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    <p>Memory Mapped Files can be a problem for big files (typically files that are of a size equivalent or bigger than the RAM), in case you eventually map the whole file. If you map only the end, that should not be a real issue.</p> <p>Anyway, here is a C# implementation that does not use Memory Mapped File, but a regular FileStream. It is based on a <code>ReverseStreamReader</code> implementation (code also included). I would be curious to see it compared to other MMF solutions in terms of performance and memory consumption.</p> <pre><code>public static void OverwriteEndLines(string filePath, int linesToStrip) { if (filePath == null) throw new ArgumentNullException("filePath"); if (linesToStrip &lt;= 0) return; using (FileStream file = new FileStream(filePath, FileMode.Open, FileAccess.ReadWrite)) { using (ReverseStreamReader reader = new ReverseStreamReader(file)) { int count = 0; do { string line = reader.ReadLine(); if (line == null) // end of file break; count++; if (count == linesToStrip) { // write CR LF for (int i = 0; i &lt; linesToStrip; i++) { file.WriteByte((byte)'\r'); file.WriteByte((byte)'\n'); } // truncate file to current stream position file.SetLength(file.Position); break; } } while (true); } } } // NOTE: we have not implemented all ReadXXX methods public class ReverseStreamReader : StreamReader { private bool _returnEmptyLine; public ReverseStreamReader(Stream stream) : base(stream) { BaseStream.Seek(0, SeekOrigin.End); } public override int Read() { if (BaseStream.Position == 0) return -1; BaseStream.Seek(-1, SeekOrigin.Current); int i = BaseStream.ReadByte(); BaseStream.Seek(-1, SeekOrigin.Current); return i; } public override string ReadLine() { if (BaseStream.Position == 0) { if (_returnEmptyLine) { _returnEmptyLine = false; return string.Empty; } return null; } int read; StringBuilder sb = new StringBuilder(); while((read = Read()) &gt;= 0) { if (read == '\n') { read = Read(); // supports windows &amp; unix format if ((read &gt; 0) &amp;&amp; (read != '\r')) { BaseStream.Position++; } else if (BaseStream.Position == 0) { // handle the special empty first line case _returnEmptyLine = true; } break; } sb.Append((char)read); } // reverse string. Note this is optional if we don't really need string content if (sb.Length &gt; 1) { char[] array = new char[sb.Length]; sb.CopyTo(0, array, 0, array.Length); Array.Reverse(array); return new string(array); } return sb.ToString(); } } </code></pre>
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    1. POMemory Mapped File to Read End of File?
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    1. USSimon Mourier
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