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//
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//
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// Copyright 2018 gRPC 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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// http://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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//
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//
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#ifndef GRPCPP_SUPPORT_PROTO_BUFFER_READER_H
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#define GRPCPP_SUPPORT_PROTO_BUFFER_READER_H
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#include <type_traits>
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#include "absl/strings/cord.h"
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#include <grpc/byte_buffer.h>
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#include <grpc/byte_buffer_reader.h>
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#include <grpc/impl/grpc_types.h>
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#include <grpc/slice.h>
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#include <grpc/support/log.h>
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#include <grpcpp/impl/codegen/config_protobuf.h>
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#include <grpcpp/impl/serialization_traits.h>
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#include <grpcpp/support/byte_buffer.h>
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#include <grpcpp/support/status.h>
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/// This header provides an object that reads bytes directly from a
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/// grpc::ByteBuffer, via the ZeroCopyInputStream interface
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namespace grpc {
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/// This is a specialization of the protobuf class ZeroCopyInputStream
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/// The principle is to get one chunk of data at a time from the proto layer,
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/// with options to backup (re-see some bytes) or skip (forward past some bytes)
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///
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/// Read more about ZeroCopyInputStream interface here:
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/// https://developers.google.com/protocol-buffers/docs/reference/cpp/google.protobuf.io.zero_copy_stream#ZeroCopyInputStream
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class ProtoBufferReader : public grpc::protobuf::io::ZeroCopyInputStream {
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public:
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/// Constructs buffer reader from \a buffer. Will set \a status() to non ok
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/// if \a buffer is invalid (the internal buffer has not been initialized).
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explicit ProtoBufferReader(ByteBuffer* buffer)
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: byte_count_(0), backup_count_(0), status_() {
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/// Implemented through a grpc_byte_buffer_reader which iterates
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/// over the slices that make up a byte buffer
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if (!buffer->Valid() ||
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!grpc_byte_buffer_reader_init(&reader_, buffer->c_buffer())) {
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status_ = Status(StatusCode::INTERNAL,
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"Couldn't initialize byte buffer reader");
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}
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}
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~ProtoBufferReader() override {
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if (status_.ok()) {
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grpc_byte_buffer_reader_destroy(&reader_);
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}
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}
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/// Give the proto library a chunk of data from the stream. The caller
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/// may safely read from data[0, size - 1].
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bool Next(const void** data, int* size) override {
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if (!status_.ok()) {
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return false;
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}
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/// If we have backed up previously, we need to return the backed-up slice
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if (backup_count_ > 0) {
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*data = GRPC_SLICE_START_PTR(*slice_) + GRPC_SLICE_LENGTH(*slice_) -
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backup_count_;
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GPR_ASSERT(backup_count_ <= INT_MAX);
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*size = static_cast<int>(backup_count_);
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backup_count_ = 0;
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return true;
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}
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/// Otherwise get the next slice from the byte buffer reader
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if (!grpc_byte_buffer_reader_peek(&reader_, &slice_)) {
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return false;
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}
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*data = GRPC_SLICE_START_PTR(*slice_);
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// On win x64, int is only 32bit
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GPR_ASSERT(GRPC_SLICE_LENGTH(*slice_) <= INT_MAX);
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byte_count_ += * size = static_cast<int>(GRPC_SLICE_LENGTH(*slice_));
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return true;
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}
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/// Returns the status of the buffer reader.
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Status status() const { return status_; }
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/// The proto library calls this to indicate that we should back up \a count
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/// bytes that have already been returned by the last call of Next.
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/// So do the backup and have that ready for a later Next.
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void BackUp(int count) override {
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GPR_ASSERT(count <= static_cast<int>(GRPC_SLICE_LENGTH(*slice_)));
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backup_count_ = count;
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}
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/// The proto library calls this to skip over \a count bytes. Implement this
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/// using Next and BackUp combined.
