* clean up code

Author: alecsammon

decompression.go

@@ -2,12 +2,10 @@ package embeddedpostgres
 
 import (
 	"archive/tar"
-	"errors"
 	"fmt"
 	"io"
 	"os"
 	"path/filepath"
-	"syscall"
 
 	"github.com/xi2/xz"
 )
@@ -58,16 +56,11 @@ func decompressTarXz(tarReader func(*xz.Reader) (func() (*tar.Header, error), fu
 		}
 
 		targetPath := filepath.Join(tempExtractPath, header.Name)
-		finalPath := filepath.Join(extractPath, header.Name)
 
 		if err := os.MkdirAll(filepath.Dir(targetPath), os.ModePerm); err != nil {
 			return errorExtractingPostgres(err)
 		}
 
-		if err := os.MkdirAll(filepath.Dir(finalPath), os.ModePerm); err != nil {
-			return errorExtractingPostgres(err)
-		}
-
 		switch header.Typeflag {
 		case tar.TypeReg:
 			outFile, err := os.OpenFile(targetPath, os.O_CREATE|os.O_RDWR, os.FileMode(header.Mode))
@@ -90,25 +83,11 @@ func decompressTarXz(tarReader func(*xz.Reader) (func() (*tar.Header, error), fu
 			if err := os.Symlink(header.Linkname, targetPath); err != nil {
 				return errorExtractingPostgres(err)
 			}
-
-		case tar.TypeDir:
-			if err := os.MkdirAll(finalPath, os.FileMode(header.Mode)); err != nil {
-				return errorExtractingPostgres(err)
-			}
-			continue
-		}
-
-		if err := os.Rename(targetPath, finalPath); err != nil {
-			// if the error is due to syscall.EEXIST then this is most likely windows, and a race condition with
-			// multiple downloads of the file. We assume that the existing file is the correct one and ignore the
-			// error
-			if errors.Is(err, syscall.EEXIST) {
-				return nil
-			}
-
-			return errorExtractingPostgres(err)
 		}
+	}
 
+	if err := renameOrIgnore(tempExtractPath, extractPath); err != nil {
+		return errorExtractingPostgres(err)
 	}
 
 	return nil

remote_fetch.go

@@ -13,7 +13,6 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"syscall"
 )
 
 // RemoteFetchStrategy provides a strategy to fetch a Postgres binary so that it is available for use.
@@ -93,7 +92,8 @@ func decompressResponse(bodyBytes []byte, contentLength int64, cacheLocator Cach
 				return errorExtractingPostgres(err)
 			}
 
-			// to prevent file corruption when multiple processes attempt to extract at the same time we download
+			// if multiple processes attempt to extract
+			// to prevent file corruption when multiple processes attempt to extract at the same time
 			// first to a cache location, and then move the file into place.
 			tmp, err := os.CreateTemp("", "embedded_postgres")
 			if err != nil {
@@ -114,14 +114,7 @@ func decompressResponse(bodyBytes []byte, contentLength int64, cacheLocator Cach
 				return errorExtractingPostgres(err)
 			}
 
-			if err := os.Rename(tmp.Name(), cacheLocation); err != nil {
-				// if the error is due to syscall.EEXIST then this is most likely windows, and a race condition with
-				// multiple downloads of the file. We assume that the existing file is the correct one and ignore the
-				// error
-				if errors.Is(err, syscall.EEXIST) {
-					return nil
-				}
-
+			if err := renameOrIgnore(tmp.Name(), cacheLocation); err != nil {
 				return errorExtractingPostgres(err)
 			}
 

rename.go

@@ -0,0 +1,27 @@
+package embeddedpostgres
+
+import (
+	"errors"
+	"os"
+	"syscall"
+)
+
+// renameOrIgnore will rename the oldpath to the newpath.
+//
+// On Unix this will be a safe atomic operation.
+// On Windows this will do nothing if the new path already exists.
+//
+// This is only safe to use if you can be sure that the newpath is either missing, or contains the same data as the
+// old path.
+func renameOrIgnore(oldpath, newpath string) error {
+	err := os.Rename(oldpath, newpath)
+
+	// if the error is due to syscall.EEXIST then this is most likely windows, and a race condition with
+	// multiple downloads of the file. We can assume that the existing file is the correct one and ignore
+	// the error
+	if errors.Is(err, syscall.EEXIST) {
+		return nil
+	}
+
+	return err
+}