libutil: turn HashModuloSink into a free function

Change-Id: I5878007502fa68c2816a0f4c61f7d0e60bdde702

3 files changed, 20 insertions, 24 deletions

diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index b2a301b00..6a298e6eb 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -2216,23 +2216,21 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
             rewriteOutput(outputRewrites);
             /* FIXME optimize and deduplicate with addToStore */
             std::string oldHashPart { scratchPath->hashPart() };
-            HashModuloSink caSink { outputHash.hashType, oldHashPart };
-            std::visit(overloaded {
-                [&](const TextIngestionMethod &) {
-                    caSink << readFileSource(actualPath);
+            auto input = std::visit(overloaded {
+                [&](const TextIngestionMethod &) -> GeneratorSource {
+                    return GeneratorSource(readFileSource(actualPath));
                 },
-                [&](const FileIngestionMethod & m2) {
+                [&](const FileIngestionMethod & m2) -> GeneratorSource {
                     switch (m2) {
                     case FileIngestionMethod::Recursive:
-                        caSink << dumpPath(actualPath);
-                        break;
+                        return GeneratorSource(dumpPath(actualPath));
                     case FileIngestionMethod::Flat:
-                        caSink << readFileSource(actualPath);
-                        break;
+                        return GeneratorSource(readFileSource(actualPath));
                     }
+                    assert(false);
                 },
             }, outputHash.method.raw);
-            auto got = caSink.finish().first;
+            auto got = computeHashModulo(outputHash.hashType, oldHashPart, input).first;
 
             auto optCA = ContentAddressWithReferences::fromPartsOpt(
                 outputHash.method,
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 98e4d7efe..757aa21e3 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -1887,25 +1887,23 @@ ContentAddress LocalStore::hashCAPath(
     const std::string_view pathHash
 )
 {
-    HashModuloSink caSink ( hashType, std::string(pathHash) );
-    std::visit(overloaded {
-        [&](const TextIngestionMethod &) {
-            caSink << readFileSource(path);
+    auto data = std::visit(overloaded {
+        [&](const TextIngestionMethod &) -> GeneratorSource {
+            return GeneratorSource(readFileSource(path));
         },
-        [&](const FileIngestionMethod & m2) {
+        [&](const FileIngestionMethod & m2) -> GeneratorSource {
             switch (m2) {
             case FileIngestionMethod::Recursive:
-                caSink << dumpPath(path);
-                break;
+                return GeneratorSource(dumpPath(path));
             case FileIngestionMethod::Flat:
-                caSink << readFileSource(path);
-                break;
+                return GeneratorSource(readFileSource(path));
             }
+            assert(false);
         },
     }, method.raw);
     return ContentAddress {
         .method = method,
-        .hash = caSink.finish().first,
+        .hash = computeHashModulo(hashType, std::string(pathHash), data).first,
     };
 }
 
diff --git a/src/libstore/make-content-addressed.cc b/src/libstore/make-content-addressed.cc
index 253609ed2..b5397541c 100644
--- a/src/libstore/make-content-addressed.cc
+++ b/src/libstore/make-content-addressed.cc
@@ -43,10 +43,10 @@ std::map<StorePath, StorePath> makeContentAddressed(
 
         sink.s = rewriteStrings(sink.s, rewrites);
 
-        HashModuloSink hashModuloSink(htSHA256, oldHashPart);
-        hashModuloSink(sink.s);
-
-        auto narModuloHash = hashModuloSink.finish().first;
+        auto narModuloHash = [&] {
+            StringSource source{sink.s};
+            return computeHashModulo(htSHA256, oldHashPart, source).first;
+        }();
 
         ValidPathInfo info {
             dstStore,