103 lines
3.2 KiB
C
103 lines
3.2 KiB
C
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// Copyright 2021 The Abseil Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_STRINGS_INTERNAL_CORD_REP_CRC_H_
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#define ABSL_STRINGS_INTERNAL_CORD_REP_CRC_H_
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#include <cassert>
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#include <cstdint>
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#include "absl/base/config.h"
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#include "absl/base/optimization.h"
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#include "absl/strings/internal/cord_internal.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace cord_internal {
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// CordRepCrc is a CordRep node intended only to appear at the top level of a
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// cord tree. It associates an "expected CRC" with the contained data, to allow
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// for easy passage of checksum data in Cord data flows.
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//
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// From Cord's perspective, the crc value has no semantics; any validation of
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// the contained checksum is the user's responsibility.
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struct CordRepCrc : public CordRep {
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CordRep* child;
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uint32_t crc;
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// Consumes `child` and returns a CordRepCrc prefixed tree containing `child`.
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// If the specified `child` is itself a CordRepCrc node, then this method
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// either replaces the existing node, or directly updates the crc value in it
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// depending on the node being shared or not, i.e.: refcount.IsOne().
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// `child` must not be null. Never returns null.
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static CordRepCrc* New(CordRep* child, uint32_t crc);
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// Destroys (deletes) the provided node. `node` must not be null.
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static void Destroy(CordRepCrc* node);
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};
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// Consumes `rep` and returns a CordRep* with any outer CordRepCrc wrapper
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// removed. This is usually a no-op (returning `rep`), but this will remove and
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// unref an outer CordRepCrc node.
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inline CordRep* RemoveCrcNode(CordRep* rep) {
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assert(rep != nullptr);
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if (ABSL_PREDICT_FALSE(rep->IsCrc())) {
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CordRep* child = rep->crc()->child;
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if (rep->refcount.IsOne()) {
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delete rep->crc();
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} else {
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CordRep::Ref(child);
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CordRep::Unref(rep);
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}
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return child;
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}
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return rep;
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}
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// Returns `rep` if it is not a CordRepCrc node, or its child if it is.
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// Does not consume or create a reference on `rep` or the returned value.
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inline CordRep* SkipCrcNode(CordRep* rep) {
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assert(rep != nullptr);
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if (ABSL_PREDICT_FALSE(rep->IsCrc())) {
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return rep->crc()->child;
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} else {
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return rep;
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}
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}
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inline const CordRep* SkipCrcNode(const CordRep* rep) {
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assert(rep != nullptr);
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if (ABSL_PREDICT_FALSE(rep->IsCrc())) {
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return rep->crc()->child;
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} else {
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return rep;
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}
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}
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inline CordRepCrc* CordRep::crc() {
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assert(IsCrc());
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return static_cast<CordRepCrc*>(this);
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}
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inline const CordRepCrc* CordRep::crc() const {
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assert(IsCrc());
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return static_cast<const CordRepCrc*>(this);
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}
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} // namespace cord_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_STRINGS_INTERNAL_CORD_REP_CRC_H_
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