pretty_memory.c

/*****************************************************************************
MIT License

Copyright (c) 2020 Yahia Farghaly Ashour

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of this software and associated documentation files (the "Software"), to deal
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SOFTWARE.
******************************************************************************/

/*
 * Author   : 	Yahia Farghaly Ashour
 *
 * Purpose  :	PrettyOS Memory Management Implementation.
 *
 * 				Memory Allocation and Deallocation routines similar to the known C functions "malloc()"
 * 				and "free()". Except the implementation here is deterministic and being in a constant time,
 * 				using memory partitions scheme.
 *
 * 				The memory management implementation here consists of a number of partitions,
 * 				definable by OS_CONFIG_MEMORY_PARTITION_COUNT. where every partition is divided into a fixed
 * 				number of memory blocks of a specific size determined when the partition is created.
 * 
 * 
 * 
 *				  +------->   Partition#01  <--------+
 *				  |                                  |
 *				  v                                  v
 *				  +----+----+----+----+----+----+----+
 *				  |    |    |    |    |    |    |    |
 *				  |    |    |    |    |    |    |    |
 *				  |    |    |    |    |    |    |    |
 *				  +----+----+----+----+----+----+----+
 *				  ^                    ^   ^
 *				  |                    |   |
 *				  +                    |   |
 *				start address          |   |
 *									   +   +
 *                                     Block
 *
 *
 * Language:  C
 * 
 * Set 1 tab = 4 spaces for better comments readability.
 */

/*
*******************************************************************************
*                               Includes Files                                *
*******************************************************************************
*/
#include "pretty_os.h"
#include "pretty_shared.h"

#if(OS_CONFIG_MEMORY_EN == OS_CONFIG_ENABLE)

static OS_MEMORY  OS_Mem_PartitionPool[OS_CONFIG_MEMORY_PARTITION_COUNT];
static OS_MEMORY* volatile pMemoryPartitionFreeList;

/*
 * Function:  OS_MemoryPartitionCreate
 * ----------------------------------
 * Create a fixed-sized memory partition which will be managed by prettyOS.
 *
 * Arguments    :  partitionBaseAddr	is the starting address of the memory partition.
 *
 *				   blockCount			is the number of the memory blocks of the created memory partition.
 *
 *				   blockSizeInBytes		is the number of bytes per memory block.
 *
 * Returns      :  == ((OS_MEMORY*)0U)  if memory partition creation fails in case of invalid of arguments or no free partition.
 * 				   != ((OS_MEMORY*)0U)  is the created memory partition.
 *
 * 				   OS_ERRNO = { OS_ERR_NONE, OS_ERR_MEM_INVALID_ADDR, OS_ERR_MEM_INVALID_BLOCK_SIZE }
 */
OS_MEMORY*
OS_MemoryPartitionCreate (void* partitionBaseAddr, OS_MEMORY_BLOCK blockCount, OS_MEMORY_BLOCK blockSizeInBytes)
{
	OS_MEMORY* 	pMemoryPart;
	CPU_t08U* 	pBlock;
	void** 		pLinkAddr;
	CPU_SR_ALLOC();

	if(partitionBaseAddr == OS_NULL(void))							/* Must be a valid pointer.													*/
	{
		OS_ERR_SET(OS_ERR_MEM_INVALID_ADDR);
		return OS_NULL(OS_MEMORY);
	}

	if(blockSizeInBytes < sizeof(void*))							/* At least, The block of a partition must have the space of a pointer.		*/
	{
		OS_ERR_SET(OS_ERR_MEM_INVALID_BLOCK_SIZE);
		return OS_NULL(OS_MEMORY);
	}

	OS_CRTICAL_BEGIN();

	pMemoryPart = pMemoryPartitionFreeList;							/* Allocate a memory partition structure.									*/
	if(pMemoryPart != OS_NULL(OS_MEMORY))
	{
		pMemoryPartitionFreeList = (OS_MEMORY*)pMemoryPartitionFreeList->nextFreeBlock;
	}

