heap_1源码分析
#include <stdlib.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 /* A few bytes might be lost to byte aligning the heap start address. */ #define configADJUSTED_HEAP_SIZE ( configTOTAL_HEAP_SIZE - portBYTE_ALIGNMENT ) //字节对齐后的内存大小 /* Allocate the memory for the heap. */ /* 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 static uint8_t ucHeap[ configTOTAL_HEAP_SIZE ]; //内存总大小 #endif /* configAPPLICATION_ALLOCATED_HEAP */ static size_t xNextFreeByte = ( size_t ) 0; /*-----------------------------------------------------------*/ void *pvPortMalloc( size_t xWantedSize ) { void *pvReturn = NULL; static uint8_t *pucAlignedHeap = NULL; /* Ensure that blocks are always aligned to the required number of bytes. */ #if( portBYTE_ALIGNMENT != 1 ) //设置为8字节对齐 { if( xWantedSize & portBYTE_ALIGNMENT_MASK ) //判断xWantedSize是不是8字节对齐也就是是不是8的倍数 { /* Byte alignment required. */ xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) ); //做8字节对齐处理 } } #endif vTaskSuspendAll(); { if( pucAlignedHeap == NULL ) { /* Ensure the heap starts on a correctly aligned boundary. */ pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) &ucHeap[ portBYTE_ALIGNMENT ] ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) ); //确保内存堆的可用起始地址也是8字节对齐的 内存堆ucHeap的起始地址是由编译器分配的，不一定是8字节对齐的，多以要计算出一个8字节对齐的地址的可用起始地址pucAlignedHeap做字节对齐 地址是从pucAlignedHeap开始使用的 } /* Check there is enough room left for the allocation. */ if( ( ( xNextFreeByte + xWantedSize ) < configADJUSTED_HEAP_SIZE ) && ( ( xNextFreeByte + xWantedSize ) > xNextFreeByte ) )/* Check for overflow. */ //检查一下可用内存是否分配，分配以后是否产生越界（超出内存堆范围）xNextFreeByte是一个全局变量，用来保存pucALignedHeap到内存堆剩余内存首地址之间的偏移值 { /* Return the next free byte then increment the index past this block. */ pvReturn = pucAlignedHeap + xNextFreeByte; //可用内存的首地址 xNextFreeByte += xWantedSize; } //申请内存，即从内存对ucHeap中割出一块内存 traceMALLOC( pvReturn, xWantedSize ); } ( void ) xTaskResumeAll(); #if( configUSE_MALLOC_FAILED_HOOK == 1 ) //内存申请失败 { if( pvReturn == NULL ) { extern void vApplicationMallocFailedHook( void ); vApplicationMallocFailedHook(); } } #endif return pvReturn; //返回申请到的内存首地址 } /*-----------------------------------------------------------*/ void vPortFree( void *pv ) { /* Memory cannot be freed using this scheme. See heap_2.c, heap_3.c and heap_4.c for alternative implementations, and the memory management pages of http://www.FreeRTOS.org for more information. */ ( void ) pv; /* Force an assert as it is invalid to call this function. */ configASSERT( pv == NULL ); } /*-----------------------------------------------------------*/ void vPortInitialiseBlocks( void ) //获取剩余内存大小 { /* Only required when static memory is not cleared. */ xNextFreeByte = ( size_t ) 0; } /*-----------------------------------------------------------*/ size_t xPortGetFreeHeapSize( void ) { return ( configADJUSTED_HEAP_SIZE - xNextFreeByte ); }