dst_codeword_heap.c

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/*****************************************************************************/
/* Copyright 1998, Hewlett-Packard Company                                   */
/* All rights reserved                                                       */
/* File: "dst_codeword_heap.c"                                               */
/* Description: Implementation of the `dst_codeword_heap' object to manage   */
/*              efficient dynamic resizing and recycling of storage for      */
/*              compressed code words produced by a coding engine.           */
/* Author: David Taubman                                                     */
/* Affiliation: Hewlett-Packard and                                          */
/*              The University of New South Wales, Australia                 */
/* Version: V3.1A                                                            */
/* Last Revised: 14 January, 1999                                            */
/*****************************************************************************/
#include <local_services.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <ifc.h>
#include "dst_codeword_heap.h"

/*****************************************************************************/
/* STATIC                        __get_unit                                  */
/*****************************************************************************/

static dst_heap_unit_ptr
  __get_unit(dst_codeword_heap_ref self)
{
  dst_heap_group_ptr scan;
  dst_heap_unit_ptr unit;
  int i;

  for (scan=self->heap; scan != NULL; scan=scan->next)
    if (scan->free_units)
      break;
  if (scan == NULL)
    {
      scan = (dst_heap_group_ptr)
        local_malloc(DST_CODE_MEM_KEY,sizeof(dst_heap_group));
      scan->next = self->heap;
      self->heap = scan;
      scan->free_units = DST_HEAP_GROUP_UNITS;
      for (unit=scan->units, i=DST_HEAP_GROUP_UNITS; i > 0; i--, unit++)
        {
          unit->next = NULL;
          unit->group = NULL;
        }
    }
  for (unit=scan->units, i=DST_HEAP_GROUP_UNITS; i > 0; i--, unit++)
    if (unit->group == NULL)
      break;
  assert(i > 0);
  scan->free_units--;
  unit->group = scan;
  unit->next = NULL;
  return(unit);
}

/*****************************************************************************/
/* STATIC                        __return_unit                               */
/*****************************************************************************/

static void
  __return_unit(dst_codeword_heap_ref self, dst_heap_unit_ptr unit)
{
  dst_heap_group_ptr group;

  group = unit->group;
  assert((group != NULL) && (group->free_units < DST_HEAP_GROUP_UNITS));
  group->free_units++;
  unit->group = NULL;
}

/*****************************************************************************/
/* STATIC                         __terminate                                */
/*****************************************************************************/

static void
  __terminate(dst_codeword_heap_ref self)
{
  dst_heap_group_ptr tmp;

  while ((tmp=self->heap) != NULL)
    {
      self->heap = tmp->next;
      local_free(tmp);
    }
  local_free(self);
}

/*****************************************************************************/
/* EXTERN                    create_dst_codeword_heap                        */
/*****************************************************************************/

dst_codeword_heap_ref
  create_dst_codeword_heap(void)
{
  dst_codeword_heap_ref result;

  result = (dst_codeword_heap_ref)
    local_malloc(DST_CODE_MEM_KEY,sizeof(dst_codeword_heap_obj));
  memset(result,0,sizeof(dst_codeword_heap_obj));
  result->get_unit = __get_unit;
  result->return_unit = __return_unit;
  result->terminate = __terminate;
  return(result);
}