[PATCH v5 01/17] lib/charset: add u16_strlcat() function

[Masahisa Kojima]

Provide u16 string version of strlcat().

Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
---
Changes in v5:
- change 3rd argument from size to count, it indicates
  the maximum u16 string count that dest buffer can have.
  Other u16_strXXX functions in U-Boot use string count, not the
  buffer size. u16_strlcat() should follow.
- update function comment to clealy describe the behavior
- use strlen() instead of strnlen(), to correctly handle
  the case if the count is smaller than or equal to initial dest count

Changes in v4:
- add blank line above the return statement

Changes in v2:
- implement u16_strlcat(with the destination buffer size in argument)
  instead of u16_strcat
 include/charset.h | 17 +++++++++++++++++
 lib/charset.c     | 22 ++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/include/charset.h b/include/charset.h
index 38908e08f0..ae356ad9a5 100644
--- a/include/charset.h
+++ b/include/charset.h
@@ -261,6 +261,23 @@ u16 *u16_strcpy(u16 *dest, const u16 *src);
  */
 u16 *u16_strdup(const void *src);
 
+/**
+ * u16_strlcat() - Append a length-limited, %NUL-terminated string to another
+ *
+ * Append the src string to the dest string, overwriting the terminating
+ * null word at the end of dest, and then adds a terminating null word.
+ *
+ * @dest:		destination buffer (must include the trailing 0x0000)
+ * @src:		source buffer (must include the trailing 0x0000)
+ * @count:		maximum number of code points that dest buffer can have,
+ *			including the trailing 0x0000
+ * Return:		total count of the created u16 string
+ *			u16_strlen(src) + min(count, u16_strlen(initial dest)),
+ *			does not include trailing 0x0000.
+ *			If return value >= count, truncation occurred.
+ */
+size_t u16_strlcat(u16 *dest, const u16 *src, size_t size);
+
 /**
  * utf16_to_utf8() - Convert an utf16 string to utf8
  *
diff --git a/lib/charset.c b/lib/charset.c
index de201cf3b9..f295dfc11a 100644
--- a/lib/charset.c
+++ b/lib/charset.c
@@ -416,6 +416,28 @@ u16 *u16_strdup(const void *src)
 	return new;
 }
 
+size_t u16_strlcat(u16 *dest, const u16 *src, size_t count)
+{
+	size_t destlen, srclen, ret;
+
+	destlen = u16_strlen(dest);
+	srclen = u16_strlen(src);
+	ret = min(count, destlen) + srclen; /* does not include trailing 0x0000 */
+
+	if (destlen >= count)
+		return ret;
+
+	dest += destlen;
+	count -= destlen;
+	if (srclen >= count)
+		srclen = count - 1 /* for trailing 0x0000 */;
+
+	memcpy(dest, src, srclen * sizeof(u16));
+	dest[srclen] = u'\0';
+
+	return ret;
+}
+
 /* Convert UTF-16 to UTF-8.  */
 uint8_t *utf16_to_utf8(uint8_t *dest, const uint16_t *src, size_t size)
 {
-- 
2.17.1