Don't throw when Position is out of range for BufferedReadStream

src/ImageSharp/IO/BufferedReadStream.cs

@@ -87,7 +87,6 @@ namespace SixLabors.ImageSharp.IO
             set
             {
                 Guard.MustBeGreaterThanOrEqualTo(value, 0, nameof(this.Position));
-                Guard.MustBeLessThanOrEqualTo(value, this.Length, nameof(this.Position));
 
                 // Only reset readBufferIndex if we are out of bounds of our working buffer
                 // otherwise we should simply move the value by the diff.

tests/ImageSharp.Tests/IO/BufferedReadStreamTests.cs

@@ -314,7 +314,7 @@ namespace SixLabors.ImageSharp.Tests.IO
 
         [Theory]
         [MemberData(nameof(BufferSizes))]
-        public void BufferedStreamThrowsOnBadPosition(int bufferSize)
+        public void BufferedStreamThrowsOnNegativePosition(int bufferSize)
         {
             this.configuration.StreamProcessingBufferSize = bufferSize;
             using (MemoryStream stream = this.CreateTestStream(bufferSize))
@@ -322,15 +322,14 @@ namespace SixLabors.ImageSharp.Tests.IO
                 using (var reader = new BufferedReadStream(this.configuration, stream))
                 {
                     Assert.Throws<ArgumentOutOfRangeException>(() => reader.Position = -stream.Length);
-                    Assert.Throws<ArgumentOutOfRangeException>(() => reader.Position = stream.Length + 1);
                 }
             }
         }
 
-        [Fact]
-        public void BufferedStreamCanSetPositionToEnd()
+        [Theory]
+        [MemberData(nameof(BufferSizes))]
+        public void BufferedStreamCanSetPositionToEnd(int bufferSize)
         {
-            var bufferSize = 8;
             this.configuration.StreamProcessingBufferSize = bufferSize;
             using (MemoryStream stream = this.CreateTestStream(bufferSize * 2))
             {
@@ -341,6 +340,21 @@ namespace SixLabors.ImageSharp.Tests.IO
             }
         }
 
+        [Theory]
+        [MemberData(nameof(BufferSizes))]
+        public void BufferedStreamCanSetPositionPastTheEnd(int bufferSize)
+        {
+            this.configuration.StreamProcessingBufferSize = bufferSize;
+            using (MemoryStream stream = this.CreateTestStream(bufferSize * 2))
+            {
+                using (var reader = new BufferedReadStream(this.configuration, stream))
+                {
+                    reader.Position = reader.Length + 1;
+                    Assert.Equal(stream.Length + 1, stream.Position);
+                }
+            }
+        }
+
         private MemoryStream CreateTestStream(int length)
         {
             var buffer = new byte[length];