[RESEND RFC PATCH v2 2/4] lib/charset: add u16_strlcat() function

[Masahisa Kojima <masahisa.kojima@linaro.org>]

Provide u16 string version of strlcat().

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
---
Changes in v2:
- implement u16_strlcat(with the destination buffer size in argument)
  instead of u16_strcat

 include/charset.h | 15 +++++++++++++++
 lib/charset.c     | 20 ++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/include/charset.h b/include/charset.h
index b93d023092..dc5fc275ec 100644
--- a/include/charset.h
+++ b/include/charset.h
@@ -259,6 +259,21 @@ 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.
+ * It will append at most size - u16_strlen(dst) - 1 bytes, NUL-terminating the result.
+ *
+ * @dest:		destination buffer (null terminated)
+ * @src:		source buffer (null terminated)
+ * @size:		destination buffer size in bytes
+ * Return:		total size of the created string in bytes.
+ *			If return value >= size, 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 f44c58d9d8..f15d5df19a 100644
--- a/lib/charset.c
+++ b/lib/charset.c
@@ -428,6 +428,26 @@ u16 *u16_strdup(const void *src)
 	return new;
 }
 
+size_t u16_strlcat(u16 *dest, const u16 *src, size_t size)
+{
+	size_t dstrlen = u16_strnlen(dest, size >> 1);
+	size_t dlen = dstrlen * sizeof(u16);
+	size_t len = u16_strlen(src) * sizeof(u16);
+	size_t ret = dlen + len;
+
+	if (dlen >= size)
+		return ret;
+
+	dest += dstrlen;
+	size -= dlen;
+	if (len >= size)
+		len = size - sizeof(u16);
+
+	memcpy(dest, src, len);
+	dest[len >> 1] = 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