	OS_CRTICAL_END();

	if(pMemoryPart == OS_NULL(OS_MEMORY))							/* If no available memory partition structure is ...						*/
	{
		OS_ERR_SET(OS_ERR_MEM_INVALID_ADDR);
		return OS_NULL(OS_MEMORY);									/* ... return NULL.															*/
	}

	pLinkAddr 	= (void**)partitionBaseAddr;						/* Get the address of the first memory block in the memory partition.		*/
	pBlock		= (CPU_t08U*)partitionBaseAddr;						/* Get the address of the first byte in the first memory block.				*/

	/* 										Create an implicit linked list of free memory blocks.												*/
	/*

	                                            +-> blockSizeInBytes  <-+



	                   +-----------------------+------------------------+-------------------------+----------------------------+
	                   |     ||                |     ||                 |     ||                  |     ||                     |
	                   | &pBlock#01 +          | &pBlock#02 +           |  &pBlock#03 +           | &pBlock#04 +               +----> NULL
	                   |     ||     |          |     ||     |           |     ||      |           |     ||     |               |
	                   |     ||     |          |     ||     |           |     ||      |           |     ||     |               |
	                   +-----------------------+------------------------+-------------------------+----------------------------+
	                                |                       |                         |                        |
	                   ^            |          ^            |           ^             |           ^            |               ^
	                   |            |          |            |           |             |           |            |               |
	                   |            |          |            |           |             |           |            |               |
	                   +            |          +            |           +             |           +            |               +
	   +-----------> pBlock         +----->  pBlock#01      +------>  pBlock#02       +------> pBlock#03       +-----------> pBlock#04
	   |
	   |
	   |
	   |
	   +
	pLinkAddr

	*/
	for(CPU_t32U i = 0; i < (blockCount - 1U);++i)
	{
		pBlock 		+= (blockSizeInBytes);							/* Get the address of the next memory block ...								*/
		*pLinkAddr 	= (void*)pBlock;								/* ... Store this address in the current memory block ...					*/
		pLinkAddr	= (void**)pBlock;								/* Then move to the next memory block.										*/
	}

	*pLinkAddr		= ((void*)0U);									/* Last memory block address points to NULL.								*/

	OS_CRTICAL_BEGIN();

	pMemoryPart->partitionBaseAddr  = partitionBaseAddr;			/* The being of the partition.												*/
	pMemoryPart->nextFreeBlock      = partitionBaseAddr;			/* The next address of the memory block.									*/
	pMemoryPart->blockSize          = blockSizeInBytes;				/* Block size in bytes.														*/
	pMemoryPart->blockCount         = blockCount;					/* Number of blocks inside this partition.									*/
	pMemoryPart->blockFreeCount     = blockCount;					/* Number of free block inside this partition. 								*/

	OS_CRTICAL_END();

	OS_ERR_SET(OS_ERR_NONE);
	return (pMemoryPart);
}

/*
 * Function:  OS_MemoryAllocateBlock
 * ---------------------------------
 * Allocate a free block from a valid memory partition.
 *
 * Arguments    :  pMemoryPart		is a pointer to a valid memory partition structure.
 *
 * Returns      :  == ((void*)0U)  if no free memory block is available or invalid pointer of memory partition structure.
 * 				   != ((void*)0U)  is the requested block of memory.
 *
 * 				   OS_ERRNO = { OS_ERR_NONE, OS_ERR_MEM_INVALID_ADDR, OS_ERR_MEM_NO_FREE_BLOCKS }
 */
void*
OS_MemoryAllocateBlock (OS_MEMORY* pMemoryPart)
{
	void* pBlock;
	CPU_SR_ALLOC();

	if(pMemoryPart == OS_NULL(OS_MEMORY))							/* Must be a valid pointer.													*/
	{
		OS_ERR_SET(OS_ERR_MEM_INVALID_ADDR);
		return OS_NULL(OS_MEMORY);
	}

