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/*
* FreeRTOS Kernel <DEVELOPMENT BRANCH>
* 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
*
*/
/*
* Message buffers build functionality on top of FreeRTOS stream buffers.
* Whereas stream buffers are used to send a continuous stream of data from one
* task or interrupt to another, message buffers are used to send variable
* length discrete messages from one task or interrupt to another. Their
* implementation is light weight, making them particularly suited for interrupt
* to task and core to core communication scenarios.
*
* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
* implementation (so also the message buffer implementation, as message buffers
* are built on top of stream buffers) assumes there is only one task or
* interrupt that will write to the buffer (the writer), and only one task or
* interrupt that will read from the buffer (the reader). It is safe for the
* writer and reader to be different tasks or interrupts, but, unlike other
* FreeRTOS objects, it is not safe to have multiple different writers or
* multiple different readers. If there are to be multiple different writers
* then the application writer must place each call to a writing API function
* (such as xMessageBufferSend()) inside a critical section and set the send
* block time to 0. Likewise, if there are to be multiple different readers
* then the application writer must place each call to a reading API function
* (such as xMessageBufferRead()) inside a critical section and set the receive
* timeout to 0.
*
* Message buffers hold variable length messages. To enable that, when a
* message is written to the message buffer an additional sizeof( size_t ) bytes
* are also written to store the message's length (that happens internally, with
* the API function). sizeof( size_t ) is typically 4 bytes on a 32-bit
* architecture, so writing a 10 byte message to a message buffer on a 32-bit
* architecture will actually reduce the available space in the message buffer
* by 14 bytes (10 byte are used by the message, and 4 bytes to hold the length
* of the message).
*/
#ifndef FREERTOS_MESSAGE_BUFFER_H
#define FREERTOS_MESSAGE_BUFFER_H
#ifndef INC_FREERTOS_H
#error "include FreeRTOS.h must appear in source files before include message_buffer.h"
#endif
/* Message buffers are built onto of stream buffers. */
#include "../../FreeRTOS-Kernel/include/stream_buffer.h"
/* *INDENT-OFF* */
#if defined( __cplusplus )
extern "C" {
#endif
/* *INDENT-ON* */
/**
* Type by which message buffers are referenced. For example, a call to
* xMessageBufferCreate() returns an MessageBufferHandle_t variable that can
* then be used as a parameter to xMessageBufferSend(), xMessageBufferReceive(),
* etc.
*/
typedef void * MessageBufferHandle_t;
/*-----------------------------------------------------------*/
/**
* message_buffer.h
*
* @code{c}
* MessageBufferHandle_t xMessageBufferCreate( size_t xBufferSizeBytes );
* @endcode
*
* Creates a new message buffer using dynamically allocated memory. See
* xMessageBufferCreateStatic() for a version that uses statically allocated
* memory (memory that is allocated at compile time).
*
* configSUPPORT_DYNAMIC_ALLOCATION must be set to 1 or left undefined in
* FreeRTOSConfig.h for xMessageBufferCreate() to be available.
*
* @param xBufferSizeBytes The total number of bytes (not messages) the message
* buffer will be able to hold at any one time. When a message is written to
* the message buffer an additional sizeof( size_t ) bytes are also written to
* store the message's length. sizeof( size_t ) is typically 4 bytes on a
* 32-bit architecture, so on most 32-bit architectures a 10 byte message will
* take up 14 bytes of message buffer space.
*
* @return If NULL is returned, then the message buffer cannot be created
* because there is insufficient heap memory available for FreeRTOS to allocate
* the message buffer data structures and storage area. A non-NULL value being
* returned indicates that the message buffer has been created successfully -
* the returned value should be stored as the handle to the created message
* buffer.
*
* Example use:
* @code{c}
*
* void vAFunction( void )
* {
* MessageBufferHandle_t xMessageBuffer;
* const size_t xMessageBufferSizeBytes = 100;
*
* // Create a message buffer that can hold 100 bytes. The memory used to hold
* // both the message buffer structure and the messages themselves is allocated
* // dynamically. Each message added to the buffer consumes an additional 4
* // bytes which are used to hold the length of the message.
* xMessageBuffer = xMessageBufferCreate( xMessageBufferSizeBytes );
*
* if( xMessageBuffer == NULL )
* {
* // There was not enough heap memory space available to create the
* // message buffer.
* }
* else
* {
* // The message buffer was created successfully and can now be used.
* }
*
* @endcode
* \defgroup xMessageBufferCreate xMessageBufferCreate
* \ingroup MessageBufferManagement
*/
#define xMessageBufferCreate( xBufferSizeBytes ) \
( MessageBufferHandle_t ) xStreamBufferGenericCreate( xBufferSizeBytes, ( size_t ) 0, pdTRUE )
/**
* message_buffer.h
*
* @code{c}
* MessageBufferHandle_t xMessageBufferCreateStatic( size_t xBufferSizeBytes,
* uint8_t *pucMessageBufferStorageArea,
* StaticMessageBuffer_t *pxStaticMessageBuffer );
* @endcode
* Creates a new message buffer using statically allocated memory. See
* xMessageBufferCreate() for a version that uses dynamically allocated memory.
*
* @param xBufferSizeBytes The size, in bytes, of the buffer pointed to by the
* pucMessageBufferStorageArea parameter. When a message is written to the
* message buffer an additional sizeof( size_t ) bytes are also written to store
* the message's length. sizeof( size_t ) is typically 4 bytes on a 32-bit
* architecture, so on most 32-bit architecture a 10 byte message will take up
* 14 bytes of message buffer space. The maximum number of bytes that can be
* stored in the message buffer is actually (xBufferSizeBytes - 1).
