From 46d11a767ccfcd6f7af0d10ccefc08ec9e2df5f4 Mon Sep 17 00:00:00 2001
From: gVisor bot <gvisor-bot@google.com>
Date: Fri, 21 Aug 2020 17:24:45 -0700
Subject: Provide fdReader/Writer for FileDescription

fdReader/Writer implements io.Reader/Writer so that they can be passed
to Merkle tree library.

PiperOrigin-RevId: 327901376
---
 pkg/sentry/vfs/file_description.go | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go
index d3abe28ee..33910e095 100644
--- a/pkg/sentry/vfs/file_description.go
+++ b/pkg/sentry/vfs/file_description.go
@@ -847,3 +847,31 @@ func (fd *FileDescription) SetAsyncHandler(newHandler func() FileAsync) FileAsyn
 	}
 	return fd.asyncHandler
 }
+
+// FileReadWriteSeeker is a helper struct to pass a FileDescription as
+// io.Reader/io.Writer/io.ReadSeeker/etc.
+type FileReadWriteSeeker struct {
+	Fd    *FileDescription
+	Ctx   context.Context
+	ROpts ReadOptions
+	WOpts WriteOptions
+}
+
+// Read implements io.ReadWriteSeeker.Read.
+func (f *FileReadWriteSeeker) Read(p []byte) (int, error) {
+	dst := usermem.BytesIOSequence(p)
+	ret, err := f.Fd.Read(f.Ctx, dst, f.ROpts)
+	return int(ret), err
+}
+
+// Seek implements io.ReadWriteSeeker.Seek.
+func (f *FileReadWriteSeeker) Seek(offset int64, whence int) (int64, error) {
+	return f.Fd.Seek(f.Ctx, offset, int32(whence))
+}
+
+// Write implements io.ReadWriteSeeker.Write.
+func (f *FileReadWriteSeeker) Write(p []byte) (int, error) {
+	buf := usermem.BytesIOSequence(p)
+	ret, err := f.Fd.Write(f.Ctx, buf, f.WOpts)
+	return int(ret), err
+}
-- 
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