heap_4.c File Reference

#include <stdlib.h>
#include "FreeRTOS.h"
#include "task.h"

Classes
struct	A_BLOCK_LINK

Macros
#define	MPU_WRAPPERS_INCLUDED_FROM_API_FILE
#define	heapMINIMUM_BLOCK_SIZE   ( ( size_t ) ( xHeapStructSize << 1 ) )
#define	heapBITS_PER_BYTE   ( ( size_t ) 8 )

Typedefs
typedef struct A_BLOCK_LINK	BlockLink_t

Functions
static void	prvInsertBlockIntoFreeList (BlockLink_t *pxBlockToInsert)
static void	prvHeapInit (void)
void *	pvPortMalloc (size_t xWantedSize)
void	vPortFree (void *pv)
size_t	xPortGetFreeHeapSize (void)
size_t	xPortGetMinimumEverFreeHeapSize (void)
void	vPortInitialiseBlocks (void)

Variables
static uint8_t	ucHeap [configTOTAL_HEAP_SIZE]
static const size_t	xHeapStructSize = ( sizeof( BlockLink_t ) + ( ( size_t ) ( portBYTE_ALIGNMENT - 1 ) ) ) & ~( ( size_t ) portBYTE_ALIGNMENT_MASK )
static BlockLink_t	xStart
static BlockLink_t *	pxEnd = NULL
static size_t	xFreeBytesRemaining = 0U
static size_t	xMinimumEverFreeBytesRemaining = 0U
static size_t	xBlockAllocatedBit = 0

Macro Definition Documentation

MPU_WRAPPERS_INCLUDED_FROM_API_FILE

#define MPU_WRAPPERS_INCLUDED_FROM_API_FILE

heapMINIMUM_BLOCK_SIZE

#define heapMINIMUM_BLOCK_SIZE   ( ( size_t ) ( xHeapStructSize << 1 ) )

heapBITS_PER_BYTE

#define heapBITS_PER_BYTE   ( ( size_t ) 8 )

Typedef Documentation

BlockLink_t

typedef struct A_BLOCK_LINK BlockLink_t

Function Documentation

prvInsertBlockIntoFreeList()

static void prvInsertBlockIntoFreeList ( BlockLink_t *  pxBlockToInsert )

static

{
BlockLink_t *pxIterator;
uint8_t *puc;
 
    /* Iterate through the list until a block is found that has a higher address
    than the block being inserted. */
    for( pxIterator = &xStart; pxIterator->pxNextFreeBlock < pxBlockToInsert; pxIterator = pxIterator->pxNextFreeBlock )
    {
        /* Nothing to do here, just iterate to the right position. */
    }
 
    /* Do the block being inserted, and the block it is being inserted after
    make a contiguous block of memory? */
    puc = ( uint8_t * ) pxIterator;
    if( ( puc + pxIterator->xBlockSize ) == ( uint8_t * ) pxBlockToInsert )
    {
        pxIterator->xBlockSize += pxBlockToInsert->xBlockSize;
        pxBlockToInsert = pxIterator;
    }
    else
    {
        mtCOVERAGE_TEST_MARKER();
    }
 
    /* Do the block being inserted, and the block it is being inserted before
    make a contiguous block of memory? */
    puc = ( uint8_t * ) pxBlockToInsert;
    if( ( puc + pxBlockToInsert->xBlockSize ) == ( uint8_t * ) pxIterator->pxNextFreeBlock )
    {
        if( pxIterator->pxNextFreeBlock != pxEnd )
        {
            /* Form one big block from the two blocks. */
            pxBlockToInsert->xBlockSize += pxIterator->pxNextFreeBlock->xBlockSize;
            pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock->pxNextFreeBlock;
        }
        else
        {
            pxBlockToInsert->pxNextFreeBlock = pxEnd;
        }
    }
    else
    {
        pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock;
    }
 
    /* If the block being inserted plugged a gab, so was merged with the block
    before and the block after, then it's pxNextFreeBlock pointer will have
    already been set, and should not be set here as that would make it point
    to itself. */
    if( pxIterator != pxBlockToInsert )
    {
        pxIterator->pxNextFreeBlock = pxBlockToInsert;
    }
    else
    {
        mtCOVERAGE_TEST_MARKER();
    }
}

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prvHeapInit()

static void prvHeapInit ( void  )

static

{
BlockLink_t *pxFirstFreeBlock;
uint8_t *pucAlignedHeap;
size_t uxAddress;
size_t xTotalHeapSize = configTOTAL_HEAP_SIZE;
 
    /* Ensure the heap starts on a correctly aligned boundary. */
    uxAddress = ( size_t ) ucHeap;
 
    if( ( uxAddress & portBYTE_ALIGNMENT_MASK ) != 0 )
    {
        uxAddress += ( portBYTE_ALIGNMENT - 1 );
        uxAddress &= ~( ( size_t ) portBYTE_ALIGNMENT_MASK );
        xTotalHeapSize -= uxAddress - ( size_t ) ucHeap;
    }
 
    pucAlignedHeap = ( uint8_t * ) uxAddress;
 
