* Started implementing the new evaluation model.

* Lots of refactorings.
* Unit tests.

src/values.cc

@@ -0,0 +1,100 @@
+#include "values.hh"
+#include "globals.hh"
+#include "db.hh"
+
+
+static void copyFile(string src, string dst)
+{
+    int res = system(("cat " + src + " > " + dst).c_str()); /* !!! escape */
+    if (WEXITSTATUS(res) != 0)
+        throw Error("cannot copy " + src + " to " + dst);
+}
+
+
+static string absValuePath(string s)
+{
+    return nixValues + "/" + s;
+}
+
+
+Hash addValue(string path)
+{
+    Hash hash = hashFile(path);
+
+    string name;
+    if (queryDB(nixDB, dbRefs, hash, name)) {
+        debug((string) hash + " already known");
+        return hash;
+    }
+
+    string baseName = baseNameOf(path);
+    
+    string targetName = (string) hash + "-" + baseName;
+
+    copyFile(path, absValuePath(targetName));
+
+    setDB(nixDB, dbRefs, hash, targetName);
+    
+    return hash;
+}
+
+
+#if 0
+/* Download object referenced by the given URL into the sources
+   directory.  Return the file name it was downloaded to. */
+string fetchURL(string url)
+{
+    string filename = baseNameOf(url);
+    string fullname = nixSourcesDir + "/" + filename;
+    struct stat st;
+    if (stat(fullname.c_str(), &st)) {
+        cerr << "fetching " << url << endl;
+        /* !!! quoting */
+        string shellCmd =
+            "cd " + nixSourcesDir + " && wget --quiet -N \"" + url + "\"";
+        int res = system(shellCmd.c_str());
+        if (WEXITSTATUS(res) != 0)
+            throw Error("cannot fetch " + url);
+    }
+    return fullname;
+}
+#endif
+
+
+string queryValuePath(Hash hash)
+{
+    bool checkedNet = false;
+
+    while (1) {
+
+        string name, url;
+
+        if (queryDB(nixDB, dbRefs, hash, name)) {
+            string fn = absValuePath(name);
+
+            /* Verify that the file hasn't changed. !!! race */
+            if (hashFile(fn) != hash)
+                throw Error("file " + fn + " is stale");
+
+            return fn;
+        }
+
+        throw Error("a file with hash " + (string) hash + " is requested, "
+            "but it is not known to exist locally or on the network");
+#if 0
+        if (checkedNet)
+            throw Error("consistency problem: file fetched from " + url + 
+                " should have hash " + (string) hash + ", but it doesn't");
+
+        if (!queryDB(nixDB, dbNetSources, hash, url))
+            throw Error("a file with hash " + (string) hash + " is requested, "
+                "but it is not known to exist locally or on the network");
+
+        checkedNet = true;
+        
+        fn = fetchURL(url);
+        
+        setDB(nixDB, dbRefs, hash, fn);
+#endif
+    }
+}