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1 // Copyright 2013 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef BASE_NUMERIC_CAST_H_ | |
darin (slow to review)
2013/01/15 18:53:29
nit: fix include guard. or maybe the file name nu
jschuh
2013/01/15 19:07:32
This was my request. I want to put the safe_numeri
scottmg
2013/01/15 19:30:17
Justin wanted it called safe_numerics with the int
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6 #define BASE_NUMERIC_CAST_H_ | |
7 | |
8 #include <limits> | |
9 | |
10 #include "base/logging.h" | |
11 | |
12 namespace base { | |
13 | |
14 // numeric_cast<> is analogous to static_cast<> for numeric types, except that | |
15 // it CHECKs that the specified numeric conversion will not overflow or | |
16 // underflow. Floating point arguments are not currently allowed (this is | |
17 // COMPILE_ASSERTd), though this could be supported if necessary. | |
18 | |
19 // The main test for whether the conversion will under or overflow. | |
20 template <class Dest, class Source> | |
darin (slow to review)
2013/01/15 18:53:29
this feels like implementation detail. perhaps it
scottmg
2013/01/15 19:30:17
Done.
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21 inline bool IsNumericCastableTo(Source source) { | |
darin (slow to review)
2013/01/15 18:53:29
nit: IsValidNumericCast?
scottmg
2013/01/15 19:30:17
Done.
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22 typedef std::numeric_limits<Source> source_limits; | |
darin (slow to review)
2013/01/15 18:53:29
nit: typedefs are usually MixedCase... SourceLimit
scottmg
2013/01/15 19:30:17
Done.
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23 typedef std::numeric_limits<Dest> dest_limits; | |
24 COMPILE_ASSERT(source_limits::is_specialized, argument_must_be_numeric); | |
25 COMPILE_ASSERT(source_limits::is_integer, argument_must_be_integral); | |
26 COMPILE_ASSERT(dest_limits::is_specialized, result_must_be_numeric); | |
27 COMPILE_ASSERT(dest_limits::is_integer, result_must_be_integral); | |
28 | |
29 // Source and Dest are the same. | |
30 if (dest_limits::digits == source_limits::digits && | |
31 dest_limits::is_signed == source_limits::is_signed) | |
32 return true; | |
33 | |
34 // Dest is wider, check for loss of sign if Dest is not signed. | |
35 if (dest_limits::digits > source_limits::digits) | |
36 return dest_limits::is_signed || source >= 0; | |
37 | |
38 // Otherwise, Dest is narrower than Source. | |
39 | |
40 // Check for underflow. | |
41 if (source_limits::is_signed && // Don't need to check if source is unsigned. | |
42 source < static_cast<Source>(dest_limits::min())) | |
43 return false; | |
44 | |
45 // Or overflow. | |
46 return source <= static_cast<Source>(dest_limits::max()); | |
47 } | |
48 | |
49 template <class Dest, class Source> | |
50 inline Dest numeric_cast(Source source) { | |
51 CHECK(IsNumericCastableTo<Dest>(source)); | |
52 return static_cast<Dest>(source); | |
53 } | |
54 | |
55 } // namespace base | |
56 | |
57 #endif // BASE_NUMERIC_CAST_H_ | |
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