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// 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 <cstdint>
#include "absl/base/config.h"
#include "absl/container/inlined_vector.h"
#include "absl/strings/internal/cord_internal.h"
#include "absl/strings/internal/cord_rep_flat.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace cord_internal {
CordRepConcat::ExtractResult CordRepConcat::ExtractAppendBuffer(
CordRepConcat* tree, size_t extra_capacity) {
absl::InlinedVector<CordRepConcat*, kInlinedVectorSize> stack;
CordRepConcat* concat = tree;
CordRep* rep = concat->right;
// Dive down the tree, making sure no edges are shared
while (concat->refcount.IsOne() && rep->IsConcat()) {
stack.push_back(concat);
concat = rep->concat();
rep = concat->right;
}
// Validate we ended on a non shared flat.
if (concat->refcount.IsOne() && rep->IsFlat() &&
rep->refcount.IsOne()) {
// Verify it has at least the requested extra capacity
CordRepFlat* flat = rep->flat();
size_t remaining = flat->Capacity() - flat->length;
if (extra_capacity > remaining) return {tree, nullptr};
// Check if we have a parent to adjust, or if we must return the left node.
rep = concat->left;
if (!stack.empty()) {
stack.back()->right = rep;
for (CordRepConcat* parent : stack) {
parent->length -= flat->length;
}
rep = tree;
}
delete concat;
return {rep, flat};
}
return {tree, nullptr};
}
} // namespace cord_internal
ABSL_NAMESPACE_END
} // namespace absl
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