osu/osu.Game/Beatmaps/Formats/Decoder.cs

81 lines
3.0 KiB
C#

// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
namespace osu.Game.Beatmaps.Formats
{
public abstract class Decoder<TOutput> : Decoder
where TOutput : new()
{
protected virtual TOutput CreateTemplateObject() => new TOutput();
public TOutput Decode(StreamReader primaryStream, params StreamReader[] otherStreams)
{
var output = CreateTemplateObject();
foreach (StreamReader stream in otherStreams.Prepend(primaryStream))
ParseStreamInto(stream, output);
return output;
}
protected abstract void ParseStreamInto(StreamReader stream, TOutput output);
}
public abstract class Decoder
{
private static readonly Dictionary<Type, Dictionary<string, Func<string, Decoder>>> decoders = new Dictionary<Type, Dictionary<string, Func<string, Decoder>>>();
static Decoder()
{
LegacyBeatmapDecoder.Register();
JsonBeatmapDecoder.Register();
LegacyStoryboardDecoder.Register();
}
/// <summary>
/// Retrieves a <see cref="Decoder"/> to parse a <see cref="Beatmap"/>.
/// </summary>
/// <param name="stream">A stream pointing to the <see cref="Beatmap"/>.</param>
public static Decoder<T> GetDecoder<T>(StreamReader stream)
where T : new()
{
if (stream == null)
throw new ArgumentNullException(nameof(stream));
if (!decoders.TryGetValue(typeof(T), out var typedDecoders))
throw new IOException(@"Unknown decoder type");
string line;
do
{
line = stream.ReadLine()?.Trim();
} while (line != null && line.Length == 0);
if (line == null)
throw new IOException(@"Unknown file format");
var decoder = typedDecoders.Select(d => line.StartsWith(d.Key) ? d.Value : null).FirstOrDefault();
if (decoder == null)
throw new IOException(@"Unknown file format");
return (Decoder<T>)decoder.Invoke(line);
}
/// <summary>
/// Registers an instantiation function for a <see cref="Decoder"/>.
/// </summary>
/// <param name="magic">A string in the file which triggers this decoder to be used.</param>
/// <param name="constructor">A function which constructs the <see cref="Decoder"/> given <paramref name="magic"/>.</param>
protected static void AddDecoder<T>(string magic, Func<string, Decoder> constructor)
{
if (!decoders.TryGetValue(typeof(T), out var typedDecoders))
decoders.Add(typeof(T), typedDecoders = new Dictionary<string, Func<string, Decoder>>());
typedDecoders[magic] = constructor;
}
}
}