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First version under SVN is V4.0.1
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Richard Barry
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236
Source/portable/MemMang/heap_2.c
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Source/portable/MemMang/heap_2.c
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/*
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FreeRTOS V4.0.1 - Copyright (C) 2003-2006 Richard Barry.
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This file is part of the FreeRTOS distribution.
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FreeRTOS is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FreeRTOS is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FreeRTOS; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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A special exception to the GPL can be applied should you wish to distribute
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a combined work that includes FreeRTOS, without being obliged to provide
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the source code for any proprietary components. See the licensing section
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of http://www.FreeRTOS.org for full details of how and when the exception
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can be applied.
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***************************************************************************
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See http://www.FreeRTOS.org for documentation, latest information, license
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and contact details. Please ensure to read the configuration and relevant
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port sections of the online documentation.
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***************************************************************************
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*/
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/*
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* A sample implementation of pvPortMalloc() and vPortFree() that permits
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* allocated blocks to be freed, but does not combine adjacent free blocks
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* into a single larger block.
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*
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* See heap_1.c and heap_3.c for alternative implementations, and the memory
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* management pages of http://www.FreeRTOS.org for more information.
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*/
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#include <stdlib.h>
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#include "FreeRTOS.h"
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#include "task.h"
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/* Setup the correct byte alignment mask for the defined byte alignment. */
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#if portBYTE_ALIGNMENT == 4
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#define heapBYTE_ALIGNMENT_MASK ( ( size_t ) 0x0003 )
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#endif
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#if portBYTE_ALIGNMENT == 2
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#define heapBYTE_ALIGNMENT_MASK ( ( size_t ) 0x0001 )
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#endif
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#if portBYTE_ALIGNMENT == 1
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#define heapBYTE_ALIGNMENT_MASK ( ( size_t ) 0x0000 )
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#endif
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#ifndef heapBYTE_ALIGNMENT_MASK
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#error "Invalid portBYTE_ALIGNMENT definition"
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#endif
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/* Allocate the memory for the heap. The struct is used to force byte
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alignment without using any non-portable code. */
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static struct xRTOS_HEAP
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{
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unsigned portLONG ulDummy;
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unsigned portCHAR ucHeap[ configTOTAL_HEAP_SIZE ];
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} xHeap;
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/* Define the linked list structure. This is used to link free blocks in order
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of their size. */
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typedef struct A_BLOCK_LINK
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{
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struct A_BLOCK_LINK *pxNextFreeBlock; /*<< The next free block in the list. */
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size_t xBlockSize; /*<< The size of the free block. */
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} xBlockLink;
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static const unsigned portSHORT heapSTRUCT_SIZE = ( sizeof( xBlockLink ) + ( sizeof( xBlockLink ) % portBYTE_ALIGNMENT ) );
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#define heapMINIMUM_BLOCK_SIZE ( ( size_t ) ( heapSTRUCT_SIZE * 2 ) )
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/* Create a couple of list links to mark the start and end of the list. */
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static xBlockLink xStart, xEnd;
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/* STATIC FUNCTIONS ARE DEFINED AS MACROS TO MINIMIZE THE FUNCTION CALL DEPTH. */
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/*
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* Insert a block into the list of free blocks - which is ordered by size of
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* the block. Small blocks at the start of the list and large blocks at the end
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* of the list.
