Correction of BufferedReadStream's Position (#60529)

nidaca · web-flow · commit 93f7682ca74f · 2025-02-21T22:22:03.000Z
diff --git a/src/Http/WebUtilities/src/BufferedReadStream.cs b/src/Http/WebUtilities/src/BufferedReadStream.cs
@@ -108,8 +108,8 @@ public override long Position
                 if (innerOffset <= _bufferCount)
                 {
                     // Yes, just skip some of the buffered data
-                    _bufferOffset += innerOffset;
-                    _bufferCount -= innerOffset;
+                    _bufferOffset += _bufferCount - innerOffset;
+                    _bufferCount = innerOffset;
                 }
                 else
                 {
diff --git a/src/Http/WebUtilities/test/MultipartReaderTests.cs b/src/Http/WebUtilities/test/MultipartReaderTests.cs
@@ -80,7 +80,6 @@ public class MultipartReaderTests
 "<!DOCTYPE html><title>Content of a.html.</title>\r\n" +
 "\r\n" +
 "--9051914041544843365972754266--\r\n";
-
     private const string TwoPartBodyIncompleteBuffer =
 "--9051914041544843365972754266\r\n" +
 "Content-Disposition: form-data; name=\"text\"\r\n" +
@@ -315,6 +314,43 @@ public void MultipartReader_BufferSizeMustBeLargerThanBoundary_Throws()
         });
     }
 
+    [Fact]
+    public async Task MultipartReader_ReadMultipartBodyWithFilesForDeferredCopy_Success()
+    {
+        var stream = MakeStream(ThreePartBody);
+        var reader = new MultipartReader(Boundary, stream);
+
+        await reader.ReadNextSectionAsync(); // skip text field section
+
+        var section = await reader.ReadNextSectionAsync();
+        Assert.NotNull(section);
+        Assert.Equal(2, section.Headers.Count);
+        Assert.Equal("form-data; name=\"file1\"; filename=\"a.txt\"", section.Headers["Content-Disposition"][0]);
+        Assert.Equal("text/plain", section.Headers["Content-Type"][0]);
+        var stream1 = section.Body;
+
+        section = await reader.ReadNextSectionAsync();
+        Assert.NotNull(section);
+        Assert.Equal(2, section.Headers.Count);
+        Assert.Equal("form-data; name=\"file2\"; filename=\"a.html\"", section.Headers["Content-Disposition"][0]);
+        Assert.Equal("text/html", section.Headers["Content-Type"][0]);
+        var stream2 = section.Body;
+
+        Assert.Null(await reader.ReadNextSectionAsync());
+
+        Assert.True(stream1.CanSeek);
+        Assert.Equal(0, stream1.Seek(0, SeekOrigin.Begin));
+        var buffer = new MemoryStream();
+        await stream1.CopyToAsync(buffer);
+        Assert.Equal("Content of a.txt.\r\n", Encoding.ASCII.GetString(buffer.ToArray()));
+
+        Assert.True(stream2.CanSeek);
+        Assert.Equal(0, stream2.Seek(0, SeekOrigin.Begin));
+        buffer = new MemoryStream();
+        await stream2.CopyToAsync(buffer);
+        Assert.Equal("<!DOCTYPE html><title>Content of a.html.</title>\r\n", Encoding.ASCII.GetString(buffer.ToArray()));
+    }
+
     [Fact]
     public async Task MultipartReader_TwoPartBodyIncompleteBuffer_TwoSectionsReadSuccessfullyThirdSectionThrows()
     {

Original file line number	Diff line number	Diff line change
`@@ -108,8 +108,8 @@ public override long Position`
`108`	`108`	`if (innerOffset <= _bufferCount)`
`109`	`109`	`{`
`110`	`110`	`// Yes, just skip some of the buffered data`
`111`		`- _bufferOffset += innerOffset;`
`112`		`- _bufferCount -= innerOffset;`
	`111`	`+ _bufferOffset += _bufferCount - innerOffset;`
	`112`	`+ _bufferCount = innerOffset;`
`113`	`113`	`}`
`114`	`114`	`else`
`115`	`115`	`{`