From 86574285ccf756417c2ce0e765c35e71c03cd5f0 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Thu, 20 Feb 2014 21:05:46 -0800
Subject: [PATCH] Don't use CountDigits for 1-2 digit numbers.

---
 format-test.cc |  2 ++
 format.h       | 12 +++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/format-test.cc b/format-test.cc
index b44e4946..e5ee65c9 100644
--- a/format-test.cc
+++ b/format-test.cc
@@ -1459,6 +1459,8 @@ TEST(FormatIntTest, FormatDec) {
   std::ostringstream os;
   os << std::numeric_limits<unsigned short>::max();
   EXPECT_EQ(os.str(), FormatDec(std::numeric_limits<unsigned short>::max()));
+  EXPECT_EQ("1", FormatDec(1));
+  EXPECT_EQ("-1", FormatDec(-1));
   EXPECT_EQ("42", FormatDec(42));
   EXPECT_EQ("-42", FormatDec(-42));
   EXPECT_EQ("42", FormatDec(42l));
diff --git a/format.h b/format.h
index 1541417a..c4b91bc4 100644
--- a/format.h
+++ b/format.h
@@ -301,7 +301,7 @@ class FormatterProxy;
 // Formats a decimal unsigned integer value writing into buffer.
 template <typename UInt, typename Char>
 void FormatDecimal(Char *buffer, UInt value, unsigned num_digits) {
-    --num_digits;
+  --num_digits;
   while (value >= 100) {
     // Integer division is slow so do it for a group of two digits instead
     // of for every digit. The idea comes from the talk by Alexandrescu
@@ -1407,6 +1407,16 @@ inline void FormatDec(char *&buffer, T value) {
     *buffer++ = '-';
     abs_value = 0 - abs_value;
   }
+  if (abs_value < 100) {
+    if (abs_value < 10) {
+      *buffer++ = static_cast<char>('0' + abs_value);
+      return;
+    }
+    unsigned index = static_cast<unsigned>(abs_value * 2);
+    *buffer++ = internal::DIGITS[index];
+    *buffer++ = internal::DIGITS[index + 1];
+    return;
+  }
   unsigned num_digits = internal::CountDigits(abs_value);
   internal::FormatDecimal(buffer, abs_value, num_digits);
   buffer += num_digits;