TBL.GodotSharp/IO/File/GodotFileStream.cs

using System;
using System.IO;
using Godot;

namespace TBL.GodotSharp.IO.File
{
    /// <summary>
    /// Wrapper for <see cref="Godot.File"/> that allows it to be used as a <see cref="System.IO.Stream"/>.
    /// </summary>
    /// <remarks>
    /// Use this if really necessary, but prefer to use .NET's built in IO classes as they will be quite a bit faster.
    /// If you need to convert a godot path to an absolute one, use <see cref="ProjectSettings.GlobalizePath(string)"/>.
    /// </remarks>
    public class GodotFileStream : Stream
    {
        private Godot.File _file;
        private Godot.File.ModeFlags _flags;

        /// <summary>
        /// Create a new instance of the <see cref="GodotFileStream"/> class.
        /// </summary>
        /// <param name="path">The path to the file to open. This accepts Godot-style <code>user://</code> and <code>res://</code> paths.</param>
        /// <param name="flags">File flags.</param>
        /// <param name="compressionMode">If not null, this will enable compression/decompression.</param>
        public GodotFileStream(string path, Godot.File.ModeFlags flags,
            Godot.File.CompressionMode? compressionMode = null)
        {
            if (path == null)
                throw new ArgumentNullException("path");

            _file = new Godot.File();
            _flags = flags;
            Error result;
            if (compressionMode.HasValue)
            {
                result = _file.OpenCompressed(path, flags, compressionMode.Value);
            }
            else
            {
                result = _file.Open(path, flags);
            }

            if (result != Error.Ok)
            {
                throw new IOException($"Unable to open \"{path}\": {result}");
            }
        }

        public override bool CanRead => _flags == Godot.File.ModeFlags.Read ||
                                        _flags == Godot.File.ModeFlags.ReadWrite ||
                                        _flags == Godot.File.ModeFlags.WriteRead;

        public override bool CanSeek => true;

        public override bool CanWrite => _flags == Godot.File.ModeFlags.Write ||
                                         _flags == Godot.File.ModeFlags.ReadWrite ||
                                         _flags == Godot.File.ModeFlags.WriteRead;

        public override long Length => checked((long)_file.GetLen());

        public override long Position
        {
            get => checked((long)_file.GetPosition());
            set => _file.Seek(value);
        }

        public override void Flush()
        {
            _file.Flush();
        }

        public override int Read(byte[] buffer, int offset, int count)
        {
            if (!_file.IsOpen())
                throw new ObjectDisposedException("File has been closed");

            if (!CanRead)
                throw new NotSupportedException($"Cannot Read on a GodotFileStream with flags {_flags}");

            if (count < 0)
                throw new ArgumentOutOfRangeException("count");

            if (offset < 0)
                throw new ArgumentOutOfRangeException("offset");

            if (count + offset > buffer.Length)
                throw new ArgumentException("count + offset is greater than the given buffer length");

            var data = _file.GetBuffer(count);
            if (_file.GetError() != Error.Ok)
                throw new IOException($"Error reading file: {_file.GetError()}");

            Array.Copy(data, 0, buffer, offset, data.Length);
            return data.Length;
        }

        public override long Seek(long offset, SeekOrigin origin)
        {
            if (!_file.IsOpen())
                throw new ObjectDisposedException("File has been closed");

            switch (origin)
            {
                case SeekOrigin.Begin:
                    _file.Seek(offset);
                    break;

                case SeekOrigin.Current:
                    _file.Seek(checked((long)_file.GetPosition()) + offset);
                    break;

                case SeekOrigin.End:
                    _file.SeekEnd(offset);
                    break;
            }

            if (_file.GetError() != Error.Ok)
                throw new IOException($"Error seeking file: {_file.GetError()}");

            return checked((long)_file.GetPosition());
        }

        public override void SetLength(long value)
        {
            throw new NotSupportedException("GodotFileStream does not support SetLength");
        }

        public override void Write(byte[] buffer, int offset, int count)
        {
            if (!_file.IsOpen())
                throw new ObjectDisposedException("File has been closed");

            if (!CanWrite)
                throw new NotSupportedException($"Cannot Write on a GodotFileStream with flags {_flags}");

            if (count < 0)
                throw new ArgumentOutOfRangeException("count");

            if (offset < 0)
                throw new ArgumentOutOfRangeException("offset");

            if (count + offset > buffer.Length)
                throw new ArgumentException("count + offset is greater than the given buffer length");

            var data = new byte[count];
            Array.Copy(buffer, offset, data, 0, count);

            _file.StoreBuffer(data);
            if (_file.GetError() != Error.Ok)
                throw new IOException($"Error writing file: {_file.GetError()}");
        }

        protected override void Dispose(bool disposing)
        {
            _file.Close();
        }
    }
}