/*-------------------------------------------------------------------------
   _realloc.c - reallocate allocated memory.

   Copyright (C) 2004, Maarten Brock, sourceforge.brock@dse.nl

   This library is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by the
   Free Software Foundation; either version 2, or (at your option) any
   later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License 
   along with this library; see the file COPYING. If not, write to the
   Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
   MA 02110-1301, USA.

   As a special exception, if you link this library with other files,
   some of which are compiled with SDCC, to produce an executable,
   this library does not by itself cause the resulting executable to
   be covered by the GNU General Public License. This exception does
   not however invalidate any other reasons why the executable file
   might be covered by the GNU General Public License.
-------------------------------------------------------------------------*/

#include <sdcc-lib.h>
#include <malloc.h>
#include <string.h>

#if defined(__SDCC_STACK_AUTO) || defined(__SDCC_z80) || defined(__SDCC_z180) || defined(__SDCC_gbz80)
  #define CRITICAL __critical
#else
  #define CRITICAL
#endif

//--------------------------------------------------------------------
//realloc function implementation for embedded system
//Non-ANSI keywords are C51 specific.
// __xdata - variable in external memory (just RAM)
//--------------------------------------------------------------------

#if _SDCC_MALLOC_TYPE_MLH

#define __xdata

typedef struct _MEMHEADER MEMHEADER;

struct _MEMHEADER
{
  MEMHEADER *   next;
  MEMHEADER *   prev;
  unsigned int  len;
  unsigned char mem;
};

#define HEADER_SIZE (sizeof(MEMHEADER)-sizeof(char))
#define MEM(x)      (&x->mem)

#else

#define MEMHEADER   struct MAH// Memory Allocation Header

MEMHEADER
{
  MEMHEADER __xdata *  next;
  unsigned int         len;
  unsigned char        mem[];
};

#define HEADER_SIZE sizeof(MEMHEADER)
#define MEM(x)      (x->mem)

#endif

extern MEMHEADER __xdata * _sdcc_prev_memheader;

// apart from finding the header
// this function also finds it's predecessor
extern MEMHEADER __xdata * _sdcc_find_memheader(void __xdata * p);

void __xdata * realloc (void * p, size_t size)
{
  register MEMHEADER __xdata * pthis;
  register MEMHEADER __xdata * pnew;
  register void __xdata * ret;

  CRITICAL
  {
    pthis = _sdcc_find_memheader(p);
    if (pthis)
    {
      if (size > (0xFFFF-HEADER_SIZE))
      {
        ret = (void __xdata *) NULL; //To prevent overflow in next line
      }
      else
      {
        size += HEADER_SIZE; //We need a memory for header too

        if ((((unsigned int)pthis->next) - ((unsigned int)pthis)) >= size)
        {//if spare is more than needed
          pthis->len = size;
          ret = p;
        }
        else
        {
          if ((_sdcc_prev_memheader) &&
              ((((unsigned int)pthis->next) -
                ((unsigned int)_sdcc_prev_memheader) -
                _sdcc_prev_memheader->len) >= size))
          {
            pnew = (MEMHEADER __xdata * )((char __xdata *)_sdcc_prev_memheader + _sdcc_prev_memheader->len);
            _sdcc_prev_memheader->next = pnew;

#if _SDCC_MALLOC_TYPE_MLH
            pthis->next->prev = pnew;
#endif

            memmove(pnew, pthis, pthis->len);
            pnew->len = size;
            ret = MEM(pnew);
          }
          else
          {
            ret = malloc(size - HEADER_SIZE);
            if (ret)
            {
              memcpy(ret, MEM(pthis), pthis->len - HEADER_SIZE);
              free(p);
            }
          }
        }
      }
    }
    else
    {
      ret = malloc(size);
    }
  }
  return ret;
}
//END OF MODULE
