* Realisation of File(...) expressions.

src/eval.cc

@@ -30,6 +30,7 @@ bool pathExists(string path)
 }
 
 
+#if 0
 /* Compute a derived value by running a program. */
 static Hash computeDerived(Hash sourceHash, string targetName,
     string platform, Hash prog, Environment env)
@@ -175,6 +176,7 @@ static Hash computeDerived(Hash sourceHash, string targetName,
 
     return targetHash;
 }
+#endif
 
 
 /* Throw an exception if the given platform string is not supported by
@@ -182,54 +184,32 @@ static Hash computeDerived(Hash sourceHash, string targetName,
 static void checkPlatform(string platform)
 {
     if (platform != thisSystem)
-        throw Error("a `" + platform +
+        throw Error(format("a `%1%' is required, but I am a `%2%'")
-            "' is required, but I am a `" + thisSystem + "'");
+            % platform % thisSystem);
 }
 
 
-string printExpr(Expr e)
+string printTerm(ATerm t)
 {
-    char * s = ATwriteToString(e);
+    char * s = ATwriteToString(t);
     return s;
 }
 
 
 /* Throw an exception with an error message containing the given
    aterm. */
-static Error badTerm(const string & msg, Expr e)
+static Error badTerm(const format & f, ATerm t)
 {
-    return Error(msg + ", in `" + printExpr(e) + "'");
+    return Error(format("%1%, in `%2%'") % f.str() % printTerm(t));
 }
 
 
-Hash hashExpr(Expr e)
+Hash hashTerm(ATerm t)
 {
-    return hashString(printExpr(e));
+    return hashString(printTerm(t));
 }
 
 
-/* Evaluate an expression; the result must be a string. */
-static string evalString(Expr e)
-{
-    e = whNormalise(e);
-    char * s;
-    if (ATmatch(e, "Str(<str>)", &s)) return s;
-    else throw badTerm("string value expected", e);
-}
-
-
-#if 0
-/* Evaluate an expression; the result must be a value reference. */
-static Hash evalHash(Expr e)
-{
-    e = evalValue(e);
-    char * s;
-    if (ATmatch(e, "Hash(<str>)", &s)) return parseHash(s);
-    else throw badTerm("value reference expected", e);
-}
-#endif
-
-
 #if 0
 /* Evaluate a list of arguments into normal form. */
 void evalArgs(ATermList args, ATermList & argsNF, Environment & env)
@@ -262,225 +242,63 @@ void evalArgs(ATermList args, ATermList & argsNF, Environment & env)
 #endif
 
