src/dawn_wire/BufferConsumer_impl.h

// Copyright 2021 The Dawn 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 DAWNWIRE_BUFFERCONSUMER_IMPL_H_
#define DAWNWIRE_BUFFERCONSUMER_IMPL_H_

#include "dawn_wire/BufferConsumer.h"

#include <limits>
#include <type_traits>

namespace dawn::wire {

    template <typename BufferT>
    template <typename T>
    WireResult BufferConsumer<BufferT>::Peek(T** data) {
        if (sizeof(T) > mSize) {
            return WireResult::FatalError;
        }

        *data = reinterpret_cast<T*>(mBuffer);
        return WireResult::Success;
    }

    template <typename BufferT>
    template <typename T>
    WireResult BufferConsumer<BufferT>::Next(T** data) {
        if (sizeof(T) > mSize) {
            return WireResult::FatalError;
        }

        *data = reinterpret_cast<T*>(mBuffer);
        mBuffer += sizeof(T);
        mSize -= sizeof(T);
        return WireResult::Success;
    }

    template <typename BufferT>
    template <typename T, typename N>
    WireResult BufferConsumer<BufferT>::NextN(N count, T** data) {
        static_assert(std::is_unsigned<N>::value, "|count| argument of NextN must be unsigned.");

        constexpr size_t kMaxCountWithoutOverflows = std::numeric_limits<size_t>::max() / sizeof(T);
        if (count > kMaxCountWithoutOverflows) {
            return WireResult::FatalError;
        }

        // Cannot overflow because |count| is not greater than |kMaxCountWithoutOverflows|.
        size_t totalSize = sizeof(T) * count;
        if (totalSize > mSize) {
            return WireResult::FatalError;
        }

        *data = reinterpret_cast<T*>(mBuffer);
        mBuffer += totalSize;
        mSize -= totalSize;
        return WireResult::Success;
    }

}  // namespace dawn::wire

#endif  // DAWNWIRE_BUFFERCONSUMER_IMPL_H_