3 files changed, 58 insertions, 1 deletions
diff --git a/src/libutil/compression.cc b/src/libutil/compression.cc
new file mode 100644
index 000000000000..446fcb781564
--- /dev/null
+++ b/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");
+    }
+}
+
+}
diff --git a/src/libutil/compression.hh b/src/libutil/compression.hh
new file mode 100644
index 000000000000..962ce5ac7767
--- /dev/null
+++ b/src/libutil/compression.hh
@@ -0,0 +1,9 @@
+#pragma once
+
+#include <string>
+
+namespace nix {
+
+std::string decompressXZ(const std::string & in);
+
+}
diff --git a/src/libutil/local.mk b/src/libutil/local.mk
index 8af2e78d9ce4..4a97b662ae62 100644
--- a/src/libutil/local.mk
+++ b/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