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

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