* In `nix-store --export', abort if the contents of a path has

  changed.  This prevents corrupt paths from spreading to other
  machines.  Note that checking the hash is cheap because we're
  hashing anyway (because of the --sign feature).

2 files changed, 9 insertions, 1 deletions

diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index eef01fe4d..bd7e33a48 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -289,6 +289,13 @@ HashSink::HashSink(HashType ht) : ht(ht)
     start(ht, *ctx);
 }
     
+HashSink::HashSink(const HashSink & h)
+{
+    ht = h.ht;
+    ctx = new Ctx;
+    *ctx = *h.ctx;
+}
+    
 HashSink::~HashSink()
 {
     delete ctx;
diff --git a/src/libutil/hash.hh b/src/libutil/hash.hh
index 062d97254..81425b234 100644
--- a/src/libutil/hash.hh
+++ b/src/libutil/hash.hh
@@ -96,6 +96,7 @@ private:
 
 public:
     HashSink(HashType ht);
+    HashSink(const HashSink & h);
     ~HashSink();
     virtual void operator () (const unsigned char * data, unsigned int len);
     Hash finish();
@@ -104,5 +105,5 @@ public:
 
 }
 
-    
+
 #endif /* !__HASH_H */