Add crash handler stuff.

Penumbra.CrashHandler/Buffers/MemoryMappedBuffer.cs

@@ -0,0 +1,215 @@
+using System.Diagnostics.CodeAnalysis;
+using System.IO.MemoryMappedFiles;
+using System.Numerics;
+using System.Text;
+
+namespace Penumbra.CrashHandler.Buffers;
+
+public class MemoryMappedBuffer : IDisposable
+{
+    private const int MinHeaderLength = 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4;
+
+    private readonly MemoryMappedFile _file;
+    private readonly MemoryMappedViewAccessor _header;
+    private readonly MemoryMappedViewAccessor[] _lines;
+
+    public readonly int Version;
+    public readonly uint LineCount;
+    public readonly uint LineCapacity;
+    private readonly uint _lineMask;
+    private bool _disposed;
+
+    protected uint CurrentLineCount
+    {
+        get => _header.ReadUInt32(16);
+        set => _header.Write(16, value);
+    }
+
+    protected uint CurrentLinePosition
+    {
+        get => _header.ReadUInt32(20);
+        set => _header.Write(20, value);
+    }
+
+    public uint TotalWrittenLines
+    {
+        get => _header.ReadUInt32(24);
+        protected set => _header.Write(24, value);
+    }
+
+    public MemoryMappedBuffer(string mapName, int version, uint lineCount, uint lineCapacity)
+    {
+        Version = version;
+        LineCount = BitOperations.RoundUpToPowerOf2(Math.Clamp(lineCount, 2, int.MaxValue >> 3));
+        LineCapacity = BitOperations.RoundUpToPowerOf2(Math.Clamp(lineCapacity, 2, int.MaxValue >> 3));
+        _lineMask = LineCount - 1;
+        var fileName = Encoding.UTF8.GetBytes(mapName);
+        var headerLength = (uint)(4 + 4 + 4 + 4 + 4 + 4 + 4 + fileName.Length + 1);
+        headerLength = (headerLength & 0b111) > 0 ? (headerLength & ~0b111u) + 0b1000 : headerLength;
+        var capacity = LineCount * LineCapacity + headerLength;
+        _file = MemoryMappedFile.CreateNew(mapName, capacity, MemoryMappedFileAccess.ReadWrite, MemoryMappedFileOptions.None,
+            HandleInheritability.Inheritable);
+        _header = _file.CreateViewAccessor(0, headerLength);
+        _header.Write(0, headerLength);
+        _header.Write(4, Version);
+        _header.Write(8, LineCount);
+        _header.Write(12, LineCapacity);
+        _header.WriteArray(28, fileName, 0, fileName.Length);
+        _header.Write(fileName.Length + 28, (byte)0);
+        _lines = Enumerable.Range(0, (int)LineCount).Select(i
+                => _file.CreateViewAccessor(headerLength + i * LineCapacity, LineCapacity, MemoryMappedFileAccess.ReadWrite))
+            .ToArray();
+    }
+
+    public MemoryMappedBuffer(string mapName, int? expectedVersion = null, uint? expectedMinLineCount = null,
+        uint? expectedMinLineCapacity = null)
+    {
+        _file = MemoryMappedFile.OpenExisting(mapName, MemoryMappedFileRights.ReadWrite, HandleInheritability.Inheritable);
+        using var headerLine = _file.CreateViewAccessor(0, 4, MemoryMappedFileAccess.Read);
+        var headerLength = headerLine.ReadUInt32(0);
+        if (headerLength < MinHeaderLength)
+            Throw($"Map {mapName} did not contain a valid header.");
+
+        _header = _file.CreateViewAccessor(0, headerLength, MemoryMappedFileAccess.ReadWrite);
+        Version = _header.ReadInt32(4);
+        LineCount = _header.ReadUInt32(8);
+        LineCapacity = _header.ReadUInt32(12);
+        _lineMask = LineCount - 1;
+        if (expectedVersion.HasValue && expectedVersion.Value != Version)
+            Throw($"Map {mapName} has version {Version} instead of {expectedVersion.Value}.");
+
+        if (LineCount < expectedMinLineCount)
+            Throw($"Map {mapName} has line count {LineCount} but line count >= {expectedMinLineCount.Value} is required.");
+
+        if (LineCapacity < expectedMinLineCapacity)
