1 files changed, 103 insertions, 0 deletions
diff --git a/format/packfile/ingest/temp.go b/format/packfile/ingest/temp.go
new file mode 100644
index 00000000..d0b7862c
--- /dev/null
+++ b/format/packfile/ingest/temp.go
@@ -0,0 +1,103 @@
+package ingest
+
+import (
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+)
+
+// openTemporaryArtifacts creates/open temp pack/idx/(rev) files under destination.
+func openTemporaryArtifacts(state *ingestState) error {
+	packName, packFile, err := createTempFile(state.destination, "tmp_pack_")
+	if err != nil {
+		return err
+	}
+
+	idxName, idxFile, err := createTempFile(state.destination, "tmp_idx_")
+	if err != nil {
+		_ = packFile.Close()
+		_ = state.destination.Remove(packName)
+
+		return err
+	}
+
+	revName := ""
+
+	var revFile *os.File
+	if state.opts.WriteRev {
+		revName, revFile, err = createTempFile(state.destination, "tmp_rev_")
+		if err != nil {
+			_ = idxFile.Close()
+			_ = state.destination.Remove(idxName)
+			_ = packFile.Close()
+			_ = state.destination.Remove(packName)
+
+			return err
+		}
+	}
+
+	state.packTmpName = packName
+	state.packFile = packFile
+	state.idxTmpName = idxName
+	state.idxFile = idxFile
+	state.revTmpName = revName
+	state.revFile = revFile
+
+	return nil
+}
+
+// closeTemporaryArtifacts closes all temporary artifact file descriptors.
+func closeTemporaryArtifacts(state *ingestState) error {
+	var out error
+
+	if state.packFile != nil {
+		err := state.packFile.Close()
+		if err != nil && out == nil {
+			out = err
+		}
+
+		state.packFile = nil
+	}
+
+	if state.idxFile != nil {
+		err := state.idxFile.Close()
+		if err != nil && out == nil {
+			out = err
+		}
+
+		state.idxFile = nil
+	}
+
+	if state.revFile != nil {
+		err := state.revFile.Close()
+		if err != nil && out == nil {
+			out = err
+		}
+
+		state.revFile = nil
+	}
+
+	return out
+}
+
+// createTempFile creates one temporary file under root using prefix.
+func createTempFile(root *os.Root, prefix string) (string, *os.File, error) {
+	for range 32 {
+		name := prefix + rand.Text()
+
+		file, err := root.OpenFile(name, os.O_CREATE|os.O_EXCL|os.O_RDWR, 0o644)
+		if err == nil {
+			return name, file, nil
+		}
+
+		if errors.Is(err, fs.ErrExist) {
+			continue
+		}
+
+		return "", nil, fmt.Errorf("packfile/ingest: create temp file %q: %w", name, err)
+	}
+
+	return "", nil, fmt.Errorf("packfile/ingest: unable to create temporary file for prefix %q", prefix)
+}