* Refactoring: hash class.

8 files changed, 266 insertions, 184 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 3b519aa55d82..a56a0ae0e8e0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,13 +1,16 @@
 bin_PROGRAMS = nix fix
+noinst_PROGRAMS = test
 
 AM_CXXFLAGS = -DSYSTEM=\"@host@\" -Wall
 
-nix_SOURCES = nix.cc db.cc util.cc md5.c
+nix_SOURCES = nix.cc db.cc util.cc hash.cc md5.c
 nix_LDADD = -ldb_cxx-4 -lATerm
 
-fix_SOURCES = fix.cc util.cc md5.c
+fix_SOURCES = fix.cc util.cc hash.cc md5.c
 fix_LDADD = -lATerm
 
+test_SOURCES = test.cc util.cc hash.cc md5.c
+
 install-data-local:
 	$(INSTALL) -d $(localstatedir)/nix
 	$(INSTALL) -d $(localstatedir)/nix/descriptors
diff --git a/src/fix.cc b/src/fix.cc
index 30303322a141..3c4c8bf539e0 100644
--- a/src/fix.cc
+++ b/src/fix.cc
@@ -10,6 +10,7 @@ extern "C" {
 }
 
 #include "util.hh"
+#include "hash.hh"
 
 
 static string nixDescriptorDir;
@@ -20,7 +21,7 @@ static bool verbose = false;
 
 /* Mapping of Fix file names to the hashes of the resulting Nix
    descriptors. */
-typedef map<string, string> DescriptorMap;
+typedef map<string, Hash> DescriptorMap;
 
 
 void registerFile(string filename)
@@ -32,12 +33,13 @@ void registerFile(string filename)
 }
 
 
-void registerURL(string hash, string url)
+void registerURL(Hash hash, string url)
 {
-    int res = system(("nix regurl " + hash + " " + url).c_str());
+    int res = system(("nix regurl " + (string) hash + " " + url).c_str());
     /* !!! escape */
     if (WEXITSTATUS(res) != 0)
-        throw Error("cannot register " + hash + " -> " + url + " with Nix");
+        throw Error("cannot register " + 
+            (string) hash + " -> " + url + " with Nix");
 }
 
 
@@ -61,7 +63,7 @@ struct EvalContext
 
 
 ATerm evaluate(ATerm e, EvalContext ctx);
-string instantiateDescriptor(string filename, EvalContext ctx);
+Hash instantiateDescriptor(string filename, EvalContext ctx);
 
 
 string evaluateStr(ATerm e, EvalContext ctx)
@@ -101,7 +103,7 @@ ATerm evaluate(ATerm e, EvalContext ctx)
         ATmatch(e, "Pkg(<str>)", &s) || 
         ATmatch(e, "File(<str>)", &s))
     {
-        checkHash(s);
+        parseHash(s);
         return e;
     }
 
@@ -131,7 +133,7 @@ ATerm evaluate(ATerm e, EvalContext ctx)
     else if (ATmatch(e, "Fix(<term>)", &e2)) {
         string filename = absPath(evaluateStr(e2, ctx), ctx.dir); /* !!! */
         return ATmake("Pkg(<str>)",
-            instantiateDescriptor(filename, ctx).c_str());
+            ((string) instantiateDescriptor(filename, ctx)).c_str());
     }
 
 #if 0
@@ -160,19 +162,18 @@ ATerm evaluate(ATerm e, EvalContext ctx)
        hash. */
     else if (ATmatch(e, "Local(<term>)", &e2)) {
         string filename = absPath(evaluateStr(e2, ctx), ctx.dir); /* !!! */
-        string hash = hashFile(filename);
+        Hash hash = hashFile(filename);
         registerFile(filename); /* !!! */
-        return ATmake("File(<str>)", hash.c_str());
+        return ATmake("File(<str>)", ((string) hash).c_str());
     }
 
     /* `Url' registers a mapping from a hash to an url with Nix, and
        returns the hash. */
     else if (ATmatch(e, "Url(<term>, <term>)", &e2, &e3)) {
-        string hash = evaluateStr(e2, ctx);
-        checkHash(hash);
+        Hash hash = parseHash(evaluateStr(e2, ctx));
         string url = evaluateStr(e3, ctx);
         registerURL(hash, url);
-        return ATmake("File(<str>)", hash.c_str());
+        return ATmake("File(<str>)", ((string) hash).c_str());
     }
 
