heap_4.c

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/*
 * FreeRTOS Kernel V10.6.2
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */
 
/*
 * A sample implementation of pvPortMalloc() and vPortFree() that combines
 * (coalescences) adjacent memory blocks as they are freed, and in so doing
 * limits memory fragmentation.
 *
 * See heap_1.c, heap_2.c and heap_3.c for alternative implementations, and the
 * memory management pages of https://www.FreeRTOS.org for more information.
 */
#include <stdlib.h>
#include <string.h>
 
/* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE prevents task.h from redefining
 * all the API functions to use the MPU wrappers.  That should only be done when
 * task.h is included from an application file. */
#define MPU_WRAPPERS_INCLUDED_FROM_API_FILE
 
#include "FreeRTOS.h"
#include "task.h"
 
#undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
 
#if ( configSUPPORT_DYNAMIC_ALLOCATION == 0 )
    #error This file must not be used if configSUPPORT_DYNAMIC_ALLOCATION is 0
#endif
 
#ifndef configHEAP_CLEAR_MEMORY_ON_FREE
    #define configHEAP_CLEAR_MEMORY_ON_FREE    0
#endif
 
/* Block sizes must not get too small. */
#define heapMINIMUM_BLOCK_SIZE    ( ( size_t ) ( xHeapStructSize << 1 ) )
 
/* Assumes 8bit bytes! */
#define heapBITS_PER_BYTE         ( ( size_t ) 8 )
 
/* Max value that fits in a size_t type. */
#define heapSIZE_MAX              ( ~( ( size_t ) 0 ) )
 
/* Check if multiplying a and b will result in overflow. */
#define heapMULTIPLY_WILL_OVERFLOW( a, b )    ( ( ( a ) > 0 ) && ( ( b ) > ( heapSIZE_MAX / ( a ) ) ) )
 
/* Check if adding a and b will result in overflow. */
#define heapADD_WILL_OVERFLOW( a, b )         ( ( a ) > ( heapSIZE_MAX - ( b ) ) )
 
/* MSB of the xBlockSize member of an BlockLink_t structure is used to track
 * the allocation status of a block.  When MSB of the xBlockSize member of
 * an BlockLink_t structure is set then the block belongs to the application.
 * When the bit is free the block is still part of the free heap space. */
#define heapBLOCK_ALLOCATED_BITMASK    ( ( ( size_t ) 1 ) << ( ( sizeof( size_t ) * heapBITS_PER_BYTE ) - 1 ) )
#define heapBLOCK_SIZE_IS_VALID( xBlockSize )    ( ( ( xBlockSize ) & heapBLOCK_ALLOCATED_BITMASK ) == 0 )
#define heapBLOCK_IS_ALLOCATED( pxBlock )        ( ( ( pxBlock->xBlockSize ) & heapBLOCK_ALLOCATED_BITMASK ) != 0 )
#define heapALLOCATE_BLOCK( pxBlock )            ( ( pxBlock->xBlockSize ) |= heapBLOCK_ALLOCATED_BITMASK )
#define heapFREE_BLOCK( pxBlock )                ( ( pxBlock->xBlockSize ) &= ~heapBLOCK_ALLOCATED_BITMASK )
 
/*-----------------------------------------------------------*/
 
/* Allocate the memory for the heap. */
#if ( configAPPLICATION_ALLOCATED_HEAP == 1 )
 
/* The application writer has already defined the array used for the RTOS
* heap - probably so it can be placed in a special segment or address. */
    extern uint8_t ucHeap[ configTOTAL_HEAP_SIZE ];
#else
    PRIVILEGED_DATA static uint8_t ucHeap[ configTOTAL_HEAP_SIZE ];
#endif /* configAPPLICATION_ALLOCATED_HEAP */
 
/* Define the linked list structure.  This is used to link free blocks in order
 * of their memory address. */
typedef struct A_BLOCK_LINK
{
    struct A_BLOCK_LINK * pxNextFreeBlock; /**< The next free block in the list. */
    size_t xBlockSize;                     /**< The size of the free block. */
} BlockLink_t;
 
/*-----------------------------------------------------------*/
 
/*
 * Inserts a block of memory that is being freed into the correct position in
 * the list of free memory blocks.  The block being freed will be merged with
 * the block in front it and/or the block behind it if the memory blocks are
 * adjacent to each other.
 */
static void prvInsertBlockIntoFreeList( BlockLink_t * pxBlockToInsert ) PRIVILEGED_FUNCTION;
 
/*
 * Called automatically to setup the required heap structures the first time
 * pvPortMalloc() is called.
 */
static void prvHeapInit( void ) PRIVILEGED_FUNCTION;
 
