104 строки
3.1 KiB
C
104 строки
3.1 KiB
C
/*
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* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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/* This code is in the public domain.
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** Version: 1.1 Author: Walt Karas
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*/
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#include "hmm_intrnl.h"
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void U(shrink_chunk)(U(descriptor) *desc, U(size_bau) n_baus_to_shrink) {
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head_record *dummy_end_block = (head_record *)
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BAUS_BACKWARD(desc->end_of_shrinkable_chunk, DUMMY_END_BLOCK_BAUS);
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#ifdef HMM_AUDIT_FAIL
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if (dummy_end_block->block_size != 0)
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/* Chunk does not have valid dummy end block. */
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HMM_AUDIT_FAIL
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#endif
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if (n_baus_to_shrink) {
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head_record *last_block = (head_record *)
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BAUS_BACKWARD(
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dummy_end_block, dummy_end_block->previous_block_size);
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#ifdef HMM_AUDIT_FAIL
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AUDIT_BLOCK(last_block)
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#endif
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if (last_block == desc->last_freed) {
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U(size_bau) bs = BLOCK_BAUS(last_block);
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/* Chunk will not be shrunk out of existence if
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** 1. There is at least one allocated block in the chunk
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** and the amount to shrink is exactly the size of the
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** last block, OR
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** 2. After the last block is shrunk, there will be enough
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** BAUs left in it to form a minimal size block. */
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int chunk_will_survive =
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(PREV_BLOCK_BAUS(last_block) && (n_baus_to_shrink == bs)) ||
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(n_baus_to_shrink <= (U(size_bau))(bs - MIN_BLOCK_BAUS));
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if (chunk_will_survive ||
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(!PREV_BLOCK_BAUS(last_block) &&
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(n_baus_to_shrink ==
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(U(size_bau))(bs + DUMMY_END_BLOCK_BAUS)))) {
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desc->last_freed = 0;
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if (chunk_will_survive) {
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bs -= n_baus_to_shrink;
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if (bs) {
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/* The last (non-dummy) block was not completely
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** eliminated by the shrink. */
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last_block->block_size = bs;
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/* Create new dummy end record.
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*/
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dummy_end_block =
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(head_record *) BAUS_FORWARD(last_block, bs);
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dummy_end_block->previous_block_size = bs;
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dummy_end_block->block_size = 0;
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#ifdef HMM_AUDIT_FAIL
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if (desc->avl_tree_root)
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AUDIT_BLOCK(PTR_REC_TO_HEAD(desc->avl_tree_root))
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#endif
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U(into_free_collection)(desc, last_block);
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} else {
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/* The last (non-dummy) block was completely
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** eliminated by the shrink. Make its head
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** the new dummy end block.
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*/
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last_block->block_size = 0;
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last_block->previous_block_size &= ~HIGH_BIT_BAU_SIZE;
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}
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}
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}
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#ifdef HMM_AUDIT_FAIL
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else
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HMM_AUDIT_FAIL
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#endif
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}
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#ifdef HMM_AUDIT_FAIL
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else
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HMM_AUDIT_FAIL
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#endif
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}
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}
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