     /* `If' provides conditional evaluation. */
@@ -199,7 +200,7 @@ string getStringFromMap(BindingsMap & bindingsMap,
 
 /* Instantiate a Fix descriptors into a Nix descriptor, recursively
    instantiating referenced descriptors as well. */
-string instantiateDescriptor(string filename, EvalContext ctx)
+Hash instantiateDescriptor(string filename, EvalContext ctx)
 {
     /* Already done? */
     DescriptorMap::iterator isInMap = ctx.done->find(filename);
@@ -256,8 +257,9 @@ string instantiateDescriptor(string filename, EvalContext ctx)
     if (!ATwriteToNamedTextFile(outTerm, tmpFilename.c_str()))
         throw Error("cannot write aterm to " + tmpFilename);
 
-    string outHash = hashFile(tmpFilename);
-    string outFilename = nixDescriptorDir + "/" + id + "-" + outHash + ".nix";
+    Hash outHash = hashFile(tmpFilename);
+    string outFilename = nixDescriptorDir + "/" + 
+        id + "-" + (string) outHash + ".nix";
     if (rename(tmpFilename.c_str(), outFilename.c_str()))
         throw Error("cannot rename " + tmpFilename + " to " + outFilename);
 
@@ -265,7 +267,8 @@ string instantiateDescriptor(string filename, EvalContext ctx)
     registerFile(outFilename);
 
     if (verbose)
-        cerr << "instantiated " << outHash << " from " << filename << endl;
+        cerr << "instantiated " << (string) outHash 
+             << " from " << filename << endl;
 
     (*ctx.done)[filename] = outHash;
     return outHash;
@@ -284,7 +287,7 @@ void instantiateDescriptors(Strings filenames)
          it != filenames.end(); it++)
     {
         string filename = absPath(*it);
-        cout << instantiateDescriptor(filename, ctx) << endl;
+        cout << (string) instantiateDescriptor(filename, ctx) << endl;
     }
 }
 
@@ -293,7 +296,7 @@ void instantiateDescriptors(Strings filenames)
 void printUsage()
 {
     cerr <<
-"Usage: fix ...
+"Usage: fix ...\n\
 ";
 }
 
