* Refactoring: move sink/source buffering into separate classes.

* Buffer the HashSink.  This speeds up hashing a bit because it
  prevents lots of calls to the hash update functions (e.g. nix-hash
  went from 9.3s to 8.7s of user time on the closure of my
  /var/run/current-system).

src/libstore/local-store.cc

@@ -1103,16 +1103,14 @@ struct HashAndWriteSink : Sink
     HashAndWriteSink(Sink & writeSink) : writeSink(writeSink), hashSink(htSHA256)
     {
     }
-    virtual void operator ()
-        (const unsigned char * data, unsigned int len)
+    virtual void operator () (const unsigned char * data, size_t len)
     {
         writeSink(data, len);
         hashSink(data, len);
     }
     Hash currentHash()
     {
-        HashSink hashSinkClone(hashSink);
-        return hashSinkClone.finish().first;
+        return hashSink.currentHash().first;
     }
 };
 
@@ -1201,8 +1199,7 @@ struct HashAndReadSource : Source
     {
         hashing = true;
     }
-    virtual void operator ()
-        (unsigned char * data, unsigned int len)
+    virtual void operator () (unsigned char * data, size_t len)
     {
         readSource(data, len);
         if (hashing) hashSink(data, len);

src/libstore/references.cc

@@ -57,11 +57,11 @@ struct RefScanSink : Sink
 
     RefScanSink() : hashSink(htSHA256) { }
     
-    void operator () (const unsigned char * data, unsigned int len);
+    void operator () (const unsigned char * data, size_t len);
 };
 
 
-void RefScanSink::operator () (const unsigned char * data, unsigned int len)
+void RefScanSink::operator () (const unsigned char * data, size_t len)
 {
     hashSink(data, len);
 

src/libstore/remote-store.cc

@@ -374,7 +374,7 @@ Path RemoteStore::importPath(bool requireSignature, Source & source)
     openConnection();
     writeInt(wopImportPath, to);
     /* We ignore requireSignature, since the worker forces it to true
-       anyway. */    
+       anyway. */
     processStderr(0, &source);
     return readStorePath(from);
 }