    /* xStart is used to hold a pointer to the first item in the list of free
    blocks.  The void cast is used to prevent compiler warnings. */
    xStart.pxNextFreeBlock = ( void * ) pucAlignedHeap;
    xStart.xBlockSize = ( size_t ) 0;
 
    /* pxEnd is used to mark the end of the list of free blocks and is inserted
    at the end of the heap space. */
    uxAddress = ( ( size_t ) pucAlignedHeap ) + xTotalHeapSize;
    uxAddress -= xHeapStructSize;
    uxAddress &= ~( ( size_t ) portBYTE_ALIGNMENT_MASK );
    pxEnd = ( void * ) uxAddress;
    pxEnd->xBlockSize = 0;
    pxEnd->pxNextFreeBlock = NULL;
 
    /* To start with there is a single free block that is sized to take up the
    entire heap space, minus the space taken by pxEnd. */
    pxFirstFreeBlock = ( void * ) pucAlignedHeap;
    pxFirstFreeBlock->xBlockSize = uxAddress - ( size_t ) pxFirstFreeBlock;
    pxFirstFreeBlock->pxNextFreeBlock = pxEnd;
 
    /* Only one block exists - and it covers the entire usable heap space. */
    xMinimumEverFreeBytesRemaining = pxFirstFreeBlock->xBlockSize;
    xFreeBytesRemaining = pxFirstFreeBlock->xBlockSize;
 
    /* Work out the position of the top bit in a size_t variable. */
    xBlockAllocatedBit = ( ( size_t ) 1 ) << ( ( sizeof( size_t ) * heapBITS_PER_BYTE ) - 1 );
}

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pvPortMalloc()

void* pvPortMalloc

(

size_t

xWantedSize

)

{
BlockLink_t *pxBlock, *pxPreviousBlock, *pxNewBlockLink;
void *pvReturn = NULL;
 
    vTaskSuspendAll();
    {
        /* If this is the first call to malloc then the heap will require
        initialisation to setup the list of free blocks. */
        if( pxEnd == NULL )
        {
            prvHeapInit();
        }
        else
        {
            mtCOVERAGE_TEST_MARKER();
        }
 
        /* Check the requested block size is not so large that the top bit is
        set.  The top bit of the block size member of the BlockLink_t structure
        is used to determine who owns the block - the application or the
        kernel, so it must be free. */
        if( ( xWantedSize & xBlockAllocatedBit ) == 0 )
        {
            /* The wanted size is increased so it can contain a BlockLink_t
            structure in addition to the requested amount of bytes. */
            if( xWantedSize > 0 )
            {
                xWantedSize += xHeapStructSize;
 
                /* Ensure that blocks are always aligned to the required number
                of bytes. */
                if( ( xWantedSize & portBYTE_ALIGNMENT_MASK ) != 0x00 )
                {
                    /* Byte alignment required. */
                    xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) );
                    configASSERT( ( xWantedSize & portBYTE_ALIGNMENT_MASK ) == 0 );
                }
                else
                {
                    mtCOVERAGE_TEST_MARKER();
                }
            }
            else
            {
                mtCOVERAGE_TEST_MARKER();
            }
 
            if( ( xWantedSize > 0 ) && ( xWantedSize <= xFreeBytesRemaining ) )
            {
                /* Traverse the list from the start (lowest address) block until
                one of adequate size is found. */
                pxPreviousBlock = &xStart;
                pxBlock = xStart.pxNextFreeBlock;
                while( ( pxBlock->xBlockSize < xWantedSize ) && ( pxBlock->pxNextFreeBlock != NULL ) )
                {
                    pxPreviousBlock = pxBlock;
                    pxBlock = pxBlock->pxNextFreeBlock;
                }
 
                /* If the end marker was reached then a block of adequate size
                was not found. */
                if( pxBlock != pxEnd )
                {
                    /* Return the memory space pointed to - jumping over the
                    BlockLink_t structure at its start. */
                    pvReturn = ( void * ) ( ( ( uint8_t * ) pxPreviousBlock->pxNextFreeBlock ) + xHeapStructSize );
 
                    /* This block is being returned for use so must be taken out
                    of the list of free blocks. */
                    pxPreviousBlock->pxNextFreeBlock = pxBlock->pxNextFreeBlock;
 
