lib: introduce common method to convert hex digits

hex_to_bin() is a little method which converts hex digit to its actual value. There are plenty of places where such functionality is needed. [[email protected]: use tolower(), saving 3 bytes, test the more common case first - it's quicker] [[email protected]: relocate tolower to make it even faster! (Joe)] Signed-off-by: Andy Shevchenko <[email protected]> Cc: Tilman Schmidt <[email protected]> Cc: Duncan Sands <[email protected]> Cc: Eric W. Biederman <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: "Richard Russon (FlatCap)" <[email protected]> Cc: John W. Linville <[email protected]> Cc: Len Brown <[email protected]> Cc: Joe Perches <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · May 25, 2010 · 9037888 · 9037888
1 parent db0fd97
commit 9037888
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diff --git a/include/linux/kernel.h b/include/linux/kernel.h
@@ -375,6 +375,8 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
 	return buf;
 }
 
+extern int hex_to_bin(char ch);
+
 #ifndef pr_fmt
 #define pr_fmt(fmt) fmt
 #endif

diff --git a/lib/hexdump.c b/lib/hexdump.c
@@ -15,6 +15,24 @@
 const char hex_asc[] = "0123456789abcdef";
 EXPORT_SYMBOL(hex_asc);
 
+/**
+ * hex_to_bin - convert a hex digit to its real value
+ * @ch: ascii character represents hex digit
+ *
+ * hex_to_bin() converts one hex digit to its actual value or -1 in case of bad
+ * input.
+ */
+int hex_to_bin(char ch)
+{
+	if ((ch >= '0') && (ch <= '9'))
+		return ch - '0';
+	ch = tolower(ch);
+	if ((ch >= 'a') && (ch <= 'f'))
+		return ch - 'a' + 10;
+	return -1;
+}
+EXPORT_SYMBOL(hex_to_bin);
+
 /**
  * hex_dump_to_buffer - convert a blob of data to "hex ASCII" in memory
  * @buf: data blob to dump