* Refactoring: put the Nix expression evaluator in its own library so

that it can be used by multiple programs.

src/libexpr/primops.cc

@@ -0,0 +1,246 @@
+#include "primops.hh"
+#include "normalise.hh"
+#include "globals.hh"
+
+
+Expr primImport(EvalState & state, Expr arg)
+{
+    ATMatcher m;
+    string path;
+    if (!(atMatch(m, arg) >> "Path" >> path))
+        throw badTerm("path expected", arg);
+    return evalFile(state, path);
+}
+
+
+static PathSet storeExprRootsCached(EvalState & state, const Path & nePath)
+{
+    DrvPaths::iterator i = state.drvPaths.find(nePath);
+    if (i != state.drvPaths.end())
+        return i->second;
+    else {
+        PathSet paths = storeExprRoots(nePath);
+        state.drvPaths[nePath] = paths;
+        return paths;
+    }
+}
+
+
+static Hash hashDerivation(EvalState & state, StoreExpr ne)
+{
+    if (ne.type == StoreExpr::neDerivation) {
+	PathSet inputs2;
+        for (PathSet::iterator i = ne.derivation.inputs.begin();
+             i != ne.derivation.inputs.end(); i++)
+        {
+            DrvHashes::iterator j = state.drvHashes.find(*i);
+            if (j == state.drvHashes.end())
+                throw Error(format("don't know expression `%1%'") % (string) *i);
+            inputs2.insert(j->second);
+        }
+	ne.derivation.inputs = inputs2;
+    }
+    return hashTerm(unparseStoreExpr(ne));
+}
+
+
+static Path copyAtom(EvalState & state, const Path & srcPath)
+{
+    /* !!! should be cached */
+    Path dstPath(addToStore(srcPath));
+
+    ClosureElem elem;
+    StoreExpr ne;
+    ne.type = StoreExpr::neClosure;
+    ne.closure.roots.insert(dstPath);
+    ne.closure.elems[dstPath] = elem;
+
+    Hash drvHash = hashDerivation(state, ne);
+    Path drvPath = writeTerm(unparseStoreExpr(ne), "");
+    state.drvHashes[drvPath] = drvHash;
+
+    printMsg(lvlChatty, format("copied `%1%' -> closure `%2%'")
+        % srcPath % drvPath);
+    return drvPath;
+}
+
+
+static string addInput(EvalState & state, 
+    Path & nePath, StoreExpr & ne)
+{
+    PathSet paths = storeExprRootsCached(state, nePath);
+    if (paths.size() != 1) abort();
+    Path path = *(paths.begin());
+    ne.derivation.inputs.insert(nePath);
+    return path;
+}
+
+
+static string processBinding(EvalState & state, Expr e, StoreExpr & ne)
+{
+    e = evalExpr(state, e);
+
+    ATMatcher m;
+    string s;
+    ATermList es;
+
+    if (atMatch(m, e) >> "Str" >> s) return s;
+    if (atMatch(m, e) >> "Uri" >> s) return s;
+    if (atMatch(m, e) >> "Bool" >> "True") return "1";
+    if (atMatch(m, e) >> "Bool" >> "False") return "";
+
+    if (atMatch(m, e) >> "Attrs" >> es) {
+        Expr a = queryAttr(e, "type");
+        if (a && evalString(state, a) == "derivation") {
+            a = queryAttr(e, "drvPath");
+            if (a) {
+                Path drvPath = evalPath(state, a);
+                return addInput(state, drvPath, ne);
+            }
+        }
+    }
+
+    if (atMatch(m, e) >> "Path" >> s) {
+        Path drvPath = copyAtom(state, s);
+        return addInput(state, drvPath, ne);
+    }
+    
+    if (atMatch(m, e) >> "List" >> es) {
+	string s;
+	bool first = true;
+        for (ATermIterator i(es); i; ++i) {
+            startNest(nest, lvlVomit, format("processing list element"));
+	    if (!first) s = s + " "; else first = false;
+	    s += processBinding(state, evalExpr(state, *i), ne);
+        }
+	return s;
+    }
+
+    if (atMatch(m, e) >> "Null") return "";
+    
+    throw badTerm("invalid derivation binding", e);
+}
+
+
+Expr primDerivation(EvalState & state, Expr args)
+{
+    startNest(nest, lvlVomit, "evaluating derivation");
+
+    ATermMap attrs;
+    args = evalExpr(state, args);
+    queryAllAttrs(args, attrs);
+
