jiayl@webrtc.org | 13a42bc | 2014-01-29 17:45:53 +0000 | [diff] [blame] | 1 | /* |
| 2 | * libjingle |
| 3 | * Copyright 2014, Google Inc. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions are met: |
| 7 | * |
| 8 | * 1. Redistributions of source code must retain the above copyright notice, |
| 9 | * this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright notice, |
| 11 | * this list of conditions and the following disclaimer in the documentation |
| 12 | * and/or other materials provided with the distribution. |
| 13 | * 3. The name of the author may not be used to endorse or promote products |
| 14 | * derived from this software without specific prior written permission. |
| 15 | * |
| 16 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| 17 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 18 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
| 19 | * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 20 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| 21 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
| 22 | * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| 23 | * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
| 24 | * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| 25 | * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 26 | */ |
| 27 | |
| 28 | // Borrowed from Chromium's src/base/numerics/safe_conversions_impl.h. |
| 29 | |
| 30 | #ifndef TALK_BASE_SAFE_CONVERSIONS_IMPL_H_ |
| 31 | #define TALK_BASE_SAFE_CONVERSIONS_IMPL_H_ |
| 32 | |
| 33 | #include <limits> |
| 34 | |
| 35 | namespace talk_base { |
| 36 | namespace internal { |
| 37 | |
| 38 | enum DstSign { |
| 39 | DST_UNSIGNED, |
| 40 | DST_SIGNED |
| 41 | }; |
| 42 | |
| 43 | enum SrcSign { |
| 44 | SRC_UNSIGNED, |
| 45 | SRC_SIGNED |
| 46 | }; |
| 47 | |
| 48 | enum DstRange { |
| 49 | OVERLAPS_RANGE, |
| 50 | CONTAINS_RANGE |
| 51 | }; |
| 52 | |
| 53 | // Helper templates to statically determine if our destination type can contain |
| 54 | // all values represented by the source type. |
| 55 | |
| 56 | template <typename Dst, typename Src, |
| 57 | DstSign IsDstSigned = std::numeric_limits<Dst>::is_signed ? |
| 58 | DST_SIGNED : DST_UNSIGNED, |
| 59 | SrcSign IsSrcSigned = std::numeric_limits<Src>::is_signed ? |
| 60 | SRC_SIGNED : SRC_UNSIGNED> |
| 61 | struct StaticRangeCheck {}; |
| 62 | |
| 63 | template <typename Dst, typename Src> |
| 64 | struct StaticRangeCheck<Dst, Src, DST_SIGNED, SRC_SIGNED> { |
| 65 | typedef std::numeric_limits<Dst> DstLimits; |
| 66 | typedef std::numeric_limits<Src> SrcLimits; |
| 67 | // Compare based on max_exponent, which we must compute for integrals. |
| 68 | static const size_t kDstMaxExponent = DstLimits::is_iec559 ? |
| 69 | DstLimits::max_exponent : |
| 70 | (sizeof(Dst) * 8 - 1); |
| 71 | static const size_t kSrcMaxExponent = SrcLimits::is_iec559 ? |
| 72 | SrcLimits::max_exponent : |
| 73 | (sizeof(Src) * 8 - 1); |
| 74 | static const DstRange value = kDstMaxExponent >= kSrcMaxExponent ? |
| 75 | CONTAINS_RANGE : OVERLAPS_RANGE; |
| 76 | }; |
| 77 | |
| 78 | template <typename Dst, typename Src> |
| 79 | struct StaticRangeCheck<Dst, Src, DST_UNSIGNED, SRC_UNSIGNED> { |
| 80 | static const DstRange value = sizeof(Dst) >= sizeof(Src) ? |
| 81 | CONTAINS_RANGE : OVERLAPS_RANGE; |
| 82 | }; |
| 83 | |
| 84 | template <typename Dst, typename Src> |
| 85 | struct StaticRangeCheck<Dst, Src, DST_SIGNED, SRC_UNSIGNED> { |
| 86 | typedef std::numeric_limits<Dst> DstLimits; |
| 87 | typedef std::numeric_limits<Src> SrcLimits; |
| 88 | // Compare based on max_exponent, which we must compute for integrals. |
| 89 | static const size_t kDstMaxExponent = DstLimits::is_iec559 ? |
| 90 | DstLimits::max_exponent : |
| 91 | (sizeof(Dst) * 8 - 1); |
| 92 | static const size_t kSrcMaxExponent = sizeof(Src) * 8; |
| 93 | static const DstRange value = kDstMaxExponent >= kSrcMaxExponent ? |
| 94 | CONTAINS_RANGE : OVERLAPS_RANGE; |
| 95 | }; |
| 96 | |
| 97 | template <typename Dst, typename Src> |
| 98 | struct StaticRangeCheck<Dst, Src, DST_UNSIGNED, SRC_SIGNED> { |
| 99 | static const DstRange value = OVERLAPS_RANGE; |
| 100 | }; |
| 101 | |
| 102 | |
| 103 | enum RangeCheckResult { |
| 104 | TYPE_VALID = 0, // Value can be represented by the destination type. |
| 105 | TYPE_UNDERFLOW = 1, // Value would overflow. |
| 106 | TYPE_OVERFLOW = 2, // Value would underflow. |
| 107 | TYPE_INVALID = 3 // Source value is invalid (i.e. NaN). |
| 108 | }; |