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bool Skip(int count) override {
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const void* data;
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int size;
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while (Next(&data, &size)) {
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if (size >= count) {
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BackUp(size - count);
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return true;
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}
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// size < count;
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count -= size;
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}
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// error or we have too large count;
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return false;
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}
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/// Returns the total number of bytes read since this object was created.
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int64_t ByteCount() const override { return byte_count_ - backup_count_; }
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#ifdef GRPC_PROTOBUF_CORD_SUPPORT_ENABLED
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/// Read the next `count` bytes and append it to the given Cord.
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// (override is conditionally omitted here to support old Protobuf which
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// doesn't have ReadCord method)
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// NOLINTNEXTLINE(modernize-use-override)
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virtual bool ReadCord(absl::Cord* cord, int count)
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#if PROTOBUF_VERSION >= 4022000
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override
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#endif
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{
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if (!status().ok()) {
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return false;
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}
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// check for backed up data
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if (backup_count() > 0) {
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if (backup_count() <= count) {
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cord->Append(MakeCordFromSlice(grpc_slice_split_tail(
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slice(), GRPC_SLICE_LENGTH(*slice()) - backup_count())));
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} else {
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cord->Append(MakeCordFromSlice(grpc_slice_sub(
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*slice(), GRPC_SLICE_LENGTH(*slice()) - backup_count(),
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GRPC_SLICE_LENGTH(*slice()) - backup_count() + count)));
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}
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int64_t take = std::min(backup_count(), static_cast<int64_t>(count));
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set_backup_count(backup_count() - take);
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count -= take;
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if (count == 0) {
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return true;
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}
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}
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while (count > 0) {
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if (!grpc_byte_buffer_reader_peek(reader(), mutable_slice_ptr())) {
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return false;
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}
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uint64_t slice_length = GRPC_SLICE_LENGTH(*slice());
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set_byte_count(ByteCount() + slice_length);
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if (slice_length <= static_cast<uint64_t>(count)) {
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cord->Append(MakeCordFromSlice(grpc_slice_ref(*slice())));
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count -= slice_length;
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} else {
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cord->Append(MakeCordFromSlice(grpc_slice_split_head(slice(), count)));
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set_backup_count(slice_length - count);
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return true;
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}
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}
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GPR_ASSERT(count == 0);
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return true;
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}
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#endif // GRPC_PROTOBUF_CORD_SUPPORT_ENABLED
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// These protected members are needed to support internal optimizations.
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// they expose internal bits of grpc core that are NOT stable. If you have
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// a use case needs to use one of these functions, please send an email to
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// https://groups.google.com/forum/#!forum/grpc-io.
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protected:
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void set_byte_count(int64_t byte_count) { byte_count_ = byte_count; }
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int64_t backup_count() { return backup_count_; }
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void set_backup_count(int64_t backup_count) { backup_count_ = backup_count; }
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grpc_byte_buffer_reader* reader() { return &reader_; }
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grpc_slice* slice() { return slice_; }
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grpc_slice** mutable_slice_ptr() { return &slice_; }
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private:
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#ifdef GRPC_PROTOBUF_CORD_SUPPORT_ENABLED
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// This function takes ownership of slice and return a newly created Cord off
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// of it.
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static absl::Cord MakeCordFromSlice(grpc_slice slice) {
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return absl::MakeCordFromExternal(
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absl::string_view(reinterpret_cast<char*>(GRPC_SLICE_START_PTR(slice)),
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GRPC_SLICE_LENGTH(slice)),
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[slice](absl::string_view /* view */) { grpc_slice_unref(slice); });
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}
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#endif // GRPC_PROTOBUF_CORD_SUPPORT_ENABLED
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int64_t byte_count_; ///< total bytes read since object creation
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int64_t backup_count_; ///< how far backed up in the stream we are
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grpc_byte_buffer_reader reader_; ///< internal object to read \a grpc_slice
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///< from the \a grpc_byte_buffer
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grpc_slice* slice_; ///< current slice passed back to the caller
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Status status_; ///< status of the entire object
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};
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} // namespace grpc
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#endif // GRPCPP_SUPPORT_PROTO_BUFFER_READER_H
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