 
-Expr substExpr(string x, Expr rep, Expr e)
-{
-    char * s;
-    Expr e2;
-
-    if (ATmatch(e, "Var(<str>)", &s))
-        if (x == s)
-            return rep;
-        else
-            return e;
-
-    if (ATmatch(e, "Lam(<str>, <term>)", &s, &e2))
-        if (x == s)
-            return e;
-    /* !!! unfair substitutions */
-
-    /* Generically substitute in subterms. */
-
-    if (ATgetType(e) == AT_APPL) {
-        AFun fun = ATgetAFun(e);
-        int arity = ATgetArity(fun);
-        ATermList args = ATempty;
-
-        for (int i = arity - 1; i >= 0; i--)
-            args = ATinsert(args, substExpr(x, rep, ATgetArgument(e, i)));
-        
-        return (ATerm) ATmakeApplList(fun, args);
-    }
-
-    if (ATgetType(e) == AT_LIST) {
-        ATermList in = (ATermList) e;
-        ATermList out = ATempty;
-
-        while (!ATisEmpty(in)) {
-            out = ATinsert(out, substExpr(x, rep, ATgetFirst(in)));
-            in = ATgetNext(in);
-        }
-
-        return (ATerm) ATreverse(out);
-    }
-
-    throw badTerm("do not know how to substitute", e);
-}
-
-
-#if 0
-Expr evalValue(Expr e)
-{
-    char * s;
-    Expr eBuildPlatform, eProg, e2, e3, e4;
-    ATermList args;
-
-    /* Value references. */
-    if (ATmatch(e, "Hash(<str>)", &s)) {
-        parseHash(s); /* i.e., throw exception if not valid */
-        return e;
-    }
-
-    /* External expression. */
-    if (ATmatch(e, "Deref(<term>)", &e2)) {
-        string fn = queryValuePath(evalHash(e2));
-        ATerm e3 = ATreadFromNamedFile(fn.c_str());
-        if (!e3) throw Error("reading aterm from " + fn);
-        return evalValue(e3);
-    }
-
-    /* Execution primitive. */
-
-    if (ATmatch(e, "Exec(<term>, <term>, [<list>])",
-                 &eBuildPlatform, &eProg, &args))
-    {
-        string buildPlatform = evalString(eBuildPlatform);
-
-        checkPlatform(buildPlatform);
-
-        Hash prog = evalHash(eProg);
-
-        Environment env;
-        ATermList argsNF;
-        evalArgs(args, argsNF, env);
-
-        Hash sourceHash = hashExpr(
-            ATmake("Exec(Str(<str>), Hash(<str>), <term>)",
-                buildPlatform.c_str(), ((string) prog).c_str(), argsNF));
-
-        /* Do we know a normal form for sourceHash? */
-        Hash targetHash;
-        string targetHashS;
-        if (queryDB(nixDB, dbNFs, sourceHash, targetHashS)) {
-            /* Yes. */
-            targetHash = parseHash(targetHashS);
-            debug("already built: " + (string) sourceHash 
-                + " -> " + (string) targetHash);
-        } else {
-            /* No, so we compute one. */
-            targetHash = computeDerived(sourceHash, 
-                (string) sourceHash + "-nf", buildPlatform, prog, env);
-        }
-
-        return ATmake("Hash(<str>)", ((string) targetHash).c_str());
-    }
-
-    /* Barf. */
-    throw badTerm("invalid expression", e);
-}
-#endif
-
-
-Expr whNormalise(Expr e)
-{
-    char * s;
-    Expr e2, e3, e4, e5;
-
-    /* Normal forms. */
-    if (ATmatch(e, "Str(<str>)", &s) ||
-        ATmatch(e, "Bool(True)") || 
-        ATmatch(e, "Bool(False)") ||
-        ATmatch(e, "Lam(<str>, <term>)", &s, &e2) ||
-        ATmatch(e, "File(<str>, <term>, <term>)", &s, &e2, &e3) ||
-        ATmatch(e, "Derive(<term>, <term>, <term>, <term>)", &e2, &e3, &e4, &e5))
-        return e;
-
-    /* Application. */
-    if (ATmatch(e, "App(<term>, <term>)", &e2, &e3)) {
-        e2 = whNormalise(e2);
-        if (!ATmatch(e2, "Lam(<str>, <term>)", &s, &e4))
-            throw badTerm("expecting lambda", e2);
-        return whNormalise(substExpr(s, e3, e4));
-    }
-
-    throw badTerm("invalid expression", e);
-}
-
-
-Expr dNormalise(Expr e)
-{
-    e = whNormalise(e);
-    /* !!! todo */
-    return e;
-}
-
-
-Expr fNormalise(Expr e)
-{
-    e = dNormalise(e);
-
-    char * s;
-    Expr e2, e3;
-
-    if (ATmatch(e, "File(<str>, <term>, [<list>])", &s, &e2, &e3)) {
-
-        ATermList refs = (ATermList) e3, refs2 = ATempty;
-        while (!ATisEmpty(refs)) {
-            ATerm ref = ATgetFirst(refs);
-            refs2 = ATinsert(refs2, fNormalise(ref));
-            refs = ATgetNext(refs);
-        }
-        refs2 = ATreverse(refs2);
-
-        return ATmake("File(<str>, <term>, <term>)", s, e2, refs2);
-
-    }
-
-    else return e;
-}
-
-
-void writeContent(string path, Content content)
-{
-    char * s;
-
-    if (ATmatch(content, "Regular(<str>)", &s)) {
-
-        int fd; /* !!! close on exception */
-        fd = open(path.c_str(), O_CREAT | O_EXCL | O_WRONLY, 0666);
-        if (fd == -1)
-            throw SysError("creating file " + path);
-
-        int len = strlen(s);
-        if (write(fd, s, len) != len)
-            throw SysError("writing file " + path);
-
-        close(fd);
-    }
-    
-    else throw badTerm("ill-formed content", content);
-}
-
-
 struct RStatus
 {
     /* !!! the comparator of this hash should match the semantics of
        the file system */
-    map<string, Hash> paths;
+//     map<string, Hash> paths;
 };
 
