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// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <limits>
#include <string>
#include <unordered_map>
#include <vector>
namespace mdns {
// Writes values into a binary packet.
class PacketWriter {
static constexpr size_t npos = std::numeric_limits<size_t>::max();
template <typename T>
static std::vector<uint8_t> Write(const T& t) {
PacketWriter writer;
writer << t;
return writer.GetPacket();
// Creates a packet writer with an empty packet vector.
// Creates a packet writer that writes to the supplied vector. The intended
// pattern here is that a buffer is moved into the writer using a call like
// |PacketWriter(std::move(my_buffer))| and moved back out when writing is
// complete using |GetPacket|. Call |position| before calling |GetPacket| to
// retrieve the size of the written data. In this way, a fixed-length buffer
// may be used repeatedly without the allocations implied by creating a new
// buffer or resizing an existing one. Note that the buffer *will* be resized
// if it's too small to accommodate the written packet.
explicit PacketWriter(std::vector<uint8_t> packet);
// Gets the current position.
size_t position() const { return position_; }
// Sets the current position.
void SetPosition(size_t position) { position_ = position; }
// Gets the packet vector and resets this |PacketWriter| after resizing the
// vector to |position()| bytes. If the caller is using the default
// constructor, allowing the writer to create its own buffer, this is a
// good way to get that buffer out of the writer once writing is complete.
// To reuse a fixed-size buffer, use the constructor that takes a packet
// parameter, |position| to get the written size and |GetPacket| to take back
// the buffer.
std::vector<uint8_t> GetResizedPacket();
// Gets the unresized packet vector and resets this |PacketWriter|. To
// size the size of the written packet, call |position()| before calling this
// method.
std::vector<uint8_t> GetPacket();
// Puts |count| bytes from |source| into the packet.
void PutBytes(size_t count, const void* source);
// Creates a bookmark for the current position.
void CreateBookmark(const std::string& label);
// Gets the position for a bookmark (established by calling |CreateBookmark|).
// Returns |npos| if the bookmark isn't found.
size_t GetBookmarkPosition(const std::string& label) const;
PacketWriter& operator<<(bool value);
PacketWriter& operator<<(uint8_t value);
PacketWriter& operator<<(uint16_t value);
PacketWriter& operator<<(uint32_t value);
PacketWriter& operator<<(uint64_t value);
PacketWriter& operator<<(int8_t value);
PacketWriter& operator<<(int16_t value);
PacketWriter& operator<<(int32_t value);
PacketWriter& operator<<(int64_t value);
PacketWriter& operator<<(const std::vector<uint8_t>& value);
std::vector<uint8_t> packet_;
size_t position_ = 0;
std::unordered_map<std::string, size_t> positions_by_label_;
// Disallow copy, assign and move.
PacketWriter(const PacketWriter&) = delete;
PacketWriter(PacketWriter&&) = delete;
PacketWriter& operator=(const PacketWriter&) = delete;
PacketWriter& operator=(PacketWriter&&) = delete;
} // namespace mdns