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86588778b1
After the preparatory introduction of LineBufferedReader, it is now possible to introduce registration of fallback decoders that won't drop input supplied in the first line of the file. A fallback decoder is used when the magic in the first line of the file does not match any of the other known decoders. In such a case, the fallback decoder is constructed and provided a LineBufferedReader instance. The process of matching magic only peeks the first non-empty line, so it is available for re-reading in Decode() using ReadLine(). There can be only one fallback decoder per type; a second attempt of registering a fallback will result in an exception to avoid bugs. To address the issue of parsing failing on badly or non-headered files, set the legacy decoders for Beatmaps and Storyboards as the fallbacks. Due to non-trivial logic, several new, passing unit tests with possible edge cases also included.
73 lines
2.3 KiB
C#
73 lines
2.3 KiB
C#
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
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// See the LICENCE file in the repository root for full licence text.
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using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Text;
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namespace osu.Game.IO
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{
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/// <summary>
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/// A <see cref="StreamReader"/>-like decorator (with more limited API) for <see cref="Stream"/>s
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/// that allows lines to be peeked without consuming.
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/// </summary>
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public class LineBufferedReader : IDisposable
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{
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private readonly StreamReader streamReader;
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private readonly Queue<string> lineBuffer;
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public LineBufferedReader(Stream stream)
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{
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streamReader = new StreamReader(stream);
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lineBuffer = new Queue<string>();
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}
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/// <summary>
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/// Reads the next line from the stream without consuming it.
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/// Subsequent calls to <see cref="PeekLine"/> without a <see cref="ReadLine"/> will return the same string.
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/// </summary>
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public string PeekLine()
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{
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if (lineBuffer.Count > 0)
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return lineBuffer.Peek();
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var line = streamReader.ReadLine();
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if (line != null)
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lineBuffer.Enqueue(line);
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return line;
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}
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/// <summary>
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/// Reads the next line from the stream and consumes it.
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/// If a line was peeked, that same line will then be consumed and returned.
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/// </summary>
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public string ReadLine() => lineBuffer.Count > 0 ? lineBuffer.Dequeue() : streamReader.ReadLine();
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/// <summary>
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/// Reads the stream to its end and returns the text read.
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/// This includes any peeked but unconsumed lines.
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/// </summary>
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public string ReadToEnd()
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{
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var remainingText = streamReader.ReadToEnd();
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if (lineBuffer.Count == 0)
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return remainingText;
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var builder = new StringBuilder();
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// this might not be completely correct due to varying platform line endings
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while (lineBuffer.Count > 0)
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builder.AppendLine(lineBuffer.Dequeue());
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builder.Append(remainingText);
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return builder.ToString();
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}
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public void Dispose()
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{
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streamReader?.Dispose();
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}
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}
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}
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