cord_analysis.cc | Explore in Territory

// Copyright 2021 The Abseil Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "absl/strings/cord_analysis.h"

#include <cassert>
#include <cstddef>
#include <cstdint>
#include <unordered_set>

#include "absl/base/config.h"
#include "absl/base/nullability.h"
#include "absl/strings/internal/cord_data_edge.h"
#include "absl/strings/internal/cord_internal.h"
#include "absl/strings/internal/cord_rep_btree.h"
#include "absl/strings/internal/cord_rep_crc.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace cord_internal {
namespace {

// Accounting mode for analyzing memory usage.
enum class Mode { … };

// CordRepRef holds a `const CordRep*` reference in rep, and depending on mode,
// holds a 'fraction' representing a cumulative inverse refcount weight.
template <Mode mode>
struct CordRepRef { … };

// RawUsage holds the computed total number of bytes.
template <Mode mode>
struct RawUsage { … };

// Overloaded representation of RawUsage that tracks the set of objects
// counted, and avoids double-counting objects referenced more than once
// by the same Cord.
template <>
struct RawUsage<Mode::kTotalMorePrecise> { … };

// Returns n / refcount avoiding a div for the common refcount == 1.
template <typename refcount_t>
double MaybeDiv(double d, refcount_t refcount) { … }

// Overloaded 'kFairShare' specialization for CordRepRef. This class holds a
// `fraction` value which represents a cumulative inverse refcount weight.
// For example, a top node with a reference count of 2 will have a fraction
// value of 1/2 = 0.5, representing the 'fair share' of memory it references.
// A node below such a node with a reference count of 5 then has a fraction of
// 0.5 / 5 = 0.1 representing the fair share of memory below that node, etc.
template <>
struct CordRepRef<Mode::kFairShare> { … };

// Overloaded 'kFairShare' specialization for RawUsage
template <>
struct RawUsage<Mode::kFairShare> { … };

// Computes the estimated memory size of the provided data edge.
// External reps are assumed 'heap allocated at their exact size'.
template <Mode mode>
void AnalyzeDataEdge(CordRepRef<mode> rep, RawUsage<mode>& raw_usage) { … }

// Computes the memory size of the provided Btree tree.
template <Mode mode>
void AnalyzeBtree(CordRepRef<mode> rep, RawUsage<mode>& raw_usage) { … }

template <Mode mode>
size_t GetEstimatedUsage(absl::Nonnull<const CordRep*> rep) { … }

}  // namespace

size_t GetEstimatedMemoryUsage(absl::Nonnull<const CordRep*> rep) { … }

size_t GetEstimatedFairShareMemoryUsage(absl::Nonnull<const CordRep*> rep) { … }

size_t GetMorePreciseMemoryUsage(absl::Nonnull<const CordRep*> rep) { … }

}  // namespace cord_internal
ABSL_NAMESPACE_END
}  // namespace absl
chromium/third_party/abseil-cpp/absl/strings/cord_analysis.cc
