libutil: turn HashModuloSink into a free function

Change-Id: I5878007502fa68c2816a0f4c61f7d0e60bdde702

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,

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,
     };
 }
 

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,

src/libutil/hash.hh

@@ -203,5 +203,12 @@ public:
     HashResult currentHash();
 };
 
+inline HashResult hashSource(HashType ht, Source & source)
+{
+    HashSink h(ht);
+    source.drainInto(h);
+    return h.finish();
+}
+
 
 }

src/libutil/references.cc

@@ -109,19 +109,12 @@ void RewritingSink::flush()
     prev.clear();
 }
 
-HashModuloSink::HashModuloSink(HashType ht, const std::string & modulus)
-    : hashSink(ht)
-    , rewritingSink(modulus, std::string(modulus.size(), 0), hashSink)
+HashResult computeHashModulo(HashType ht, const std::string & modulus, Source & source)
 {
-}
+    HashSink hashSink(ht);
+    RewritingSink rewritingSink(modulus, std::string(modulus.size(), 0), hashSink);
 
-void HashModuloSink::operator () (std::string_view data)
-{
-    rewritingSink(data);
-}
-
-HashResult HashModuloSink::finish()
-{
+    source.drainInto(rewritingSink);
     rewritingSink.flush();
 
     /* Hash the positions of the self-references. This ensures that a

src/libutil/references.hh

@@ -41,16 +41,6 @@ struct RewritingSink : Sink
     void flush();
 };
 
-struct HashModuloSink : AbstractHashSink
-{
-    HashSink hashSink;
-    RewritingSink rewritingSink;
-
-    HashModuloSink(HashType ht, const std::string & modulus);
-
-    void operator () (std::string_view data) override;
-
-    HashResult finish() override;
-};
+HashResult computeHashModulo(HashType ht, const std::string & modulus, Source & source);
 
 }

src/nix/hash.cc

@@ -76,23 +76,19 @@ struct CmdHashBase : Command
     void run() override
     {
         for (auto path : paths) {
-
-            std::unique_ptr<AbstractHashSink> hashSink;
-            if (modulus)
-                hashSink = std::make_unique<HashModuloSink>(ht, *modulus);
-            else
-                hashSink = std::make_unique<HashSink>(ht);
-
+            auto source = [&] () -> GeneratorSource {
                 switch (mode) {
                 case FileIngestionMethod::Flat:
-                *hashSink << readFileSource(path);
-                break;
+                    return GeneratorSource(readFileSource(path));
                 case FileIngestionMethod::Recursive:
-                *hashSink << dumpPath(path);
-                break;
+                    return GeneratorSource(dumpPath(path));
                 }
+                assert(false);
+            }();
 
-            Hash h = hashSink->finish().first;
+            Hash h = modulus
+                ? computeHashModulo(ht, *modulus, source).first
+                : hashSource(ht, source).first;
             if (truncate && h.hashSize > 20) h = compressHash(h, 20);
             logger->cout(h.to_string(base, base == SRI));
         }