Add numeric_cast for checked integral narrowing casts

base/safe_numerics_unittest.cc

Index: base/safe_numerics_unittest.cc
diff --git a/base/safe_numerics_unittest.cc b/base/safe_numerics_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7e4b02a4b61546adf57b28831dbc266c998c0ac9
--- /dev/null
+++ b/base/safe_numerics_unittest.cc
@@ -0,0 +1,77 @@
+// 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/safe_numerics.h"
+
+namespace base {
+namespace internal {
+
+TEST(SafeNumerics, NumericCast) {
+  int small_positive = 1;
+  int small_negative = -1;
+  int large_positive = INT_MAX;
+  int large_negative = INT_MIN;
+
+  // Narrow signed destination.
+  EXPECT_TRUE(IsValidNumericCast<signed char>(small_positive));
+  EXPECT_TRUE(IsValidNumericCast<signed char>(small_negative));
+  EXPECT_FALSE(IsValidNumericCast<signed char>(large_positive));
+  EXPECT_FALSE(IsValidNumericCast<signed char>(large_negative));
+  EXPECT_TRUE(IsValidNumericCast<signed short>(small_positive));
+  EXPECT_TRUE(IsValidNumericCast<signed short>(small_negative));
+
+  // Narrow unsigned destination.
+  EXPECT_TRUE(IsValidNumericCast<unsigned char>(small_positive));
+  EXPECT_FALSE(IsValidNumericCast<unsigned char>(small_negative));
+  EXPECT_FALSE(IsValidNumericCast<unsigned char>(large_positive));
+  EXPECT_FALSE(IsValidNumericCast<unsigned char>(large_negative));
+  EXPECT_FALSE(IsValidNumericCast<unsigned short>(small_negative));
+  EXPECT_FALSE(IsValidNumericCast<unsigned short>(large_negative));
+
+  // Same width signed destination.
+  EXPECT_TRUE(IsValidNumericCast<signed int>(small_positive));
+  EXPECT_TRUE(IsValidNumericCast<signed int>(small_negative));
+  EXPECT_TRUE(IsValidNumericCast<signed int>(large_positive));
+  EXPECT_TRUE(IsValidNumericCast<signed int>(large_negative));
+
+  // Same width unsigned destination.
+  EXPECT_TRUE(IsValidNumericCast<unsigned int>(small_positive));
+  EXPECT_FALSE(IsValidNumericCast<unsigned int>(small_negative));
+  EXPECT_TRUE(IsValidNumericCast<unsigned int>(large_positive));
+  EXPECT_FALSE(IsValidNumericCast<unsigned int>(large_negative));
+
+  // Wider signed destination.
+  EXPECT_TRUE(IsValidNumericCast<long long>(small_positive));
+  EXPECT_TRUE(IsValidNumericCast<long long>(large_negative));
+  EXPECT_TRUE(IsValidNumericCast<long long>(small_positive));
+  EXPECT_TRUE(IsValidNumericCast<long long>(large_negative));
+
+  // Wider unsigned destination.
+  EXPECT_TRUE(IsValidNumericCast<unsigned long long>(small_positive));
+  EXPECT_FALSE(IsValidNumericCast<unsigned long long>(small_negative));
+  EXPECT_TRUE(IsValidNumericCast<unsigned long long>(large_positive));
+  EXPECT_FALSE(IsValidNumericCast<unsigned long long>(large_negative));
+
+  // Negative to size_t.
+  EXPECT_FALSE(IsValidNumericCast<size_t>(small_negative));
+  EXPECT_FALSE(IsValidNumericCast<size_t>(large_negative));
+
+  // Various edge cases.
+  EXPECT_TRUE(IsValidNumericCast<int>(static_cast<short>(SHRT_MIN)));
+  EXPECT_FALSE(
+      IsValidNumericCast<unsigned short>(static_cast<short>(SHRT_MIN)));
+  EXPECT_FALSE(IsValidNumericCast<unsigned short>(SHRT_MIN));
+
+  // 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);
+}
+
+}  // namespace internal
+}  // namespace base