text: #include "stdio.h"
  #ifndef mips
  #include "stdlib.h"
  #endif
  #include "xlisp.h"
  #include "sound.h"
  
  #include "falloc.h"
  #include "cext.h"
  #include "congen.h"
  
  void congen_free(snd_susp_type a_susp);
  
  
  typedef struct congen_susp_struct {
      snd_susp_node susp;
      long terminate_cnt;
      sound_type sndin;
      long sndin_cnt;
      sample_block_values_type sndin_ptr;
  
      double value;
      double rise_factor;
      double fall_factor;
  } congen_susp_node, *congen_susp_type;
  
  
  void congen_n_fetch(snd_susp_type a_susp, snd_list_type snd_list)
  {
      congen_susp_type susp = (congen_susp_type) a_susp;
      int cnt = 0; /* how many samples computed */
      int togo;
      int n;
      sample_block_type out;
      register sample_block_values_type out_ptr;
  
      register sample_block_values_type out_ptr_reg;
  
      register double value_reg;
      register double rise_factor_reg;
      register double fall_factor_reg;
      register sample_block_values_type sndin_ptr_reg;
      falloc_sample_block(out, "congen_n_fetch");
      out_ptr = out->samples;
      snd_list->block = out;
  
      while (cnt < max_sample_block_len) { /* outer loop */
  	/* first compute how many samples to generate in inner loop: */
  	/* don't overflow the output sample block: */
  	togo = max_sample_block_len - cnt;
  
  	/* don't run past the sndin input sample block: */
  	susp_check_term_samples(sndin, sndin_ptr, sndin_cnt);
  	togo = min(togo, susp->sndin_cnt);
  
  	/* don't run past terminate time */
  	if (susp->terminate_cnt != UNKNOWN &&
  	    susp->terminate_cnt <= susp->susp.current + cnt + togo) {
  	    togo = susp->terminate_cnt - (susp->susp.current + cnt);
  	    if (togo < 0) togo = 0;  /* avoids rounding errros */
  	    if (togo == 0) break;
  	}
  
  	n = togo;
  	value_reg = susp->value;
  	rise_factor_reg = susp->rise_factor;
  	fall_factor_reg = susp->fall_factor;
  	sndin_ptr_reg = susp->sndin_ptr;
  	out_ptr_reg = out_ptr;
  	if (n) do { /* the inner sample computation loop */
              sample_type current = *sndin_ptr_reg++;
              if (current > value_reg) {
                  value_reg = current - (current - value_reg) * rise_factor_reg;
              } else {
                  value_reg = current - (current - value_reg) * fall_factor_reg;
              }
              *out_ptr_reg++ = (sample_type) value_reg;
  	} while (--n); /* inner loop */
  
  	susp->value = value_reg;
  	/* using sndin_ptr_reg is a bad idea on RS/6000: */
  	susp->sndin_ptr += togo;
  	out_ptr += togo;
  	susp_took(sndin_cnt, togo);
  	cnt += togo;
      } /* outer loop */
  
      /* test for termination */
      if (togo == 0 && cnt == 0) {
  	snd_list_terminate(snd_list);
      } else {
  	snd_list->block_len = cnt;
  	susp->susp.current += cnt;
      }
  } /* congen_n_fetch */
  
  
  void congen_s_fetch(snd_susp_type a_susp, snd_list_type snd_list)
  {
      congen_susp_type susp = (congen_susp_type) a_susp;
      int cnt = 0; /* how many samples computed */
      int togo;
      int n;
      sample_block_type out;
      register sample_block_values_type out_ptr;
  
      register sample_block_values_type out_ptr_reg;
  
      register double value_reg;
      register double rise_factor_reg;
      register double fall_factor_reg;
      register sample_type sndin_scale_reg = susp->sndin->scale;
      register sample_block_values_type sndin_ptr_reg;
      falloc_sample_block(out, "congen_s_fetch");
      out_ptr = out->samples;
      snd_list->block = out;
  
      while (cnt < max_sample_block_len) { /* outer loop */
  	/* first compute how many samples to generate in inner loop: */
  	/* don't overflow the output sample block: */
  	togo = max_sample_block_len - cnt;
  
  	/* don't run past the sndin input sample block: */
  	susp_check_term_samples(sndin, sndin_ptr, sndin_cnt);
  	togo = min(togo, susp->sndin_cnt);
  
