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 #include <inttypes.h>
  13
  14 #include "sync.h"
  15
  16 #define SYNC_MAX 4096           /* max # of sync points */
  17
  18 /*
  19  * This lot manages the current set of sync points by means of a
  20  * heap (priority queue) structure.
  21  */
  22
  23 static struct Sync {
  24     uint32_t pos;
  25     uint32_t length;
  26 } *synx;
  27 static int nsynx;
  28
  29 void init_sync(void)
  30 {
  31     /*
  32      * I'd like to allocate an array of size SYNC_MAX, then write
  33      * `synx--' which would allow numbering the array from one
  34      * instead of zero without wasting memory. Sadly I don't trust
  35      * this to work in 16-bit Large model, so it's staying the way
  36      * it is. Btw, we don't care about freeing this array, since it
  37      * has to last for the duration of the program and will then be
  38      * auto-freed on exit. And I'm lazy ;-)
  39      *
  40      * Speaking of 16-bit Large model, that's also the reason I'm
  41      * not declaring this array statically - by doing it
  42      * dynamically I avoid problems with the total size of DGROUP
  43      * in Borland C.
  44      */
  45     synx = malloc((SYNC_MAX + 1) * sizeof(*synx));
  46     if (!synx) {
  47         fprintf(stderr, "ndisasm: not enough memory for sync array\n");
  48         exit(1);
  49     }
  50     nsynx = 0;
  51 }
  52
  53 void add_sync(uint32_t pos, uint32_t length)
  54 {
  55     int i;
  56
  57     if (nsynx == SYNC_MAX)
  58         return;                 /* can't do anything - overflow */
  59
  60     nsynx++;
  61     synx[nsynx].pos = pos;
  62     synx[nsynx].length = length;
  63
  64     for (i = nsynx; i > 1; i /= 2) {
  65         if (synx[i / 2].pos > synx[i].pos) {
  66             struct Sync t;
  67             t = synx[i / 2];    /* structure copy */
  68             synx[i / 2] = synx[i];      /* structure copy again */
  69             synx[i] = t;        /* another structure copy */
  70         }
  71     }
  72 }
  73
  74 uint32_t next_sync(uint32_t position, uint32_t *length)
  75 {
  76     while (nsynx > 0 && synx[1].pos + synx[1].length <= position) {
  77         int i, j;
  78         struct Sync t;
  79         t = synx[nsynx];        /* structure copy */
  80         synx[nsynx] = synx[1];  /* structure copy */
  81         synx[1] = t;            /* ditto */
  82
  83         nsynx--;
  84
  85         i = 1;
  86         while (i * 2 <= nsynx) {
  87             j = i * 2;
  88             if (synx[j].pos < synx[i].pos &&
  89                 (j + 1 > nsynx || synx[j + 1].pos > synx[j].pos)) {
  90                 t = synx[j];    /* structure copy */
  91                 synx[j] = synx[i];      /* lots of these... */
  92                 synx[i] = t;    /* ...aren't there? */
  93                 i = j;
  94             } else if (j + 1 <= nsynx && synx[j + 1].pos < synx[i].pos) {
  95                 t = synx[j + 1];        /* structure copy */
  96                 synx[j + 1] = synx[i];  /* structure <yawn> copy */
  97                 synx[i] = t;    /* structure copy <zzzz....> */
  98                 i = j + 1;
  99             } else
 100                 break;
 101         }
 102     }
 103
 104     if (nsynx > 0) {
 105         if (length)
 106             *length = synx[1].length;
 107         return synx[1].pos;
 108     } else {
 109         if (length)
 110             *length = 0L;
 111         return ULONG_MAX;
 112     }
 113 }