2 * FreeRTOS Kernel V10.1.0
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3 * Copyright (C) 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software.
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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17 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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18 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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19 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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20 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 * http://www.FreeRTOS.org
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23 * http://aws.amazon.com/freertos
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25 * 1 tab == 4 spaces!
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29 * A sample implementation of pvPortMalloc() and vPortFree() that combines
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30 * (coalescences) adjacent memory blocks as they are freed, and in so doing
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31 * limits memory fragmentation.
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33 * See heap_1.c, heap_2.c and heap_3.c for alternative implementations, and the
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34 * memory management pages of http://www.FreeRTOS.org for more information.
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38 /* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE prevents task.h from redefining
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39 all the API functions to use the MPU wrappers. That should only be done when
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40 task.h is included from an application file. */
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41 #define MPU_WRAPPERS_INCLUDED_FROM_API_FILE
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43 #include "FreeRTOS.h"
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46 #undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
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48 #if( configSUPPORT_DYNAMIC_ALLOCATION == 0 )
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49 #error This file must not be used if configSUPPORT_DYNAMIC_ALLOCATION is 0
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52 /* Block sizes must not get too small. */
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53 #define heapMINIMUM_BLOCK_SIZE ( ( size_t ) ( xHeapStructSize << 1 ) )
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55 /* Assumes 8bit bytes! */
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56 #define heapBITS_PER_BYTE ( ( size_t ) 8 )
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58 /* Allocate the memory for the heap. */
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59 #if( configAPPLICATION_ALLOCATED_HEAP == 1 )
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60 /* The application writer has already defined the array used for the RTOS
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61 heap - probably so it can be placed in a special segment or address. */
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62 extern uint8_t ucHeap[ configTOTAL_HEAP_SIZE ];
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64 static uint8_t ucHeap[ configTOTAL_HEAP_SIZE ];
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65 #endif /* configAPPLICATION_ALLOCATED_HEAP */
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67 /* Define the linked list structure. This is used to link free blocks in order
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68 of their memory address. */
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69 typedef struct A_BLOCK_LINK
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71 struct A_BLOCK_LINK *pxNextFreeBlock; /*<< The next free block in the list. */
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72 size_t xBlockSize; /*<< The size of the free block. */
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75 /*-----------------------------------------------------------*/
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78 * Inserts a block of memory that is being freed into the correct position in
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79 * the list of free memory blocks. The block being freed will be merged with
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80 * the block in front it and/or the block behind it if the memory blocks are
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81 * adjacent to each other.
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83 static void prvInsertBlockIntoFreeList( BlockLink_t *pxBlockToInsert );
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86 * Called automatically to setup the required heap structures the first time
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87 * pvPortMalloc() is called.
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89 static void prvHeapInit( void );
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91 /*-----------------------------------------------------------*/
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93 /* The size of the structure placed at the beginning of each allocated memory
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94 block must by correctly byte aligned. */
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95 static const size_t xHeapStructSize = ( sizeof( BlockLink_t ) + ( ( size_t ) ( portBYTE_ALIGNMENT - 1 ) ) ) & ~( ( size_t ) portBYTE_ALIGNMENT_MASK );
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97 /* Create a couple of list links to mark the start and end of the list. */
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98 static BlockLink_t xStart, *pxEnd = NULL;
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100 /* Keeps track of the number of free bytes remaining, but says nothing about
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102 static size_t xFreeBytesRemaining = 0U;
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103 static size_t xMinimumEverFreeBytesRemaining = 0U;
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105 /* Gets set to the top bit of an size_t type. When this bit in the xBlockSize
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106 member of an BlockLink_t structure is set then the block belongs to the
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107 application. When the bit is free the block is still part of the free heap
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109 static size_t xBlockAllocatedBit = 0;
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111 /*-----------------------------------------------------------*/
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113 void *pvPortMalloc( size_t xWantedSize )
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115 BlockLink_t *pxBlock, *pxPreviousBlock, *pxNewBlockLink;
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116 void *pvReturn = NULL;
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120 /* If this is the first call to malloc then the heap will require
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121 initialisation to setup the list of free blocks. */
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122 if( pxEnd == NULL )
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128 mtCOVERAGE_TEST_MARKER();
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131 /* Check the requested block size is not so large that the top bit is
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132 set. The top bit of the block size member of the BlockLink_t structure
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133 is used to determine who owns the block - the application or the
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134 kernel, so it must be free. */
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135 if( ( xWantedSize & xBlockAllocatedBit ) == 0 )
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137 /* The wanted size is increased so it can contain a BlockLink_t
