1 files changed, 37 insertions, 0 deletions
diff --git a/format/packfile/ingest/flush.go b/format/packfile/ingest/flush.go
new file mode 100644
index 00000000..96753170
--- /dev/null
+++ b/format/packfile/ingest/flush.go
@@ -0,0 +1,37 @@
+package ingest
+
+import "fmt"
+
+// flush writes all consumed-but-unflushed bytes to destination pack file.
+func (scanner *streamScanner) flush() error {
+	return scanner.flushConsumedPrefix()
+}
+
+// flushConsumedPrefix writes scanner.buf[:scanner.off] and compacts unread
+// bytes to the start of buffer.
+func (scanner *streamScanner) flushConsumedPrefix() error {
+	if scanner.off == 0 {
+		return nil
+	}
+
+	written := 0
+	for written < scanner.off {
+		n, err := scanner.dstFile.Write(scanner.buf[written:scanner.off])
+		if err != nil {
+			return &DestinationWriteError{Op: fmt.Sprintf("write pack: %v", err)}
+		}
+
+		if n == 0 {
+			return &DestinationWriteError{Op: "write pack: short write"}
+		}
+
+		written += n
+	}
+
+	unread := scanner.n - scanner.off
+	copy(scanner.buf[:unread], scanner.buf[scanner.off:scanner.n])
+	scanner.off = 0
+	scanner.n = unread
+
+	return nil
+}