From f1c0b2c0e16154e738f342f2defa42c4d9348c4c Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 1 Oct 2018 17:05:55 +0200
Subject: [PATCH] Add O(1)-memory copyPath() function

---
 src/libutil/archive.cc | 9 +++++++++
 src/libutil/archive.hh | 2 ++
 2 files changed, 11 insertions(+)

diff --git a/src/libutil/archive.cc b/src/libutil/archive.cc
index 3aa120270..db544a212 100644
--- a/src/libutil/archive.cc
+++ b/src/libutil/archive.cc
@@ -375,4 +375,13 @@ void copyNAR(Source & source, Sink & sink)
 }
 
 
+void copyPath(const Path & from, const Path & to)
+{
+    auto source = sinkToSource([&](Sink & sink) {
+        dumpPath(from, sink);
+    });
+    restorePath(to, *source);
+}
+
+
 }
diff --git a/src/libutil/archive.hh b/src/libutil/archive.hh
index 25be426c1..768fe2536 100644
--- a/src/libutil/archive.hh
+++ b/src/libutil/archive.hh
@@ -77,6 +77,8 @@ void restorePath(const Path & path, Source & source);
 /* Read a NAR from 'source' and write it to 'sink'. */
 void copyNAR(Source & source, Sink & sink);
 
+void copyPath(const Path & from, const Path & to);
+
 
 extern const std::string narVersionMagic1;