linux-kernel - [PATCH v3 1/3] lib/string: introduce ascii2utf16le() helper

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Date:   Mon, 6 Feb 2017 15:03:38 +0100
From:   Richard Leitner <richard.leitner@...data.com>
To:     <linux-usb@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <gregkh@...uxfoundation.org>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <akpm@...ux-foundation.org>,
        <andriy.shevchenko@...ux.intel.com>, <keescook@...omium.org>,
        <dev@...l1n.net>, Richard Leitner <richard.leitner@...data.com>
Subject: [PATCH v3 1/3] lib/string: introduce ascii2utf16le() helper

For USB string descriptors we need to convert ASCII strings to UTF16-LE.
Therefore make a simple helper function (based on ascii2desc from
drivers/usb/core/hcd.c) for that purpose.

Signed-off-by: Richard Leitner <richard.leitner@...data.com>
---
 include/linux/string.h |  1 +
 lib/string.c           | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 26b6f6a..48fd0c6 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -135,6 +135,7 @@ static inline int strtobool(const char *s, bool *res)
 }
 
 int match_string(const char * const *array, size_t n, const char *string);
+unsigned int ascii2utf16le(char const *s, u8 *buf, unsigned int len);
 
 #ifdef CONFIG_BINARY_PRINTF
 int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args);
diff --git a/lib/string.c b/lib/string.c
index ed83562..a113e3e 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -952,3 +952,29 @@ char *strreplace(char *s, char old, char new)
 	return s;
 }
 EXPORT_SYMBOL(strreplace);
+
+/**
+ * ascii2utf16le() - Helper routine for producing UTF-16LE string descriptors
+ * @s: Null-terminated ASCII (actually ISO-8859-1) string
+ * @buf: Buffer for UTF-16LE string
+ * @len: Length (in bytes; may be odd) of UTF-16LE buffer.
+ *
+ * Return: The number of bytes filled in: 2*strlen(s) or @len, whichever is less
+ */
+unsigned int ascii2utf16le(char const *s, u8 *buf, unsigned int len)
+{
+	unsigned int n, t = 2 * strlen(s);
+
+	if (len > t)
+		len = t;
+	n = len;
+	while (n--) {
+		t = (unsigned char)*s++;
+		*buf++ = t;
+		if (!n--)
+			break;
+		*buf++ = t >> 8;
+	}
+	return len;
+}
+EXPORT_SYMBOL(ascii2utf16le);
-- 
2.1.4