/*-----------------------------------------------------------*/
 
/* The size of the structure placed at the beginning of each allocated memory
 * block must by correctly byte aligned. */
static const size_t xHeapStructSize = ( sizeof( BlockLink_t ) + ( ( size_t ) ( portBYTE_ALIGNMENT - 1 ) ) ) & ~( ( size_t ) portBYTE_ALIGNMENT_MASK );
 
/* Create a couple of list links to mark the start and end of the list. */
PRIVILEGED_DATA static BlockLink_t xStart;
PRIVILEGED_DATA static BlockLink_t * pxEnd = NULL;
 
/* Keeps track of the number of calls to allocate and free memory as well as the
 * number of free bytes remaining, but says nothing about fragmentation. */
PRIVILEGED_DATA static size_t xFreeBytesRemaining = 0U;
PRIVILEGED_DATA static size_t xMinimumEverFreeBytesRemaining = 0U;
PRIVILEGED_DATA static size_t xNumberOfSuccessfulAllocations = 0;
PRIVILEGED_DATA static size_t xNumberOfSuccessfulFrees = 0;
 
/*-----------------------------------------------------------*/
 
void * pvPortMalloc( size_t xWantedSize )
{
    BlockLink_t * pxBlock;
    BlockLink_t * pxPreviousBlock;
    BlockLink_t * pxNewBlockLink;
    void * pvReturn = NULL;
    size_t xAdditionalRequiredSize;
 
    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();
        }
 
        if( xWantedSize > 0 )
        {
            /* The wanted size must be increased so it can contain a BlockLink_t
             * structure in addition to the requested amount of bytes. */
            if( heapADD_WILL_OVERFLOW( xWantedSize, xHeapStructSize ) == 0 )
            {
                xWantedSize += xHeapStructSize;
 
                /* Ensure that blocks are always aligned to the required number
                 * of bytes. */
                if( ( xWantedSize & portBYTE_ALIGNMENT_MASK ) != 0x00 )
                {
                    /* Byte alignment required. */
                    xAdditionalRequiredSize = portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK );
 
                    if( heapADD_WILL_OVERFLOW( xWantedSize, xAdditionalRequiredSize ) == 0 )
                    {
                        xWantedSize += xAdditionalRequiredSize;
                    }
                    else
                    {
                        xWantedSize = 0;
                    }
                }
                else
                {
                    mtCOVERAGE_TEST_MARKER();
                }
            }
            else
            {
                xWantedSize = 0;
            }
        }
        else
        {
            mtCOVERAGE_TEST_MARKER();
        }
 
        /* Check the block size we are trying to allocate 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( heapBLOCK_SIZE_IS_VALID( xWantedSize ) != 0 )
        {
            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. */
                    heapALLOCATE_BLOCK( pxBlock );
                    pxBlock->pxNextFreeBlock = NULL;
                    xNumberOfSuccessfulAllocations++;
                }
                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 )
        {
            vApplicationMallocFailedHook();
        }
        else
        {
            mtCOVERAGE_TEST_MARKER();
        }
    }
    #endif /* if ( configUSE_MALLOC_FAILED_HOOK == 1 ) */
 
    configASSERT( ( ( ( size_t ) pvReturn ) & ( size_t ) portBYTE_ALIGNMENT_MASK ) == 0 );
    return pvReturn;
}
/*-----------------------------------------------------------*/
 
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;
 
        configASSERT( heapBLOCK_IS_ALLOCATED( pxLink ) != 0 );
        configASSERT( pxLink->pxNextFreeBlock == NULL );
 
        if( heapBLOCK_IS_ALLOCATED( pxLink ) != 0 )
        {
            if( pxLink->pxNextFreeBlock == NULL )
            {
                /* The block is being returned to the heap - it is no longer
                 * allocated. */
                heapFREE_BLOCK( pxLink );
                #if ( configHEAP_CLEAR_MEMORY_ON_FREE == 1 )
                {
                    ( void ) memset( puc + xHeapStructSize, 0, pxLink->xBlockSize - xHeapStructSize );
                }
                #endif
 
                vTaskSuspendAll();
                {
                    /* Add this block to the list of free blocks. */
                    xFreeBytesRemaining += pxLink->xBlockSize;
                    traceFREE( pv, pxLink->xBlockSize );
                    prvInsertBlockIntoFreeList( ( ( BlockLink_t * ) pxLink ) );
                    xNumberOfSuccessfulFrees++;
                }
                ( void ) xTaskResumeAll();
            }
            else
            {
                mtCOVERAGE_TEST_MARKER();
            }
        }
        else
        {
            mtCOVERAGE_TEST_MARKER();
        }
    }
}
/*-----------------------------------------------------------*/
 
size_t xPortGetFreeHeapSize( void )
{
    return xFreeBytesRemaining;
}
/*-----------------------------------------------------------*/
 
