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 <stdlib.h>
  11 #include <limits.h>
  12
  13 #include "sync.h"
  14
  15 #define SYNC_MAX 4096                  /* max # of sync points */
  16
  17 /*
  18  * This lot manages the current set of sync points by means of a
  19  * heap (priority queue) structure.
  20  */
  21
  22 static struct Sync {
  23     unsigned long pos;
  24     unsigned long length;
  25 } *synx;
  26 static int nsynx;
  27
  28 void init_sync(void) {
  29     /*
  30      * I'd like to allocate an array of size SYNC_MAX, then write
  31      * `synx--' which would allow numbering the array from one
  32      * instead of zero without wasting memory. Sadly I don't trust
  33      * this to work in 16-bit Large model, so it's staying the way
  34      * it is. Btw, we don't care about freeing this array, since it
  35      * has to last for the duration of the program and will then be
  36      * auto-freed on exit. And I'm lazy ;-)
  37      *
  38      * Speaking of 16-bit Large model, that's also the reason I'm
  39      * not declaring this array statically - by doing it
  40      * dynamically I avoid problems with the total size of DGROUP
  41      * in Borland C.
  42      */
  43     synx = malloc((SYNC_MAX+1) * sizeof(*synx));
  44     if (!synx) {
  45         fprintf(stderr, "ndisasm: not enough memory for sync array\n");
  46         exit(1);
  47     }
  48     nsynx = 0;
  49 }
  50
  51 void add_sync(unsigned long pos, unsigned long length) {
  52     int i;
  53
  54     if (nsynx == SYNC_MAX)
  55         return;                        /* can't do anything - overflow */
  56
  57     nsynx++;
  58     synx[nsynx].pos = pos;
  59     synx[nsynx].length = length;
  60
  61     for (i = nsynx; i > 1; i /= 2) {
  62         if (synx[i/2].pos > synx[i].pos) {
  63             struct Sync t;
  64             t = synx[i/2];             /* structure copy */
  65             synx[i/2] = synx[i];       /* structure copy again */
  66             synx[i] = t;               /* another structure copy */
  67         }
  68     }
  69 }
  70
  71 unsigned long next_sync(unsigned long position, unsigned long *length) {
  72     while (nsynx > 0 && synx[1].pos + synx[1].length <= position) {
  73         int i, j;
  74         struct Sync t;
  75         t = synx[nsynx];               /* structure copy */
  76         synx[nsynx] = synx[1];         /* structure copy */
  77         synx[1] = t;                   /* ditto */
  78
  79         nsynx--;
  80
  81         i = 1;
  82         while (i*2 <= nsynx) {
  83             j = i*2;
  84             if (synx[j].pos < synx[i].pos &&
  85                 (j+1 > nsynx || synx[j+1].pos > synx[j].pos)) {
  86                 t = synx[j];           /* structure copy */
  87                 synx[j] = synx[i];     /* lots of these... */
  88                 synx[i] = t;           /* ...aren't there? */
  89                 i = j;
  90             } else if (j+1 <= nsynx && synx[j+1].pos < synx[i].pos) {
  91                 t = synx[j+1];         /* structure copy */
  92                 synx[j+1] = synx[i];   /* structure <yawn> copy */
  93                 synx[i] = t;           /* structure copy <zzzz....> */
  94                 i = j+1;
  95             } else
  96                 break;
  97         }
  98     }
  99
 100     if (nsynx > 0) {
 101         if (length)
 102             *length = synx[1].length;
 103         return synx[1].pos;
 104     } else {
 105         if (length)
 106             *length = 0L;
 107         return ULONG_MAX;
 108     }
 109 }