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This commit is contained in:
Tilen Majerle 2019-10-31 00:53:56 +01:00
parent fa8eeb6a66
commit 192620d561
1 changed files with 14 additions and 6 deletions
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20
lwmem/src/lwmem/lwmem.c
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@ -666,12 +666,16 @@ LWMEM_PREF(realloc)(void* const ptr, const size_t size) {
/* Move memory from block to block previous to current */
void* const old_data_ptr = LWMEM_GET_PTR_FROM_BLOCK(block);
void* const new_data_ptr = LWMEM_GET_PTR_FROM_BLOCK(prev);
LWMEM_MEMMOVE(new_data_ptr, old_data_ptr, block_size); /* Copy old buffer size to new location */
/*
* If memmove overwrites metadata of current block (when shifting content up),
* it is not an issue as we know its size and next is already NULL
* it is not an issue as we know its size (block_size) and next is already NULL.
*
* Memmove must be used to guarantee move of data as addresses + their sizes may overlap
*
* Metadata of "prev" are not modified during memmove
*/
LWMEM_MEMMOVE(new_data_ptr, old_data_ptr, block_size);
lwmem.mem_available_bytes -= prev->size;/* For now decrease effective available bytes */
prev->size += block_size; /* Increase size of input block size */
@ -686,9 +690,9 @@ LWMEM_PREF(realloc)(void* const ptr, const size_t size) {
/*
* At this point, it was not possible to expand existing block with free before or free after due to:
* - Input block & next free block do not create contiguous block or its new size is too small
* - Last free block & input block do not create contiguous block or its new size is too small
* - Previous free block & input block do not create contiguous block or its new size is too small
*
* Last option is to check if last free block before "prev", input block "block" and next free block "prev->next" create contiguous block
* Last option is to check if previous free block "prev", input block "block" and next free block "prev->next" create contiguous block
* and size of new block (from 3 contiguous blocks) together is big enough
*/
if ((LWMEM_TO_BYTE_PTR(prev) + prev->size) == LWMEM_TO_BYTE_PTR(block) /* Input block and free block before create contiguous block */
@ -700,8 +704,12 @@ LWMEM_PREF(realloc)(void* const ptr, const size_t size) {
void* const new_data_ptr = LWMEM_GET_PTR_FROM_BLOCK(prev);
/*
* It is necessary to use memmove and not memcpy as memmove takes care of memory overlapping
* It is not a problem if data shifted up overwrite old block metadata
* If memmove overwrites metadata of current block (when shifting content up),
* it is not an issue as we know its size (block_size) and next is already NULL.
*
* Memmove must be used to guarantee move of data as addresses + their sizes may overlap
*
* Metadata of "prev" are not modified during memmove
*/
LWMEM_MEMMOVE(new_data_ptr, old_data_ptr, block_size); /* Copy old buffer size to new location */