diff --git a/src/hash.cc b/src/hash.cc
new file mode 100644
index 000000000000..25d76bd15cf2
--- /dev/null
+++ b/src/hash.cc
@@ -0,0 +1,87 @@
+extern "C" {
+#include "md5.h"
+}
+
+#include "hash.hh"
+#include <iostream>
+
+
+/* Create a zeroed hash object. */
+Hash::Hash()
+{
+    memset(hash, 0, sizeof(hash));
+}
+
+
+/* Check whether two hash are equal. */
+bool Hash::operator == (Hash & h2)
+{
+    for (unsigned int i = 0; i < hashSize; i++)
+        if (hash[i] != h2.hash[i]) return false;
+    return true;
+}
+
+
+/* Check whether two hash are not equal. */
+bool Hash::operator != (Hash & h2)
+{
+    return !(*this == h2);
+}
+
+
+/* Convert a hash code into a hexadecimal representation. */
+Hash::operator string() const
+{
+    ostringstream str;
+    for (unsigned int i = 0; i < hashSize; i++) {
+        str.fill('0');
+        str.width(2);
+        str << hex << (int) hash[i];
+    }
+    return str.str();
+}
+
+    
+/* Parse a hexadecimal representation of a hash code. */
+Hash parseHash(const string & s)
+{
+    Hash hash;
+    for (unsigned int i = 0; i < Hash::hashSize; i++) {
+        string s2(s, i * 2, 2);
+        if (!isxdigit(s2[0]) || !isxdigit(s2[1])) 
+            throw BadRefError("invalid hash: " + s);
+        istringstream str(s2);
+        int n;
+        str >> hex >> n;
+        hash.hash[i] = n;
+    }
+    return hash;
+}
+
+
+/* Verify that a reference is valid (that is, is a MD5 hash code). */
+bool isHash(const string & s)
+{
+    if (s.length() != 32) return false;
+    for (int i = 0; i < 32; i++) {
+        char c = s[i];
+        if (!((c >= '0' && c <= '9') ||
+              (c >= 'a' && c <= 'f')))
+            return false;
+    }
+    return true;
+}
+
+
+/* Compute the MD5 hash of a file. */
+Hash hashFile(const string & fileName)
+{
+    Hash hash;
+    FILE * file = fopen(fileName.c_str(), "rb");
+    if (!file)
+        throw Error("file `" + fileName + "' does not exist");
+    int err = md5_stream(file, hash.hash);
+    fclose(file);
+    if (err) throw Error("cannot hash file");
+    return hash;
+}
diff --git a/src/hash.hh b/src/hash.hh
new file mode 100644
index 000000000000..162b2b1c8fb6
--- /dev/null
+++ b/src/hash.hh
@@ -0,0 +1,34 @@
+#ifndef __HASH_H
+#define __HASH_H
+
+#include <string>
+
+#include "util.hh"
+
+using namespace std;
+
+
+struct Hash
+{
+    static const unsigned int hashSize = 16;
+    unsigned char hash[hashSize];
+
+    Hash();
+    bool operator == (Hash & h2);
+    bool operator != (Hash & h2);
+    operator string() const;
+};
+
+
+class BadRefError : public Error
+{
+public:
+    BadRefError(string _err) : Error(_err) { };
+};
+
+
+Hash parseHash(const string & s);
+bool isHash(const string & s);
+Hash hashFile(const string & fileName);
+
+#endif /* !__HASH_H */
diff --git a/src/nix.cc b/src/nix.cc
index 7f5ca927bbbb..ea33e5e2803e 100644
--- a/src/nix.cc
+++ b/src/nix.cc
@@ -16,6 +16,7 @@ extern "C" {
 }
 
 #include "util.hh"
+#include "hash.hh"
 #include "db.hh"
 
 using namespace std;
@@ -58,7 +59,7 @@ string fetchURL(string url)
    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(string hash)
+string getFile(Hash hash)
 {
     bool checkedNet = false;
 
@@ -77,10 +78,10 @@ string getFile(string hash)
 
         if (checkedNet)
             throw Error("consistency problem: file fetched from " + url + 
-                " should have hash " + hash + ", but it doesn't");
+                " should have hash " + (string) hash + ", but it doesn't");
 
         if (!queryDB(nixDB, dbNetSources, hash, url))
-            throw Error("a file with hash " + hash + " is requested, "
+            throw Error("a file with hash " + (string) hash + " is requested, "
                 "but it is not known to exist locally or on the network");
 
         checkedNet = true;
@@ -95,7 +96,7 @@ string getFile(string hash)
 typedef map<string, string> Params;
 
 
-void readPkgDescr(const string & hash,
+void readPkgDescr(Hash hash,
     Params & pkgImports, Params & fileImports, Params & arguments)
 {
     string pkgfile;
@@ -112,15 +113,15 @@ void readPkgDescr(const string & hash,
     char * cname;
     ATerm value;
     while (ATmatch(bindings, "[Bind(<str>, <term>), <list>]", 
-               &cname, &value, &bindings)) 
+               &cname, &value, &bindings))
     {
         string name(cname);
         char * arg;
         if (ATmatch(value, "Pkg(<str>)", &arg)) {
-            checkHash(arg);
+            parseHash(arg);
             pkgImports[name] = arg;
         } else if (ATmatch(value, "File(<str>)", &arg)) {
-            checkHash(arg);
+            parseHash(arg);
             fileImports[name] = arg;
         } else if (ATmatch(value, "Str(<str>)", &arg))
             arguments[name] = arg;
@@ -136,13 +137,13 @@ void readPkgDescr(const string & hash,
 }
 
 
-string getPkg(string hash);
+string getPkg(Hash hash);
 
 
 typedef map<string, string> Environment;
 
