lily/duration.cc

   1 /*
   2   duration.cc -- implement Duration
   3
   4   source file of the LilyPond music typesetter
   5
   6   (c) 1997--2007 Jan Nieuwenhuizen <janneke@gnu.org>
   7   Han-Wen Nienhuys <hanwen@xs4all.nl>
   8 */
   9
  10 #include "duration.hh"
  11
  12 #include "misc.hh"
  13 #include "lily-proto.hh"
  14
  15 #include "ly-smobs.icc"
  16
  17 int
  18 Duration::compare (Duration const &left, Duration const &right)
  19 {
  20   return Rational::compare (left.get_length (), right.get_length ());
  21 }
  22
  23 Duration::Duration ()
  24 {
  25   durlog_ = 0;
  26   dots_ = 0;
  27   factor_ = Rational (1, 1);
  28 }
  29
  30 Duration::Duration (int log, int d)
  31 {
  32   durlog_ = log;
  33   dots_ = d;
  34   factor_ = Rational (1, 1);
  35 }
  36
  37 Duration::Duration (Rational r, bool scale)
  38 {
  39   factor_ = Rational (1, 1);
  40
  41   if (r.num () == 0.0)
  42     {
  43       durlog_ = 0;
  44       dots_ = 0;
  45     }
  46   else
  47     {
  48       /* we want to find the integer k for which 2q/p > 2^k >= q/p.
  49          It's simple to check that k' = \floor \log q - \floor \log p
  50          satisfies the left inequality and is within a factor of 2 of
  51          satistying the right one. Therefore either k = k' or k = k'+1 */
  52
  53       int p = r.num ();
  54       int q = r.den ();
  55       int k = intlog2 (q) - intlog2 (p);
  56       if ((p << k) < q)
  57         k++;
  58
  59       assert ((p << k) >= q && (p << (k-1)) < q);
  60
  61       /* If we were to write out log (p/q) in base 2, then the position of the
  62          first non-zero bit (ie. k in our notation) would be the durlog
  63          and the number of consecutive 1s after that bit would be the number of
  64          dots */
  65       p = (p << k) - q;
  66       dots_ = 0;
  67       while ((p *= 2) >= q)
  68         {
  69           p -= q;
  70           dots_++;
  71         }
  72
  73       /* we only go up to 64th notes */
  74       if (k > 6)
  75         {
  76           durlog_ = 6;
  77           dots_ = 0;
  78         }
  79       else
  80         durlog_ = k;
  81
  82       if (scale || k > 6)
  83         factor_ = r / get_length ();
  84     }
  85 }
  86
  87 Duration
  88 Duration::compressed (Rational m) const
  89 {
  90   Duration d (*this);
  91   d.factor_ *= m;
  92   return d;
  93 }
  94
  95 Rational
  96 Duration::get_length () const
  97 {
  98   Rational mom (1 << abs (durlog_));
  99
 100   if (durlog_ > 0)
 101     mom = Rational (1) / mom;
 102
 103   Rational delta = mom;
 104   for (int i = 0; i < dots_; i++)
 105     {
 106       delta /= Rational (2);
 107       mom += delta;
 108     }
 109
 110   return mom * factor_;
 111 }
 112
 113 string
 114 Duration::to_string () const
 115 {
 116   string s;
 117
 118   if (durlog_ < 0)
 119     s = "log = " + ::to_string (durlog_);
 120   else
 121     s = ::to_string (1 << durlog_);
 122
 123   s += ::to_string ('.', dots_);
 124   if (factor_ != Moment (Rational (1, 1)))
 125     s += "*" + factor_.to_string ();
 126   return s;
 127 }
 128
 129 IMPLEMENT_TYPE_P (Duration, "ly:duration?");
 130
 131 SCM
 132 Duration::mark_smob (SCM)
 133 {
 134   return SCM_EOL;
 135 }
 136
 137 IMPLEMENT_SIMPLE_SMOBS (Duration);
 138 int
 139 Duration::print_smob (SCM s, SCM port, scm_print_state *)
 140 {
 141   Duration *r = (Duration *) SCM_CELL_WORD_1 (s);
 142
 143   scm_puts ("#<Duration ", port);
 144   scm_display (ly_string2scm (r->to_string ()), port);
 145   scm_puts (" >", port);
 146
 147   return 1;
 148 }
 149
 150 SCM
 151 Duration::equal_p (SCM a, SCM b)
 152 {
 153   Duration *p = (Duration *) SCM_CELL_WORD_1 (a);
 154   Duration *q = (Duration *) SCM_CELL_WORD_1 (b);
 155
 156   bool eq = p->dots_ == q->dots_
 157     && p->durlog_ == q->durlog_
 158     && p->factor_ == q->factor_;
 159
 160   return eq ? SCM_BOOL_T : SCM_BOOL_F;
 161 }
 162
 163 int
 164 Duration::duration_log () const
 165 {
 166   return durlog_;
 167 }
 168
 169 int
 170 Duration::dot_count () const
 171 {
 172   return dots_;
 173 }