- tweak: refactor funny

Nebula.Shared/Utils/StreamHelper.cs

@@ -0,0 +1,54 @@
+using System.Buffers;
+
+namespace Nebula.Shared.Utils;
+
+public static class StreamHelper
+{
+    public static async ValueTask<byte[]> ReadExactAsync(this Stream stream, int amount, CancellationToken? cancel)
+    {
+        var data = new byte[amount];
+        await ReadExactAsync(stream, data, cancel);
+        return data;
+    }
+
+    public static async ValueTask ReadExactAsync(this Stream stream, Memory<byte> into, CancellationToken? cancel)
+    {
+        while (into.Length > 0)
+        {
+            var read = await stream.ReadAsync(into);
+
+            // Check EOF.
+            if (read == 0)
+                throw new EndOfStreamException();
+
+            into = into[read..];
+        }
+    }
+
+    public static async Task CopyAmountToAsync(
+        this Stream stream,
+        Stream to,
+        int amount,
+        int bufferSize,
+        CancellationToken cancel)
+    {
+        var buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
+
+        while (amount > 0)
+        {
+            Memory<byte> readInto = buffer;
+            if (amount < readInto.Length)
+                readInto = readInto[..amount];
+
+            var read = await stream.ReadAsync(readInto, cancel);
+            if (read == 0)
+                throw new EndOfStreamException();
+
+            amount -= read;
+
+            readInto = readInto[..read];
+
+            await to.WriteAsync(readInto, cancel);
+        }
+    }
+}