vpx_mem/memory_manager/hmm_resize.c

/*
 *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */


/* This code is in the public domain.
** Version: 1.1  Author: Walt Karas
*/

#include "hmm_intrnl.h"

int U(resize)(U(descriptor) *desc, void *mem, U(size_aau) n)
{
    U(size_aau) i;
    head_record *next_head_ptr;
    head_record *head_ptr = PTR_REC_TO_HEAD(mem);

    /* Flag. */
    int next_block_free;

    /* Convert n from desired block size in AAUs to BAUs. */
    n += HEAD_AAUS;
    n = DIV_ROUND_UP(n, HMM_BLOCK_ALIGN_UNIT);

    if (n < MIN_BLOCK_BAUS)
        n = MIN_BLOCK_BAUS;

#ifdef HMM_AUDIT_FAIL

    AUDIT_BLOCK(head_ptr)

    if (!IS_BLOCK_ALLOCATED(head_ptr))
        HMM_AUDIT_FAIL

        if (desc->avl_tree_root)
            AUDIT_BLOCK(PTR_REC_TO_HEAD(desc->avl_tree_root))

#endif

            i = head_ptr->block_size;

    next_head_ptr =
        (head_record *) BAUS_FORWARD(head_ptr, head_ptr->block_size);

    next_block_free =
        (next_head_ptr == desc->last_freed) ||
        !IS_BLOCK_ALLOCATED(next_head_ptr);

    if (next_block_free)
        /* Block can expand into next free block. */
        i += BLOCK_BAUS(next_head_ptr);

    if (n > i)
        /* Not enough room for block to expand. */
        return(-1);

    if (next_block_free)
    {
#ifdef HMM_AUDIT_FAIL
        AUDIT_BLOCK(next_head_ptr)
#endif

        if (next_head_ptr == desc->last_freed)
            desc->last_freed = 0;
        else
            U(out_of_free_collection)(desc, next_head_ptr);

        next_head_ptr =
            (head_record *) BAUS_FORWARD(head_ptr, (U(size_bau)) i);
    }

    /* Set i to number of "extra" BAUs. */
    i -= n;

    if (i < MIN_BLOCK_BAUS)
        /* Not enough extra BAUs to be a block on their own, so just keep them
        ** in the block being resized.
        */
    {
        n += i;
        i = n;
    }
    else
    {
        /* There are enough "leftover" BAUs in the next block to
        ** form a remainder block. */

        head_record *rem_head_ptr;

        rem_head_ptr = (head_record *) BAUS_FORWARD(head_ptr, n);

        rem_head_ptr->previous_block_size = (U(size_bau)) n;
        rem_head_ptr->block_size = (U(size_bau)) i;

        if (desc->last_freed)
        {
#ifdef HMM_AUDIT_FAIL
            AUDIT_BLOCK(desc->last_freed)
#endif

            U(into_free_collection)(desc, (head_record *)(desc->last_freed));

            desc->last_freed = 0;
        }

        desc->last_freed = rem_head_ptr;
    }

    head_ptr->block_size = (U(size_bau)) n;
    next_head_ptr->previous_block_size = (U(size_bau)) i;

    return(0);
}