 
-void fetchDeps(string hash, Environment & env)
+void fetchDeps(Hash hash, Environment & env)
 {
     /* Read the package description file. */
     Params pkgImports, fileImports, arguments;
@@ -156,7 +157,7 @@ void fetchDeps(string hash, Environment & env)
         cerr << "fetching package dependency "
              << it->first << " <- " << it->second
              << endl;
-        env[it->first] = getPkg(it->second);
+        env[it->first] = getPkg(parseHash(it->second));
     }
 
     for (Params::iterator it = fileImports.begin();
@@ -168,7 +169,7 @@ void fetchDeps(string hash, Environment & env)
 
         string file;
 
-        file = getFile(it->second);
+        file = getFile(parseHash(it->second));
 
         env[it->first] = file;
     }
@@ -198,7 +199,7 @@ string getFromEnv(const Environment & env, const string & key)
 }
 
 
-string queryPkgId(const string & hash)
+string queryPkgId(Hash hash)
 {
     Params pkgImports, fileImports, arguments;
     readPkgDescr(hash, pkgImports, fileImports, arguments);
@@ -206,7 +207,7 @@ string queryPkgId(const string & hash)
 }
 
 
-void installPkg(string hash)
+void installPkg(Hash hash)
 {
     string pkgfile;
     string src;
@@ -223,14 +224,15 @@ void installPkg(string hash)
     string id = getFromEnv(env, "id");
 
     /* Construct a path for the installed package. */
-    path = nixHomeDir + "/pkg/" + id + "-" + hash;
+    path = nixHomeDir + "/pkg/" + id + "-" + (string) hash;
 
     /* Create the path. */
     if (mkdir(path.c_str(), 0777))
         throw Error("unable to create directory " + path);
 
     /* Create a log file. */
-    string logFileName = nixLogDir + "/" + id + "-" + hash + ".log";
+    string logFileName = 
+        nixLogDir + "/" + id + "-" + (string) hash + ".log";
     /* !!! auto-pclose on exit */
     FILE * logFile = popen(("tee " + logFileName + " >&2").c_str(), "w"); /* !!! escaping */
     if (!logFile)
@@ -256,11 +258,11 @@ void installPkg(string hash)
                 }
 
                 /* Try to use a prebuilt. */
-                string prebuiltHash, prebuiltFile;
-                if (queryDB(nixDB, dbPrebuilts, hash, prebuiltHash)) {
+                string prebuiltHashS, prebuiltFile;
+                if (queryDB(nixDB, dbPrebuilts, hash, prebuiltHashS)) {
 
                     try {
-                        prebuiltFile = getFile(prebuiltHash);
+                        prebuiltFile = getFile(parseHash(prebuiltHashS));
                     } catch (Error e) {
                         cerr << "cannot obtain prebuilt (ignoring): " << e.what() << endl;
                         goto build;
@@ -339,17 +341,16 @@ void installPkg(string hash)
 }
 
 
-string getPkg(string hash)
+string getPkg(Hash hash)
 {
     string path;
-    checkHash(hash);
     while (!queryDB(nixDB, dbInstPkgs, hash, path))
         installPkg(hash);
     return path;
 }
 
 
-void runPkg(string hash, 
+void runPkg(Hash hash, 
     Strings::iterator firstArg, 
     Strings::iterator lastArg)
 {
@@ -389,7 +390,7 @@ void runPkg(string hash,
 }
 
 
-void ensurePkg(string hash)
+void ensurePkg(Hash hash)
 {
     Params pkgImports, fileImports, arguments;
     readPkgDescr(hash, pkgImports, fileImports, arguments);
@@ -403,10 +404,9 @@ void ensurePkg(string hash)
 }
 
 
-void delPkg(string hash)
+void delPkg(Hash hash)
 {
     string path;
-    checkHash(hash);
     if (queryDB(nixDB, dbInstPkgs, hash, path)) {
         int res = system(("chmod -R +w " + path + " && rm -rf " + path).c_str()); // !!! escaping
         delDB(nixDB, dbInstPkgs, hash); // not a bug ??? 
@@ -423,7 +423,7 @@ void exportPkgs(string outDir,
     outDir = absPath(outDir);
 
     for (Strings::iterator it = firstHash; it != lastHash; it++) {
-        string hash = *it;
+        Hash hash = parseHash(*it);
         string pkgDir = getPkg(hash);
         string tmpFile = outDir + "/export_tmp";
 
