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// Copyright 2020 The Pigweed 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
// 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.
#pragma once
#include <cstddef>
#include <type_traits>
#include "pw_span/span.h"
#include "pw_status/status_with_size.h"
namespace pw {
namespace internal {
template <typename T>
struct FunctionTraits;
template <typename T, typename ReturnType, typename... Args>
struct FunctionTraits<ReturnType (T::*)(Args...)> {
using Class = T;
using Return = ReturnType;
} // namespace internal
// Writes bytes to an unspecified output. Provides a Write function that takes a
// span of bytes and returns a Status.
class Output {
virtual StatusWithSize Write(span<const std::byte> data) = 0;
// Convenience wrapper for writing data from a pointer and length.
StatusWithSize Write(const void* data, size_t size_bytes) {
return Write(span(static_cast<const std::byte*>(data), size_bytes));
~Output() = default;
// Output adapter that calls a method on a class with a span of bytes. If the
// method returns void instead of the expected Status, Write always returns
// Status::OK.
template <auto kMethod>
class OutputToMethod final : public Output {
using Class = typename internal::FunctionTraits<decltype(kMethod)>::Class;
constexpr OutputToMethod(Class* object) : object_(*object) {}
StatusWithSize Write(span<const std::byte> data) override {
using Return = typename internal::FunctionTraits<decltype(kMethod)>::Return;
if constexpr (std::is_void_v<Return>) {
return StatusWithSize(data.size());
} else {
return (object_.*kMethod)(data);
Class& object_;
// Output adapter that calls a free function.
class OutputToFunction final : public Output {
OutputToFunction(StatusWithSize (*function)(span<const std::byte>))
: function_(function) {}
StatusWithSize Write(span<const std::byte> data) override {
return function_(data);
StatusWithSize (*function_)(span<const std::byte>);
} // namespace pw