cord_analysis.h (2506B)
1 // Copyright 2021 The Abseil Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef ABSL_STRINGS_CORD_ANALYSIS_H_ 16 #define ABSL_STRINGS_CORD_ANALYSIS_H_ 17 18 #include <cstddef> 19 #include <cstdint> 20 21 #include "absl/base/config.h" 22 #include "absl/base/nullability.h" 23 #include "absl/strings/internal/cord_internal.h" 24 25 namespace absl { 26 ABSL_NAMESPACE_BEGIN 27 namespace cord_internal { 28 29 // Returns the *approximate* number of bytes held in full or in part by this 30 // Cord (which may not remain the same between invocations). Cords that share 31 // memory could each be "charged" independently for the same shared memory. 32 size_t GetEstimatedMemoryUsage(absl::Nonnull<const CordRep*> rep); 33 34 // Returns the *approximate* number of bytes held in full or in part by this 35 // Cord for the distinct memory held by this cord. This is similar to 36 // `GetEstimatedMemoryUsage()`, except that if the cord has multiple references 37 // to the same memory, that memory is only counted once. 38 // 39 // For example: 40 // absl::Cord cord; 41 // cord.append(some_other_cord); 42 // cord.append(some_other_cord); 43 // // Calls GetEstimatedMemoryUsage() and counts `other_cord` twice: 44 // cord.EstimatedMemoryUsage(kTotal); 45 // // Calls GetMorePreciseMemoryUsage() and counts `other_cord` once: 46 // cord.EstimatedMemoryUsage(kTotalMorePrecise); 47 // 48 // This is more expensive than `GetEstimatedMemoryUsage()` as it requires 49 // deduplicating all memory references. 50 size_t GetMorePreciseMemoryUsage(absl::Nonnull<const CordRep*> rep); 51 52 // Returns the *approximate* number of bytes held in full or in part by this 53 // CordRep weighted by the sharing ratio of that data. For example, if some data 54 // edge is shared by 4 different Cords, then each cord is attribute 1/4th of 55 // the total memory usage as a 'fair share' of the total memory usage. 56 size_t GetEstimatedFairShareMemoryUsage(absl::Nonnull<const CordRep*> rep); 57 58 } // namespace cord_internal 59 ABSL_NAMESPACE_END 60 } // namespace absl 61 62 63 #endif // ABSL_STRINGS_CORD_ANALYSIS_H_