@@ -435,42 +435,38 @@ void exportPkgs(string outDir,
         string prebuiltHash = hashFile(tmpFile);
         string pkgId = queryPkgId(hash);
         string prebuiltFile = outDir + "/" +
-            pkgId + "-" + hash + "-" + prebuiltHash + ".tar.bz2";
+            pkgId + "-" + (string) hash + "-" + prebuiltHash + ".tar.bz2";
         
         rename(tmpFile.c_str(), prebuiltFile.c_str());
     }
 }
 
 
-void registerPrebuilt(string pkgHash, string prebuiltHash)
+void registerPrebuilt(Hash pkgHash, Hash prebuiltHash)
 {
-    checkHash(pkgHash);
-    checkHash(prebuiltHash);
     setDB(nixDB, dbPrebuilts, pkgHash, prebuiltHash);
 }
 
 
-string registerFile(string filename)
+Hash registerFile(string filename)
 {
     filename = absPath(filename);
-    string hash = hashFile(filename);
+    Hash hash = hashFile(filename);
     setDB(nixDB, dbRefs, hash, filename);
     return hash;
 }
 
 
-void registerURL(string hash, string url)
+void registerURL(Hash hash, string url)
 {
-    checkHash(hash);
     setDB(nixDB, dbNetSources, hash, url);
     /* !!! currently we allow only one network source per hash */
 }
 
 
 /* This is primarily used for bootstrapping. */
-void registerInstalledPkg(string hash, string path)
+void registerInstalledPkg(Hash hash, string path)
 {
-    checkHash(hash);
     if (path == "")
         delDB(nixDB, dbInstPkgs, hash);
     else
@@ -498,12 +494,13 @@ void verifyDB()
          it != fileRefs.end(); it++)
     {
         try {
-            if (hashFile(it->second) != it->first) {
+            Hash hash = parseHash(it->first);
+            if (hashFile(it->second) != hash) {
                 cerr << "file " << it->second << " has changed\n";
                 delDB(nixDB, dbRefs, it->first);
             }
-        } catch (BadRefError e) { /* !!! better error check */ 
-            cerr << "file " << it->second << " has disappeared\n";
+        } catch (Error e) { /* !!! better error check */ 
+            cerr << "error: " << e.what() << endl;
             delDB(nixDB, dbRefs, it->first);
         }
     }
@@ -544,7 +541,7 @@ void printInfo(Strings::iterator first, Strings::iterator last)
 {
     for (Strings::iterator it = first; it != last; it++) {
         try {
-            cout << *it << " " << queryPkgId(*it) << endl;
+            cout << *it << " " << queryPkgId(parseHash(*it)) << endl;
         } catch (Error & e) { // !!! more specific
             cout << *it << " (descriptor missing)\n";
         }
@@ -559,7 +556,7 @@ void computeClosure(Strings::iterator first, Strings::iterator last,
     set<string> doneSet;
 
     while (!workList.empty()) {
-        string hash = workList.front();
+        Hash hash = parseHash(workList.front());
         workList.pop_front();
         
         if (doneSet.find(hash) == doneSet.end()) {
@@ -605,7 +602,7 @@ void printGraph(Strings::iterator first, Strings::iterator last)
          it != allHashes.end(); it++)
     {
         Params pkgImports, fileImports, arguments;
-        readPkgDescr(*it, pkgImports, fileImports, arguments);
+        readPkgDescr(parseHash(*it), pkgImports, fileImports, arguments);
 
         cout << dotQuote(*it) << "[label = \"" 
              << getFromEnv(arguments, "id")
@@ -633,8 +630,8 @@ void fetch(string id)
     }
 
     /* Register it by hash. */
-    string hash = registerFile(fn);
-    cout << hash << endl;
+    Hash hash = registerFile(fn);
+    cout << (string) hash << endl;
 }
 