 
-static void realise2(RStatus & status, Expr e)
+static void realise(RStatus & status, FState fs)
 {
     char * s;
     Content content;
     ATermList refs;
     
-    if (!ATmatch(e, "File(<str>, <term>, [<list>])", &s, &content, &refs))
+    if (ATmatch(fs, "File(<str>, <term>, [<list>])", &s, &content, &refs)) {
-        throw badTerm("not f-normalised", e);
-
         string path(s);
 
+        if (path[0] != '/') throw Error("absolute path expected: " + path);
+
+        /* Realise referenced paths. */
         while (!ATisEmpty(refs)) {
-        realise2(status, ATgetFirst(refs));
+            realise(status, ATgetFirst(refs));
             refs = ATgetNext(refs);
         }
 
-    writeContent(path, content);
+        if (!ATmatch(content, "Hash(<str>)", &s))
+            throw badTerm("hash expected", content);
+        Hash hash = parseHash(s);
+
+        /* Perhaps the path already exists and has the right hash? */
+        if (pathExists(path)) {
+            if (hash == hashPath(path)) {
+                debug(format("path %1% already has hash %2%")
+                    % path % (string) hash);
+                return;
+            }
+
+            throw Error(format("path %1% exists, but does not have hash %2%")
+                % path % (string) hash);
+        }
+
+        /* Do we know a path with that hash?  If so, copy it. */
+        string path2 = queryFromStore(hash);
+        copyFile(path2, path);
+    }
+
+    else if (ATmatch(fs, "Derive()")) {
+        
+        
+    }
+
+    else throw badTerm("bad file system state expression", fs);
 }
 
 
-void realise(Expr e)
+void realiseFState(FState fs)
 {
     RStatus status;
-    realise2(status, e);
+    realise(status, fs);
 }

src/eval.hh

@@ -10,14 +10,12 @@ extern "C" {
 using namespace std;
 
 
-/* \section{Abstract syntax of Nix expressions}
+/* \section{Abstract syntax of Nix file system state expressions}
 
-   An expression describes a (partial) state of the file system in a
+   A Nix file system state expression, or FState, describes a
-   referentially transparent way.  The operational effect of
+   (partial) state of the file system.
-   evaluating an expression is that the state described by the
-   expression is realised.
 
-     File : Path * Content * [Expr] -> Expr
+     File : Path * Content * [FState] -> FState
 
    File(path, content, refs) specifies a file object (its full path
    and contents), along with all file objects referenced by it (that
@@ -25,7 +23,7 @@ using namespace std;
    self-referential.  This prevents us from having to deal with
    cycles.
 
-     Derive : String * Path * [Expr] * [Expr] * [Expr] -> Expr
+     Derive : String * Path * [FState] * [Path] * [(String, String)] -> [FState]
 
    Derive(platform, builder, ins, outs, env) specifies the creation of
    new file objects (in paths declared by `outs') by the execution of
@@ -33,14 +31,6 @@ using namespace std;
    place in a file system state given by `ins'.  `env' specifies a
    mapping of strings to strings.
 
