* addToStore() in nix-worker: don't write the NAR dump received from

the client to a temporary directory, as that is highly inefficient.

src/libstore/local-store.cc

@@ -655,24 +655,12 @@ void LocalStore::invalidatePath(const Path & path)
 }
 
 
-Path LocalStore::addToStore(const Path & _srcPath,
-    bool recursive, HashType hashAlgo, PathFilter & filter)
+Path LocalStore::addToStoreFromDump(const string & dump, const string & name,
+    bool recursive, HashType hashAlgo)
 {
-    Path srcPath(absPath(_srcPath));
-    debug(format("adding `%1%' to the store") % srcPath);
+    Hash h = hashString(hashAlgo, dump);
 
-    /* Read the whole path into memory. This is not a very scalable
-       method for very large paths, but `copyPath' is mainly used for
-       small files. */
-    StringSink sink;
-    if (recursive) 
-        dumpPath(srcPath, sink, filter);
-    else
-        sink.s = readFile(srcPath);
-
-    Hash h = hashString(hashAlgo, sink.s);
-
-    Path dstPath = makeFixedOutputPath(recursive, hashAlgo, h, baseNameOf(srcPath));
+    Path dstPath = makeFixedOutputPath(recursive, hashAlgo, h, name);
 
     addTempRoot(dstPath);
 
@@ -688,10 +676,10 @@ Path LocalStore::addToStore(const Path & _srcPath,
             if (pathExists(dstPath)) deletePathWrapped(dstPath);
 
             if (recursive) {
-                StringSource source(sink.s);
+                StringSource source(dump);
                 restorePath(dstPath, source);
             } else
-                writeStringToFile(dstPath, sink.s);
+                writeStringToFile(dstPath, dump);
 
             canonicalisePathMetaData(dstPath);
 
@@ -701,7 +689,7 @@ Path LocalStore::addToStore(const Path & _srcPath,
                sha256); otherwise, compute it here. */
             registerValidPath(dstPath,
                 (recursive && hashAlgo == htSHA256) ? h :
-                (recursive ? hashString(htSHA256, sink.s) : hashPath(htSHA256, dstPath)),
+                (recursive ? hashString(htSHA256, dump) : hashPath(htSHA256, dstPath)),
                 PathSet(), "");
         }
 
@@ -712,6 +700,25 @@ Path LocalStore::addToStore(const Path & _srcPath,
 }
 
 
+Path LocalStore::addToStore(const Path & _srcPath,
+    bool recursive, HashType hashAlgo, PathFilter & filter)
+{
+    Path srcPath(absPath(_srcPath));
+    debug(format("adding `%1%' to the store") % srcPath);
+
+    /* Read the whole path into memory. This is not a very scalable
+       method for very large paths, but `copyPath' is mainly used for
+       small files. */
+    StringSink sink;
+    if (recursive) 
+        dumpPath(srcPath, sink, filter);
+    else
+        sink.s = readFile(srcPath);
+
+    return addToStoreFromDump(sink.s, baseNameOf(srcPath), recursive, hashAlgo);
+}
+
+
 Path LocalStore::addTextToStore(const string & name, const string & s,
     const PathSet & references)
 {

src/libstore/local-store.hh

@@ -93,6 +93,13 @@ public:
         bool recursive = true, HashType hashAlgo = htSHA256,
         PathFilter & filter = defaultPathFilter);
 
+    /* Like addToStore(), but the contents of the path are contained
+       in `dump', which is either a NAR serialisation (if recursive ==
+       true) or simply the contents of a regular file (if recursive ==
+       false). */
+    Path addToStoreFromDump(const string & dump, const string & name,
+        bool recursive = true, HashType hashAlgo = htSHA256);
+
     Path addTextToStore(const string & name, const string & s,
         const PathSet & references);
 

src/nix-worker/nix-worker.cc

@@ -223,6 +223,43 @@ struct TunnelSource : Source
 };
 
 
+/* If the NAR archive contains a single file at top-level, then save
+   the contents of the file to `s'.  Otherwise barf. */
+struct RetrieveRegularNARSink : ParseSink
+{
+    string s;
+
+    void createDirectory(const Path & path)
+    {
+        throw Error("regular file expected");
+    }
+
+    void receiveContents(unsigned char * data, unsigned int len)
+    {
+        s.append((const char *) data, len);
+    }
+
+    void createSymlink(const Path & path, const string & target)
+    {
+        throw Error("regular file expected");
+    }
+};
+
+
+/* Adapter class of a Source that saves all data read to `s'. */
+struct SavingSourceAdapter : Source
+{
+    Source & orig;
+    string s;
+    SavingSourceAdapter(Source & orig) : orig(orig) { }
+    void operator () (unsigned char * data, unsigned int len)
+    {
+        orig(data, len);
+        s.append((const char *) data, len);
+    }
+};
+
+
 static void performOp(unsigned int clientVersion,
     Source & from, Sink & to, unsigned int op)
 {
@@ -299,13 +336,22 @@ static void performOp(unsigned int clientVersion,
         }
         HashType hashAlgo = parseHashType(s);
 
-        Path tmp = createTempDir();
-        AutoDelete delTmp(tmp);
-        Path tmp2 = tmp + "/" + baseName;
-        restorePath(tmp2, from);
+        SavingSourceAdapter savedNAR(from);
+        RetrieveRegularNARSink savedRegular;
+        
+        if (recursive) {
+            /* Get the entire NAR dump from the client and save it to
+               a string so that we can pass it to
+               addToStoreFromDump(). */
+            ParseSink sink; /* null sink; just parse the NAR */
+            parseDump(sink, savedNAR);
+        } else {
+            parseDump(savedRegular, from);
+        }
             
         startWork();
-        Path path = store->addToStore(tmp2, recursive, hashAlgo);
+        Path path = dynamic_cast<LocalStore *>(store.get())
+            ->addToStoreFromDump(recursive ? savedNAR.s : savedRegular.s, baseName, recursive, hashAlgo);
         stopWork();
         
         writeString(path, to);