X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=lily%2Fduration.cc;h=194ce3a89e2e3187b302e83ea615a399595e277c;hb=e90f0536f9be39ada0bef0aeb0d275dec3b2fb5b;hp=1618489027dd7d74c53c9e4952fb4a6b0fce4be3;hpb=a276a19dc6bd57832db3107f2f2cbb04cb4677b6;p=lilypond.git

diff --git a/lily/duration.cc b/lily/duration.cc
index 1618489027..194ce3a89e 100644
--- a/lily/duration.cc
+++ b/lily/duration.cc
@@ -1,10 +1,21 @@
 /*
-  duration.cc -- implement Duration
+  This file is part of LilyPond, the GNU music typesetter.
 
-  source file of the LilyPond music typesetter
-
-  (c) 1997--2007 Jan Nieuwenhuizen <janneke@gnu.org>
+  Copyright (C) 1997--2011 Jan Nieuwenhuizen <janneke@gnu.org>
   Han-Wen Nienhuys <hanwen@xs4all.nl>
+
+  LilyPond is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  LilyPond is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with LilyPond.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #include "duration.hh"
@@ -34,6 +45,56 @@ Duration::Duration (int log, int d)
   factor_ = Rational (1, 1);
 }
 
+Duration::Duration (Rational r, bool scale)
+{
+  factor_ = Rational (1, 1);
+
+  if (r.num () == 0.0)
+    {
+      durlog_ = 0;
+      dots_ = 0;
+    }
+  else
+    {
+      /* we want to find the integer k for which 2q/p > 2^k >= q/p.
+	 It's simple to check that k' = \floor \log q - \floor \log p
+	 satisfies the left inequality and is within a factor of 2 of
+	 satistying the right one. Therefore either k = k' or k = k'+1 */
+
+      int p = (int) r.num ();
+      int q = (int) r.den ();
+      int k = intlog2 (q) - intlog2 (p);
+      if (shift_left(p, k) < q)
+	k++;
+
+      assert (shift_left(p, k) >= q && shift_left(p, (k-1)) < q);
+
+      /* If we were to write out log (p/q) in base 2, then the position of the
+	 first non-zero bit (ie. k in our notation) would be the durlog
+	 and the number of consecutive 1s after that bit would be the number of
+	 dots */
+      p = shift_left(p, k) - q;
+      dots_ = 0;
+      while ((p *= 2) >= q)
+	{
+	  p -= q;
+	  dots_++;
+	}
+
+      /* we only go up to 64th notes */
+      if (k > 6)
+	{
+	  durlog_ = 6;
+	  dots_ = 0;
+	}
+      else
+	durlog_ = k;
+
+      if (scale || k > 6)
+	factor_ = r / get_length ();
+    }
+}
+
 Duration
 Duration::compressed (Rational m) const
 {