Merge remote-tracking branch 'upstream/master' into single-ca-drv-build

src/libutil/archive.cc

@@ -366,11 +366,7 @@ void copyNAR(Source & source, Sink & sink)
 
     ParseSink parseSink; /* null sink; just parse the NAR */
 
-    LambdaSource wrapper([&](unsigned char * data, size_t len) {
-        auto n = source.read(data, len);
-        sink(data, n);
-        return n;
-    });
+    TeeSource wrapper { source, sink };
 
     parseDump(parseSink, wrapper);
 }

src/libutil/hash.cc

@@ -136,6 +136,8 @@ std::string Hash::to_string(Base base, bool includeType) const
     return s;
 }
 
+Hash Hash::dummy(htSHA256);
+
 Hash Hash::parseSRI(std::string_view original) {
     auto rest = original;
 

src/libutil/hash.hh

@@ -59,9 +59,6 @@ private:
     Hash(std::string_view s, HashType type, bool isSRI);
 
 public:
-    /* Check whether a hash is set. */
-    operator bool () const { return (bool) type; }
-
     /* Check whether two hash are equal. */
     bool operator == (const Hash & h2) const;
 
@@ -105,6 +102,8 @@ public:
         assert(type == htSHA1);
         return std::string(to_string(Base16, false), 0, 7);
     }
+
+    static Hash dummy;
 };
 
 /* Helper that defaults empty hashes to the 0 hash. */

src/libutil/serialise.hh

@@ -231,6 +231,17 @@ struct SizedSource : Source
     }
 };
 
+/* A sink that that just counts the number of bytes given to it */
+struct LengthSink : Sink
+{
+    uint64_t length = 0;
+
+    virtual void operator () (const unsigned char * _, size_t len)
+    {
+        length += len;
+    }
+};
+
 /* Convert a function into a sink. */
 struct LambdaSink : Sink
 {