* Started implementing the new evaluation model.

* Lots of refactorings.
* Unit tests.

src/nix.cc

@@ -11,155 +11,15 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
-extern "C" {
-#include <aterm1.h>
-}
-
 #include "util.hh"
 #include "hash.hh"
 #include "db.hh"
+#include "nix.hh"
+#include "eval.hh"
 
 using namespace std;
 
 
-/* Database names. */
-
-/* dbRefs :: Hash -> FileName
-
-   Maintains a mapping from hashes to filenames within the NixValues
-   directory.  This mapping is for performance only; it can be
-   reconstructed unambiguously from the nixValues directory.  The
-   reason is that names in this directory are not printed hashes but
-   also might carry some descriptive element (e.g.,
-   "aterm-2.0-ae749a...").  Without this mapping, looking up a value
-   would take O(n) time because we would need to read the entire
-   directory. */
-static string dbRefs = "refs";
-
-/* dbNFs :: Hash -> Hash
-
-   Each pair (h1, h2) in this mapping records the fact that h2 is a
-   normal form obtained by evaluating the value h1.
-
-   We would really like to have h2 be the hash of the object
-   referenced by h2.  However, that gives a cyclic dependency: to
-   compute the hash (and thus the file name) of the object, we need to
-   compute the object, but to do that, we need the file name of the
-   object.
-
-   So for now we abandon the requirement that 
-
-     hashFile(dbRefs[h]) == h.
-
-   I.e., this property does not hold for computed normal forms.
-   Rather, we use h2 = hash(h1).  This allows dbNFs to be
-   reconstructed.  Perhaps using a pseudo random number would be
-   better to prevent the system from being subverted in some way.
-*/
-static string dbNFs = "nfs";
-
-/* dbNetSources :: Hash -> URL
-
-   Each pair (hash, url) in this mapping states that the object
-   identified by hash can be obtained by fetching the object pointed
-   to by url. 
-
-   TODO: this should be Hash -> [URL]
-
-   TODO: factor this out into a separate tool? */
-static string dbNetSources = "netsources";
-
-
-/* Path names. */
-
-/* nixValues is the directory where all Nix values (both files and
-   directories, and both normal and non-normal forms) live. */
-static string nixValues;
-
-/* nixLogDir is the directory where we log evaluations. */ 
-static string nixLogDir;
-
-/* nixDB is the file name of the Berkeley DB database where we
-   maintain the dbXXX mappings. */
-static string nixDB;
-
-
-/* Abstract syntax of Nix values:
-
-   e := Hash(h) -- external reference
-      | Str(s) -- string constant
-      | Bool(b) -- boolean constant
-      | Name(e) -- "&" operator; pointer (file name) formation
-      | App(e, e) -- application
-      | Lam(x, e) -- lambda abstraction
-      | Exec(platform, e, e*)
-          -- primitive; execute e with args e* on platform
-      ;
-*/
-
-
-/* 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;
-}
-
-
-/* Obtain an object with the given hash.  If a file with that hash is
-   known to exist in the local file system (as indicated by the dbRefs
-   database), we use that.  Otherwise, we attempt to fetch it from the
-   network (using dbNetSources).  We verify that the file has the
-   right hash. */
-string getFile(Hash hash)
-{
-    bool checkedNet = false;
-
-    while (1) {
-
-        string fn, url;
-
-        if (queryDB(nixDB, dbRefs, hash, fn)) {
-
-            /* Verify that the file hasn't changed. !!! race */
-            if (hashFile(fn) != hash)
-                throw Error("file " + fn + " is stale");
-
-            return fn;
-        }
-
-        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);
-    }
-}
-
-
-typedef map<string, string> Params;
-
-
 void readPkgDescr(Hash hash,
     Params & pkgImports, Params & fileImports, Params & arguments)
 {
@@ -204,9 +64,6 @@ void readPkgDescr(Hash hash,
 string getPkg(Hash hash);
 
 
-typedef map<string, string> Environment;
-
-
 void fetchDeps(Hash hash, Environment & env)
 {
     /* Read the package description file. */
@@ -538,15 +395,6 @@ void registerInstalledPkg(Hash hash, string path)
 }
 
 
-void initDB()
-{
-    createDB(nixDB, dbRefs);
-    createDB(nixDB, dbInstPkgs);
-    createDB(nixDB, dbPrebuilts);
-    createDB(nixDB, dbNetSources);
-}
-
-
 void verifyDB()
 {
     /* Check that all file references are still valid. */