Add the nix-store --serve command

This is essentially the substituter API operating on the local store,
which will be used by the ssh substituter. It runs in a loop rather than
just taking one command so that in the future nix will be able to keep
one connection open for multiple instances of the substituter.

Signed-off-by: Shea Levy <shea@shealevy.com>

3 files changed, 55 insertions, 0 deletions

diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 0f250a3c7..1a13e7ca3 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -258,6 +258,37 @@ string StoreAPI::makeValidityRegistration(const PathSet & paths,
 }
 
 
+void StoreAPI::serve(Source & in, Sink & out, bool sign)
+{
+    for (string cmd = readString(in); !cmd.empty(); cmd = readString(in)) {
+        if (cmd == "query") {
+            for (cmd = readString(in); !cmd.empty(); cmd = readString(in)) {
+                PathSet paths = readStrings<PathSet>(in);
+                if (cmd == "have") {
+                    writeStrings(queryValidPaths(paths), out);
+                } else if (cmd == "info") {
+                    // !!! Maybe we want a queryPathInfos?
+                    foreach (PathSet::iterator, i, paths) {
+                        ValidPathInfo info = queryPathInfo(*i);
+                        writeString(info.path, out);
+                        writeString(info.deriver, out);
+                        writeStrings(info.references, out);
+                        // !!! Maybe we want compression?
+                        writeLongLong(info.narSize, out); // downloadSize
+                        writeLongLong(info.narSize, out);
+                    }
+                    writeString("", out);
+                } else
+                    throw Error(format("Unknown serve query `%1%'") % cmd);
+            }
+        } else if (cmd == "substitute")
+            exportPath(readString(in), sign, out);
+        else
+            throw Error(format("Unknown serve command `%1%'") % cmd);
+    }
+}
+
+
 ValidPathInfo decodeValidPathInfo(std::istream & str, bool hashGiven)
 {
     ValidPathInfo info;
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index a82fe3221..57cf51794 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -248,6 +248,10 @@ public:
        `nix-store --register-validity'. */
     string makeValidityRegistration(const PathSet & paths,
         bool showDerivers, bool showHash);
+
+    /* Serve the store for ssh substituters by taking commands
+     * from in and printing results to out */
+    void serve(Source & in, Sink & out, bool sign);
 };
 
 
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 69a98fe47..fb1d3f541 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -834,6 +834,24 @@ static void opClearFailedPaths(Strings opFlags, Strings opArgs)
 }
 
 
+// Serve the nix store in a way usable by a restricted ssh user
+static void opServe(Strings opFlags, Strings opArgs)
+{
+    if (!opArgs.empty())
+        throw UsageError("no arguments expected");
+    // Could eventually take a username argument?
+    bool sign;
+    foreach (Strings::iterator, i, opFlags)
+        if (*i == "--sign") sign = true;
+        else throw UsageError(format("unknown flag `%1%'") % *i);
+
+    FdSource in(STDIN_FILENO);
+    FdSink out(STDOUT_FILENO);
+
+    store->serve(in, out, sign);
+}
+
+
 /* Scan the arguments; find the operation, set global flags, put all
    other flags in a list, and put all other arguments in another
    list. */
@@ -904,6 +922,8 @@ void run(Strings args)
             indirectRoot = true;
         else if (arg == "--no-output")
             noOutput = true;
+        else if (arg == "--serve")
+            op = opServe;
         else if (arg[0] == '-') {
             opFlags.push_back(arg);
             if (arg == "--max-freed" || arg == "--max-links" || arg == "--max-atime") { /* !!! hack */