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138 structure in addition to the requested amount of bytes. */
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139 if( xWantedSize > 0 )
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141 xWantedSize += xHeapStructSize;
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143 /* Ensure that blocks are always aligned to the required number
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145 if( ( xWantedSize & portBYTE_ALIGNMENT_MASK ) != 0x00 )
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147 /* Byte alignment required. */
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148 xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) );
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149 configASSERT( ( xWantedSize & portBYTE_ALIGNMENT_MASK ) == 0 );
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153 mtCOVERAGE_TEST_MARKER();
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158 mtCOVERAGE_TEST_MARKER();
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161 if( ( xWantedSize > 0 ) && ( xWantedSize <= xFreeBytesRemaining ) )
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163 /* Traverse the list from the start (lowest address) block until
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164 one of adequate size is found. */
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165 pxPreviousBlock = &xStart;
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166 pxBlock = xStart.pxNextFreeBlock;
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167 while( ( pxBlock->xBlockSize < xWantedSize ) && ( pxBlock->pxNextFreeBlock != NULL ) )
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169 pxPreviousBlock = pxBlock;
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170 pxBlock = pxBlock->pxNextFreeBlock;
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173 /* If the end marker was reached then a block of adequate size
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175 if( pxBlock != pxEnd )
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177 /* Return the memory space pointed to - jumping over the
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178 BlockLink_t structure at its start. */
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179 pvReturn = ( void * ) ( ( ( uint8_t * ) pxPreviousBlock->pxNextFreeBlock ) + xHeapStructSize );
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181 /* This block is being returned for use so must be taken out
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182 of the list of free blocks. */
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183 pxPreviousBlock->pxNextFreeBlock = pxBlock->pxNextFreeBlock;
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185 /* If the block is larger than required it can be split into
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187 if( ( pxBlock->xBlockSize - xWantedSize ) > heapMINIMUM_BLOCK_SIZE )
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189 /* This block is to be split into two. Create a new
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190 block following the number of bytes requested. The void
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191 cast is used to prevent byte alignment warnings from the
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193 pxNewBlockLink = ( void * ) ( ( ( uint8_t * ) pxBlock ) + xWantedSize );
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194 configASSERT( ( ( ( size_t ) pxNewBlockLink ) & portBYTE_ALIGNMENT_MASK ) == 0 );
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196 /* Calculate the sizes of two blocks split from the
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198 pxNewBlockLink->xBlockSize = pxBlock->xBlockSize - xWantedSize;
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199 pxBlock->xBlockSize = xWantedSize;
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201 /* Insert the new block into the list of free blocks. */
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202 prvInsertBlockIntoFreeList( pxNewBlockLink );
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206 mtCOVERAGE_TEST_MARKER();
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209 xFreeBytesRemaining -= pxBlock->xBlockSize;
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211 if( xFreeBytesRemaining < xMinimumEverFreeBytesRemaining )
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213 xMinimumEverFreeBytesRemaining = xFreeBytesRemaining;
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217 mtCOVERAGE_TEST_MARKER();
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220 /* The block is being returned - it is allocated and owned
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221 by the application and has no "next" block. */
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222 pxBlock->xBlockSize |= xBlockAllocatedBit;
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223 pxBlock->pxNextFreeBlock = NULL;
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227 mtCOVERAGE_TEST_MARKER();
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232 mtCOVERAGE_TEST_MARKER();
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237 mtCOVERAGE_TEST_MARKER();
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240 traceMALLOC( pvReturn, xWantedSize );
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242 ( void ) xTaskResumeAll();
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244 #if( configUSE_MALLOC_FAILED_HOOK == 1 )
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246 if( pvReturn == NULL )
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248 extern void vApplicationMallocFailedHook( void );
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249 vApplicationMallocFailedHook();
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253 mtCOVERAGE_TEST_MARKER();
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258 configASSERT( ( ( ( size_t ) pvReturn ) & ( size_t ) portBYTE_ALIGNMENT_MASK ) == 0 );
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261 /*-----------------------------------------------------------*/
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263 void vPortFree( void *pv )
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265 uint8_t *puc = ( uint8_t * ) pv;
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266 BlockLink_t *pxLink;
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270 /* The memory being freed will have an BlockLink_t structure immediately
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272 puc -= xHeapStructSize;
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274 /* This casting is to keep the compiler from issuing warnings. */
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275 pxLink = ( void * ) puc;
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277 /* Check the block is actually allocated. */
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278 configASSERT( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 );
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279 configASSERT( pxLink->pxNextFreeBlock == NULL );
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281 if( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 )
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283 if( pxLink->pxNextFreeBlock == NULL )
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285 /* The block is being returned to the heap - it is no longer
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287 pxLink->xBlockSize &= ~xBlockAllocatedBit;
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291 /* Add this block to the list of free blocks. */
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292 xFreeBytesRemaining += pxLink->xBlockSize;
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293 traceFREE( pv, pxLink->xBlockSize );
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294 prvInsertBlockIntoFreeList( ( ( BlockLink_t * ) pxLink ) );
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296 ( void ) xTaskResumeAll();
