<nix/fetchurl.nix>: Support xz-compressed NARs

configure.ac

@@ -218,6 +218,10 @@ PKG_CHECK_MODULES([SODIUM], [libsodium],
 AC_SUBST(HAVE_SODIUM, [$have_sodium])
 
 
+# Look for liblzma, a required dependency.
+PKG_CHECK_MODULES([LIBLZMA], [liblzma], [CXXFLAGS="$LIBLZMA_CFLAGS $CXXFLAGS"])
+
+
 # Whether to use the Boehm garbage collector.
 AC_ARG_ENABLE(gc, AC_HELP_STRING([--enable-gc],
   [enable garbage collection in the Nix expression evaluator (requires Boehm GC) [default=no]]),

release.nix

@@ -83,7 +83,7 @@ let
         src = tarball;
 
         buildInputs =
-          [ curl perl bzip2 openssl pkgconfig sqlite boehmgc ]
+          [ curl perl bzip2 xz openssl pkgconfig sqlite boehmgc ]
           ++ lib.optional stdenv.isLinux libsodium;
 
         configureFlags = ''

src/libstore/builtins.cc

@@ -2,6 +2,7 @@
 #include "download.hh"
 #include "store-api.hh"
 #include "archive.hh"
+#include "compression.hh"
 
 namespace nix {
 
@@ -28,6 +29,8 @@ void builtinFetchurl(const BasicDerivation & drv)
 
     auto unpack = drv.env.find("unpack");
     if (unpack != drv.env.end() && unpack->second == "1") {
+        if (string(data.data, 0, 6) == string("\xfd" "7zXZ\0", 6))
+            data.data = decompressXZ(data.data);
         StringSource source(data.data);
         restorePath(storePath, source);
     } else

src/libutil/compression.cc

@@ -0,0 +1,46 @@
+#include "compression.hh"
+#include "types.hh"
+
+#include <lzma.h>
+
+namespace nix {
+
+std::string decompressXZ(const std::string & in)
+{
+    lzma_stream strm = LZMA_STREAM_INIT;
+
+    lzma_ret ret = lzma_stream_decoder(
+        &strm, UINT64_MAX, LZMA_CONCATENATED);
+    if (ret != LZMA_OK)
+        throw Error("unable to initialise lzma decoder");
+
+    lzma_action action = LZMA_RUN;
+    uint8_t outbuf[BUFSIZ];
+    string res;
+    strm.next_in = (uint8_t *) in.c_str();
+    strm.avail_in = in.size();
+    strm.next_out = outbuf;
+    strm.avail_out = sizeof(outbuf);
+
+    while (true) {
+
+        if (strm.avail_in == 0)
+            action = LZMA_FINISH;
+
+        lzma_ret ret = lzma_code(&strm, action);
+
+        if (strm.avail_out == 0 || ret == LZMA_STREAM_END) {
+            res.append((char *) outbuf, sizeof(outbuf) - strm.avail_out);
+            strm.next_out = outbuf;
+            strm.avail_out = sizeof(outbuf);
+        }
+
+        if (ret == LZMA_STREAM_END)
+            return res;
+
+        if (ret != LZMA_OK)
+            throw Error("error while decompressing xz file");
+    }
+}
+
+}

src/libutil/compression.hh

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <string>
+
+namespace nix {
+
+std::string decompressXZ(const std::string & in);
+
+}

src/libutil/local.mk

@@ -6,8 +6,10 @@ libutil_DIR := $(d)
 
 libutil_SOURCES := $(wildcard $(d)/*.cc)
 
+libutil_LDFLAGS = -llzma
+
 ifeq ($(HAVE_OPENSSL), 1)
-  libutil_LDFLAGS = $(OPENSSL_LIBS)
+  libutil_LDFLAGS += $(OPENSSL_LIBS)
 else
   libutil_SOURCES += $(d)/md5.c $(d)/sha1.c $(d)/sha256.c
 endif

tests/fetchurl.sh

@@ -2,12 +2,14 @@ source common.sh
 
 clearStore
 
+# Test fetching a flat file.
 hash=$(nix-hash --flat --type sha256 ./fetchurl.sh)
 
 outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file://$(pwd)/fetchurl.sh --argstr sha256 $hash --no-out-link)
 
 cmp $outPath fetchurl.sh
 
+# Test unpacking a NAR.
 rm -rf $TEST_ROOT/archive
 mkdir -p $TEST_ROOT/archive
 cp ./fetchurl.sh $TEST_ROOT/archive
@@ -25,3 +27,15 @@ echo $outPath | grep -q 'xyzzy'
 
 test -x $outPath/fetchurl.sh
 test -L $outPath/symlink
+
+nix-store --delete $outPath
+
+# Test unpacking a compressed NAR.
+narxz=$TEST_ROOT/archive.nar.xz
+rm -f $narxz
+xz --keep $nar
+outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file://$narxz --argstr sha256 $hash \
+          --arg unpack true --argstr name xyzzy --no-out-link)
+
+test -x $outPath/fetchurl.sh
+test -L $outPath/symlink