FreeRTOS/Source/portable/MemMang/heap_2.c

   1 /*
   2     FreeRTOS V6.0.5 - Copyright (C) 2010 Real Time Engineers Ltd.
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  24
  25     This file is part of the FreeRTOS distribution.
  26
  27     FreeRTOS is free software; you can redistribute it and/or modify it under
  28     the terms of the GNU General Public License (version 2) as published by the
  29     Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
  30     ***NOTE*** The exception to the GPL is included to allow you to distribute
  31     a combined work that includes FreeRTOS without being obliged to provide the
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  35     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
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  37     License and the FreeRTOS license exception along with FreeRTOS; if not it
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  52 */
  53
  54 /*
  55  * A sample implementation of pvPortMalloc() and vPortFree() that permits
  56  * allocated blocks to be freed, but does not combine adjacent free blocks
  57  * into a single larger block.
  58  *
  59  * See heap_1.c and heap_3.c for alternative implementations, and the memory
  60  * management pages of http://www.FreeRTOS.org for more information.
  61  */
  62 #include <stdlib.h>
  63
  64 /* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE prevents task.h from redefining
  65 all the API functions to use the MPU wrappers.  That should only be done when
  66 task.h is included from an application file. */
  67 #define MPU_WRAPPERS_INCLUDED_FROM_API_FILE
  68
  69 #include "FreeRTOS.h"
  70 #include "task.h"
  71
  72 #undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
  73
  74 /* Allocate the memory for the heap.  The struct is used to force byte
  75 alignment without using any non-portable code. */
  76 static union xRTOS_HEAP
  77 {
  78         #if portBYTE_ALIGNMENT == 8
  79                 volatile portDOUBLE dDummy;
  80         #else
  81                 volatile unsigned long ulDummy;
  82         #endif
  83         unsigned char ucHeap[ configTOTAL_HEAP_SIZE ];
  84 } xHeap;
  85
  86 /* Define the linked list structure.  This is used to link free blocks in order
  87 of their size. */
  88 typedef struct A_BLOCK_LINK
  89 {
  90         struct A_BLOCK_LINK *pxNextFreeBlock;   /*<< The next free block in the list. */
  91         size_t xBlockSize;                                              /*<< The size of the free block. */
  92 } xBlockLink;
  93
  94
  95 static const unsigned short  heapSTRUCT_SIZE    = ( sizeof( xBlockLink ) + portBYTE_ALIGNMENT - ( sizeof( xBlockLink ) % portBYTE_ALIGNMENT ) );
  96 #define heapMINIMUM_BLOCK_SIZE  ( ( size_t ) ( heapSTRUCT_SIZE * 2 ) )
  97
  98 /* Create a couple of list links to mark the start and end of the list. */
  99 static xBlockLink xStart, xEnd;
 100
 101 /* Keeps track of the number of free bytes remaining, but says nothing about
 102 fragmentation. */
 103 static size_t xFreeBytesRemaining = configTOTAL_HEAP_SIZE;
 104
 105 /* STATIC FUNCTIONS ARE DEFINED AS MACROS TO MINIMIZE THE FUNCTION CALL DEPTH. */
 106
 107 /*
 108  * Insert a block into the list of free blocks - which is ordered by size of
 109  * the block.  Small blocks at the start of the list and large blocks at the end
 110  * of the list.
 111  */
 112 #define prvInsertBlockIntoFreeList( pxBlockToInsert )                                                           \
 113 {                                                                                                                                                                       \
 114 xBlockLink *pxIterator;                                                                                                                         \
 115 size_t xBlockSize;                                                                                                                                      \
 116                                                                                                                                                                         \
 117         xBlockSize = pxBlockToInsert->xBlockSize;                                                                               \
 118                                                                                                                                                                         \
 119         /* Iterate through the list until a block is found that has a larger size */    \
 120         /* than the block we are inserting. */                                                                                  \
 121         for( pxIterator = &xStart; pxIterator->pxNextFreeBlock->xBlockSize < xBlockSize; pxIterator = pxIterator->pxNextFreeBlock )     \
 122         {                                                                                                                                                               \
 123                 /* There is nothing to do here - just iterate to the correct position. */       \
 124         }                                                                                                                                                               \
 125                                                                                                                                                                         \
 126         /* Update the list to include the block being inserted in the correct */                \
 127         /* position. */                                                                                                                                 \
 128         pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock;                                 \
 129         pxIterator->pxNextFreeBlock = pxBlockToInsert;                                                                  \
 130 }
 131 /*-----------------------------------------------------------*/
 132
 133 #define prvHeapInit()                                                                                                                           \
 134 {                                                                                                                                                                       \
 135 xBlockLink *pxFirstFreeBlock;                                                                                                           \
 136                                                                                                                                                                         \
 137         /* xStart is used to hold a pointer to the first item in the list of free */    \
 138         /* blocks.  The void cast is used to prevent compiler warnings. */                              \
 139         xStart.pxNextFreeBlock = ( void * ) xHeap.ucHeap;                                                               \
 140         xStart.xBlockSize = ( size_t ) 0;                                                                                               \
 141                                                                                                                                                                         \
