* Store attribute sets as a vector instead of a map (i.e. a red-black

  tree).  This saves a lot of memory.  The vector should be sorted so
  that names can be looked up using binary search, but this is not the
  case yet.  (Surprisingly, looking up attributes using linear search
  doesn't have a big impact on performance.)

  Memory consumption for

    $ nix-instantiate /etc/nixos/nixos/tests -A bittorrent.test --readonly-mode

  on x86_64-linux with GC enabled is now 185 MiB (compared to 946
  MiB on the trunk).

1 files changed, 37 insertions, 28 deletions

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 01cbf7a7c2..20b8395088 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -119,18 +119,18 @@ static void prim_genericClosure(EvalState & state, Value * * args, Value & v)
         args[0]->attrs->find(state.symbols.create("startSet"));
     if (startSet == args[0]->attrs->end())
         throw EvalError("attribute `startSet' required");
-    state.forceList(*startSet->second.value);
+    state.forceList(*startSet->value);
 
     list<Value *> workSet;
-    for (unsigned int n = 0; n < startSet->second.value->list.length; ++n)
-        workSet.push_back(startSet->second.value->list.elems[n]);
+    for (unsigned int n = 0; n < startSet->value->list.length; ++n)
+        workSet.push_back(startSet->value->list.elems[n]);
 
     /* Get the operator. */
     Bindings::iterator op =
         args[0]->attrs->find(state.symbols.create("operator"));
     if (op == args[0]->attrs->end())
         throw EvalError("attribute `operator' required");
-    state.forceValue(*op->second.value);
+    state.forceValue(*op->value);
 
     /* Construct the closure by applying the operator to element of
        `workSet', adding the result to `workSet', continuing until
@@ -147,15 +147,15 @@ static void prim_genericClosure(EvalState & state, Value * * args, Value & v)
             e->attrs->find(state.symbols.create("key"));
         if (key == e->attrs->end())
             throw EvalError("attribute `key' required");
-        state.forceValue(*key->second.value);
+        state.forceValue(*key->value);
 
-        if (doneKeys.find(*key->second.value) != doneKeys.end()) continue;
-        doneKeys.insert(*key->second.value);
+        if (doneKeys.find(*key->value) != doneKeys.end()) continue;
+        doneKeys.insert(*key->value);
         res.push_back(*e);
         
         /* Call the `operator' function with `e' as argument. */
         Value call;
-        mkApp(call, *op->second.value, *e);
+        mkApp(call, *op->value, *e);
         state.forceList(call);
 
         /* Add the values returned by the operator to the work set. */
@@ -322,9 +322,9 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
     if (attr == args[0]->attrs->end())
         throw EvalError("required attribute `name' missing");
     string drvName;
-    Pos & posDrvName(*attr->second.pos);
+    Pos & posDrvName(*attr->pos);
     try {        
-        drvName = state.forceStringNoCtx(*attr->second.value);
+        drvName = state.forceStringNoCtx(*attr->value);
     } catch (Error & e) {
         e.addPrefix(format("while evaluating the derivation attribute `name' at %1%:\n") % posDrvName);
         throw;
@@ -339,7 +339,7 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
     bool outputHashRecursive = false;
 
     foreach (Bindings::iterator, i, *args[0]->attrs) {
-        string key = i->first;
+        string key = i->name;
         startNest(nest, lvlVomit, format("processing attribute `%1%'") % key);
 
         try {
@@ -347,9 +347,9 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
             /* The `args' attribute is special: it supplies the
                command-line arguments to the builder. */
             if (key == "args") {
-                state.forceList(*i->second.value);
-                for (unsigned int n = 0; n < i->second.value->list.length; ++n) {
-                    string s = state.coerceToString(*i->second.value->list.elems[n], context, true);
+                state.forceList(*i->value);
+                for (unsigned int n = 0; n < i->value->list.length; ++n) {
+                    string s = state.coerceToString(*i->value->list.elems[n], context, true);
                     drv.args.push_back(s);
                 }
             }
@@ -357,11 +357,11 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
             /* All other attributes are passed to the builder through
                the environment. */
             else {
-                string s = state.coerceToString(*i->second.value, context, true);
+                string s = state.coerceToString(*i->value, context, true);
                 drv.env[key] = s;
                 if (key == "builder") drv.builder = s;
-                else if (i->first == state.sSystem) drv.platform = s;
-                else if (i->first == state.sName) drvName = s;
+                else if (i->name == state.sSystem) drv.platform = s;
+                else if (i->name == state.sName) drvName = s;
                 else if (key == "outputHash") outputHash = s;
                 else if (key == "outputHashAlgo") outputHashAlgo = s;
                 else if (key == "outputHashMode") {
@@ -373,7 +373,7 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
 
