[PATCH v5 08/16] include/grub/charset.h: Add grub_utf16_to_utf8_alloc()

[Vitaly Kuzmichev]

This patch adds a wrapper function to perform conversion of UTF-16
string to UTF-8 string using inline function grub_utf16_to_utf8(), but
pre-allocating necessary space for the target buffer. This behavior is
similar to existing inversed function grub_utf8_to_utf16_alloc()
in kern/misc.c.

Signed-off-by: Vitaly Kuzmichev <vitaly.kuzmichev@rtsoft.de>
---
 include/grub/charset.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/include/grub/charset.h b/include/grub/charset.h
index 099f23fbe..4324fefb8 100644
--- a/include/grub/charset.h
+++ b/include/grub/charset.h
@@ -20,6 +20,9 @@
 #define GRUB_CHARSET_HEADER    1
 
 #include <grub/types.h>
+#include <grub/safemath.h>
+#include <grub/mm.h>
+#include <grub/i18n.h>
 
 #define GRUB_UINT8_1_LEADINGBIT 0x80
 #define GRUB_UINT8_2_LEADINGBITS 0xc0
@@ -304,6 +307,31 @@ grub_utf16_strnlen (const void *s, grub_size_t maxlen)
   return len;
 }
 
+/* Convert UTF-16 to UTF-8. Allocates buffer of necessary space. */
+static inline grub_uint8_t *
+grub_utf16_to_utf8_alloc (const void *utf16, grub_size_t maxlen,
+                         grub_utf16_type_t type)
+{
+  grub_size_t len16, size;
+  grub_uint8_t *utf8;
+
+  len16 = grub_utf16_strnlen (utf16, maxlen);
+
+  /* Check for integer overflow */
+  if (grub_mul (len16, GRUB_MAX_UTF8_PER_UTF16, &size) ||
+      grub_add (size, 1, &size))
+    {
+      grub_error (GRUB_ERR_BAD_ARGUMENT, N_("string too long"));
+      return NULL;
+    }
+
+  utf8 = grub_malloc (size);
+  if (utf8)
+    *grub_utf16_to_utf8 (utf8, utf16, len16, type) = '\0';
+
+  return utf8;
+}
+
 #define GRUB_MAX_UTF8_PER_LATIN1 2
 
 /* Convert Latin1 to UTF-8.  */
-- 
2.34.1