unicode: Extract the UCS4 to UTF-16 conversion to a separate function

Reuse the function for the UTF-8 to UTF-16 conversion, but also make
it available for internal use by cairo.

1 files changed, 33 insertions, 6 deletions

diff --git a/src/cairo-unicode.c b/src/cairo-unicode.c
index 88de39516..7933d12af 100644
--- a/src/cairo-unicode.c
+++ b/src/cairo-unicode.c
@@ -342,6 +342,38 @@ _cairo_ucs4_to_utf8 (uint32_t  unicode,
     return bytes;
 }
 
+/**
+ * _cairo_ucs4_to_utf16:
+ * @unicode: a UCS-4 character
+ * @utf16: buffer to write utf16 string into. Must have at least 2
+ * elements. Or %NULL.
+ *
+ * This space left intentionally blank.
+ *
+ * Return value: Number of elements in the utf16 string or 0 if an
+ * invalid unicode character
+ **/
+int
+_cairo_ucs4_to_utf16 (uint32_t  unicode,
+		      uint16_t *utf16)
+{
+    int len;
+
+    if (unicode < 0x10000) {
+	if (utf16)
+	    utf16[0] = unicode;
+	return 1;
+    } else if (unicode < 0x110000) {
+	if (utf16) {
+	    utf16[0] = (unicode - 0x10000) / 0x400 + 0xd800;
+	    utf16[1] = (unicode - 0x10000) % 0x400 + 0xdc00;
+	}
+	return 2;
+    } else {
+	return 0;
+    }
+}
+
 #if CAIRO_HAS_UTF8_TO_UTF16
 /**
  * _cairo_utf8_to_utf16:
@@ -401,12 +433,7 @@ _cairo_utf8_to_utf16 (const char *str,
     for (i = 0; i < n16;) {
 	uint32_t wc = _utf8_get_char (in);
 
-	if (wc < 0x10000) {
-	    str16[i++] = wc;
-	} else {
-	    str16[i++] = (wc - 0x10000) / 0x400 + 0xd800;
-	    str16[i++] = (wc - 0x10000) % 0x400 + 0xdc00;
-	}
+	i += _cairo_ucs4_to_utf16 (wc, str16 + i);
 
 	in = UTF8_NEXT_CHAR (in);
     }