unicode_ispunct(cy_unicode_t ch);
 int             org_cherry_unicode_iscntrl(cy_unicode_t ch);
 
+int 			org_cherry_unicode_to_utf8(cy_byte_t* out, cy_unicode_t ch);
+
 int		        org_cherry_utf8_validate(const cy_byte_t* str);
 int		        org_cherry_utf8_compare(const cy_byte_t* str1, const cy_byte_t* str2);
 

source/unicode.c

@@ -447,3 +447,43 @@ org_cherry_utf8_validate(const cy_byte_t* str)
 	return (trails == 0);
 }
 
+
+int 
+org_cherry_unicode_to_utf8(cy_byte_t* out, cy_unicode_t ch)
+{
+	size_t length = 0;
+	cy_byte_t first;
+	int i;
+
+	if(ch < 0x80) {
+		first = 0x00;
+		length = 1;
+	} else if(ch < 0x800) {
+		first = 0xC0;
+		length = 2;
+	} else if(ch < 0x10000) {
+		first = 0xE0;
+		length = 3;
+	} else if(ch < 0x200000) {
+		first = 0xF0;
+		length = 4;
+	} else if(ch < 0x4000000) {
+		first = 0xF8;
+		length = 5;
+	} else {
+		first = 0xFC;
+		length = 6;
+	}
+
+	if(out) {
+		for(i = length - 1; i > 0; --i) {
+			out[i] = (ch & 0x3F) | 0x80;
+			ch >>= 6;
+		}
+		out[0] = ch | first;
+	}
+
+	return length;
+}
+
+