[PATCH 1/2] lib: hexdump: use a look-up table to do hex_to_bin

[zengzhaoxiu]

From: Zhaoxiu Zeng <zhaoxiu.zeng@xxxxxxxxx>

Signed-off-by: Zhaoxiu Zeng <zhaoxiu.zeng@xxxxxxxxx>
---
 include/linux/kernel.h | 15 ++++++++++++++-
 lib/hexdump.c          | 36 +++++++++++++++++++-----------------
 2 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 94aa10f..72a0432 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -532,7 +532,20 @@ static inline char *hex_byte_pack_upper(char *buf, u8 byte)
 	return buf;
 }
 
-extern int hex_to_bin(char ch);
+extern const int8_t h2b_lut[];
+
+/**
+ * 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.
+ */
+static inline int hex_to_bin(char ch)
+{
+	return h2b_lut[(unsigned char)ch];
+}
+
 extern int __must_check hex2bin(u8 *dst, const char *src, size_t count);
 extern char *bin2hex(char *dst, const void *src, size_t count);
 
diff --git a/lib/hexdump.c b/lib/hexdump.c
index 992457b..878697f 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -18,23 +18,25 @@ EXPORT_SYMBOL(hex_asc);
 const char hex_asc_upper[] = "0123456789ABCDEF";
 EXPORT_SYMBOL(hex_asc_upper);
 
-/**
- * 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);
+const int8_t h2b_lut[] = {
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
+	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+};
+EXPORT_SYMBOL(h2b_lut);
 
 /**
  * hex2bin - convert an ascii hexadecimal string to its binary representation
-- 
2.7.4