Make <nix/unpack-channel.nix> a builtin builder

This was the last function using a shell script, so this allows us to
get rid of tar, coreutils, bash etc.

src/libstore/build.cc

@@ -3128,6 +3128,8 @@ void DerivationGoal::runChild()
                     builtinFetchurl(drv2, netrcData);
                 else if (drv->builder == "builtin:buildenv")
                     builtinBuildenv(drv2);
+                else if (drv->builder == "builtin:unpack-channel")
+                    builtinUnpackChannel(drv2);
                 else
                     throw Error(format("unsupported builtin function '%1%'") % string(drv->builder, 8));
                 _exit(0);

src/libstore/builtins.hh

@@ -7,5 +7,6 @@ namespace nix {
 // TODO: make pluggable.
 void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData);
 void builtinBuildenv(const BasicDerivation & drv);
+void builtinUnpackChannel(const BasicDerivation & drv);
 
 }

src/libstore/builtins/unpack-channel.cc

@@ -0,0 +1,39 @@
+#include "rust.hh"
+#include "builtins.hh"
+#include "compression.hh"
+
+namespace nix {
+
+void builtinUnpackChannel(const BasicDerivation & drv)
+{
+    auto getAttr = [&](const string & name) {
+        auto i = drv.env.find(name);
+        if (i == drv.env.end()) throw Error("attribute '%s' missing", name);
+        return i->second;
+    };
+
+    Path out = getAttr("out");
+    auto channelName = getAttr("channelName");
+    auto src = getAttr("src");
+
+    createDirs(out);
+
+    auto source = sinkToSource([&](Sink & sink) {
+        auto decompressor =
+            hasSuffix(src, ".bz2") ? makeDecompressionSink("bzip2", sink) :
+            hasSuffix(src, ".xz") ? makeDecompressionSink("xz", sink) :
+            makeDecompressionSink("none", sink);
+        readFile(src, *decompressor);
+        decompressor->finish();
+    });
+
+    unpack_tarfile(*source, out);
+
+    auto entries = readDirectory(out);
+    if (entries.size() != 1)
+        throw Error("channel tarball '%s' contains more than one file", src);
+    if (rename((out + "/" + entries[0].name).c_str(), (out + "/" + channelName).c_str()) == -1)
+        throw SysError("renaming channel directory");
+}
+
+}

src/libstore/local.mk

@@ -6,7 +6,7 @@ libstore_DIR := $(d)
 
 libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc)
 
-libstore_LIBS = libutil
+libstore_LIBS = libutil libnixrust
 
 libstore_LDFLAGS = $(SQLITE3_LIBS) -lbz2 $(LIBCURL_LIBS) $(SODIUM_LIBS) -pthread
 ifneq ($(OS), FreeBSD)

src/libstore/rust.hh

@@ -1,9 +1,4 @@
-#include "command.hh"
-#include "store-api.hh"
-#include "common-args.hh"
-#include "compression.hh"
-
-using namespace nix;
+#include "serialise.hh"
 
 namespace rust {
 
@@ -47,37 +42,3 @@ struct Source
 extern "C" {
     bool unpack_tarfile(rust::Source source, rust::StringSlice dest_dir);
 }
-
-struct CmdTest : StoreCommand
-{
-    CmdTest()
-    {
-    }
-
-    std::string name() override
-    {
-        return "test";
-    }
-
-    std::string description() override
-    {
-        return "bla bla";
-    }
-
-    void run(ref<Store> store) override
-    {
-        auto source = sinkToSource([&](Sink & sink) {
-            auto decompressor = makeDecompressionSink("bzip2", sink);
-            readFile("./nix-2.2.tar.bz2", *decompressor);
-            decompressor->finish();
-        });
-
-        std::string destDir = "./dest";
-
-        deletePath(destDir);
-
-        unpack_tarfile(*source, destDir);
-    }
-};
-
-static RegisterCommand r(make_ref<CmdTest>());

src/nix/local.mk

@@ -15,9 +15,9 @@ nix_SOURCES := \
   $(wildcard src/nix-prefetch-url/*.cc) \
   $(wildcard src/nix-store/*.cc) \
 
-nix_LIBS = libexpr libmain libstore libutil libnixrust
+nix_LIBS = libexpr libmain libstore libutil
 
-nix_LDFLAGS = -pthread $(SODIUM_LIBS) $(EDITLINE_LIBS) $(BOOST_LDFLAGS) -lboost_context -lboost_thread -lboost_system -Lnix-rust/target/release
+nix_LDFLAGS = -pthread $(SODIUM_LIBS) $(EDITLINE_LIBS) $(BOOST_LDFLAGS) -lboost_context -lboost_thread -lboost_system
 
 $(foreach name, \
   nix-build nix-channel nix-collect-garbage nix-copy-closure nix-daemon nix-env nix-hash nix-instantiate nix-prefetch-url nix-shell nix-store, \