libpayload: UTF-16LE to ASCII conversion

This patch adds a simple function to convert a string in UTF-16LE
to ASCII.

TEST=Ran against a string found in a GPT with the intended outcome
BRANCH=none
BUG=none

Change-Id: I94ec0a32f5712259d3d0caec2233c992330228e3
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 1104db8328a197c7ccf6959a238277f416a2113a
Original-Signed-off-by: Dan Ehrenberg <dehrenberg@chromium.org>
Original-Change-Id: I50ca5bfdfbef9e084321b2beb1b8d4194ca5af9c
Original-Reviewed-on: https://chromium-review.googlesource.com/231456
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/8733
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/payloads/libpayload/libc/string.c b/payloads/libpayload/libc/string.c
index 71dd1a6d1b..99857493c0 100644
--- a/payloads/libpayload/libc/string.c
+++ b/payloads/libpayload/libc/string.c
@@ -653,3 +653,22 @@ char *strerror(int errnum)
 	snprintf(errstr, sizeof(errstr), "Unknown error %d", errnum);
 	return errstr;
 }
+
+/*
+ * Simple routine to convert UTF-16 to ASCII, giving up with ? if too high.
+ * A single code point may convert to ?? if not in the BMP.
+ * @param utf16_string A string encoded in UTF-16LE
+ * @param maxlen Maximum possible length of the string in code points
+ * @return Newly allocated ASCII string
+ */
+char *utf16le_to_ascii(uint16_t *utf16_string, int maxlen)
+{
+	char *ascii_string = xmalloc(maxlen + 1);  /* +1 for trailing \0 */
+	ascii_string[maxlen] = '\0';
+	int i;
+	for (i = 0; i < maxlen; i++) {
+		uint16_t wchar = utf16_string[i];
+		ascii_string[i] = wchar > 0x7f ? '?' : (char)wchar;
+	}
+	return ascii_string;
+}