 
@@ -648,60 +645,60 @@ void fetch(Strings::iterator first, Strings::iterator last)
 void printUsage()
 {
     cerr <<
-"Usage: nix SUBCOMMAND OPTIONS...
-
-Subcommands:
-
-  init
-    Initialize the database.
-
-  verify
-    Remove stale entries from the database.
-
-  regfile FILENAME...
-    Register each FILENAME keyed by its hash.
-
-  reginst HASH PATH
-    Register an installed package.
-
-  getpkg HASH...
-    For each HASH, ensure that the package referenced by HASH is
-    installed. Print out the path of the installation on stdout.
-
-  delpkg HASH...
-    Uninstall the package referenced by each HASH, disregarding any
-    dependencies that other packages may have on HASH.
-
-  listinst
-    Prints a list of installed packages.
-
-  run HASH ARGS...
-    Run the descriptor referenced by HASH with the given arguments.
-
-  ensure HASH...
-    Like getpkg, but if HASH refers to a run descriptor, fetch only
-    the dependencies.
-
-  export DIR HASH...
-    Export installed packages to DIR.
-
-  regprebuilt HASH1 HASH2
-    Inform Nix that an export HASH2 can be used to fast-build HASH1.
-
-  info HASH...
-    Print information about the specified descriptors.
-
-  closure HASH...
-    Determine the closure of the set of descriptors under the import
-    relation, starting at the given roots.
-
-  graph HASH...
-    Like closure, but print a dot graph specification.
-
-  fetch ID...  
-    Fetch the objects identified by ID and place them in the Nix
-    sources directory.  ID can be a hash or URL.  Print out the hash
-    of the object.
+"Usage: nix SUBCOMMAND OPTIONS...\n\
+\n\
+Subcommands:\n\
+\n\
+  init\n\
+    Initialize the database.\n\
+\n\
+  verify\n\
+    Remove stale entries from the database.\n\
+\n\
+  regfile FILENAME...\n\
+    Register each FILENAME keyed by its hash.\n\
+\n\
+  reginst HASH PATH\n\
+    Register an installed package.\n\
+\n\
+  getpkg HASH...\n\
+    For each HASH, ensure that the package referenced by HASH is\n\
+    installed. Print out the path of the installation on stdout.\n\
+\n\
+  delpkg HASH...\n\
+    Uninstall the package referenced by each HASH, disregarding any\n\
+    dependencies that other packages may have on HASH.\n\
+\n\
+  listinst\n\
+    Prints a list of installed packages.\n\
+\n\
+  run HASH ARGS...\n\
+    Run the descriptor referenced by HASH with the given arguments.\n\
+\n\
+  ensure HASH...\n\
+    Like getpkg, but if HASH refers to a run descriptor, fetch only\n\
+    the dependencies.\n\
+\n\
+  export DIR HASH...\n\
+    Export installed packages to DIR.\n\
+\n\
+  regprebuilt HASH1 HASH2\n\
+    Inform Nix that an export HASH2 can be used to fast-build HASH1.\n\
+\n\
+  info HASH...\n\
+    Print information about the specified descriptors.\n\
+\n\
+  closure HASH...\n\
+    Determine the closure of the set of descriptors under the import\n\
+    relation, starting at the given roots.\n\
+\n\
+  graph HASH...\n\
+    Like closure, but print a dot graph specification.\n\
+\n\
+  fetch ID...\n\
+    Fetch the objects identified by ID and place them in the Nix\n\
+    sources directory.  ID can be a hash or URL.  Print out the hash\n\
+    of the object.\n\
 ";
 }
 
