lib: add some utf16 handling helpers

We'll eventually want these in a few places in efi_loader, and also
vsprintf.

Signed-off-by: Rob Clark <robdclark@gmail.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/include/charset.h b/include/charset.h
new file mode 100644
index 0000000000..39279f746a
--- /dev/null
+++ b/include/charset.h
@@ -0,0 +1,65 @@
+/*
+ *  charset conversion utils
+ *
+ *  Copyright (c) 2017 Rob Clark
+ *
+ *  SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#ifndef __CHARSET_H_
+#define __CHARSET_H_
+
+#define MAX_UTF8_PER_UTF16 4
+
+/**
+ * utf16_strlen() - Get the length of an utf16 string
+ *
+ * Returns the number of 16 bit characters in an utf16 string, not
+ * including the terminating NULL character.
+ *
+ * @in     the string to measure
+ * @return the string length
+ */
+size_t utf16_strlen(const uint16_t *in);
+
+/**
+ * utf16_strnlen() - Get the length of a fixed-size utf16 string.
+ *
+ * Returns the number of 16 bit characters in an utf16 string,
+ * not including the terminating NULL character, but at most
+ * 'count' number of characters.  In doing this, utf16_strnlen()
+ * looks at only the first 'count' characters.
+ *
+ * @in     the string to measure
+ * @count  the maximum number of characters to count
+ * @return the string length, up to a maximum of 'count'
+ */
+size_t utf16_strnlen(const uint16_t *in, size_t count);
+
+/**
+ * utf16_strcpy() - UTF16 equivalent of strcpy()
+ */
+uint16_t *utf16_strcpy(uint16_t *dest, const uint16_t *src);
+
+/**
+ * utf16_strdup() - UTF16 equivalent of strdup()
+ */
+uint16_t *utf16_strdup(const uint16_t *s);
+
+/**
+ * utf16_to_utf8() - Convert an utf16 string to utf8
+ *
+ * Converts 'size' characters of the utf16 string 'src' to utf8
+ * written to the 'dest' buffer.
+ *
+ * NOTE that a single utf16 character can generate up to 4 utf8
+ * characters.  See MAX_UTF8_PER_UTF16.
+ *
+ * @dest   the destination buffer to write the utf8 characters
+ * @src    the source utf16 string
+ * @size   the number of utf16 characters to convert
+ * @return the pointer to the first unwritten byte in 'dest'
+ */
+uint8_t *utf16_to_utf8(uint8_t *dest, const uint16_t *src, size_t size);
+
+#endif /* __CHARSET_H_ */