-     Str : String -> Expr
-
-   A string constant.
-
-     Tup : Expr * Expr -> Expr
-
-   Tuples of expressions.
-
      [ !!! NOT IMPLEMENTED 
        Regular : String -> Content
        Directory : [(String, Content)] -> Content
@@ -49,7 +39,11 @@ using namespace std;
      CHash : Hash -> Content
 
    File content, given either in situ, or through an external reference
-   to the file system or url-space decorated with a hash to preserve purity.
+   to the file system or url-space decorated with a hash to preserve
+   purity.
+
+   A FState expression is in {\em $f$-normal form} if all Derive nodes
+   have been reduced to File nodes.
 
    DISCUSSION: the idea is that a Regular/Directory is interchangeable
    with its CHash.  This would appear to break referential
@@ -60,63 +54,20 @@ using namespace std;
    CHash, we should also export the file object referenced by that
    CHash.
 
-
-   \section{Reduction rules}
-
-   ...
-
-
-   \section{Normals forms}
-
-   An expression is in {\em weak head normal form} if it is a lambda,
-   a string or boolean value, or a File or Derive value.
-
-   An expression is in {\em $d$-normal form} if it matches the
-   signature FExpr:
-
-     File : String * Content * [DExpr] -> DExpr
-     Derive : String * Path * [Tup] * [Tup2] -> DExpr
-
-     Tup : Str * DExpr -> Tup
-     Tup : Str * Str -> Tup
-
-     Tup : Str * Str -> Tup2
-
-     Str : String -> Str
-
-   These are Nix expressions in which the file system result of Derive
-   expressions has not yet been computed.  This is useful for, e.g.,
-   querying dependencies.
-
-   An expression is in {\em $f$-normal form} if it matches the
-   signature FExpr:
-
-     File : String * Content * [FExpr] -> FExpr
-
-   These are completely evaluated Nix expressions.
-
 */
 
-typedef ATerm Expr;
+typedef ATerm FState;
 typedef ATerm Content;
 
 
-/* Expression normalisation. */
-Expr whNormalise(Expr e);
-Expr dNormalise(Expr e);
-Expr fNormalise(Expr e);
-
 /* Realise a $f$-normalised expression in the file system. */
-void realise(Expr e);
+void realiseFState(FState fs);
 
 /* Return a canonical textual representation of an expression. */
-string printExpr(Expr e);
+string printTerm(ATerm t);
 
-/* Perform variable substitution. */
+/* Hash an aterm. */
-Expr substExpr(string x, Expr rep, Expr e);
+Hash hashTerm(ATerm t);
-
-/* Hash an expression. */
-Hash hashExpr(Expr e);
 
 
 #endif /* !__EVAL_H */

src/globals.cc

@@ -6,7 +6,7 @@ string dbRefs = "refs";
 string dbNFs = "nfs";
 string dbNetSources = "netsources";
 
-string nixValues = "/UNINIT";
+string nixStore = "/UNINIT";
 string nixLogDir = "/UNINIT";
 string nixDB = "/UNINIT";
 

src/globals.hh

@@ -8,15 +8,10 @@ using namespace std;
 
 /* Database names. */
 
-/* dbRefs :: Hash -> FileName
+/* dbRefs :: Hash -> Path
 
-   Maintains a mapping from hashes to filenames within the NixValues
+   Maintains a mapping from hashes to paths.  This is what we use to
-   directory.  This mapping is for performance only; it can be
+   resolve CHash(hash) content descriptors. */
-   reconstructed unambiguously.  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. */
 extern string dbRefs;
 
 /* dbNFs :: Hash -> Hash
@@ -45,11 +40,11 @@ extern string dbNetSources;
 
 /* Path names. */
 
-/* nixValues is the directory where all Nix values (both files and
+/* nixStore is the directory where we generally store atomic and
-   directories, and both normal and non-normal forms) live. */
+   derived files. */
-extern string nixValues;
+extern string nixStore;
 
