From 235b2c0a2a7b4aeca22cc0622852ae681ddc0aae Mon Sep 17 00:00:00 2001
From: Kevin Bost <kitokeboo@gmail.com>
Date: Sun, 25 Feb 2024 00:26:15 -0800
Subject: [PATCH] Fixing issue with StreamSegment.Adjust

It was improperly checking the offset parameter when it should have been checking the length parameter.
I added a test to cover the various adjust cases to ensure that it works as expected.
---
 src/DotNext.IO/IO/StreamSegment.cs         |  4 ++--
 src/DotNext.Tests/IO/StreamSegmentTests.cs | 17 ++++++++++++++++-
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/DotNext.IO/IO/StreamSegment.cs b/src/DotNext.IO/IO/StreamSegment.cs
index 58155d96d..58882666e 100644
--- a/src/DotNext.IO/IO/StreamSegment.cs
+++ b/src/DotNext.IO/IO/StreamSegment.cs
@@ -40,11 +40,11 @@ public StreamSegment(Stream stream, bool leaveOpen = true)
     /// </remarks>
     /// <param name="offset">The offset in the underlying stream.</param>
     /// <param name="length">The length of the segment.</param>
-    /// <exception cref="ArgumentOutOfRangeException"><paramref name="length"/> is larger than the reamining length of the underlying stream; or <paramref name="offset"/> if greater than the length of the underlying stream.</exception>
+    /// <exception cref="ArgumentOutOfRangeException"><paramref name="length"/> is larger than the remaining length of the underlying stream; or <paramref name="offset"/> if greater than the length of the underlying stream.</exception>
     public void Adjust(long offset, long length)
     {
         ArgumentOutOfRangeException.ThrowIfGreaterThan((ulong)offset, (ulong)BaseStream.Length, nameof(offset));
-        ArgumentOutOfRangeException.ThrowIfGreaterThan((ulong)offset, (ulong)(BaseStream.Length - offset), nameof(length));
+        ArgumentOutOfRangeException.ThrowIfGreaterThan((ulong)length, (ulong)(BaseStream.Length - offset), nameof(length));
 
         this.length = length;
         this.offset = offset;
diff --git a/src/DotNext.Tests/IO/StreamSegmentTests.cs b/src/DotNext.Tests/IO/StreamSegmentTests.cs
index a9b81b730..e1f6326b6 100644
--- a/src/DotNext.Tests/IO/StreamSegmentTests.cs
+++ b/src/DotNext.Tests/IO/StreamSegmentTests.cs
@@ -1,7 +1,22 @@
-namespace DotNext.IO;
+using System.Text;
+
+namespace DotNext.IO;
 
 public sealed class StreamSegmentTests : Test
 {
+    [Theory]
+    [InlineData(0, 4, "This")]
+    [InlineData(5, 2, "is")]
+    [InlineData(10, 4, "test")]
+    public static void AdjustSetsSegmentOfStream(int offset, int length, string expected)
+    {
+        using var ms = new MemoryStream(Encoding.UTF8.GetBytes("This is a test"));
+        using var segment = new StreamSegment(ms);
+        segment.Adjust(offset, length);
+        StreamReader reader = new(segment);
+        Equal(expected, reader.ReadToEnd());
+    }
+
     [Fact]
     public static void ReadByteSequentially()
     {