iot_static_memory_common.c File Reference

Implementation of common static memory functions in iot_static_memory.h. More...

#include "iot_config.h"
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include "platform/iot_threads.h"
#include "iot_static_memory.h"
#include "iot_atomic.h"

Functions
int32_t	IotStaticMemory_FindFree (uint32_t *pInUse, size_t limit)
	Find a free buffer using the "in-use" flags. More...
void	IotStaticMemory_ReturnInUse (void *ptr, void *pPool, uint32_t *pInUse, size_t limit, size_t elementSize)
	Return an "in-use" buffer. More...
size_t	Iot_MessageBufferSize (void)
	Get the fixed size of a message buffer. More...
void *	Iot_MallocMessageBuffer (size_t size)
	Get an empty message buffer. More...
void	Iot_FreeMessageBuffer (void *ptr)
	Free an in-use message buffer. More...

Variables
static uint32_t	_pInUseMessageBuffers [IOT_MESSAGE_BUFFERS] = { 0U }
	Message buffer in-use flags.
static char	_pMessageBuffers [IOT_MESSAGE_BUFFERS][IOT_MESSAGE_BUFFER_SIZE] = { { 0 } }
	Message buffers.

Detailed Description

Implementation of common static memory functions in iot_static_memory.h.

Function Documentation

IotStaticMemory_FindFree()

int32_t IotStaticMemory_FindFree	(	uint32_t *	pInUse,
		size_t	limit
	)

Find a free buffer using the "in-use" flags.

If a free buffer is found, this function marks the buffer in-use. This function is common to the static memory implementation.

Parameters

[in]	pInUse	The "in-use" flags to search.
[in]	limit	How many flags to check, i.e. the size of pInUse.

Returns

The index of a free buffer; -1 if no free buffers are available.

Example:

// To use this function, first declare two arrays. One provides the statically-allocated
// objects, the other provides flags to determine which objects are in-use.
#define NUMBER_OF_OBJECTS    ...
#define OBJECT_SIZE          ...
static uint32_t _pInUseObjects[ NUMBER_OF_OBJECTS ] = { 0 };
static uint8_t _pObjects[ NUMBER_OF_OBJECTS ][ OBJECT_SIZE ] = { { 0 } }; // Placeholder for objects.

// The function to statically allocate objects. Must have the same signature
// as malloc().
void * Iot_MallocObject( size_t size )
{
    int32_t freeIndex = -1;
    void * pNewObject = NULL;

    // Check that sizes match.
    if( size != OBJECT_SIZE )
    {
        // Get the index of a free object.
        freeIndex = IotStaticMemory_FindFree( _pInUseMessageBuffers,
                                              IOT_MESSAGE_BUFFERS );

        if( freeIndex != -1 )
        {
            pNewBuffer = &( _pMessageBuffers[ freeIndex ][ 0 ] );
        }
    }

    return pNewBuffer;
}

IotStaticMemory_ReturnInUse()

void IotStaticMemory_ReturnInUse	(	void *	ptr,
		void *	pPool,
		uint32_t *	pInUse,
		size_t	limit,
		size_t	elementSize
	)

Return an "in-use" buffer.

This function is common to the static memory implementation.

Parameters

[in]	ptr	Pointer to the buffer to return.
[in]	pPool	The pool of buffers that the in-use buffer was allocated from.
[in]	pInUse	The "in-use" flags for pPool.
[in]	limit	How many buffers (and flags) to check while searching for ptr.
[in]	elementSize	The size of a single element in pPool.

Example:

// To use this function, first declare two arrays. One provides the statically-allocated
// objects, the other provides flags to determine which objects are in-use.
#define NUMBER_OF_OBJECTS    ...
#define OBJECT_SIZE          ...
static uint32_t _pInUseObjects[ NUMBER_OF_OBJECTS ] = { 0 };
static uint8_t _pObjects[ NUMBER_OF_OBJECTS ][ OBJECT_SIZE ] = { { 0 } }; // Placeholder for objects.

// The function to free statically-allocated objects. Must have the same signature
// as free().
void Iot_FreeObject( void * ptr )
{
    IotStaticMemory_ReturnInUse( ptr,
                                _pObjects,
                                _pInUseObjects,
                                NUMBER_OF_OBJECTS,
                                OBJECT_SIZE );
}

Iot_MessageBufferSize()

size_t Iot_MessageBufferSize

(

void

)

Get the fixed size of a message buffer.

The size of the message buffers are known at compile time, but it is a constant that may not be visible to all source files. This function allows other source files to know the size of a message buffer.

Returns

The size, in bytes, of a single message buffer.

Iot_MallocMessageBuffer()

void* Iot_MallocMessageBuffer

(

size_t

size

)

Get an empty message buffer.

This function is the analog of malloc for message buffers.

Parameters

[in]

size

Requested size for a message buffer.

Returns

Pointer to the start of a message buffer. If the size argument is larger than the fixed size of a message buffer or no message buffers are available, NULL is returned.

Iot_FreeMessageBuffer()

void Iot_FreeMessageBuffer

(

void *

ptr

)

Free an in-use message buffer.

This function is the analog of free for message buffers.

Parameters

[in]

ptr

Pointer to the message buffer to free.