Add numeric_cast for checked integral narrowing casts

base/numeric_cast_unittest.cc

Index: base/numeric_cast_unittest.cc
===================================================================
--- base/numeric_cast_unittest.cc	(revision 0)
+++ base/numeric_cast_unittest.cc	(revision 0)
@@ -0,0 +1,66 @@
+// Copyright 2013 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.
+
+#include <gtest/gtest.h>
+
+#include <vector>
+
+#include "base/numeric_cast.h"
+
+TEST(NumericCast, Test) {
+  int small_positive = 1;
+  int small_negative = -1;
+  int large_positive = INT_MAX;
+  int large_negative = INT_MIN;
+
+  // Narrow signed destination.
+  EXPECT_TRUE(base::IsNumericCastableTo<signed char>(small_positive));
+  EXPECT_TRUE(base::IsNumericCastableTo<signed char>(small_negative));
+  EXPECT_FALSE(base::IsNumericCastableTo<signed char>(large_positive));
+  EXPECT_FALSE(base::IsNumericCastableTo<signed char>(large_negative));
+
+  // Narrow unsigned destination.
+  EXPECT_TRUE(base::IsNumericCastableTo<unsigned char>(small_positive));
+  EXPECT_FALSE(base::IsNumericCastableTo<unsigned char>(small_negative));
+  EXPECT_FALSE(base::IsNumericCastableTo<unsigned char>(large_positive));
+  EXPECT_FALSE(base::IsNumericCastableTo<unsigned char>(large_negative));
+
+  // Same width signed destination.
+  EXPECT_TRUE(base::IsNumericCastableTo<signed int>(small_positive));
+  EXPECT_TRUE(base::IsNumericCastableTo<signed int>(small_negative));
+  EXPECT_TRUE(base::IsNumericCastableTo<signed int>(large_positive));
+  EXPECT_TRUE(base::IsNumericCastableTo<signed int>(large_negative));
+
+  // Same width unsigned destination.
+  EXPECT_TRUE(base::IsNumericCastableTo<unsigned int>(small_positive));
+  EXPECT_FALSE(base::IsNumericCastableTo<unsigned int>(small_negative));
+  EXPECT_TRUE(base::IsNumericCastableTo<unsigned int>(large_positive));
+  EXPECT_FALSE(base::IsNumericCastableTo<unsigned int>(large_negative));
+
+  // Wider signed destination.
+  EXPECT_TRUE(base::IsNumericCastableTo<long long>(small_positive));
+  EXPECT_TRUE(base::IsNumericCastableTo<long long>(large_negative));
+  EXPECT_TRUE(base::IsNumericCastableTo<long long>(small_positive));
+  EXPECT_TRUE(base::IsNumericCastableTo<long long>(large_negative));
+
+  // Wider unsigned destination.
+  EXPECT_TRUE(base::IsNumericCastableTo<unsigned long long>(small_positive));
+  EXPECT_FALSE(base::IsNumericCastableTo<unsigned long long>(small_negative));
+  EXPECT_TRUE(base::IsNumericCastableTo<unsigned long long>(large_positive));
+  EXPECT_FALSE(base::IsNumericCastableTo<unsigned long long>(large_negative));
+
+  // Negative to size_t.
+  EXPECT_FALSE(base::IsNumericCastableTo<size_t>(small_negative));
+  EXPECT_FALSE(base::IsNumericCastableTo<size_t>(large_negative));
+
+  // These shouldn't compile.
+  // EXPECT_TRUE(base::IsNumericCastableTo<float>(0.0));
+  // EXPECT_TRUE(base::IsNumericCastableTo<double>(0.0f));
+  // EXPECT_FALSE(base::IsNumericCastableTo<int>(DBL_MAX));
+
+  // Confirm that numeric_cast<> actually compiles.
+  std::vector<int> v;
+  unsigned int checked_size = base::numeric_cast<unsigned int>(v.size());
+  EXPECT_EQ(0, checked_size);
+}