Add CheckedNumeric::AssignIfValid() method

base/numerics/safe_numerics_unittest.cc

 // 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 <stddef.h>
 #include <stdint.h>
 
 #include <limits>
 #include <type_traits>
 
@@ skipping 746 matching lines @@
   static_assert(
       std::is_same<float, decltype(double_max.ValueFloating<float>())>::value,
       "ValueFloating returning incorrect type.");
   EXPECT_FALSE(int8_min.template IsValid<uint8_t>());
   EXPECT_TRUE(int8_max.template IsValid<uint8_t>());
   EXPECT_EQ(static_cast<int>(numeric_limits<int8_t>::min()),
             int8_min.template ValueOrDie<int>());
   EXPECT_TRUE(int8_max.template IsValid<uint32_t>());
   EXPECT_EQ(static_cast<int>(numeric_limits<int8_t>::max()),
             int8_max.template ValueOrDie<int>());
+  uint8_t uint8_dest = 0;
+  int16_t int16_dest = 0;
+  double double_dest = 0;
+  EXPECT_TRUE(int8_max.AssignIfValid(&uint8_dest));
+  EXPECT_EQ(static_cast<uint8_t>(numeric_limits<int8_t>::max()), uint8_dest);
+  EXPECT_FALSE(int8_min.AssignIfValid(&uint8_dest));
+  EXPECT_TRUE(int8_max.AssignIfValid(&int16_dest));
+  EXPECT_EQ(static_cast<int16_t>(numeric_limits<int8_t>::max()), int16_dest);
+  EXPECT_TRUE(int8_min.AssignIfValid(&int16_dest));
+  EXPECT_EQ(static_cast<int16_t>(numeric_limits<int8_t>::min()), int16_dest);
+  EXPECT_FALSE(double_max.AssignIfValid(&uint8_dest));
+  EXPECT_FALSE(double_max.AssignIfValid(&int16_dest));
+  EXPECT_TRUE(double_max.AssignIfValid(&double_dest));
+  EXPECT_EQ(numeric_limits<double>::max(), double_dest);
 }
 
 TEST(SafeNumerics, SaturatedCastChecks) {
   float not_a_number = std::numeric_limits<float>::infinity() -
                        std::numeric_limits<float>::infinity();
   EXPECT_TRUE(std::isnan(not_a_number));
   EXPECT_DEATH_IF_SUPPORTED(
       (saturated_cast<int, base::CheckOnFailure>(not_a_number)),
       "");
 }
@@ skipping 108 matching lines @@
   EXPECT_EQ(static_cast<decltype(d)>(-.5), d);
   auto e = CheckMod(CheckNum(20), 3).ValueOrDie();
   EXPECT_EQ(static_cast<decltype(e)>(2), e);
   auto f = CheckLsh(1, CheckNum(2)).ValueOrDie();
   EXPECT_EQ(static_cast<decltype(f)>(4), f);
   auto g = CheckRsh(4, CheckNum(2)).ValueOrDie();
   EXPECT_EQ(static_cast<decltype(g)>(1), g);
   auto h = CheckRsh(CheckAdd(1, 1, 1, 1), CheckSub(4, 2)).ValueOrDie();
   EXPECT_EQ(static_cast<decltype(h)>(1), h);
 }