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

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");
+    }
+}
+
+}