lib/ucs2_string: Add ucs2 -> utf8 helper functions

This adds ucs2_utf8size(), which tells us how big our ucs2 string is in
bytes, and ucs2_as_utf8, which translates from ucs2 to utf8..

Signed-off-by: Peter Jones <pjones@redhat.com>
Tested-by: Lee, Chun-Yi <jlee@suse.com>
Acked-by: Matthew Garrett <mjg59@coreos.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>

2 files changed, 66 insertions, 0 deletions

diff --git a/include/linux/ucs2_string.h b/include/linux/ucs2_string.h
index cbb20afdbc01..bb679b48f408 100644
--- a/include/linux/ucs2_string.h
+++ b/include/linux/ucs2_string.h
@@ -11,4 +11,8 @@ unsigned long ucs2_strlen(const ucs2_char_t *s);
 unsigned long ucs2_strsize(const ucs2_char_t *data, unsigned long maxlength);
 int ucs2_strncmp(const ucs2_char_t *a, const ucs2_char_t *b, size_t len);
 
+unsigned long ucs2_utf8size(const ucs2_char_t *src);
+unsigned long ucs2_as_utf8(u8 *dest, const ucs2_char_t *src,
+                           unsigned long maxlength);
+
 #endif /* _LINUX_UCS2_STRING_H_ */
diff --git a/lib/ucs2_string.c b/lib/ucs2_string.c
index 6f500ef2301d..17dd74e21ef9 100644
--- a/lib/ucs2_string.c
+++ b/lib/ucs2_string.c
@@ -49,3 +49,65 @@ ucs2_strncmp(const ucs2_char_t *a, const ucs2_char_t *b, size_t len)
         }
 }
 EXPORT_SYMBOL(ucs2_strncmp);
+
+unsigned long
+ucs2_utf8size(const ucs2_char_t *src)
+{
+        unsigned long i;
+        unsigned long j = 0;
+
+        for (i = 0; i < ucs2_strlen(src); i++) {
+                u16 c = src[i];
+
+                if (c > 0x800)
+                        j += 3;
+                else if (c > 0x80)
+                        j += 2;
+                else
+                        j += 1;
+        }
+
+        return j;
+}
+EXPORT_SYMBOL(ucs2_utf8size);
+
+/*
+ * copy at most maxlength bytes of whole utf8 characters to dest from the
+ * ucs2 string src.
+ *
+ * The return value is the number of characters copied, not including the
+ * final NUL character.
+ */
+unsigned long
+ucs2_as_utf8(u8 *dest, const ucs2_char_t *src, unsigned long maxlength)
+{
+        unsigned int i;
+        unsigned long j = 0;
+        unsigned long limit = ucs2_strnlen(src, maxlength);
+
+        for (i = 0; maxlength && i < limit; i++) {
+                u16 c = src[i];
+
+                if (c > 0x800) {
+                        if (maxlength < 3)
+                                break;
+                        maxlength -= 3;
+                        dest[j++] = 0xe0 | (c & 0xf000) >> 12;
+                        dest[j++] = 0x80 | (c & 0x0fc0) >> 8;
+                        dest[j++] = 0x80 | (c & 0x003f);
+                } else if (c > 0x80) {
+                        if (maxlength < 2)
+                                break;
+                        maxlength -= 2;
+                        dest[j++] = 0xc0 | (c & 0xfe0) >> 5;
+                        dest[j++] = 0x80 | (c & 0x01f);
+                } else {
+                        maxlength -= 1;
+                        dest[j++] = c & 0x7f;
+                }
+        }
+        if (maxlength)
+                dest[j] = '\0';
+        return j;
+}
+EXPORT_SYMBOL(ucs2_as_utf8);