size_t xPortGetMinimumEverFreeHeapSize( void )
{
    return xMinimumEverFreeBytesRemaining;
}
/*-----------------------------------------------------------*/
 
void vPortInitialiseBlocks( void )
{
    /* This just exists to keep the linker quiet. */
}
/*-----------------------------------------------------------*/
 
void * pvPortCalloc( size_t xNum,
                     size_t xSize )
{
    void * pv = NULL;
 
    if( heapMULTIPLY_WILL_OVERFLOW( xNum, xSize ) == 0 )
    {
        pv = pvPortMalloc( xNum * xSize );
 
        if( pv != NULL )
        {
            ( void ) memset( pv, 0, xNum * xSize );
        }
    }
 
    return pv;
}
/*-----------------------------------------------------------*/
 
static void prvHeapInit( void ) /* PRIVILEGED_FUNCTION */
{
    BlockLink_t * pxFirstFreeBlock;
    uint8_t * pucAlignedHeap;
    portPOINTER_SIZE_TYPE uxAddress;
    size_t xTotalHeapSize = configTOTAL_HEAP_SIZE;
 
    /* Ensure the heap starts on a correctly aligned boundary. */
    uxAddress = ( portPOINTER_SIZE_TYPE ) ucHeap;
 
    if( ( uxAddress & portBYTE_ALIGNMENT_MASK ) != 0 )
    {
        uxAddress += ( portBYTE_ALIGNMENT - 1 );
        uxAddress &= ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK );
        xTotalHeapSize -= ( size_t ) ( uxAddress - ( portPOINTER_SIZE_TYPE ) 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 = ( portPOINTER_SIZE_TYPE ) ( pucAlignedHeap + xTotalHeapSize );
    uxAddress -= xHeapStructSize;
    uxAddress &= ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK );
    pxEnd = ( BlockLink_t * ) 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 = ( BlockLink_t * ) pucAlignedHeap;
    pxFirstFreeBlock->xBlockSize = ( size_t ) ( uxAddress - ( portPOINTER_SIZE_TYPE ) pxFirstFreeBlock );
    pxFirstFreeBlock->pxNextFreeBlock = pxEnd;
 
    /* Only one block exists - and it covers the entire usable heap space. */
    xMinimumEverFreeBytesRemaining = pxFirstFreeBlock->xBlockSize;
    xFreeBytesRemaining = pxFirstFreeBlock->xBlockSize;
}
/*-----------------------------------------------------------*/
 
static void prvInsertBlockIntoFreeList( BlockLink_t * pxBlockToInsert ) /* PRIVILEGED_FUNCTION */
{
    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();
    }
}
/*-----------------------------------------------------------*/
 
void vPortGetHeapStats( HeapStats_t * pxHeapStats )
{
    BlockLink_t * pxBlock;
    size_t xBlocks = 0, xMaxSize = 0, xMinSize = portMAX_DELAY; /* portMAX_DELAY used as a portable way of getting the maximum value. */
 
    vTaskSuspendAll();
    {
        pxBlock = xStart.pxNextFreeBlock;
 
        /* pxBlock will be NULL if the heap has not been initialised.  The heap
         * is initialised automatically when the first allocation is made. */
        if( pxBlock != NULL )
        {
            while( pxBlock != pxEnd )
            {
                /* Increment the number of blocks and record the largest block seen
                 * so far. */
                xBlocks++;
 
                if( pxBlock->xBlockSize > xMaxSize )
                {
                    xMaxSize = pxBlock->xBlockSize;
                }
 
                if( pxBlock->xBlockSize < xMinSize )
                {
                    xMinSize = pxBlock->xBlockSize;
                }
 
                /* Move to the next block in the chain until the last block is
                 * reached. */
                pxBlock = pxBlock->pxNextFreeBlock;
            }
        }
    }
    ( void ) xTaskResumeAll();
 
    pxHeapStats->xSizeOfLargestFreeBlockInBytes = xMaxSize;
    pxHeapStats->xSizeOfSmallestFreeBlockInBytes = xMinSize;
    pxHeapStats->xNumberOfFreeBlocks = xBlocks;
 
    taskENTER_CRITICAL();
    {
        pxHeapStats->xAvailableHeapSpaceInBytes = xFreeBytesRemaining;
        pxHeapStats->xNumberOfSuccessfulAllocations = xNumberOfSuccessfulAllocations;
        pxHeapStats->xNumberOfSuccessfulFrees = xNumberOfSuccessfulFrees;
        pxHeapStats->xMinimumEverFreeBytesRemaining = xMinimumEverFreeBytesRemaining;
    }
    taskEXIT_CRITICAL();
}
/*-----------------------------------------------------------*/