                    /* If the block is larger than required it can be split into
                    two. */
                    if( ( pxBlock->xBlockSize - xWantedSize ) > heapMINIMUM_BLOCK_SIZE )
                    {
                        /* This block is to be split into two.  Create a new
                        block following the number of bytes requested. The void
                        cast is used to prevent byte alignment warnings from the
                        compiler. */
                        pxNewBlockLink = ( void * ) ( ( ( uint8_t * ) pxBlock ) + xWantedSize );
                        configASSERT( ( ( ( size_t ) pxNewBlockLink ) & portBYTE_ALIGNMENT_MASK ) == 0 );
 
                        /* Calculate the sizes of two blocks split from the
                        single block. */
                        pxNewBlockLink->xBlockSize = pxBlock->xBlockSize - xWantedSize;
                        pxBlock->xBlockSize = xWantedSize;
 
                        /* Insert the new block into the list of free blocks. */
                        prvInsertBlockIntoFreeList( pxNewBlockLink );
                    }
                    else
                    {
                        mtCOVERAGE_TEST_MARKER();
                    }
 
                    xFreeBytesRemaining -= pxBlock->xBlockSize;
 
                    if( xFreeBytesRemaining < xMinimumEverFreeBytesRemaining )
                    {
                        xMinimumEverFreeBytesRemaining = xFreeBytesRemaining;
                    }
                    else
                    {
                        mtCOVERAGE_TEST_MARKER();
                    }
 
                    /* The block is being returned - it is allocated and owned
                    by the application and has no "next" block. */
                    pxBlock->xBlockSize |= xBlockAllocatedBit;
                    pxBlock->pxNextFreeBlock = NULL;
                }
                else
                {
                    mtCOVERAGE_TEST_MARKER();
                }
            }
            else
            {
                mtCOVERAGE_TEST_MARKER();
            }
        }
        else
        {
            mtCOVERAGE_TEST_MARKER();
        }
 
        traceMALLOC( pvReturn, xWantedSize );
    }
    ( void ) xTaskResumeAll();
 
    #if( configUSE_MALLOC_FAILED_HOOK == 1 )
    {
        if( pvReturn == NULL )
        {
            extern void vApplicationMallocFailedHook( void );
            vApplicationMallocFailedHook();
        }
        else
        {
            mtCOVERAGE_TEST_MARKER();
        }
    }
    #endif
 
    configASSERT( ( ( ( size_t ) pvReturn ) & ( size_t ) portBYTE_ALIGNMENT_MASK ) == 0 );
    return pvReturn;
}

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vPortFree()

void vPortFree

(

void *

pv

)

{
uint8_t *puc = ( uint8_t * ) pv;
BlockLink_t *pxLink;
 
    if( pv != NULL )
    {
        /* The memory being freed will have an BlockLink_t structure immediately
        before it. */
        puc -= xHeapStructSize;
 
        /* This casting is to keep the compiler from issuing warnings. */
        pxLink = ( void * ) puc;
 
        /* Check the block is actually allocated. */
        configASSERT( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 );
        configASSERT( pxLink->pxNextFreeBlock == NULL );
 
        if( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 )
        {
            if( pxLink->pxNextFreeBlock == NULL )
            {
                /* The block is being returned to the heap - it is no longer
                allocated. */
                pxLink->xBlockSize &= ~xBlockAllocatedBit;
 
                vTaskSuspendAll();
                {
                    /* Add this block to the list of free blocks. */
                    xFreeBytesRemaining += pxLink->xBlockSize;
                    traceFREE( pv, pxLink->xBlockSize );
                    prvInsertBlockIntoFreeList( ( ( BlockLink_t * ) pxLink ) );
                }
                ( void ) xTaskResumeAll();
            }
            else
            {
                mtCOVERAGE_TEST_MARKER();
            }
        }
        else
        {
            mtCOVERAGE_TEST_MARKER();
        }
    }
}

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xPortGetFreeHeapSize()

size_t xPortGetFreeHeapSize

(

void

)

{
    return xFreeBytesRemaining;
}

xPortGetMinimumEverFreeHeapSize()

size_t xPortGetMinimumEverFreeHeapSize

(

void

)

{
    return xMinimumEverFreeBytesRemaining;
}

vPortInitialiseBlocks()

void vPortInitialiseBlocks

(

void

)

{
    /* This just exists to keep the linker quiet. */
}

Variable Documentation

ucHeap

uint8_t ucHeap[configTOTAL_HEAP_SIZE]

static

xHeapStructSize

const size_t xHeapStructSize = ( sizeof( BlockLink_t ) + ( ( size_t ) ( portBYTE_ALIGNMENT - 1 ) ) ) & ~( ( size_t ) portBYTE_ALIGNMENT_MASK )

static

xStart

BlockLink_t xStart

static

pxEnd

BlockLink_t * pxEnd = NULL

static

xFreeBytesRemaining

size_t xFreeBytesRemaining = 0U

static

xMinimumEverFreeBytesRemaining

size_t xMinimumEverFreeBytesRemaining = 0U

static

xBlockAllocatedBit

size_t xBlockAllocatedBit = 0

static