// Copyright (c) the JPEG XL Project Authors. All rights reserved.

//

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

#ifndef LIB_JXL_BASE_SPAN_H_

#define LIB_JXL_BASE_SPAN_H_

// Span (array view) is a non-owning container that provides cheap "cut"

// operations and could be used as "ArrayLike" data source for PaddedBytes.

#include <cstddef>

#include <cstdint>

#include <type_traits>

#include <vector>

#include "lib/jxl/base/status.h"

namespace jxl {

template <typename T>

class Span {

 public:

  constexpr Span() noexcept : Span(nullptr, 0) {}

  constexpr Span(T* array, size_t length) noexcept

      : ptr_(array), len_(length) {}

  template <size_t N>

  explicit constexpr Span(T (&a)[N]) noexcept : Span(a, N) {}

  template <typename U>

  constexpr Span(U* array, size_t length) noexcept

      : ptr_(reinterpret_cast<T*>(array)), len_(length) {

    static_assert(sizeof(U) == sizeof(T), "Incompatible type of source.");

  }

  template <typename ArrayLike>

  explicit constexpr Span(const ArrayLike& other) noexcept

      : Span(reinterpret_cast<T*>(other.data()), other.size()) {

    static_assert(sizeof(*other.data()) == sizeof(T),

                  "Incompatible type of source.");

  }

  using NCT = typename std::remove_const<T>::type;

  constexpr T* data() const noexcept { return ptr_; }

  constexpr size_t size() const noexcept { return len_; }

  constexpr bool empty() const noexcept { return len_ == 0; }

  constexpr T* begin() const noexcept { return data(); }

  constexpr T* end() const noexcept { return data() + size(); }

  constexpr T& operator[](size_t i) const noexcept {

    // MSVC 2015 accepts this as constexpr, but not ptr_[i]

    return *(data() + i);

  }

  Status remove_prefix(size_t n) noexcept {

    JXL_ENSURE(size() >= n);

    ptr_ += n;

    len_ -= n;

    return true;

  }

  void AppendTo(std::vector<NCT>& dst) const {

    dst.insert(dst.end(), begin(), end());

  }

  std::vector<NCT> Copy() const { return std::vector<NCT>(begin(), end()); }

 private:

  T* ptr_;

  size_t len_;

};

using Bytes = Span<const uint8_t>;

}  // namespace jxl

#endif  // LIB_JXL_BASE_SPAN_H_