Add support for UUID generation

1 files changed, 90 insertions, 0 deletions

diff --git a/libbutl/uuid-freebsd.cxx b/libbutl/uuid-freebsd.cxx
new file mode 100644
index 0000000..184799d
--- /dev/null
+++ b/libbutl/uuid-freebsd.cxx
@@ -0,0 +1,90 @@
+// file      : libbutl/uuid-freebsd.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2018 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUILD2_BOOTSTRAP
+
+#include <libbutl/uuid.hxx>
+
+#include <sys/uuid.h>
+
+#include <errno.h>
+
+#include <cassert>
+#include <cstring>      // memcpy()
+#include <system_error>
+
+using namespace std;
+
+namespace butl
+{
+  void
+  uuid_throw_weak (); // uuid.cxx
+
+  uuid uuid_system_generator::
+  generate (bool strong)
+  {
+    // While FreeBSD shares the uuid_*() (<uuid.h>, uuid(3)) API with other
+    // BSDs, its documentation is quite light on the kind of UUID we get and
+    // with what guarantees. The implementation of uuid_create() simply calls
+    // the uuidgen() system call (<sys/uuid.h>, uuidgen(2)) which has some
+    // details.
+    //
+    // Specifically (and as of FreeBSD 11.2), we get a version 1 (MAC/time-
+    // based) UUID and it seems there is provision for getting the time in a
+    // collision-safe:
+    //
+    // "According to the algorithm of generating time-based UUIDs, this will
+    //  also force a new random clock sequence, thereby increasing the
+    //  likelihood for the identifier to be unique."
+    //
+    // So we will assume a MAC/time-based UUID is strong. We also assume a
+    // random UUID is strong as well in case in the future this will becomes
+    // the default (as seems to be the trend); presumably, FreeBSD folks are
+    // smart enough not to start return random UUIDs without a good source of
+    // randomness, at least not by default.
+    //
+    struct ::uuid d;
+
+    if (uuidgen (&d, 1) != 0)
+      throw system_error (errno, system_category ());
+
+    uuid r;
+
+    // This is effectively just memcpy() but let's reference the member names
+    // in case anything changes on either side.
+    //
+    r.time_low = d.time_low;
+    r.time_mid = d.time_mid;
+    r.time_hiv = d.time_hi_and_version;
+    r.clock_seq_hir = d.clock_seq_hi_and_reserved;
+    r.clock_seq_low = d.clock_seq_low;
+    memcpy (r.node, d.node, 6);
+
+    assert (r.variant () == uuid_variant::dce); // Sanity check.
+
+    if (strong)
+    {
+      switch (r.version ())
+      {
+      case uuid_version::time:
+      case uuid_version::random: break;
+      default:                   uuid_throw_weak ();
+      }
+    }
+
+    return r;
+  }
+
+  void uuid_system_generator::
+  initialize ()
+  {
+  }
+
+  void uuid_system_generator::
+  terminate ()
+  {
+  }
+}
+
+#endif // BUILD2_BOOTSTRAP