-/* nixLogDir is the directory where we log evaluations. */ 
+/* nixLogDir is the directory where we log various operations. */ 
 extern string nixLogDir;
 
 /* nixDB is the file name of the Berkeley DB database where we

src/hash.cc

@@ -14,7 +14,7 @@ Hash::Hash()
 }
 
 
-bool Hash::operator == (Hash & h2)
+bool Hash::operator == (Hash h2)
 {
     for (unsigned int i = 0; i < hashSize; i++)
         if (hash[i] != h2.hash[i]) return false;
@@ -22,7 +22,7 @@ bool Hash::operator == (Hash & h2)
 }
 
 
-bool Hash::operator != (Hash & h2)
+bool Hash::operator != (Hash h2)
 {
     return !(*this == h2);
 }

src/hash.hh

@@ -17,10 +17,10 @@ struct Hash
     Hash();
 
     /* Check whether two hash are equal. */
-    bool operator == (Hash & h2);
+    bool operator == (Hash h2);
 
     /* Check whether two hash are not equal. */
-    bool operator != (Hash & h2);
+    bool operator != (Hash h2);
 
     /* Convert a hash code into a hexadecimal representation. */
     operator string() const;

src/test.cc

@@ -11,20 +11,16 @@
 #include "globals.hh"
 
 
-typedef Expr (* Normaliser) (Expr);
+void realise(FState fs)
-
-
-void eval(Normaliser n, Expr e)
 {
-    e = n(e);
+    realiseFState(fs);
-    cout << (string) hashExpr(e) << ": " << printExpr(e) << endl;
 }
 
 
-void evalFail(Normaliser n, Expr e)
+void realiseFail(FState fs)
 {
     try {
-        e = n(e);
+        realiseFState(fs);
         abort();
     } catch (Error e) {
         cout << "error (expected): " << e.what() << endl;
@@ -96,7 +92,7 @@ void runTests()
     string testDir = absPath("scratch");
     cout << testDir << endl;
 
-    nixValues = testDir;
+    nixStore = testDir;
     nixLogDir = testDir;
     nixDB = testDir + "/db";
 
@@ -104,6 +100,7 @@ void runTests()
 
     /* Expression evaluation. */
 
+#if 0
     eval(whNormalise,
         ATmake("Str(\"Hello World\")"));
     eval(whNormalise,
@@ -138,10 +135,27 @@ void runTests()
     eval(fNormalise, e2);
 
     realise(e2);
+#endif
+
+    Hash builder1h;
+    string builder1fn;
+    addToStore("./test-builder-1.sh", builder1fn, builder1h);
+
+    FState fs1 = ATmake(
+        "File(<str>, Hash(<str>), [])", 
+        builder1fn.c_str(),
+        ((string) builder1h).c_str());
+    realiseFState(fs1);
+    realiseFState(fs1);
+
+    FState fs2 = ATmake(
+        "File(<str>, Hash(<str>), [])", 
+        (builder1fn + "_bla").c_str(),
+        ((string) builder1h).c_str());
+    realiseFState(fs2);
+    realiseFState(fs2);
 
 #if 0
-    Hash builder1 = addValue("./test-builder-1.sh");
-
     Expr e1 = ATmake("Exec(Str(<str>), Hash(<str>), [])",
         thisSystem.c_str(), ((string) builder1).c_str());
 

src/util.cc

@@ -78,7 +78,7 @@ void deletePath(string path)
 }
 
 
-void debug(string s)
+void debug(const format & f)
 {
-    cerr << "debug: " << s << endl;
+    cerr << format("debug: %1%\n") % f.str();
 }

src/util.hh

@@ -7,7 +7,10 @@
 
 #include <unistd.h>
 
+#include <boost/format.hpp>
+
 using namespace std;
+using namespace boost;
 
 
 class Error : public exception
@@ -16,7 +19,7 @@ protected:
     string err;
 public:
     Error() { }
-    Error(string _err) { err = _err; }
+    Error(format f) { err = f.str(); }
     ~Error() throw () { }
     const char * what() const throw () { return err.c_str(); }
 };
@@ -59,7 +62,7 @@ string baseNameOf(string path);
 void deletePath(string path);
 
