heap.c

   1 static char RCSId[] = "$Id: heap.c,v 1.1 1993/06/29 15:55:18 root Exp $";
   2 static char Copyright[] = "Copyright  Robert J. Amstadt, 1993";
   3
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include "prototypes.h"
   7
   8 typedef struct heap_mem_desc_s
   9 {
  10     struct heap_mem_desc_s *prev, *next;
  11     int   length;
  12 } MDESC;
  13
  14 MDESC *FreeList;
  15
  16 /**********************************************************************
  17  *                                      HEAP_LocalInit
  18  */
  19 void
  20 HEAP_LocalInit(void *start, int length)
  21 {
  22     FreeList = (MDESC *) start;
  23     FreeList->prev = NULL;
  24     FreeList->next = NULL;
  25     FreeList->length = length - sizeof(MDESC);
  26 }
  27
  28 /**********************************************************************
  29  *                                      HEAP_LocalAlloc
  30  */
  31 void *
  32 HEAP_LocalAlloc(int flags, int bytes)
  33 {
  34     MDESC *m, *m_new;
  35
  36 #ifdef HEAP_DEBUG
  37     printf("LocalAlloc: flags %x, bytes %d, ", flags, bytes);
  38 #endif
  39
  40     /*
  41      * Find free block big enough.
  42      */
  43     for (m = FreeList; m != NULL; m = m->next)
  44     {
  45         if (m->length == bytes && m->length < bytes + 4 * sizeof(MDESC))
  46         {
  47             break;
  48         }
  49         else if (m->length > bytes)
  50         {
  51             m_new = m + (bytes / sizeof(MDESC)) + 2;
  52             if (m->prev == NULL)
  53                 FreeList = m_new;
  54             else
  55                 m->prev->next = m_new;
  56
  57             if (m->next != NULL)
  58                 m->next->prev = m_new;
  59
  60             m_new->next = m->next;
  61             m_new->prev = m->prev;
  62             m_new->length = m->length - ((int) m_new - (int) m);
  63             m->length -= (m_new->length + sizeof(MDESC));
  64
  65 #ifdef HEAP_DEBUG
  66             printf("Returning %x\n", (int) (m + 1));
  67 #endif
  68             return (void *) (m + 1);
  69         }
  70     }
  71
  72     if (m != NULL)
  73     {
  74         if (m->prev == NULL)
  75             FreeList = m->next;
  76         else
  77             m->prev->next = m->next;
  78
  79         if (m->next != NULL)
  80             m->next->prev = m->prev;
  81
  82 #ifdef HEAP_DEBUG
  83         printf("Returning %x\n", (int) (m + 1));
  84 #endif
  85         return (void *) (m + 1);
  86     }
  87
  88 #ifdef HEAP_DEBUG
  89     printf("Returning 0\n");
  90 #endif
  91     return 0;
  92 }
  93