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1 // Copyright 2011 the V8 project authors. All rights reserved. | 1 // Copyright 2011 the V8 project authors. All rights reserved. |
2 // Redistribution and use in source and binary forms, with or without | 2 // Redistribution and use in source and binary forms, with or without |
3 // modification, are permitted provided that the following conditions are | 3 // modification, are permitted provided that the following conditions are |
4 // met: | 4 // met: |
5 // | 5 // |
6 // * Redistributions of source code must retain the above copyright | 6 // * Redistributions of source code must retain the above copyright |
7 // notice, this list of conditions and the following disclaimer. | 7 // notice, this list of conditions and the following disclaimer. |
8 // * Redistributions in binary form must reproduce the above | 8 // * Redistributions in binary form must reproduce the above |
9 // copyright notice, this list of conditions and the following | 9 // copyright notice, this list of conditions and the following |
10 // disclaimer in the documentation and/or other materials provided | 10 // disclaimer in the documentation and/or other materials provided |
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196 return static_cast<int>(length); | 196 return static_cast<int>(length); |
197 } | 197 } |
198 | 198 |
199 | 199 |
200 // ---------------------------------------------------------------------------- | 200 // ---------------------------------------------------------------------------- |
201 // BitField is a help template for encoding and decode bitfield with | 201 // BitField is a help template for encoding and decode bitfield with |
202 // unsigned content. | 202 // unsigned content. |
203 template<class T, int shift, int size> | 203 template<class T, int shift, int size> |
204 class BitField { | 204 class BitField { |
205 public: | 205 public: |
| 206 // A uint32_t mask of bit field. To use all bits of a uint32 in a |
| 207 // bitfield without compiler warnings we have to compute 2^32 without |
| 208 // using a shift count of 32. |
| 209 static const uint32_t kMask = ((1U << shift) << size) - (1U << shift); |
| 210 |
| 211 // Value for the field with all bits set. |
| 212 static const T kMax = static_cast<T>((1U << size) - 1); |
| 213 |
206 // Tells whether the provided value fits into the bit field. | 214 // Tells whether the provided value fits into the bit field. |
207 static bool is_valid(T value) { | 215 static bool is_valid(T value) { |
208 return (static_cast<uint32_t>(value) & ~((1U << (size)) - 1)) == 0; | 216 return (static_cast<uint32_t>(value) & ~kMax) == 0; |
209 } | |
210 | |
211 // Returns a uint32_t mask of bit field. | |
212 static uint32_t mask() { | |
213 // To use all bits of a uint32 in a bitfield without compiler warnings we | |
214 // have to compute 2^32 without using a shift count of 32. | |
215 return ((1U << shift) << size) - (1U << shift); | |
216 } | 217 } |
217 | 218 |
218 // Returns a uint32_t with the bit field value encoded. | 219 // Returns a uint32_t with the bit field value encoded. |
219 static uint32_t encode(T value) { | 220 static uint32_t encode(T value) { |
220 ASSERT(is_valid(value)); | 221 ASSERT(is_valid(value)); |
221 return static_cast<uint32_t>(value) << shift; | 222 return static_cast<uint32_t>(value) << shift; |
222 } | 223 } |
223 | 224 |
224 // Returns a uint32_t with the bit field value updated. | 225 // Returns a uint32_t with the bit field value updated. |
225 static uint32_t update(uint32_t previous, T value) { | 226 static uint32_t update(uint32_t previous, T value) { |
226 return (previous & ~mask()) | encode(value); | 227 return (previous & ~kMask) | encode(value); |
227 } | 228 } |
228 | 229 |
229 // Extracts the bit field from the value. | 230 // Extracts the bit field from the value. |
230 static T decode(uint32_t value) { | 231 static T decode(uint32_t value) { |
231 return static_cast<T>((value & mask()) >> shift); | 232 return static_cast<T>((value & kMask) >> shift); |
232 } | |
233 | |
234 // Value for the field with all bits set. | |
235 static T max() { | |
236 return decode(mask()); | |
237 } | 233 } |
238 }; | 234 }; |
239 | 235 |
240 | 236 |
241 // ---------------------------------------------------------------------------- | 237 // ---------------------------------------------------------------------------- |
242 // Hash function. | 238 // Hash function. |
243 | 239 |
244 // Thomas Wang, Integer Hash Functions. | 240 // Thomas Wang, Integer Hash Functions. |
245 // http://www.concentric.net/~Ttwang/tech/inthash.htm | 241 // http://www.concentric.net/~Ttwang/tech/inthash.htm |
246 static inline uint32_t ComputeIntegerHash(uint32_t key) { | 242 static inline uint32_t ComputeIntegerHash(uint32_t key) { |
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915 ASSERT(element < static_cast<int>(sizeof(T) * CHAR_BIT)); | 911 ASSERT(element < static_cast<int>(sizeof(T) * CHAR_BIT)); |
916 return 1 << element; | 912 return 1 << element; |
917 } | 913 } |
918 | 914 |
919 T bits_; | 915 T bits_; |
920 }; | 916 }; |
921 | 917 |
922 } } // namespace v8::internal | 918 } } // namespace v8::internal |
923 | 919 |
924 #endif // V8_UTILS_H_ | 920 #endif // V8_UTILS_H_ |
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