headerfs: use runtime.GOOS instead of build flag

Author: mohamedawnallah

headerfs/store.go

@@ -100,6 +100,9 @@ type File interface {
 	Stat() (os.FileInfo, error)
 	Sync() error
 	Truncate(size int64) error
+
+	// Returns the name of the file.
+	Name() string
 }
 
 // headerStore combines a on-disk set of headers within a flat file in addition
@@ -112,8 +115,6 @@ type File interface {
 type headerStore struct {
 	mtx sync.RWMutex // nolint:structcheck // false positive because used as embedded struct only
 
-	fileName string
-
 	file File
 
 	*headerIndex
@@ -153,7 +154,6 @@ func newHeaderStore(db walletdb.DB, filePath string,
 	}
 
 	return &headerStore{
-		fileName:    flatFileName,
 		file:        headerFile,
 		headerIndex: index,
 	}, nil
@@ -800,7 +800,7 @@ func (f *filterHeaderStore) maybeResetHeaderState(
 		if err := f.file.Close(); err != nil {
 			return true, err
 		}
-		if err := os.Remove(f.fileName); err != nil {
+		if err := os.Remove(f.file.Name()); err != nil {
 			return true, err
 		}
 		return true, nil

headerfs/truncate.go

@@ -1,9 +1,9 @@
-//go:build !windows
-// +build !windows
-
 package headerfs
 
-import "fmt"
+import (
+	"os"
+	"runtime"
+)
 
 // singleTruncate truncates a single header from the end of the header file.
 // This can be used in the case of a re-org to remove the last header from the
@@ -22,18 +22,27 @@ func (h *headerStore) singleTruncate() error {
 
 	// Next, we'll determine the number of bytes we need to truncate from
 	// the end of the file.
-	var truncateLength int64
-	switch h.indexType {
-	case Block:
-		truncateLength = 80
-	case RegularFilter:
-		truncateLength = 32
-	default:
-		return fmt.Errorf("unknown index type: %v", h.indexType)
+	truncateLength, err := h.indexType.Size()
+	if err != nil {
+		return err
+	}
+	newSize := fileSize - int64(truncateLength)
+
+	// On Windows, we need to close, truncate, and reopen the file.
+	if runtime.GOOS == "windows" {
+		fileName := h.file.Name()
+		if err = h.file.Close(); err != nil {
+			return err
+		}
+
+		if err = os.Truncate(fileName, newSize); err != nil {
+			return err
+		}
+
+		fileFlags := os.O_RDWR | os.O_APPEND | os.O_CREATE
+		h.file, err = os.OpenFile(fileName, fileFlags, 0644)
+		return err
 	}
 
-	// Finally, we'll use both of these values to calculate the new size of
-	// the file and truncate it accordingly.
-	newSize := fileSize - truncateLength
 	return h.file.Truncate(newSize)
 }