/* Copyright 2019-2020 Canaan Inc.
 *
 * 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.
 */
#pragma once
#include <xtl/xspan.hpp>
#include <cstring>

namespace nncase
{
namespace runtime
{
    class span_reader
    {
    public:
        span_reader(xtl::span<const uint8_t> span)
            : span_(span)
        {
        }

        bool empty() const noexcept { return span_.empty(); }

        template <class T>
        T read()
        {
            auto value = *reinterpret_cast<const T *>(span_.data());
            advance(sizeof(T));
            return value;
        }

        template <class T>
        T read_unaligned()
        {
            T value;
            std::memcpy(&value, span_.data(), sizeof(T));
            advance(sizeof(T));
            return value;
        }

        template <class T>
        void read(T &value)
        {
            value = *reinterpret_cast<const T *>(span_.data());
            advance(sizeof(T));
        }

        template <class T>
        void read_span(xtl::span<const T> &span, size_t size)
        {
            span = { reinterpret_cast<const T *>(span_.data()), size };
            advance(sizeof(T) * size);
        }

        template <class T, ptrdiff_t N>
        void read_span(xtl::span<const T, N> &span)
        {
            span = { reinterpret_cast<const T *>(span_.data()), N };
            advance(sizeof(T) * N);
        }

        void read_avail(xtl::span<const uint8_t> &span)
        {
            span = span_;
            span_ = {};
        }

        template <class T>
        const T *peek() const noexcept
        {
            return reinterpret_cast<const T *>(span_.data());
        }

        template <class T>
        void get_array(const T *&value, size_t size)
        {
            value = peek<T>();
            advance(size * sizeof(T));
        }

        template <class T>
        void get_ref(const T *&value)
        {
            value = peek<T>();
            advance(sizeof(T));
        }

        void skip(size_t count)
        {
            advance(count);
        }

    private:
        void advance(size_t count)
        {
            span_ = span_.subspan(count);
        }

    private:
        xtl::span<const uint8_t> span_;
    };
}
}