	OS_CRTICAL_BEGIN();

	if(pMemoryPart->blockFreeCount > 0U)							/* See if there are any available blocks.									*/
	{
		pBlock = pMemoryPart->nextFreeBlock;						/* Point to the next free memory block.										*/
		pMemoryPart->nextFreeBlock = *(void**)pBlock;				/* Set the next free memory block to point to the next new free block.		*/
		--(pMemoryPart->blockFreeCount);							/* Decrease the number of free blocks by 1 .								*/
		OS_CRTICAL_END();
		OS_ERR_SET(OS_ERR_NONE);
		return (pBlock);
	}

	OS_CRTICAL_END();
	OS_ERR_SET(OS_ERR_MEM_NO_FREE_BLOCKS);							/* No free memory block in this partition.									*/
	return OS_NULL(void);											/* Return NULL.																*/
}

/*
 * Function:  OS_MemoryRestoreBlock
 * --------------------------------
 * Free/Restore a block to a valid memory partition.
 *
 * Arguments    :  	pMemoryPart		is a pointer to a valid memory partition structure.
 *
 * 					pBlock			is a pointer to the released block of the partition pointed by 'pMemoryPart'
 *
 * Returns      :	None.
 *
 * 				   	OS_ERRNO = { OS_ERR_NONE, OS_ERR_MEM_INVALID_ADDR, OS_ERR_MEM_FULL_PARTITION }
 *
 * Note(s)		:	This function is not aware if the returned block is the actually block which is allocated
 * 					from the given partition 'pMemoryPart'.
 * 					So, Caution must be considered. Otherwise, the software can be crashed.
 */
void
OS_MemoryRestoreBlock (OS_MEMORY* pMemoryPart, void* pBlock)
{
	CPU_SR_ALLOC();

	if(pMemoryPart == OS_NULL(OS_MEMORY))							/* Must be a valid pointer.													*/
	{
		OS_ERR_SET(OS_ERR_MEM_INVALID_ADDR);
		return;
	}

	if(pBlock == OS_NULL(void))										/* Must be a valid pointer.													*/
	{
		OS_ERR_SET(OS_ERR_MEM_INVALID_ADDR);
		return;
	}

	OS_CRTICAL_BEGIN();

	if(pMemoryPart->blockFreeCount < pMemoryPart->blockCount)		/* Assert that not all blocks are returned.									*/
	{
		*(void**)pBlock = pMemoryPart->nextFreeBlock;				/* Insert the free block into the free memory block list.					*/
		pMemoryPart->nextFreeBlock = pBlock;						/* Adjust the new free memory block list head. 								*/
		++(pMemoryPart->blockFreeCount);							/* Increase the number of free blocks by 1 .								*/
		OS_CRTICAL_END();
		OS_ERR_SET(OS_ERR_NONE);
		return;
	}

	OS_CRTICAL_END();
	OS_ERR_SET(OS_ERR_MEM_FULL_PARTITION);							/* ALL memory blocks have returned to the memory partition.					*/
	return;
}

/*
 * Function:  OS_Memory_Init
 * --------------------
 * Initialize The Memory Partition Manager.
 *
 * Arguments    :  None.
 *
 * Returns      :  None.
 *
 * Note(s)      :   1) This function is for internal use.
 */
void OS_Memory_Init (void)
{
	OS_MemoryByteClear((CPU_t08U*)&OS_Mem_PartitionPool[0], sizeof(OS_Mem_PartitionPool));			/* Clear Structure data.						*/

	for(CPU_t32U idx = 0; idx < OS_CONFIG_MEMORY_PARTITION_COUNT - 1; ++idx)						/* Point to a chain of OS Memory Structures.	*/
	{
		OS_Mem_PartitionPool[idx].nextFreeBlock = (void*)&OS_Mem_PartitionPool[idx+1];
	}

	OS_Mem_PartitionPool[OS_CONFIG_MEMORY_PARTITION_COUNT - 1].nextFreeBlock = OS_NULL(void);

	pMemoryPartitionFreeList = &OS_Mem_PartitionPool[0];											/* Point to the first Free OS Memory Structure.	*/
}

#endif	/* OS_CONFIG_MEMORY_EN 	*/