1 files changed, 110 insertions, 0 deletions
diff --git a/vpx_mem/memory_manager/hmm_shrink.c b/vpx_mem/memory_manager/hmm_shrink.c
new file mode 100644
index 000000000..5ef9b233f
--- /dev/null
+++ b/vpx_mem/memory_manager/hmm_shrink.c
@@ -0,0 +1,110 @@
+/*
+ *  Copyright (c) 2010 The VP8 project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license and patent
+ *  grant that can be found in the LICENSE file in the root of the source
+ *  tree. 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"
+
+void U(shrink_chunk)(U(descriptor) *desc, U(size_bau) n_baus_to_shrink)
+{
+    head_record *dummy_end_block = (head_record *)
+                                   BAUS_BACKWARD(desc->end_of_shrinkable_chunk, DUMMY_END_BLOCK_BAUS);
+
+#ifdef HMM_AUDIT_FAIL
+
+    if (dummy_end_block->block_size != 0)
+        /* Chunk does not have valid dummy end block. */
+        HMM_AUDIT_FAIL
+
+#endif
+
+        if (n_baus_to_shrink)
+        {
+            head_record *last_block = (head_record *)
+                                      BAUS_BACKWARD(
+                                          dummy_end_block, dummy_end_block->previous_block_size);
+
+#ifdef HMM_AUDIT_FAIL
+            AUDIT_BLOCK(last_block)
+#endif
+
+            if (last_block == desc->last_freed)
+            {
+                U(size_bau) bs = BLOCK_BAUS(last_block);
+
+                /* Chunk will not be shrunk out of existence if
+                ** 1.  There is at least one allocated block in the chunk
+                **     and the amount to shrink is exactly the size of the
+                **     last block, OR
+                ** 2.  After the last block is shrunk, there will be enough
+                **     BAUs left in it to form a minimal size block. */
+                int chunk_will_survive =
+                    (PREV_BLOCK_BAUS(last_block) && (n_baus_to_shrink == bs)) ||
+                    (n_baus_to_shrink <= (U(size_bau))(bs - MIN_BLOCK_BAUS));
+
+                if (chunk_will_survive ||
+                    (!PREV_BLOCK_BAUS(last_block) &&
+                     (n_baus_to_shrink ==
+                      (U(size_bau))(bs + DUMMY_END_BLOCK_BAUS))))
+                {
+                    desc->last_freed = 0;
+
+                    if (chunk_will_survive)
+                    {
+                        bs -= n_baus_to_shrink;
+
+                        if (bs)
+                        {
+                            /* The last (non-dummy) block was not completely
+                            ** eliminated by the shrink. */
+
+                            last_block->block_size = bs;
+
+                            /* Create new dummy end record.
+                            */
+                            dummy_end_block =
+                                (head_record *) BAUS_FORWARD(last_block, bs);
+                            dummy_end_block->previous_block_size = bs;
+                            dummy_end_block->block_size = 0;
+
+#ifdef HMM_AUDIT_FAIL
+
+                            if (desc->avl_tree_root)
+                                AUDIT_BLOCK(PTR_REC_TO_HEAD(desc->avl_tree_root))
+#endif
+
+                                U(into_free_collection)(desc, last_block);
+                        }
+                        else
+                        {
+                            /* The last (non-dummy) block was completely
+                            ** eliminated by the shrink.  Make its head
+                            ** the new dummy end block.
+                            */
+                            last_block->block_size = 0;
+                            last_block->previous_block_size &= ~HIGH_BIT_BAU_SIZE;
+                        }
+                    }
+                }
+
+#ifdef HMM_AUDIT_FAIL
+                else
+                    HMM_AUDIT_FAIL
+#endif
+                }
+
+#ifdef HMM_AUDIT_FAIL
+            else
+                HMM_AUDIT_FAIL
+#endif
+            }
+}