base: Add HexDigitToInt function to string_util.h

Removed duplicated HexToInt functions and converted the callers along the way.

BUG=None
TEST=trybots and out/Debug/base_unittests --gtest_filter=StringUtilTest.HexDigitToInt

Signed-off-by: Thiago Farina <tfarina@chromium.org>

Review URL: http://codereview.chromium.org/2836069

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@54473 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 46 insertions, 19 deletions

diff --git a/base/json/json_reader.cc b/base/json/json_reader.cc
index 1255ac5..0d6abc4 100644
--- a/base/json/json_reader.cc
+++ b/base/json/json_reader.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -20,18 +20,6 @@ static const int kStackLimit = 100;
 
 namespace {
 
-inline int HexToInt(wchar_t c) {
-  if ('0' <= c && c <= '9') {
-    return c - '0';
-  } else if ('A' <= c && c <= 'F') {
-    return c - 'A' + 10;
-  } else if ('a' <= c && c <= 'f') {
-    return c - 'a' + 10;
-  }
-  NOTREACHED();
-  return 0;
-}
-
 // A helper method for ParseNumberToken.  It reads an int from the end of
 // token.  The method returns false if there is no valid integer at the end of
 // the token.
@@ -493,15 +481,15 @@ Value* JSONReader::DecodeString(const Token& token) {
           break;
 
         case 'x':
-          decoded_str.push_back((HexToInt(*(token.begin + i + 1)) << 4) +
-                                HexToInt(*(token.begin + i + 2)));
+          decoded_str.push_back((HexDigitToInt(*(token.begin + i + 1)) << 4) +
+                                HexDigitToInt(*(token.begin + i + 2)));
           i += 2;
           break;
         case 'u':
-          decoded_str.push_back((HexToInt(*(token.begin + i + 1)) << 12 ) +
-                                (HexToInt(*(token.begin + i + 2)) << 8) +
-                                (HexToInt(*(token.begin + i + 3)) << 4) +
-                                HexToInt(*(token.begin + i + 4)));
+          decoded_str.push_back((HexDigitToInt(*(token.begin + i + 1)) << 12 ) +
+                                (HexDigitToInt(*(token.begin + i + 2)) << 8) +
+                                (HexDigitToInt(*(token.begin + i + 3)) << 4) +
+                                HexDigitToInt(*(token.begin + i + 4)));
           i += 4;
           break;
 
diff --git a/base/string_util.h b/base/string_util.h
index 762779c..97b5100 100644
--- a/base/string_util.h
+++ b/base/string_util.h
@@ -380,6 +380,18 @@ inline bool IsHexDigit(Char c) {
          (c >= 'a' && c <= 'f');
 }
 
+template <typename Char>
+inline Char HexDigitToInt(Char c) {
+  DCHECK(IsHexDigit(c));
+  if (c >= '0' && c <= '9')
+    return c - '0';
+  if (c >= 'A' && c <= 'F')
+    return c - 'A' + 10;
+  if (c >= 'a' && c <= 'f')
+    return c - 'a' + 10;
+  return 0;
+}
+
 // Returns true if it's a whitespace character.
 inline bool IsWhitespace(wchar_t c) {
   return wcschr(kWhitespaceWide, c) != NULL;
diff --git a/base/string_util_unittest.cc b/base/string_util_unittest.cc
index f063fcc..4d3fc1c 100644
--- a/base/string_util_unittest.cc
+++ b/base/string_util_unittest.cc
@@ -633,6 +633,33 @@ TEST(StringUtilTest, ReplaceFirstSubstringAfterOffset) {
   }
 }
 
+TEST(StringUtilTest, HexDigitToInt) {
+  EXPECT_EQ(0, HexDigitToInt('0'));
+  EXPECT_EQ(1, HexDigitToInt('1'));
+  EXPECT_EQ(2, HexDigitToInt('2'));
+  EXPECT_EQ(3, HexDigitToInt('3'));
+  EXPECT_EQ(4, HexDigitToInt('4'));
+  EXPECT_EQ(5, HexDigitToInt('5'));
+  EXPECT_EQ(6, HexDigitToInt('6'));
+  EXPECT_EQ(7, HexDigitToInt('7'));
+  EXPECT_EQ(8, HexDigitToInt('8'));
+  EXPECT_EQ(9, HexDigitToInt('9'));
+  EXPECT_EQ(10, HexDigitToInt('A'));
+  EXPECT_EQ(11, HexDigitToInt('B'));
+  EXPECT_EQ(12, HexDigitToInt('C'));
+  EXPECT_EQ(13, HexDigitToInt('D'));
+  EXPECT_EQ(14, HexDigitToInt('E'));
+  EXPECT_EQ(15, HexDigitToInt('F'));
+
+  // Verify the lower case as well.
+  EXPECT_EQ(10, HexDigitToInt('a'));
+  EXPECT_EQ(11, HexDigitToInt('b'));
+  EXPECT_EQ(12, HexDigitToInt('c'));
+  EXPECT_EQ(13, HexDigitToInt('d'));
+  EXPECT_EQ(14, HexDigitToInt('e'));
+  EXPECT_EQ(15, HexDigitToInt('f'));
+}
+
 // This checks where we can use the assignment operator for a va_list. We need
 // a way to do this since Visual C doesn't support va_copy, but assignment on
 // va_list is not guaranteed to be a copy. See StringAppendVT which uses this