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300 mtCOVERAGE_TEST_MARKER();
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305 mtCOVERAGE_TEST_MARKER();
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309 /*-----------------------------------------------------------*/
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311 size_t xPortGetFreeHeapSize( void )
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313 return xFreeBytesRemaining;
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315 /*-----------------------------------------------------------*/
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317 size_t xPortGetMinimumEverFreeHeapSize( void )
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319 return xMinimumEverFreeBytesRemaining;
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321 /*-----------------------------------------------------------*/
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323 void vPortInitialiseBlocks( void )
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325 /* This just exists to keep the linker quiet. */
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327 /*-----------------------------------------------------------*/
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329 static void prvHeapInit( void )
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331 BlockLink_t *pxFirstFreeBlock;
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332 uint8_t *pucAlignedHeap;
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334 size_t xTotalHeapSize = configTOTAL_HEAP_SIZE;
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336 /* Ensure the heap starts on a correctly aligned boundary. */
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337 uxAddress = ( size_t ) ucHeap;
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339 if( ( uxAddress & portBYTE_ALIGNMENT_MASK ) != 0 )
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341 uxAddress += ( portBYTE_ALIGNMENT - 1 );
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342 uxAddress &= ~( ( size_t ) portBYTE_ALIGNMENT_MASK );
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343 xTotalHeapSize -= uxAddress - ( size_t ) ucHeap;
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346 pucAlignedHeap = ( uint8_t * ) uxAddress;
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348 /* xStart is used to hold a pointer to the first item in the list of free
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349 blocks. The void cast is used to prevent compiler warnings. */
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350 xStart.pxNextFreeBlock = ( void * ) pucAlignedHeap;
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351 xStart.xBlockSize = ( size_t ) 0;
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353 /* pxEnd is used to mark the end of the list of free blocks and is inserted
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354 at the end of the heap space. */
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355 uxAddress = ( ( size_t ) pucAlignedHeap ) + xTotalHeapSize;
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356 uxAddress -= xHeapStructSize;
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357 uxAddress &= ~( ( size_t ) portBYTE_ALIGNMENT_MASK );
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358 pxEnd = ( void * ) uxAddress;
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359 pxEnd->xBlockSize = 0;
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360 pxEnd->pxNextFreeBlock = NULL;
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362 /* To start with there is a single free block that is sized to take up the
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363 entire heap space, minus the space taken by pxEnd. */
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364 pxFirstFreeBlock = ( void * ) pucAlignedHeap;
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365 pxFirstFreeBlock->xBlockSize = uxAddress - ( size_t ) pxFirstFreeBlock;
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366 pxFirstFreeBlock->pxNextFreeBlock = pxEnd;
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368 /* Only one block exists - and it covers the entire usable heap space. */
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369 xMinimumEverFreeBytesRemaining = pxFirstFreeBlock->xBlockSize;
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370 xFreeBytesRemaining = pxFirstFreeBlock->xBlockSize;
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372 /* Work out the position of the top bit in a size_t variable. */
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373 xBlockAllocatedBit = ( ( size_t ) 1 ) << ( ( sizeof( size_t ) * heapBITS_PER_BYTE ) - 1 );
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375 /*-----------------------------------------------------------*/
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377 static void prvInsertBlockIntoFreeList( BlockLink_t *pxBlockToInsert )
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379 BlockLink_t *pxIterator;
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382 /* Iterate through the list until a block is found that has a higher address
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383 than the block being inserted. */
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384 for( pxIterator = &xStart; pxIterator->pxNextFreeBlock < pxBlockToInsert; pxIterator = pxIterator->pxNextFreeBlock )
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386 /* Nothing to do here, just iterate to the right position. */
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389 /* Do the block being inserted, and the block it is being inserted after
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390 make a contiguous block of memory? */
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391 puc = ( uint8_t * ) pxIterator;
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392 if( ( puc + pxIterator->xBlockSize ) == ( uint8_t * ) pxBlockToInsert )
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394 pxIterator->xBlockSize += pxBlockToInsert->xBlockSize;
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395 pxBlockToInsert = pxIterator;
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399 mtCOVERAGE_TEST_MARKER();
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402 /* Do the block being inserted, and the block it is being inserted before
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403 make a contiguous block of memory? */
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404 puc = ( uint8_t * ) pxBlockToInsert;
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405 if( ( puc + pxBlockToInsert->xBlockSize ) == ( uint8_t * ) pxIterator->pxNextFreeBlock )
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407 if( pxIterator->pxNextFreeBlock != pxEnd )
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409 /* Form one big block from the two blocks. */
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410 pxBlockToInsert->xBlockSize += pxIterator->pxNextFreeBlock->xBlockSize;
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411 pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock->pxNextFreeBlock;
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415 pxBlockToInsert->pxNextFreeBlock = pxEnd;
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420 pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock;
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423 /* If the block being inserted plugged a gab, so was merged with the block
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424 before and the block after, then it's pxNextFreeBlock pointer will have
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425 already been set, and should not be set here as that would make it point
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427 if( pxIterator != pxBlockToInsert )
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429 pxIterator->pxNextFreeBlock = pxBlockToInsert;
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433 mtCOVERAGE_TEST_MARKER();
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