Use a RewritingSink in derivation goal

Possibly this will make it stream

1 files changed, 9 insertions, 6 deletions

diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 6f7ab8a3d..4650b8bae 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -2384,13 +2384,16 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
             if (!outputRewrites.empty()) {
                 debug("rewriting hashes in '%1%'; cross fingers", actualPath);
 
-                /* FIXME: this is in-memory. */
-                StringSink sink;
-                dumpPath(actualPath, sink);
+                /* FIXME: Is this actually streaming? */
+                auto source = sinkToSource([&](Sink & nextSink) {
+                    RewritingSink rsink(outputRewrites, nextSink);
+                    dumpPath(actualPath, rsink);
+                    rsink.flush();
+                });
+                Path tmpPath = actualPath + ".tmp";
+                restorePath(tmpPath, *source);
                 deletePath(actualPath);
-                sink.s = rewriteStrings(sink.s, outputRewrites);
-                StringSource source(sink.s);
-                restorePath(actualPath, source);
+                movePath(tmpPath, actualPath);
 
                 /* FIXME: set proper permissions in restorePath() so
                    we don't have to do another traversal. */