realloc.c

上课老师给的8086仿真器

/***********************************************************************/
/*  This file is part of the C51 Compiler package                      */
/*  Copyright KEIL ELEKTRONIK GmbH 1993                                */
/***********************************************************************/
/*                                                                     */
/*  REALLOC.C:                                                         */
/*                                                                     */
/*  To translate this file use C51 with the following invocation:      */
/*                                                                     */
/*     C51 REALLOC.C  <memory model>                                   */
/*                                                                     */
/*  To link the modified REALLOC.OBJ file to your application use the  */
/*  following L51 invocation:                                          */
/*                                                                     */
/*     L51 <your object file list>, REALLOC.OBJ <controls>             */
/*                                                                     */
/***********************************************************************/

#include <string.h>

extern free (void *);
extern void *malloc (int);

struct mem  {
  struct mem xdata *next;
  struct mem xdata *prev;
  unsigned int       len;
  unsigned char      mem[1];
};


void *realloc (struct mem xdata *p, unsigned int size)  {
  void xdata *p1;

  if (!p) return ((void *) 0);
  p = (void xdata *) p - (sizeof (struct mem) - 1);
  if ((((unsigned int) p->next) - ((unsigned int) p)) >=
      ((sizeof (struct mem) - 1) + size))  {
    p->len = size + sizeof (struct mem) - 1;
    return (p->mem);
  }
  p1 = malloc (size);
  if (!p1) return ((void *) 0);
  memcpy (p1, p->mem, p->len);
  free (p->mem);
  return (p1);
}