+    /* Build the derivation expression by processing the attributes. */
+    StoreExpr ne;
+    ne.type = StoreExpr::neDerivation;
+
+    string drvName;
+    Path outPath;
+    Hash outHash;
+    bool outHashGiven = false;
+
+    for (ATermIterator i(attrs.keys()); i; ++i) {
+        string key = aterm2String(*i);
+        Expr value = attrs.get(key);
+        startNest(nest, lvlVomit, format("processing attribute `%1%'") % key);
+
+        /* The `args' attribute is special: it supplies the
+           command-line arguments to the builder. */
+        if (key == "args") {
+            throw Error("args not implemented");
+#if 0
+            ATermList args;
+            if (!(ATmatch(value, "[<list>]", &args))
+                throw badTerm("list expected", value);
+            while (!ATisEmpty(args)) {
+                Expr arg = evalExpr(state, ATgetFirst(args));
+                ne.derivation.args.push_back(processBinding(state, arg, ne));
+                args = ATgetNext(args);
+            }
+#endif
+        }
+
+        /* All other attributes are passed to the builder through the
+           environment. */
+        else {
+            string s = processBinding(state, value, ne);
+            ne.derivation.env[key] = s;
+            if (key == "builder") ne.derivation.builder = s;
+            else if (key == "system") ne.derivation.platform = s;
+            else if (key == "name") drvName = s;
+            else if (key == "outPath") outPath = s;
+            else if (key == "id") { 
+                outHash = parseHash(s);
+                outHashGiven = true;
+            }
+        }
+    }
+    
+    /* Do we have all required attributes? */
+    if (ne.derivation.builder == "")
+        throw badTerm("required attribute `builder' missing", args);
+    if (ne.derivation.platform == "")
+        throw badTerm("required attribute `system' missing", args);
+    if (drvName == "")
+        throw badTerm("required attribute `name' missing", args);
+        
+    /* Determine the output path. */
+    if (!outHashGiven) outHash = hashDerivation(state, ne);
+    if (outPath == "")
+        /* Hash the Nix expression with no outputs to produce a
+           unique but deterministic path name for this derivation. */
+        outPath = canonPath(nixStore + "/" + 
+            ((string) outHash).c_str() + "-" + drvName);
+    ne.derivation.env["out"] = outPath;
+    ne.derivation.outputs.insert(outPath);
+
+    /* Write the resulting term into the Nix store directory. */
+    Hash drvHash = outHashGiven
+        ? hashString((string) outHash + outPath)
+        : hashDerivation(state, ne);
+    Path drvPath = writeTerm(unparseStoreExpr(ne), "-d-" + drvName);
+    state.drvHashes[drvPath] = drvHash;
+
+    printMsg(lvlChatty, format("instantiated `%1%' -> `%2%'")
+        % drvName % drvPath);
+
+    attrs.set("outPath", ATmake("Path(<str>)", outPath.c_str()));
+    attrs.set("drvPath", ATmake("Path(<str>)", drvPath.c_str()));
+    attrs.set("type", ATmake("Str(\"derivation\")"));
+
+    return makeAttrs(attrs);
+}
+
+
+Expr primBaseNameOf(EvalState & state, Expr arg)
+{
+    string s = evalString(state, arg);
+    return ATmake("Str(<str>)", baseNameOf(s).c_str());
+}
+
+
+Expr primToString(EvalState & state, Expr arg)
+{
+    arg = evalExpr(state, arg);
+    ATMatcher m;
+    string s;
+    if (atMatch(m, arg) >> "Str" >> s ||
+        atMatch(m, arg) >> "Path" >> s ||
+        atMatch(m, arg) >> "Uri" >> s)
+        return ATmake("Str(<str>)", s.c_str());
+    else throw badTerm("cannot coerce to string", arg);
+}
+
+
+Expr primNull(EvalState & state)
+{
+    return ATmake("Null");
+}
+
+
+Expr primIsNull(EvalState & state, Expr arg)
+{
+    arg = evalExpr(state, arg);
+    ATMatcher m;
+    return makeBool(atMatch(m, arg) >> "Null");
+}