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>

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_ */

lib/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_OF_LIVE) += of_live.o
 obj-$(CONFIG_CMD_DHRYSTONE) += dhry/
 
 obj-$(CONFIG_AES) += aes.o
+obj-y += charset.o
 obj-$(CONFIG_USB_TTY) += circbuf.o
 obj-y += crc7.o
 obj-y += crc8.o

lib/charset.c

@@ -0,0 +1,101 @@
+/*
+ *  charset conversion utils
+ *
+ *  Copyright (c) 2017 Rob Clark
+ *
+ *  SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#include <common.h>
+#include <charset.h>
+#include <malloc.h>
+
+/*
+ * utf8/utf16 conversion mostly lifted from grub
+ */
+
+size_t utf16_strlen(const uint16_t *in)
+{
+	size_t i;
+	for (i = 0; in[i]; i++);
+	return i;
+}
+
+size_t utf16_strnlen(const uint16_t *in, size_t count)
+{
+	size_t i;
+	for (i = 0; count-- && in[i]; i++);
+	return i;
+}
+
+uint16_t *utf16_strcpy(uint16_t *dest, const uint16_t *src)
+{
+	uint16_t *tmp = dest;
+
+	while ((*dest++ = *src++) != '\0')
+		/* nothing */;
+	return tmp;
+
+}
+
+uint16_t *utf16_strdup(const uint16_t *s)
+{
+	uint16_t *new;
+	if (!s || !(new = malloc((utf16_strlen(s) + 1) * 2)))
+		return NULL;
+	utf16_strcpy(new, s);
+	return new;
+}
+
+/* Convert UTF-16 to UTF-8.  */
+uint8_t *utf16_to_utf8(uint8_t *dest, const uint16_t *src, size_t size)
+{
+	uint32_t code_high = 0;
+
+	while (size--) {
+		uint32_t code = *src++;
+
+		if (code_high) {
+			if (code >= 0xDC00 && code <= 0xDFFF) {
+				/* Surrogate pair.  */
+				code = ((code_high - 0xD800) << 10) + (code - 0xDC00) + 0x10000;
+
+				*dest++ = (code >> 18) | 0xF0;
+				*dest++ = ((code >> 12) & 0x3F) | 0x80;
+				*dest++ = ((code >> 6) & 0x3F) | 0x80;
+				*dest++ = (code & 0x3F) | 0x80;
+			} else {
+				/* Error...  */
+				*dest++ = '?';
+				/* *src may be valid. Don't eat it.  */
+				src--;
+			}
+
+			code_high = 0;
+		} else {
+			if (code <= 0x007F) {
+				*dest++ = code;
+			} else if (code <= 0x07FF) {
+				*dest++ = (code >> 6) | 0xC0;
+				*dest++ = (code & 0x3F) | 0x80;
+			} else if (code >= 0xD800 && code <= 0xDBFF) {
+				code_high = code;
+				continue;
+			} else if (code >= 0xDC00 && code <= 0xDFFF) {
+				/* Error... */
+				*dest++ = '?';
+			} else if (code < 0x10000) {
+				*dest++ = (code >> 12) | 0xE0;
+				*dest++ = ((code >> 6) & 0x3F) | 0x80;
+				*dest++ = (code & 0x3F) | 0x80;
+			} else {
+				*dest++ = (code >> 18) | 0xF0;
+				*dest++ = ((code >> 12) & 0x3F) | 0x80;
+				*dest++ = ((code >> 6) & 0x3F) | 0x80;
+				*dest++ = (code & 0x3F) | 0x80;
+			}
+		}
+	}
+
+	return dest;
+}

lib/efi_loader/efi_console.c

@@ -7,6 +7,7 @@
  */
 
 #include <common.h>
+#include <charset.h>
 #include <efi_loader.h>
 
 static bool console_size_queried;
@@ -138,20 +139,8 @@ static efi_status_t EFIAPI efi_cout_reset(
 
 static void print_unicode_in_utf8(u16 c)
 {
-	char utf8[4] = { 0 };
-	char *b = utf8;
-
-	if (c < 0x80) {
-		*(b++) = c;
-	} else if (c < 0x800) {
-		*(b++) = 192 + c / 64;
-		*(b++) = 128 + c % 64;
-	} else {
-		*(b++) = 224 + c / 4096;
-		*(b++) = 128 + c / 64 % 64;
-		*(b++) = 128 + c % 64;
-	}
-
+	char utf8[MAX_UTF8_PER_UTF16] = { 0 };
+	utf16_to_utf8((u8 *)utf8, &c, 1);
 	puts(utf8);
 }