  	/* don't run past terminate time */
  	if (susp->terminate_cnt != UNKNOWN &&
  	    susp->terminate_cnt <= susp->susp.current + cnt + togo) {
  	    togo = susp->terminate_cnt - (susp->susp.current + cnt);
  	    if (togo < 0) togo = 0;  /* avoids rounding errros */
  	    if (togo == 0) break;
  	}
  
  	n = togo;
  	value_reg = susp->value;
  	rise_factor_reg = susp->rise_factor;
  	fall_factor_reg = susp->fall_factor;
  	sndin_ptr_reg = susp->sndin_ptr;
  	out_ptr_reg = out_ptr;
  	if (n) do { /* the inner sample computation loop */
              sample_type current = (sndin_scale_reg * *sndin_ptr_reg++);
              if (current > value_reg) {
                  value_reg = current - (current - value_reg) * rise_factor_reg;
              } else {
                  value_reg = current - (current - value_reg) * fall_factor_reg;
              }
              *out_ptr_reg++ = (sample_type) value_reg;
  	} while (--n); /* inner loop */
  
  	susp->value = value_reg;
  	/* using sndin_ptr_reg is a bad idea on RS/6000: */
  	susp->sndin_ptr += togo;
  	out_ptr += togo;
  	susp_took(sndin_cnt, togo);
  	cnt += togo;
      } /* outer loop */
  
      /* test for termination */
      if (togo == 0 && cnt == 0) {
  	snd_list_terminate(snd_list);
      } else {
  	snd_list->block_len = cnt;
  	susp->susp.current += cnt;
      }
  } /* congen_s_fetch */
  
  
  void congen_toss_fetch(snd_susp_type a_susp, snd_list_type snd_list)
      {
      congen_susp_type susp = (congen_susp_type) a_susp;
      time_type final_time = susp->susp.t0;
      long n;
  
      /* fetch samples from sndin up to final_time for this block of zeros */
      while ((round((final_time - susp->sndin->t0) * susp->sndin->sr)) >=
  	   susp->sndin->current)
  	susp_get_samples(sndin, sndin_ptr, sndin_cnt);
      /* convert to normal processing when we hit final_count */
      /* we want each signal positioned at final_time */
      n = round((final_time - susp->sndin->t0) * susp->sndin->sr -
           (susp->sndin->current - susp->sndin_cnt));
      susp->sndin_ptr += n;
      susp_took(sndin_cnt, n);
      susp->susp.fetch = susp->susp.keep_fetch;
      (*(susp->susp.fetch))(a_susp, snd_list);
  }
  
  
  void congen_mark(snd_susp_type a_susp)
  {
      congen_susp_type susp = (congen_susp_type) a_susp;
      sound_xlmark(susp->sndin);
  }
  
  
  void congen_free(snd_susp_type a_susp)
  {
      congen_susp_type susp = (congen_susp_type) a_susp;
      sound_unref(susp->sndin);
      ffree_generic(susp, sizeof(congen_susp_node), "congen_free");
  }
  
  
  void congen_print_tree(snd_susp_type a_susp, int n)
  {
      congen_susp_type susp = (congen_susp_type) a_susp;
      indent(n);
      stdputstr("sndin:");
      sound_print_tree_1(susp->sndin, n);
  }
  
  
  sound_type snd_make_congen(sound_type sndin, double risetime, double falltime)
  {
      register congen_susp_type susp;
      rate_type sr = sndin->sr;
      time_type t0 = sndin->t0;
      int interp_desc = 0;
      sample_type scale_factor = 1.0F;
      time_type t0_min = t0;
      falloc_generic(susp, congen_susp_node, "snd_make_congen");
      susp->value = 0;
      susp->rise_factor = exp(log(0.5) / (sndin->sr * risetime));
      susp->fall_factor = exp(log(0.5) / (sndin->sr * falltime));
  
      /* select a susp fn based on sample rates */
      interp_desc = (interp_desc << 2) + interp_style(sndin, sr);
      switch (interp_desc) {
        case INTERP_n: susp->susp.fetch = congen_n_fetch; break;
        case INTERP_s: susp->susp.fetch = congen_s_fetch; break;
        default: snd_badsr(); break;
      }
  
      susp->terminate_cnt = UNKNOWN;
      /* handle unequal start times, if any */
      if (t0 < sndin->t0) sound_prepend_zeros(sndin, t0);
      /* minimum start time over all inputs: */
      t0_min = min(sndin->t0, t0);
      /* how many samples to toss before t0: */
      susp->susp.toss_cnt = (long) ((t0 - t0_min) * sr + 0.5);
      if (susp->susp.toss_cnt > 0) {
          susp->susp.keep_fetch = susp->susp.fetch;
          susp->susp.fetch = congen_toss_fetch;
      }
  
      /* initialize susp state */
      susp->susp.free = congen_free;
      susp->susp.sr = sr;
      susp->susp.t0 = t0;
      susp->susp.mark = congen_mark;
      susp->susp.print_tree = congen_print_tree;
      susp->susp.name = "congen";
      susp->susp.log_stop_cnt = UNKNOWN;
      susp->susp.current = 0;
      susp->sndin = sndin;
      susp->sndin_cnt = 0;
      return sound_create((snd_susp_type)susp, t0, sr, scale_factor);
  }
  
  
  sound_type snd_congen(sound_type sndin, double risetime, double falltime)
  {
      sound_type sndin_copy = sound_copy(sndin);
      return snd_make_congen(sndin_copy, risetime, falltime);
  }
  