seq.c

   1 /*
   2    Cantaveria - action adventure platform game
   3    Copyright (C) 2009 2010 Evan Rinehart
   4
   5    This program is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU General Public License
   7    as published by the Free Software Foundation; either version 2
   8    of the License, or (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to
  17
  18    The Free Software Foundation, Inc.
  19    51 Franklin Street, Fifth Floor
  20    Boston, MA  02110-1301, USA
  21
  22    evanrinehart@gmail.com
  23 */
  24 #include <stdlib.h>
  25
  26 #include <seq.h>
  27
  28 static struct {
  29         int tick;
  30         int terr; // number 1/1323000 ticks
  31
  32         int loop_start;
  33         int loop_end;
  34         int looping;
  35
  36         event* next_event;
  37         event* events;
  38 } my;
  39
  40 void seq_init(){
  41
  42 }
  43
  44 int would_loop(){
  45         return my.looping && my.next_event->tick > my.loop_end;
  46 }
  47
  48 event* get_event_after(int tick){
  49         return NULL;
  50 }
  51
  52 event* get_next_event(){
  53         if(would_loop()){
  54                 return get_event_after(my.loop_start);
  55         }
  56         else {
  57                 return my.next_event;
  58         }
  59 }
  60
  61
  62
  63 int get_next_tick(){
  64         event* e = get_next_event();
  65         return e ? e->tick : -1;
  66 }
  67
  68 int distance_to_next(){
  69         int next_tick = get_next_tick();
  70         if(next_tick < 0) return -1;
  71
  72         return would_loop() ?
  73                 next_tick - my.loop_start + my.loop_end - my.tick :
  74                 next_tick - my.tick;
  75
  76 }
  77
  78
  79 /* below are three functions that the synth uses to
  80 control the sequencer. it finds control events, advances
  81 the event pointer, and finally advances the tick count */
  82
  83 //returns samples from now an event will occur
  84 //if no event will occur in sbound samples, returns -1
  85 int seq_lookahead(int sbound){
  86 return -1;
  87         int tbound = sbound*46080/1323000;
  88         int T = distance_to_next();
  89         if(T < 0) return -1;
  90         return T > tbound ?
  91                 -1 :
  92                 T*1 + 0;
  93 }
  94
  95 //returns the next event that would play
  96 //if there is no such event, returns NULL
  97 event* seq_get_event(){
  98 return NULL;
  99         //needs to handle looping
 100 }
 101
 102
 103 //advance the tick position
 104 void seq_advance(int samples){
 105 return;
 106         // 46080 1/1323000 ticks = 1 sample
 107         int N = 46080 * samples;
 108         int D = 1323000;
 109         my.terr += N;
 110         my.tick += N/D + my.terr/D;
 111         my.terr %= D;
 112 //needs to handle looping
 113 }
 114
 115
 116 /* IMPORTANT
 117 it might well be simpler to implement looping as
 118 an event which exists at the loop point after all
 119 other events that occur at that time which sends
 120 the sequence to a specific tick */