perf: 提高 Content 缓存模式性能

binding/csharp/IP2Region.Net/Internal/Abstractions/AbstractCacheStrategy.cs

@@ -8,32 +8,26 @@ using System.Buffers;
 
 namespace IP2Region.Net.Internal.Abstractions;
 
-internal abstract class AbstractCacheStrategy
+internal abstract class AbstractCacheStrategy(string xdbPath)
 {
-    protected readonly FileStream XdbFileStream;
     private const int BufferSize = 4096;
 
     internal int IoCount { get; private set; }
 
-    protected AbstractCacheStrategy(string xdbPath)
-    {
-        XdbFileStream = new FileStream(xdbPath, FileMode.Open, FileAccess.Read, FileShare.Read, BufferSize,
-            useAsync: true);
-    }
-
     internal virtual ReadOnlyMemory<byte> GetData(int offset, int length)
     {
         byte[] buffer = ArrayPool<byte>.Shared.Rent(length);
         int totalBytesRead = 0;
         try
         {
-            XdbFileStream.Seek(offset, SeekOrigin.Begin);
+            var stream = GetXdbFileStream();
+            stream.Seek(offset, SeekOrigin.Begin);
 
             int bytesRead;
             while (totalBytesRead < length)
             {
                 int bytesToRead = Math.Min(BufferSize, length - totalBytesRead);
-                bytesRead = XdbFileStream.Read(buffer, totalBytesRead, bytesToRead);
+                bytesRead = stream.Read(buffer, totalBytesRead, bytesToRead);
                 totalBytesRead += bytesRead;
 
                 IoCount++;
@@ -46,4 +40,15 @@ internal abstract class AbstractCacheStrategy
 
         return new ReadOnlyMemory<byte>(buffer, 0, totalBytesRead);
     }
+
+    FileStream? _xdbFileStream;
+
+    protected FileStream GetXdbFileStream()
+    {
+        if (_xdbFileStream == null)
+        {
+            _xdbFileStream = new FileStream(xdbPath, FileMode.Open, FileAccess.Read, FileShare.Read, BufferSize, FileOptions.RandomAccess);
+        }
+        return _xdbFileStream;
+    }
 }

binding/csharp/IP2Region.Net/Internal/ContentCacheStrategy.cs

@@ -8,19 +8,18 @@ using IP2Region.Net.Internal.Abstractions;
 
 namespace IP2Region.Net.Internal;
 
-class ContentCacheStrategy : AbstractCacheStrategy
+class ContentCacheStrategy(string xdbPath) : AbstractCacheStrategy(xdbPath)
 {
-    readonly ReadOnlyMemory<byte> _cacheData;
+    ReadOnlyMemory<byte> _cacheData = ReadOnlyMemory<byte>.Empty;
-
-    public ContentCacheStrategy(string xdbPath) : base(xdbPath)
-    {
-        _cacheData = base.GetData(0, (int)XdbFileStream.Length);
-        XdbFileStream.Close();
-        XdbFileStream.Dispose();
-    }
 
     internal override ReadOnlyMemory<byte> GetData(int offset, int length)
     {
+        if (_cacheData.IsEmpty)
+        {
+            using var reader = base.GetXdbFileStream();
+            _cacheData = base.GetData(0, (int)reader.Length);
+        }
+
         return _cacheData.Slice(offset, length);
     }
 }

binding/csharp/IP2Region.Net/XDB/Util.cs

@@ -38,8 +38,13 @@ public static class Util
             throw new FileNotFoundException("xdb file not fould.", dbPath);
         }
 
-        XdbVersion ret = default;
         using var reader = File.OpenRead(dbPath);
+        return await GetVersionAsync(reader, token);
+    }
+
+    internal static async Task<XdbVersion> GetVersionAsync(FileStream reader, CancellationToken token = default)
+    {
+        XdbVersion ret = default;
         var buffer = ArrayPool<byte>.Shared.Rent(256);
 
         try