@@ -743,29 +740,31 @@ void run(Strings::iterator argCur, Strings::iterator argEnd)
         verifyDB();
     } else if (cmd == "getpkg") {
         for (Strings::iterator it = argCur; it != argEnd; it++) {
-            string path = getPkg(*it);
+            string path = getPkg(parseHash(*it));
             cout << path << endl;
         }
     } else if (cmd == "delpkg") {
-        for_each(argCur, argEnd, delPkg);
+        for (Strings::iterator it = argCur; it != argEnd; it++)
+            delPkg(parseHash(*it));
     } else if (cmd == "run") {
         if (argc < 1) throw argcError;
-        runPkg(*argCur, argCur + 1, argEnd);
+        runPkg(parseHash(*argCur), argCur + 1, argEnd);
     } else if (cmd == "ensure") {
-        for_each(argCur, argEnd, ensurePkg);
+        for (Strings::iterator it = argCur; it != argEnd; it++)
+            ensurePkg(parseHash(*it));
     } else if (cmd == "export") {
         if (argc < 1) throw argcError;
         exportPkgs(*argCur, argCur + 1, argEnd);
     } else if (cmd == "regprebuilt") {
         if (argc != 2) throw argcError;
-        registerPrebuilt(*argCur, argCur[1]);
+        registerPrebuilt(parseHash(argCur[0]), parseHash(argCur[1]));
     } else if (cmd == "regfile") {
         for_each(argCur, argEnd, registerFile);
     } else if (cmd == "regurl") {
-        registerURL(argCur[0], argCur[1]);
+        registerURL(parseHash(argCur[0]), argCur[1]);
     } else if (cmd == "reginst") {
         if (argc != 2) throw argcError;
-        registerInstalledPkg(*argCur, argCur[1]);
+        registerInstalledPkg(parseHash(argCur[0]), argCur[1]);
     } else if (cmd == "listinst") {
         if (argc != 0) throw argcError;
         listInstalledPkgs();
diff --git a/src/test.cc b/src/test.cc
new file mode 100644
index 000000000000..cce226ba9267
--- /dev/null
+++ b/src/test.cc
@@ -0,0 +1,16 @@
+#include <iostream>
+
+#include "hash.hh"
+
+int main(int argc, char * * argv)
+{
+    Hash h = hashFile("/etc/passwd");
+    
+    cout << (string) h << endl;
+
+    h = parseHash("0b0ffd0538622bfe20b92c4aa57254d9");
+    
+    cout << (string) h << endl;
+
+    return 0;
+}
diff --git a/src/util.cc b/src/util.cc
index 4b7bbac3dd07..299fc942f2ef 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -27,53 +27,6 @@ string absPath(string filename, string dir)
 }
 
 
-static string printHash(unsigned char * buf)
-{
-    ostringstream str;
-    for (int i = 0; i < 16; i++) {
-        str.fill('0');
-        str.width(2);
-        str << hex << (int) buf[i];
-    }
-    return str.str();
-}
-
-    
-/* Verify that a reference is valid (that is, is a MD5 hash code). */
-bool isHash(const string & s)
-{
-    if (s.length() != 32) return false;
-    for (int i = 0; i < 32; i++) {
-        char c = s[i];
-        if (!((c >= '0' && c <= '9') ||
-              (c >= 'a' && c <= 'f')))
-            return false;
-    }
-    return true;
-}
-
-
-void checkHash(const string & s)
-{
-    if (!isHash(s)) throw BadRefError("invalid reference: " + s);
-}
-
-
-/* Compute the MD5 hash of a file. */
-string hashFile(string filename)
-{
-    unsigned char hash[16];
-    FILE * file = fopen(filename.c_str(), "rb");
-    if (!file)
-        throw BadRefError("file `" + filename + "' does not exist");
-    int err = md5_stream(file, hash);
-    fclose(file);
-    if (err) throw BadRefError("cannot hash file");
-    return printHash(hash);
-}
-
-
-
 /* Return the directory part of the given path, i.e., everything
    before the final `/'. */
 string dirOf(string s)
diff --git a/src/util.hh b/src/util.hh
index 2c09efc4d88f..d1a195609503 100644
--- a/src/util.hh
+++ b/src/util.hh
@@ -7,10 +7,6 @@
 
 #include <unistd.h>
 
-extern "C" {
-#include "md5.h"
-}
-
 using namespace std;
 
 
@@ -29,12 +25,6 @@ public:
     UsageError(string _err) : Error(_err) { };
 };
 
-class BadRefError : public Error
-{
-public:
-    BadRefError(string _err) : Error(_err) { };
-};
-
 
 typedef vector<string> Strings;
 
@@ -50,9 +40,6 @@ extern string nixHomeDirEnvVar;
 
 
 string absPath(string filename, string dir = "");
-bool isHash(const string & s);
-void checkHash(const string & s);
-string hashFile(string filename);
 string dirOf(string s);
 string baseNameOf(string s);