         } catch (Error & e) {
             e.addPrefix(format("while evaluating the derivation attribute `%1%' at %2%:\n")
-                % key % *i->second.pos);
+                % key % *i->pos);
             e.addPrefix(format("while instantiating the derivation named `%1%' at %2%:\n")
                 % drvName % posDrvName);
             throw;
@@ -690,7 +690,7 @@ static void prim_attrNames(EvalState & state, Value * * args, Value & v)
 
     StringSet names;
     foreach (Bindings::iterator, i, *args[0]->attrs)
-        names.insert(i->first);
+        names.insert(i->name);
 
     unsigned int n = 0;
     foreach (StringSet::iterator, i, names)
@@ -708,8 +708,8 @@ static void prim_getAttr(EvalState & state, Value * * args, Value & v)
     if (i == args[1]->attrs->end())
         throw EvalError(format("attribute `%1%' missing") % attr);
     // !!! add to stack trace?
-    state.forceValue(*i->second.value);
-    v = *i->second.value;
+    state.forceValue(*i->value);
+    v = *i->value;
 }
 
 
@@ -735,11 +735,18 @@ static void prim_removeAttrs(EvalState & state, Value * * args, Value & v)
     state.forceAttrs(*args[0]);
     state.forceList(*args[1]);
 
-    state.cloneAttrs(*args[0], v);
-
+    /* Get the attribute names to be removed. */
+    std::set<Symbol> names;
     for (unsigned int i = 0; i < args[1]->list.length; ++i) {
         state.forceStringNoCtx(*args[1]->list.elems[i]);
-        v.attrs->erase(state.symbols.create(args[1]->list.elems[i]->string.s));
+        names.insert(state.symbols.create(args[1]->list.elems[i]->string.s));
+    }
+
+    /* Copy all attributes not in that set. */
+    state.mkAttrs(v);
+    foreach (Bindings::iterator, i, *args[0]->attrs) {
+        if (names.find(i->name) == names.end())
+            v.attrs->push_back(*i);
     }
 }
 
@@ -761,13 +768,15 @@ static void prim_listToAttrs(EvalState & state, Value * * args, Value & v)
         Bindings::iterator j = v2.attrs->find(state.sName);
         if (j == v2.attrs->end())
             throw TypeError("`name' attribute missing in a call to `listToAttrs'");
-        string name = state.forceStringNoCtx(*j->second.value);
+        string name = state.forceStringNoCtx(*j->value);
         
         Bindings::iterator j2 = v2.attrs->find(state.symbols.create("value"));
         if (j2 == v2.attrs->end())
             throw TypeError("`value' attribute missing in a call to `listToAttrs'");
 
-        (*v.attrs)[state.symbols.create(name)] = j2->second;
+        Attr & a = (*v.attrs)[state.symbols.create(name)];
+        a.value = j2->value;
+        a.pos = j2->pos;
     }
 }
 
@@ -783,9 +792,9 @@ static void prim_intersectAttrs(EvalState & state, Value * * args, Value & v)
     state.mkAttrs(v);
 
     foreach (Bindings::iterator, i, *args[0]->attrs) {
-        Bindings::iterator j = args[1]->attrs->find(i->first);
+        Bindings::iterator j = args[1]->attrs->find(i->name);
         if (j != args[1]->attrs->end())
-            (*v.attrs)[j->first] = j->second;
+            v.attrs->push_back(*j);
     }
 }