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*/
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#define prvInsertBlockIntoFreeList( pxBlockToInsert ) \
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{ \
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xBlockLink *pxIterator; \
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size_t xBlockSize; \
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\
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xBlockSize = pxBlockToInsert->xBlockSize; \
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\
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/* Iterate through the list until a block is found that has a larger size */ \
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/* than the block we are inserting. */ \
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for( pxIterator = &xStart; pxIterator->pxNextFreeBlock->xBlockSize < xBlockSize; pxIterator = pxIterator->pxNextFreeBlock ) \
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{ \
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/* There is nothing to do here - just iterate to the correct position. */ \
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} \
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\
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/* Update the list to include the block being inserted in the correct */ \
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/* position. */ \
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pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock; \
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pxIterator->pxNextFreeBlock = pxBlockToInsert; \
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}
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/*-----------------------------------------------------------*/
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#define prvHeapInit() \
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{ \
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xBlockLink *pxFirstFreeBlock; \
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\
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/* xStart is used to hold a pointer to the first item in the list of free */ \
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/* blocks. The void cast is used to prevent compiler warnings. */ \
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xStart.pxNextFreeBlock = ( void * ) xHeap.ucHeap; \
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xStart.xBlockSize = ( size_t ) 0; \
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\
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/* xEnd is used to mark the end of the list of free blocks. */ \
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xEnd.xBlockSize = configTOTAL_HEAP_SIZE; \
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xEnd.pxNextFreeBlock = NULL; \
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\
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/* To start with there is a single free block that is sized to take up the \
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entire heap space. */ \
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pxFirstFreeBlock = ( void * ) xHeap.ucHeap; \
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pxFirstFreeBlock->xBlockSize = configTOTAL_HEAP_SIZE; \
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pxFirstFreeBlock->pxNextFreeBlock = &xEnd; \
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}
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/*-----------------------------------------------------------*/
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void *pvPortMalloc( size_t xWantedSize )
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{
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xBlockLink *pxBlock, *pxPreviousBlock, *pxNewBlockLink;
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static portBASE_TYPE xHeapHasBeenInitialised = pdFALSE;
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void *pvReturn = NULL;
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vTaskSuspendAll();
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{
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/* If this is the first call to malloc then the heap will require
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initialisation to setup the list of free blocks. */
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if( xHeapHasBeenInitialised == pdFALSE )
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{
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prvHeapInit();
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xHeapHasBeenInitialised = pdTRUE;
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}
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/* The wanted size is increased so it can contain a xBlockLink
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structure in addition to the requested amount of bytes. */
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if( xWantedSize > 0 )
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{
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xWantedSize += heapSTRUCT_SIZE;
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/* Ensure that blocks are always aligned to the required number of bytes. */
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if( xWantedSize & heapBYTE_ALIGNMENT_MASK )
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{
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/* Byte alignment required. */
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xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & heapBYTE_ALIGNMENT_MASK ) );
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}
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}
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if( ( xWantedSize > 0 ) && ( xWantedSize < configTOTAL_HEAP_SIZE ) )
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{
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/* Blocks are stored in byte order - traverse the list from the start
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(smallest) block until one of adequate size is found. */
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pxPreviousBlock = &xStart;
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pxBlock = xStart.pxNextFreeBlock;
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while( ( pxBlock->xBlockSize < xWantedSize ) && ( pxBlock->pxNextFreeBlock ) )
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{
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pxPreviousBlock = pxBlock;
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pxBlock = pxBlock->pxNextFreeBlock;
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}
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/* If we found the end marker then a block of adequate size was not found. */
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if( pxBlock != &xEnd )
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{
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/* Return the memory space - jumping over the xBlockLink structure
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at its start. */
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pvReturn = ( void * ) ( ( ( unsigned portCHAR * ) pxPreviousBlock->pxNextFreeBlock ) + heapSTRUCT_SIZE );
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/* This block is being returned for use so must be taken our of the
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list of free blocks. */
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pxPreviousBlock->pxNextFreeBlock = pxBlock->pxNextFreeBlock;
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/* If the block is larger than required it can be split into two. */
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if( ( pxBlock->xBlockSize - xWantedSize ) > heapMINIMUM_BLOCK_SIZE )
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{
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/* This block is to be split into two. Create a new block
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following the number of bytes requested. The void cast is
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used to prevent byte alignment warnings from the compiler. */
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pxNewBlockLink = ( void * ) ( ( ( unsigned portCHAR * ) pxBlock ) + xWantedSize );
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/* Calculate the sizes of two blocks split from the single
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block. */
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pxNewBlockLink->xBlockSize = pxBlock->xBlockSize - xWantedSize;
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pxBlock->xBlockSize = xWantedSize;
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/* Insert the new block into the list of free blocks. */
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prvInsertBlockIntoFreeList( ( pxNewBlockLink ) );
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}
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}
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}
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}
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xTaskResumeAll();
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return pvReturn;
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}
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/*-----------------------------------------------------------*/
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void vPortFree( void *pv )
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{
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unsigned portCHAR *puc = ( unsigned portCHAR * ) pv;
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xBlockLink *pxLink;
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if( pv )
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{
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/* The memory being freed will have an xBlockLink structure immediately
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before it. */
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puc -= heapSTRUCT_SIZE;
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/* This casting is to keep the compiler from issuing warnings. */
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pxLink = ( void * ) puc;
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vTaskSuspendAll();
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{
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/* Add this block to the list of free blocks. */
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prvInsertBlockIntoFreeList( ( ( xBlockLink * ) pxLink ) );
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}
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xTaskResumeAll();
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}
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}
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/*-----------------------------------------------------------*/
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