+            Throw($"Map {mapName} has line capacity {LineCapacity} but line capacity >= {expectedMinLineCapacity.Value} is required.");
+
+        var name = ReadString(GetSpan(_header, 28));
+        if (name != mapName)
+            Throw($"Map {mapName} does not contain its map name at the expected location.");
+
+        _lines = Enumerable.Range(0, (int)LineCount).Select(i
+                => _file.CreateViewAccessor(headerLength + i * LineCapacity, LineCapacity, MemoryMappedFileAccess.ReadWrite))
+            .ToArray();
+
+        [DoesNotReturn]
+        void Throw(string text)
+        {
+            _file.Dispose();
+            _disposed = true;
+            throw new Exception(text);
+        }
+    }
+
+    public void Dispose()
+    {
+        Dispose(true);
+        GC.SuppressFinalize(this);
+        _disposed = true;
+    }
+
+    protected static string ReadString(Span<byte> span)
+    {
+        if (span.IsEmpty)
+            throw new Exception("String from empty span requested.");
+
+        var termination = span.IndexOf((byte)0);
+        if (termination < 0)
+            throw new Exception("String in span is not terminated.");
+
+        return Encoding.UTF8.GetString(span[..termination]);
+    }
+
+    protected static int WriteString(string text, Span<byte> span)
+    {
+        var bytes = Encoding.UTF8.GetBytes(text);
+        var length = bytes.Length + 1;
+        if (length > span.Length)
+            throw new Exception($"String {text} is too long to write into span.");
+
+        bytes.CopyTo(span);
+        span[bytes.Length] = 0;
+        return length;
+    }
+
+    protected static int WriteSpan(ReadOnlySpan<byte> input, Span<byte> span)
+    {
+        var length = input.Length + 1;
+        if (length > span.Length)
+            throw new Exception("Byte array is too long to write into span.");
+
+        input.CopyTo(span);
+        span[input.Length] = 0;
+        return length;
+    }
+
+    protected Span<byte> GetLine(int i)
+    {
+        if (i < 0 || i > LineCount)
+            return null;
+
+        lock (_header)
+        {
+            var lineIdx = CurrentLinePosition + i & _lineMask;
+            if (lineIdx > CurrentLineCount)
+                return null;
+
+            return GetSpan(_lines[lineIdx]);
+        }
+    }
+
+
+    protected MemoryMappedViewAccessor GetCurrentLineLocking()
+    {
+        MemoryMappedViewAccessor view;
+        lock (_header)
+        {
+            var currentLineCount = CurrentLineCount;
+            if (currentLineCount == LineCount)
+            {
+                var currentLinePos = CurrentLinePosition;
+                view = _lines[currentLinePos]!;
+                CurrentLinePosition = currentLinePos + 1 & _lineMask;
+            }
+            else
+            {
+                view = _lines[currentLineCount];
+                ++CurrentLineCount;
+            }
+
+            ++TotalWrittenLines;
+            _header.Flush();
+        }
+
+        return view;
+    }
+
+    protected static Span<byte> GetSpan(MemoryMappedViewAccessor accessor, int offset = 0)
+        => GetSpan(accessor, offset, (int)accessor.Capacity - offset);
+
+    protected static unsafe Span<byte> GetSpan(MemoryMappedViewAccessor accessor, int offset, int size)
+    {
+        byte* ptr = null;
+        accessor.SafeMemoryMappedViewHandle.AcquirePointer(ref ptr);
+        size = Math.Min(size, (int)accessor.Capacity - offset);
+        if (size < 0)
+            return [];
+
+        var span = new Span<byte>(ptr + offset + accessor.PointerOffset, size);
+        return span;
+    }
+
+    protected void Dispose(bool disposing)
+    {
+        if (_disposed)
+            return;
+
+        _header.Dispose();
+        foreach (var line in _lines)
+            line.Dispose();
+        _file.Dispose();
+    }
+
+    ~MemoryMappedBuffer()
+        => Dispose(false);
+}