nix-collect-garbage: translate to C++

src/nix-collect-garbage/local.mk

@@ -0,0 +1,7 @@
+programs += nix-collect-garbage
+
+nix-collect-garbage_DIR := $(d)
+
+nix-collect-garbage_SOURCES := $(d)/nix-collect-garbage.cc
+
+nix-collect-garbage_LIBS = libmain libstore libutil libformat

src/nix-collect-garbage/nix-collect-garbage.cc

@@ -0,0 +1,87 @@
+#include "hash.hh"
+#include "shared.hh"
+#include "globals.hh"
+
+#include <iostream>
+
+using namespace nix;
+
+std::string gen = "";
+bool dryRun = false;
+
+void runProgramSimple(Path program, const Strings & args)
+{
+    checkInterrupt();
+
+    /* Fork. */
+    Pid pid = startProcess([&]() {
+        Strings args_(args);
+        args_.push_front(program);
+        auto cargs = stringsToCharPtrs(args_);
+
+        execv(program.c_str(), (char * *) &cargs[0]);
+
+        throw SysError(format("executing ‘%1%’") % program);
+    });
+
+    pid.wait(true);
+}
+
+
+/* If `-d' was specified, remove all old generations of all profiles.
+ * Of course, this makes rollbacks to before this point in time
+ * impossible. */
+
+void removeOldGenerations(std::string dir)
+{
+    for (auto & i : readDirectory(dir)) {
+        checkInterrupt();
+
+        auto path = dir + "/" + i.name; 
+        auto type = getFileType(path);
+
+        if (type == DT_LNK) {
+            auto link = readLink(path);
+            if (link.find("link") != string::npos) {
+                printMsg(lvlInfo, format("removing old generations of profile %1%") % path);
+
+                runProgramSimple(settings.nixBinDir + "/nix-env", Strings{"-p", path, "--delete-generations", gen, dryRun ? "--dry-run" : ""});
+            }
+        } else if (type == DT_DIR) {
+            removeOldGenerations(path);
+        }
+    }
+}
+
+int main(int argc, char * * argv)
+{
+    bool removeOld = false;
+    Strings extraArgs;
+
+    return handleExceptions(argv[0], [&]() {
+        initNix();
+
+        parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
+            if (*arg == "--help")
+                showManPage("nix-collect-garbage");
+            else if (*arg == "--version")
+                printVersion("nix-collect-garbage");
+            else if (*arg == "--delete-old" || *arg == "-d") removeOld = true;
+            else if (*arg == "--delete-older-than") {
+                removeOld = true;
+                gen = getArg(*arg, arg, end);
+            }
+            else if (*arg == "--dry-run") dryRun = true;
+            else
+                extraArgs.push_back(*arg);
+            return true;
+        });
+
+        auto profilesDir = settings.nixStateDir + "/profiles";
+        if (removeOld) removeOldGenerations(profilesDir);
+
+        // Run the actual garbage collector.
+        if (!dryRun) runProgramSimple(settings.nixBinDir + "/nix-store", Strings{"--gc"});
+    });
+}
+