sync.c

   1 /* sync.c   the Netwide Disassembler synchronisation processing module
   2  *
   3  * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
   4  * Julian Hall. All rights reserved. The software is
   5  * redistributable under the licence given in the file "Licence"
   6  * distributed in the NASM archive.
   7  */
   8
   9 #include <stdio.h>
  10 #include <limits.h>
  11
  12 #include "sync.h"
  13
  14 #define SYNC_MAX 4096                  /* max # of sync points */
  15
  16 /*
  17  * This lot manages the current set of sync points by means of a
  18  * heap (priority queue) structure.
  19  */
  20
  21 static struct Sync {
  22     unsigned long pos;
  23     unsigned long length;
  24 } synx[SYNC_MAX+1];                    /* synx[0] never used - who cares :) */
  25 static int nsynx;
  26
  27 void init_sync(void) {
  28     nsynx = 0;
  29 }
  30
  31 void add_sync(unsigned long pos, unsigned long length) {
  32     int i;
  33
  34     if (nsynx == SYNC_MAX)
  35         return;                        /* can't do anything - overflow */
  36
  37     nsynx++;
  38     synx[nsynx].pos = pos;
  39     synx[nsynx].length = length;
  40
  41     for (i = nsynx; i > 1; i /= 2) {
  42         if (synx[i/2].pos > synx[i].pos) {
  43             struct Sync t;
  44             t = synx[i/2];             /* structure copy */
  45             synx[i/2] = synx[i];       /* structure copy again */
  46             synx[i] = t;               /* another structure copy */
  47         }
  48     }
  49 }
  50
  51 unsigned long next_sync(unsigned long position, unsigned long *length) {
  52     while (nsynx > 0 && synx[1].pos + synx[1].length <= position) {
  53         int i, j;
  54         struct Sync t;
  55         t = synx[nsynx];               /* structure copy */
  56         synx[nsynx] = synx[1];         /* structure copy */
  57         synx[1] = t;                   /* ditto */
  58
  59         nsynx--;
  60
  61         i = 1;
  62         while (i*2 <= nsynx) {
  63             j = i*2;
  64             if (synx[j].pos < synx[i].pos &&
  65                 (j+1 > nsynx || synx[j+1].pos > synx[j].pos)) {
  66                 t = synx[j];           /* structure copy */
  67                 synx[j] = synx[i];     /* lots of these... */
  68                 synx[i] = t;           /* ...aren't there? */
  69                 i = j;
  70             } else if (j+1 <= nsynx && synx[j+1].pos < synx[i].pos) {
  71                 t = synx[j+1];         /* structure copy */
  72                 synx[j+1] = synx[i];   /* structure <yawn> copy */
  73                 synx[i] = t;           /* structure copy <zzzz....> */
  74                 i = j+1;
  75             } else
  76                 break;
  77         }
  78     }
  79
  80     if (nsynx > 0) {
  81         if (length)
  82             *length = synx[1].length;
  83         return synx[1].pos;
  84     } else {
  85         if (length)
  86             *length = 0L;
  87         return ULONG_MAX;
  88     }
  89 }