FixedSizeList<T>

// The MIT License (MIT)

// Copyright (c) 2019 Ltd Cadwise-N

// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

using System;
using Guard;
using JetBrains.Annotations;

namespace Cadwise.Collections
{
    public sealed class FixedSizeList<T>
    {
        private readonly T[] _backend;

        private int _firstFreeSlot;

        public FixedSizeList(int capacity)
        {
            ThrowIf.Argument.NegativeOrZero(capacity, nameof(capacity));

            _backend = new T[capacity];
        }

        public void Add(T item)
        {
            ThrowIf.Precondition.Failed(false == Full(), "list is full");

            _backend[_firstFreeSlot] = item;
            ++_firstFreeSlot;
        }

        public void Clear()
        {
            for (int i = 0; i < _firstFreeSlot; ++i)
            {
                _backend[i] = default(T);
            }

            _firstFreeSlot = 0;
        }

        [Pure]
        public bool Full()
        {
            return _firstFreeSlot == _backend.Length;
        }

        [Pure]
        public int GetCapacity()
        {
            return _backend.Length;
        }

        [Pure]
        public int GetLength()
        {
            return _firstFreeSlot;
        }

        [Pure]
        public ReadOnlySpan<T> Access()
        {
            return _backend.AsSpan(0, _firstFreeSlot);
        }
    }
}