Macros

#define NULL_BUFFER 0x0000

Typedefs

typedef uint16_t Buffer
typedef Buffer MessageBufferQueue
typedef Buffer PacketHeader
typedef Buffer EmberMessageBuffer
typedef void(* Marker ) ( Buffer *buffer)
typedef void(* BufferMarker ) (void)

Functions

Buffer emAllocateBuffer (uint16_t dataSizeInBytes)
Allocates a buffer.
uint8_t * emGetBufferPointer ( Buffer buffer)
gets a pointer to the specified buffer
uint16_t emGetBufferLength ( Buffer buffer)
gets the length of the specified buffer
Buffer emFillStringBuffer (const uint8_t *contents)
allocates a buffer and fills it with the given null terminated string
Buffer emFillBuffer (const uint8_t *contents, uint16_t length)
Allocates a buffer and fills with length bytes of contents.
uint16_t emBufferBytesUsed (void)
returns the number of bytes of buffer space currently in use
uint16_t emBufferBytesRemaining (void)
returns the number of available bytes remaining in the buffer system
uint16_t emBufferBytesTotal (void)
returns the number of bytes allocated to the buffer system
bool emIsValidBuffer ( Buffer buffer)
returns whether the given buffer is valid
void emSetBufferLength ( Buffer buffer, uint16_t length)
Truncates the buffer. New length cannot be longer than the old length.
void emSetBufferLengthFromEnd ( Buffer buffer, uint16_t length)
Truncates the buffer, removing bytes from the front. New length cannot be longer than the old length.
void emReclaimUnusedBuffers (const BufferMarker *markers)
Reclaims unused buffers and compacts the heap.
void emMarkBuffer ( Buffer *root)
Marks the passed buffer. Called from Marker function.
void emMarkBufferWeak ( Buffer *root)
weakly mark buffer

Detailed Description

These buffers are contiguous blocks of bytes. Buffers are allocated linearly from a single chunk of memory. When space gets short any buffers still in use can be moved to the beginning of buffer memory, which consolidates any unused space.

'Buffer' values are actually offsets from the beginning of buffer memory. Using uint8_ts would require additional memory for the mapping between the uint8_ts and memory locations.

In fact, Buffers are offsets from one before the beginning of buffer memory. The first buffer is thus 0x0001. This allows us to use 0x0000 as the null buffer, just as C uses zero for the null pointer.

In general the buffer functions are not safe for use in ISRs. The one exception is the PHY->MAC queue, which is handled specially. It is safe for an ISR to allocate a new buffer and put it on the PHY->MAC queue.

Any code which holds on to buffers beyond the context in which they are allocated must provide a marking function to prevent them from being garbage collected. See emReclaimUnusedBuffers for details.

Macro Definition Documentation

NULL_BUFFER

#define NULL_BUFFER   0x0000

Typedef Documentation

Buffer

typedef uint16_t Buffer

BufferMarker

typedef void(* BufferMarker) (void)

EmberMessageBuffer

Marker

typedef void(* Marker) ( Buffer *buffer)

MessageBufferQueue

PacketHeader

Function Documentation

emAllocateBuffer()

Buffer emAllocateBuffer ( uint16_t dataSizeInBytes )

Allocates a buffer.

emBufferBytesRemaining()

uint16_t emBufferBytesRemaining ( void )

returns the number of available bytes remaining in the buffer system

emBufferBytesTotal()

uint16_t emBufferBytesTotal ( void )

returns the number of bytes allocated to the buffer system

emBufferBytesUsed()

uint16_t emBufferBytesUsed ( void )

returns the number of bytes of buffer space currently in use

emFillBuffer()

Buffer emFillBuffer ( const uint8_t * contents,
uint16_t length
)

Allocates a buffer and fills with length bytes of contents.

emFillStringBuffer()

Buffer emFillStringBuffer ( const uint8_t * contents )

allocates a buffer and fills it with the given null terminated string

'contents' may be NULL, in which case NULL_BUFFER is returned.

emGetBufferLength()

uint16_t emGetBufferLength ( Buffer buffer )

gets the length of the specified buffer

emGetBufferPointer()

uint8_t* emGetBufferPointer ( Buffer buffer )

gets a pointer to the specified buffer

emIsValidBuffer()

bool emIsValidBuffer ( Buffer buffer )

returns whether the given buffer is valid

emMarkBuffer()

void emMarkBuffer ( Buffer * root )

Marks the passed buffer. Called from Marker function.

emMarkBufferWeak()

void emMarkBufferWeak ( Buffer * root )

weakly mark buffer

emMarkBufferWeak only operates during the update references phase if emMark Buffer is called on the same buffer elsewhere, the weak reference will be updated. If a buffer is only weakly marked, the update phase will replace it with NULL_BUFFER

emReclaimUnusedBuffers()

void emReclaimUnusedBuffers ( const BufferMarker * markers )

Reclaims unused buffers and compacts the heap.

Reclaims all buffers not reachable from 'roots', the PHY->MAC queue, by one of marker functions. The marker functions should call their argument on all known buffer references.

The idea is that single top level references, such as a queue, can be put in 'roots', whereas buffers stored in data structures, such as the retry table, are handled by marker functions.

Surviving buffers moved to the beginning of the heap, which amalgamates the free memory into a single contiguous block. This should only be called when there are no references to buffers outside of 'roots', the PHY->MAC queue, and the locations passed to the marker functions.

IMPORTANT: BufferMarker routines should not reference buffers after they have been marked. The buffers may be in an inconsistent state until the reclaimation has completed.

Right: void myBufferMarker(void) { ... myBuffer ... emMarkBuffer(&myBuffer); }

Wrong: void myBufferMarker(void) { emMarkBuffer(&myBuffer); ... myBuffer ... }

emSetBufferLength()

void emSetBufferLength ( Buffer buffer,
uint16_t length
)

Truncates the buffer. New length cannot be longer than the old length.

emSetBufferLengthFromEnd()

void emSetBufferLengthFromEnd ( Buffer buffer,
uint16_t length
)

Truncates the buffer, removing bytes from the front. New length cannot be longer than the old length.