From b6e9e69c96b4402b042bd72101f0f7cb5bde419b Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Fri, 8 Aug 2025 13:29:22 +1000
Subject: [PATCH] Fix build on Windows

---
 storage/file-piece.go        |  8 ++------
 storage/seek-data_unix.go    | 19 +++++++++++++++++++
 storage/seek-data_windows.go | 10 ++++++++++
 3 files changed, 31 insertions(+), 6 deletions(-)
 create mode 100644 storage/seek-data_unix.go
 create mode 100644 storage/seek-data_windows.go

diff --git a/storage/file-piece.go b/storage/file-piece.go
index d50c509a..54f1556b 100644
--- a/storage/file-piece.go
+++ b/storage/file-piece.go
@@ -12,8 +12,6 @@ import (
 
 	g "github.com/anacrolix/generics"
 	"github.com/anacrolix/missinggo/v2/panicif"
-	"golang.org/x/sys/unix"
-
 	"github.com/anacrolix/torrent/metainfo"
 	"github.com/anacrolix/torrent/segments"
 )
@@ -318,10 +316,8 @@ func (me *filePieceImpl) writeFileTo(w io.Writer, fileIndex int, extent segments
 	panicif.GreaterThan(extent.End(), file.FileInfo.Length)
 	extentRemaining := extent.Length
 	var dataOffset int64
-	dataOffset, err = unix.Seek(int(f.Fd()), extent.Start, unix.SEEK_DATA)
-	if err == unix.ENXIO {
-		// File has no more data. Treat as short write like io.CopyN.
-		err = io.EOF
+	dataOffset, err = seekData(f, extent.Start)
+	if err == io.EOF {
 		return
 	}
 	panicif.Err(err)
diff --git a/storage/seek-data_unix.go b/storage/seek-data_unix.go
new file mode 100644
index 00000000..35e0dee0
--- /dev/null
+++ b/storage/seek-data_unix.go
@@ -0,0 +1,19 @@
+//go:build unix
+
+package storage
+
+import (
+	"io"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func seekData(f *os.File, offset int64) (ret int64, err error) {
+	ret, err = unix.Seek(int(f.Fd()), offset, unix.SEEK_DATA)
+	if err == unix.ENXIO {
+		// File has no more data. Treat as short write like io.CopyN.
+		err = io.EOF
+	}
+	return
+}
diff --git a/storage/seek-data_windows.go b/storage/seek-data_windows.go
new file mode 100644
index 00000000..ccfe202f
--- /dev/null
+++ b/storage/seek-data_windows.go
@@ -0,0 +1,10 @@
+package storage
+
+import (
+	"io"
+	"os"
+)
+
+func seekData(f *os.File, offset int64) (ret int64, err error) {
+	return f.Seek(offset, io.SeekStart)
+}
-- 
2.51.0