 
-void debug(string s);
+void debug(const format & f);
 
 
 #endif /* !__UTIL_H */

src/values.cc

@@ -34,7 +34,7 @@ struct CopySource : RestoreSource
 };
 
 
-static void copyFile(string src, string dst)
+void copyFile(string src, string dst)
 {
     /* Unfortunately C++ doesn't support coprocedures, so we have no
        nice way to chain CopySink and CopySource together.  Instead we
@@ -83,33 +83,25 @@ static void copyFile(string src, string dst)
 }
 
 
-static string absValuePath(string s)
+void addToStore(string srcPath, string & dstPath, Hash & hash)
 {
-    return nixValues + "/" + s;
+    srcPath = absPath(srcPath);
-}
 
+    hash = hashPath(srcPath);
 
-Hash addValue(string path)
+    string path;
-{
+    if (queryDB(nixDB, dbRefs, hash, path)) {
-    path = absPath(path);
-
-    Hash hash = hashPath(path);
-
-    string name;
-    if (queryDB(nixDB, dbRefs, hash, name)) {
         debug((string) hash + " already known");
-        return hash;
+        dstPath = path;
+        return;
     }
 
-    string baseName = baseNameOf(path);
+    string baseName = baseNameOf(srcPath);
+    dstPath = nixStore + "/" + (string) hash + "-" + baseName;
 
-    string targetName = (string) hash + "-" + baseName;
+    copyFile(srcPath, dstPath);
 
-    copyFile(path, absValuePath(targetName));
+    setDB(nixDB, dbRefs, hash, dstPath);
-
-    setDB(nixDB, dbRefs, hash, targetName);
-    
-    return hash;
 }
 
 
@@ -135,28 +127,28 @@ string fetchURL(string url)
 #endif
 
 
-void deleteValue(Hash hash)
+void deleteFromStore(Hash hash)
 {
-    string name;
+    string fn;
-    if (queryDB(nixDB, dbRefs, hash, name)) {
+    if (queryDB(nixDB, dbRefs, hash, fn)) {
-        string fn = absValuePath(name);
+        string prefix = nixStore + "/";
+        if (string(fn, prefix.size()) != prefix)
+            throw Error("path " + fn + " is not in the store");
         deletePath(fn);
         delDB(nixDB, dbRefs, hash);
     }
 }
 
 
-/* !!! bad name, "query" implies no side effect => getValuePath() */
+string queryFromStore(Hash hash)
-string queryValuePath(Hash hash)
 {
     bool checkedNet = false;
 
     while (1) {
 
-        string name, url;
+        string fn, url;
 
-        if (queryDB(nixDB, dbRefs, hash, name)) {
+        if (queryDB(nixDB, dbRefs, hash, fn)) {
-            string fn = absValuePath(name);
 
             /* Verify that the file hasn't changed. !!! race !!! slow */
             if (hashPath(fn) != hash)

src/values.hh

@@ -8,21 +8,17 @@
 using namespace std;
 
 
-/* Copy a value to the nixValues directory and register it in dbRefs.
+void copyFile(string src, string dst);
+
+/* Copy a file to the nixStore directory and register it in dbRefs.
    Return the hash code of the value. */
-Hash addValue(string pathName);
+void addToStore(string srcPath, string & dstPath, Hash & hash);
 
+/* Delete a value from the nixStore directory. */
+void deleteFromStore(Hash hash);
 
-/* Delete a value from the nixValues directory. */
+/* !!! */
-void deleteValue(Hash hash);
+string queryFromStore(Hash hash);
-
-
-/* Obtain the path of a value 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 queryValuePath(Hash hash);
 
 
 #endif /* !__VALUES_H */