parsed_metadata.h | Explore in Territory

// Copyright 2021 gRPC 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
//
//     http://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.

#ifndef GRPC_SRC_CORE_LIB_TRANSPORT_PARSED_METADATA_H
#define GRPC_SRC_CORE_LIB_TRANSPORT_PARSED_METADATA_H

#include <grpc/support/port_platform.h>

#include <string.h>

#include <cstdint>
#include <string>
#include <type_traits>
#include <utility>

#include "absl/functional/function_ref.h"
#include "absl/meta/type_traits.h"
#include "absl/strings/match.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"

#include <grpc/slice.h>

#include "src/core/lib/gprpp/time.h"
#include "src/core/lib/slice/slice.h"

namespace grpc_core {

MetadataParseErrorFn;

namespace metadata_detail {

// Helper to determine whether a traits metadata is inlinable inside a memento,
// or (if not) we'll need to take the memory allocation path.
template <typename Which>
struct HasSimpleMemento { … };

// Storage type for a single metadata entry.
Buffer;

// Given a key and a value, concatenate together to make a debug string.
// Split out to avoid template bloat.
std::string MakeDebugString(absl::string_view key, absl::string_view value);

// Wrapper around MakeDebugString.
// For the value part, use two functions - one to extract a typed field from
// Buffer, and a second (sourced from the trait) to generate a displayable debug
// string from the field value. We try to maximize indirection/code sharing here
// as this is not critical path code and we'd like to avoid some code bloat -
// better to scale by number of types than then number of metadata traits!
template <typename Field, typename CompatibleWithField, typename Display>
GPR_ATTRIBUTE_NOINLINE std::string MakeDebugStringPipeline(
    absl::string_view key, const Buffer& value,
    Field (*field_from_buffer)(const Buffer&),
    Display (*display_from_field)(CompatibleWithField)) { … }

// Extract a trivial field value from a Buffer - for MakeDebugStringPipeline.
template <typename Field>
Field FieldFromTrivial(const Buffer& value) { … }

// Extract a pointer field value from a Buffer - for MakeDebugStringPipeline.
template <typename Field>
Field FieldFromPointer(const Buffer& value) { … }

// Extract a Slice from a Buffer.
Slice SliceFromBuffer(const Buffer& buffer);

// Unref the grpc_slice part of a Buffer (assumes it is in fact a grpc_slice).
void DestroySliceValue(const Buffer& value);

// Destroy a trivial memento (empty function).
void DestroyTrivialMemento(const Buffer& value);

// Set a slice value in a container
template <Slice (*MementoToValue)(Slice)>
void SetSliceValue(Slice* set, const Buffer& value) { … }

}  // namespace metadata_detail

// A parsed metadata value.
// This type captures a type erased MementoType from one trait of
// MetadataContainer, and provides utilities to manipulate that and to set it on
// a MetadataContainer.
template <typename MetadataContainer>
class ParsedMetadata { … };

namespace metadata_detail {}  // namespace metadata_detail

template <typename MetadataContainer>
const typename ParsedMetadata<MetadataContainer>::VTable*
ParsedMetadata<MetadataContainer>::EmptyVTable() { … }

template <typename MetadataContainer>
template <typename Which>
const typename ParsedMetadata<MetadataContainer>::VTable*
ParsedMetadata<MetadataContainer>::TrivialTraitVTable() { … }

template <typename MetadataContainer>
template <typename Which>
const typename ParsedMetadata<MetadataContainer>::VTable*
ParsedMetadata<MetadataContainer>::NonTrivialTraitVTable() { … }

template <typename MetadataContainer>
template <typename Which>
const typename ParsedMetadata<MetadataContainer>::VTable*
ParsedMetadata<MetadataContainer>::SliceTraitVTable() { … }

template <typename MetadataContainer>
const typename ParsedMetadata<MetadataContainer>::VTable*
ParsedMetadata<MetadataContainer>::KeyValueVTable(absl::string_view key) { … }

}  // namespace grpc_core

#endif  // GRPC_SRC_CORE_LIB_TRANSPORT_PARSED_METADATA_H
chromium/third_party/grpc/src/src/core/lib/transport/parsed_metadata.h