 142         /* xEnd is used to mark the end of the list of free blocks. */                                  \
 143         xEnd.xBlockSize = configTOTAL_HEAP_SIZE;                                                                                \
 144         xEnd.pxNextFreeBlock = NULL;                                                                                                    \
 145                                                                                                                                                                         \
 146         /* To start with there is a single free block that is sized to take up the              \
 147         entire heap space. */                                                                                                                   \
 148         pxFirstFreeBlock = ( void * ) xHeap.ucHeap;                                                                             \
 149         pxFirstFreeBlock->xBlockSize = configTOTAL_HEAP_SIZE;                                                   \
 150         pxFirstFreeBlock->pxNextFreeBlock = &xEnd;                                                                              \
 151 }
 152 /*-----------------------------------------------------------*/
 153
 154 void *pvPortMalloc( size_t xWantedSize )
 155 {
 156 xBlockLink *pxBlock, *pxPreviousBlock, *pxNewBlockLink;
 157 static portBASE_TYPE xHeapHasBeenInitialised = pdFALSE;
 158 void *pvReturn = NULL;
 159
 160         vTaskSuspendAll();
 161         {
 162                 /* If this is the first call to malloc then the heap will require
 163                 initialisation to setup the list of free blocks. */
 164                 if( xHeapHasBeenInitialised == pdFALSE )
 165                 {
 166                         prvHeapInit();
 167                         xHeapHasBeenInitialised = pdTRUE;
 168                 }
 169
 170                 /* The wanted size is increased so it can contain a xBlockLink
 171                 structure in addition to the requested amount of bytes. */
 172                 if( xWantedSize > 0 )
 173                 {
 174                         xWantedSize += heapSTRUCT_SIZE;
 175
 176                         /* Ensure that blocks are always aligned to the required number of bytes. */
 177                         if( xWantedSize & portBYTE_ALIGNMENT_MASK )
 178                         {
 179                                 /* Byte alignment required. */
 180                                 xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) );
 181                         }
 182                 }
 183
 184                 if( ( xWantedSize > 0 ) && ( xWantedSize < configTOTAL_HEAP_SIZE ) )
 185                 {
 186                         /* Blocks are stored in byte order - traverse the list from the start
 187                         (smallest) block until one of adequate size is found. */
 188                         pxPreviousBlock = &xStart;
 189                         pxBlock = xStart.pxNextFreeBlock;
 190                         while( ( pxBlock->xBlockSize < xWantedSize ) && ( pxBlock->pxNextFreeBlock ) )
 191                         {
 192                                 pxPreviousBlock = pxBlock;
 193                                 pxBlock = pxBlock->pxNextFreeBlock;
 194                         }
 195
 196                         /* If we found the end marker then a block of adequate size was not found. */
 197                         if( pxBlock != &xEnd )
 198                         {
 199                                 /* Return the memory space - jumping over the xBlockLink structure
 200                                 at its start. */
 201                                 pvReturn = ( void * ) ( ( ( unsigned char * ) pxPreviousBlock->pxNextFreeBlock ) + heapSTRUCT_SIZE );
 202
 203                                 /* This block is being returned for use so must be taken our of the
 204                                 list of free blocks. */
 205                                 pxPreviousBlock->pxNextFreeBlock = pxBlock->pxNextFreeBlock;
 206
 207                                 /* If the block is larger than required it can be split into two. */
 208                                 if( ( pxBlock->xBlockSize - xWantedSize ) > heapMINIMUM_BLOCK_SIZE )
 209                                 {
 210                                         /* This block is to be split into two.  Create a new block
 211                                         following the number of bytes requested. The void cast is
 212                                         used to prevent byte alignment warnings from the compiler. */
 213                                         pxNewBlockLink = ( void * ) ( ( ( unsigned char * ) pxBlock ) + xWantedSize );
 214
 215                                         /* Calculate the sizes of two blocks split from the single
 216                                         block. */
 217                                         pxNewBlockLink->xBlockSize = pxBlock->xBlockSize - xWantedSize;
 218                                         pxBlock->xBlockSize = xWantedSize;
 219
 220                                         /* Insert the new block into the list of free blocks. */
 221                                         prvInsertBlockIntoFreeList( ( pxNewBlockLink ) );
 222                                 }
 223
 224                                 xFreeBytesRemaining -= xWantedSize;
 225                         }
 226                 }
 227         }
 228         xTaskResumeAll();
 229
 230         #if( configUSE_MALLOC_FAILED_HOOK == 1 )
 231         {
 232                 if( pvReturn == NULL )
 233                 {
 234                         extern void vApplicationMallocFailedHook( void );
 235                         vApplicationMallocFailedHook();
 236                 }
 237         }
 238         #endif
 239
 240         return pvReturn;
 241 }
 242 /*-----------------------------------------------------------*/
 243
 244 void vPortFree( void *pv )
 245 {
 246 unsigned char *puc = ( unsigned char * ) pv;
 247 xBlockLink *pxLink;
 248
 249         if( pv )
 250         {
 251                 /* The memory being freed will have an xBlockLink structure immediately
 252                 before it. */
 253                 puc -= heapSTRUCT_SIZE;
 254
 255                 /* This casting is to keep the compiler from issuing warnings. */
 256                 pxLink = ( void * ) puc;
 257
 258                 vTaskSuspendAll();
 259                 {
 260                         /* Add this block to the list of free blocks. */
 261                         prvInsertBlockIntoFreeList( ( ( xBlockLink * ) pxLink ) );
 262                         xFreeBytesRemaining += pxLink->xBlockSize;
 263                 }
 264                 xTaskResumeAll();
 265         }
 266 }
 267 /*-----------------------------------------------------------*/
 268
 269 size_t xPortGetFreeHeapSize( void )
 270 {
 271         return xFreeBytesRemaining;
 272 }
 273 /*-----------------------------------------------------------*/
 274
 275 void vPortInitialiseBlocks( void )
 276 {
 277         /* This just exists to keep the linker quiet. */
 278 }