vpx_mem/memory_manager/hmm_resize.c

   1 /*
   2  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
   3  *
   4  *  Use of this source code is governed by a BSD-style license
   5  *  that can be found in the LICENSE file in the root of the source
   6  *  tree. An additional intellectual property rights grant can be found
   7  *  in the file PATENTS.  All contributing project authors may
   8  *  be found in the AUTHORS file in the root of the source tree.
   9  */
  10
  11
  12 /* This code is in the public domain.
  13 ** Version: 1.1  Author: Walt Karas
  14 */
  15
  16 #include "hmm_intrnl.h"
  17
  18 int U(resize)(U(descriptor) *desc, void *mem, U(size_aau) n)
  19 {
  20     U(size_aau) i;
  21     head_record *next_head_ptr;
  22     head_record *head_ptr = PTR_REC_TO_HEAD(mem);
  23
  24     /* Flag. */
  25     int next_block_free;
  26
  27     /* Convert n from desired block size in AAUs to BAUs. */
  28     n += HEAD_AAUS;
  29     n = DIV_ROUND_UP(n, HMM_BLOCK_ALIGN_UNIT);
  30
  31     if (n < MIN_BLOCK_BAUS)
  32         n = MIN_BLOCK_BAUS;
  33
  34 #ifdef HMM_AUDIT_FAIL
  35
  36     AUDIT_BLOCK(head_ptr)
  37
  38     if (!IS_BLOCK_ALLOCATED(head_ptr))
  39         HMM_AUDIT_FAIL
  40
  41         if (desc->avl_tree_root)
  42             AUDIT_BLOCK(PTR_REC_TO_HEAD(desc->avl_tree_root))
  43
  44 #endif
  45
  46             i = head_ptr->block_size;
  47
  48     next_head_ptr =
  49         (head_record *) BAUS_FORWARD(head_ptr, head_ptr->block_size);
  50
  51     next_block_free =
  52         (next_head_ptr == desc->last_freed) ||
  53         !IS_BLOCK_ALLOCATED(next_head_ptr);
  54
  55     if (next_block_free)
  56         /* Block can expand into next free block. */
  57         i += BLOCK_BAUS(next_head_ptr);
  58
  59     if (n > i)
  60         /* Not enough room for block to expand. */
  61         return(-1);
  62
  63     if (next_block_free)
  64     {
  65 #ifdef HMM_AUDIT_FAIL
  66         AUDIT_BLOCK(next_head_ptr)
  67 #endif
  68
  69         if (next_head_ptr == desc->last_freed)
  70             desc->last_freed = 0;
  71         else
  72             U(out_of_free_collection)(desc, next_head_ptr);
  73
  74         next_head_ptr =
  75             (head_record *) BAUS_FORWARD(head_ptr, (U(size_bau)) i);
  76     }
  77
  78     /* Set i to number of "extra" BAUs. */
  79     i -= n;
  80
  81     if (i < MIN_BLOCK_BAUS)
  82         /* Not enough extra BAUs to be a block on their own, so just keep them
  83         ** in the block being resized.
  84         */
  85     {
  86         n += i;
  87         i = n;
  88     }
  89     else
  90     {
  91         /* There are enough "leftover" BAUs in the next block to
  92         ** form a remainder block. */
  93
  94         head_record *rem_head_ptr;
  95
  96         rem_head_ptr = (head_record *) BAUS_FORWARD(head_ptr, n);
  97
  98         rem_head_ptr->previous_block_size = (U(size_bau)) n;
  99         rem_head_ptr->block_size = (U(size_bau)) i;
 100
 101         if (desc->last_freed)
 102         {
 103 #ifdef HMM_AUDIT_FAIL
 104             AUDIT_BLOCK(desc->last_freed)
 105 #endif
 106
 107             U(into_free_collection)(desc, (head_record *)(desc->last_freed));
 108
 109             desc->last_freed = 0;
 110         }
 111
 112         desc->last_freed = rem_head_ptr;
 113     }
 114
 115     head_ptr->block_size = (U(size_bau)) n;
 116     next_head_ptr->previous_block_size = (U(size_bau)) i;
 117
 118     return(0);
 119 }