| 109 | |
| 110 | // This macro creates a RangeCheckResult from an upper and lower bound |
| 111 | // check by taking advantage of the fact that only NaN can be out of range in |
| 112 | // both directions at once. |
| 113 | #define BASE_NUMERIC_RANGE_CHECK_RESULT(is_in_upper_bound, is_in_lower_bound) \ |
| 114 | RangeCheckResult(((is_in_upper_bound) ? 0 : TYPE_OVERFLOW) | \ |
| 115 | ((is_in_lower_bound) ? 0 : TYPE_UNDERFLOW)) |
| 116 | |
| 117 | template <typename Dst, |
| 118 | typename Src, |
| 119 | DstSign IsDstSigned = std::numeric_limits<Dst>::is_signed ? |
| 120 | DST_SIGNED : DST_UNSIGNED, |
| 121 | SrcSign IsSrcSigned = std::numeric_limits<Src>::is_signed ? |
| 122 | SRC_SIGNED : SRC_UNSIGNED, |
| 123 | DstRange IsSrcRangeContained = StaticRangeCheck<Dst, Src>::value> |
| 124 | struct RangeCheckImpl {}; |
| 125 | |
| 126 | // The following templates are for ranges that must be verified at runtime. We |
| 127 | // split it into checks based on signedness to avoid confusing casts and |
| 128 | // compiler warnings on signed an unsigned comparisons. |
| 129 | |
| 130 | // Dst range always contains the result: nothing to check. |
| 131 | template <typename Dst, typename Src, DstSign IsDstSigned, SrcSign IsSrcSigned> |
| 132 | struct RangeCheckImpl<Dst, Src, IsDstSigned, IsSrcSigned, CONTAINS_RANGE> { |
| 133 | static RangeCheckResult Check(Src value) { |
| 134 | return TYPE_VALID; |
| 135 | } |
| 136 | }; |
| 137 | |
| 138 | // Signed to signed narrowing. |
| 139 | template <typename Dst, typename Src> |
| 140 | struct RangeCheckImpl<Dst, Src, DST_SIGNED, SRC_SIGNED, OVERLAPS_RANGE> { |
| 141 | static RangeCheckResult Check(Src value) { |
| 142 | typedef std::numeric_limits<Dst> DstLimits; |
| 143 | return DstLimits::is_iec559 ? |
| 144 | BASE_NUMERIC_RANGE_CHECK_RESULT( |
| 145 | value <= static_cast<Src>(DstLimits::max()), |
| 146 | value >= static_cast<Src>(DstLimits::max() * -1)) : |
| 147 | BASE_NUMERIC_RANGE_CHECK_RESULT( |
| 148 | value <= static_cast<Src>(DstLimits::max()), |
| 149 | value >= static_cast<Src>(DstLimits::min())); |
| 150 | } |
| 151 | }; |
| 152 | |
| 153 | // Unsigned to unsigned narrowing. |
| 154 | template <typename Dst, typename Src> |
| 155 | struct RangeCheckImpl<Dst, Src, DST_UNSIGNED, SRC_UNSIGNED, OVERLAPS_RANGE> { |
| 156 | static RangeCheckResult Check(Src value) { |
| 157 | typedef std::numeric_limits<Dst> DstLimits; |
| 158 | return BASE_NUMERIC_RANGE_CHECK_RESULT( |
| 159 | value <= static_cast<Src>(DstLimits::max()), true); |
| 160 | } |
| 161 | }; |
| 162 | |
| 163 | // Unsigned to signed. |
| 164 | template <typename Dst, typename Src> |
| 165 | struct RangeCheckImpl<Dst, Src, DST_SIGNED, SRC_UNSIGNED, OVERLAPS_RANGE> { |
| 166 | static RangeCheckResult Check(Src value) { |
| 167 | typedef std::numeric_limits<Dst> DstLimits; |
| 168 | return sizeof(Dst) > sizeof(Src) ? TYPE_VALID : |
| 169 | BASE_NUMERIC_RANGE_CHECK_RESULT( |
| 170 | value <= static_cast<Src>(DstLimits::max()), true); |
| 171 | } |
| 172 | }; |
| 173 | |
| 174 | // Signed to unsigned. |
| 175 | template <typename Dst, typename Src> |
| 176 | struct RangeCheckImpl<Dst, Src, DST_UNSIGNED, SRC_SIGNED, OVERLAPS_RANGE> { |
| 177 | static RangeCheckResult Check(Src value) { |
| 178 | typedef std::numeric_limits<Dst> DstLimits; |
| 179 | typedef std::numeric_limits<Src> SrcLimits; |
| 180 | // Compare based on max_exponent, which we must compute for integrals. |
| 181 | static const size_t kDstMaxExponent = sizeof(Dst) * 8; |
| 182 | static const size_t kSrcMaxExponent = SrcLimits::is_iec559 ? |
| 183 | SrcLimits::max_exponent : |
| 184 | (sizeof(Src) * 8 - 1); |
| 185 | return (kDstMaxExponent >= kSrcMaxExponent) ? |
| 186 | BASE_NUMERIC_RANGE_CHECK_RESULT(true, value >= static_cast<Src>(0)) : |
| 187 | BASE_NUMERIC_RANGE_CHECK_RESULT( |
| 188 | value <= static_cast<Src>(DstLimits::max()), |
| 189 | value >= static_cast<Src>(0)); |
| 190 | } |
| 191 | }; |
| 192 | |
| 193 | template <typename Dst, typename Src> |
| 194 | inline RangeCheckResult RangeCheck(Src value) { |
| 195 | COMPILE_ASSERT(std::numeric_limits<Src>::is_specialized, |
| 196 | argument_must_be_numeric); |
| 197 | COMPILE_ASSERT(std::numeric_limits<Dst>::is_specialized, |
| 198 | result_must_be_numeric); |
| 199 | return RangeCheckImpl<Dst, Src>::Check(value); |
| 200 | } |
| 201 | |
| 202 | } // namespace internal |
| 203 | } // namespace talk_base |
| 204 | |
| 205 | #endif // TALK_BASE_SAFE_CONVERSIONS_IMPL_H_ |