Add XML output to `nix-store'.

* src/nix-store/Makefile.am (nix_store_SOURCES): Add `xmlgraph.cc' and
  `xmlgraph.hh'.

* src/nix-store/help.txt (Operations): Document `--xml'.

* src/nix-store/nix-store.cc (opQuery): Handle `--xml'.

* src/nix-store/xmlgraph.cc, src/nix-store/xmlgraph.hh: New files.

src/nix-store/Makefile.am

@@ -1,6 +1,9 @@
 bin_PROGRAMS = nix-store
 
-nix_store_SOURCES = nix-store.cc dotgraph.cc dotgraph.hh help.txt
+nix_store_SOURCES =				\
+  nix-store.cc dotgraph.cc dotgraph.hh help.txt	\
+  xmlgraph.cc xmlgraph.hh
+
 nix_store_LDADD = ../libmain/libmain.la ../libstore/libstore.la ../libutil/libutil.la \
  ../boost/format/libformat.la @ADDITIONAL_NETWORK_LIBS@
 

src/nix-store/help.txt

@@ -39,6 +39,7 @@ Query flags:
   --referrers-closure: print all paths (in)directly refering to the path
   --tree: print a tree showing the dependency graph of the path
   --graph: print a dot graph rooted at given path
+  --xml: emit an XML representation of the graph rooted at the given path
   --hash: print the SHA-256 hash of the contents of the path
   --roots: print the garbage collector roots that point to the path
 

src/nix-store/nix-store.cc

@@ -6,6 +6,7 @@
 #include "archive.hh"
 #include "shared.hh"
 #include "dotgraph.hh"
+#include "xmlgraph.hh"
 #include "local-store.hh"
 #include "util.hh"
 #include "help.txt.hh"
@@ -226,7 +227,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
 {
     enum { qOutputs, qRequisites, qReferences, qReferrers
          , qReferrersClosure, qDeriver, qBinding, qHash
-         , qTree, qGraph, qResolve, qRoots } query = qOutputs;
+         , qTree, qGraph, qXml, qResolve, qRoots } query = qOutputs;
     bool useOutput = false;
     bool includeOutputs = false;
     bool forceRealise = false;
@@ -249,6 +250,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
         else if (*i == "--hash") query = qHash;
         else if (*i == "--tree") query = qTree;
         else if (*i == "--graph") query = qGraph;
+        else if (*i == "--xml") query = qXml;
         else if (*i == "--resolve") query = qResolve;
         else if (*i == "--roots") query = qRoots;
         else if (*i == "--use-output" || *i == "-u") useOutput = true;
@@ -331,6 +333,14 @@ static void opQuery(Strings opFlags, Strings opArgs)
             break;
         }
 
+        case qXml: {
+            PathSet roots;
+            foreach (Strings::iterator, i, opArgs)
+                roots.insert(maybeUseOutput(followLinksToStorePath(*i), useOutput, forceRealise));
+            printXmlGraph(roots);
+            break;
+        }
+
         case qResolve: {
             foreach (Strings::iterator, i, opArgs)
                 cout << format("%1%\n") % followLinksToStorePath(*i);

src/nix-store/xmlgraph.cc

@@ -0,0 +1,71 @@
+#include "xmlgraph.hh"
+#include "util.hh"
+#include "store-api.hh"
+
+#include <iostream>
+
+
+using std::cout;
+
+namespace nix {
+
+
+static inline const string & xmlQuote(const string & s)
+{
+    // Luckily, store paths shouldn't contain any character that needs to be
+    // quoted.
+    return s;
+}
+
+
+static string makeEdge(const string & src, const string & dst)
+{
+    format f = format("  <edge src=\"%1%\" dst=\"%2%\"/>\n")
+      % xmlQuote(src) % xmlQuote(dst);
+    return f.str();
+}
+
+
+static string makeNode(const string & id)
+{
+    format f = format("  <node name=\"%1%\"/>\n") % xmlQuote(id);
+    return f.str();
+}
+
+
+void printXmlGraph(const PathSet & roots)
+{
+    PathSet workList(roots);
+    PathSet doneSet;
+
+    cout << "<?xml version='1.0' encoding='utf-8'?>\n"
+	 << "<nix>\n";
+
+    while (!workList.empty()) {
+	Path path = *(workList.begin());
+	workList.erase(path);
+
+	if (doneSet.find(path) != doneSet.end()) continue;
+	doneSet.insert(path);
+
+	cout << makeNode(path);
+
+	PathSet references;
+	store->queryReferences(path, references);
+
+	for (PathSet::iterator i = references.begin();
+	     i != references.end(); ++i)
+	{
+	    if (*i != path) {
+		workList.insert(*i);
+		cout << makeEdge(*i, path);
+	    }
+	}
+
+    }
+
+    cout << "</nix>\n";
+}
+
+
+}

src/nix-store/xmlgraph.hh

@@ -0,0 +1,12 @@
+#ifndef __XMLGRAPH_H
+#define __XMLGRAPH_H
+
+#include "types.hh"
+
+namespace nix {
+
+void printXmlGraph(const PathSet & roots);
+
+}
+
+#endif /* !__XMLGRAPH_H */