*
* @param pucMessageBufferStorageArea Must point to a uint8_t array that is at
* least xBufferSizeBytes big. This is the array to which messages are
* copied when they are written to the message buffer.
*
* @param pxStaticMessageBuffer Must point to a variable of type
* StaticMessageBuffer_t, which will be used to hold the message buffer's data
* structure.
*
* @return If the message buffer is created successfully then a handle to the
* created message buffer is returned. If either pucMessageBufferStorageArea or
* pxStaticmessageBuffer are NULL then NULL is returned.
*
* Example use:
* @code{c}
*
* // Used to dimension the array used to hold the messages. The available space
* // will actually be one less than this, so 999.
#define STORAGE_SIZE_BYTES 1000
*
* // Defines the memory that will actually hold the messages within the message
* // buffer.
* static uint8_t ucStorageBuffer[ STORAGE_SIZE_BYTES ];
*
* // The variable used to hold the message buffer structure.
* StaticMessageBuffer_t xMessageBufferStruct;
*
* void MyFunction( void )
* {
* MessageBufferHandle_t xMessageBuffer;
*
* xMessageBuffer = xMessageBufferCreateStatic( sizeof( ucStorageBuffer ),
* ucStorageBuffer,
* &xMessageBufferStruct );
*
* // As neither the pucMessageBufferStorageArea or pxStaticMessageBuffer
* // parameters were NULL, xMessageBuffer will not be NULL, and can be used to
* // reference the created message buffer in other message buffer API calls.
*
* // Other code that uses the message buffer can go here.
* }
*
* @endcode
* \defgroup xMessageBufferCreateStatic xMessageBufferCreateStatic
* \ingroup MessageBufferManagement
*/
#define xMessageBufferCreateStatic( xBufferSizeBytes, pucMessageBufferStorageArea, pxStaticMessageBuffer ) \
( MessageBufferHandle_t ) xStreamBufferGenericCreateStatic( xBufferSizeBytes, 0, pdTRUE, pucMessageBufferStorageArea, pxStaticMessageBuffer )
/**
* message_buffer.h
*
* @code{c}
* size_t xMessageBufferSend( MessageBufferHandle_t xMessageBuffer,
* const void *pvTxData,
* size_t xDataLengthBytes,
* TickType_t xTicksToWait );
* @endcode
*
* Sends a discrete message to the message buffer. The message can be any
* length that fits within the buffer's free space, and is copied into the
* buffer.
*
* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
* implementation (so also the message buffer implementation, as message buffers
* are built on top of stream buffers) assumes there is only one task or
* interrupt that will write to the buffer (the writer), and only one task or
* interrupt that will read from the buffer (the reader). It is safe for the
* writer and reader to be different tasks or interrupts, but, unlike other
* FreeRTOS objects, it is not safe to have multiple different writers or
* multiple different readers. If there are to be multiple different writers
* then the application writer must place each call to a writing API function
* (such as xMessageBufferSend()) inside a critical section and set the send
* block time to 0. Likewise, if there are to be multiple different readers
* then the application writer must place each call to a reading API function
* (such as xMessageBufferRead()) inside a critical section and set the receive
* block time to 0.
*
* Use xMessageBufferSend() to write to a message buffer from a task. Use
* xMessageBufferSendFromISR() to write to a message buffer from an interrupt
* service routine (ISR).
*
* @param xMessageBuffer The handle of the message buffer to which a message is
* being sent.
*
* @param pvTxData A pointer to the message that is to be copied into the
* message buffer.
*
* @param xDataLengthBytes The length of the message. That is, the number of
* bytes to copy from pvTxData into the message buffer. When a message is
* written to the message buffer an additional sizeof( size_t ) bytes are also
* written to store the message's length. sizeof( size_t ) is typically 4 bytes
* on a 32-bit architecture, so on most 32-bit architecture setting
* xDataLengthBytes to 20 will reduce the free space in the message buffer by 24
* bytes (20 bytes of message data and 4 bytes to hold the message length).
*
* @param xTicksToWait The maximum amount of time the calling task should remain
* in the Blocked state to wait for enough space to become available in the
* message buffer, should the message buffer have insufficient space when
* xMessageBufferSend() is called. The calling task will never block if
* xTicksToWait is zero. The block time is specified in tick periods, so the
* absolute time it represents is dependent on the tick frequency. The macro
* pdMS_TO_TICKS() can be used to convert a time specified in milliseconds into
* a time specified in ticks. Setting xTicksToWait to portMAX_DELAY will cause
* the task to wait indefinitely (without timing out), provided
* INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h. Tasks do not use any
* CPU time when they are in the Blocked state.
*
* @return The number of bytes written to the message buffer. If the call to
* xMessageBufferSend() times out before there was enough space to write the
* message into the message buffer then zero is returned. If the call did not
* time out then xDataLengthBytes is returned.
*
* Example use:
* @code{c}
* void vAFunction( MessageBufferHandle_t xMessageBuffer )
* {
* size_t xBytesSent;
* uint8_t ucArrayToSend[] = { 0, 1, 2, 3 };
* char *pcStringToSend = "String to send";
* const TickType_t x100ms = pdMS_TO_TICKS( 100 );
*
* // Send an array to the message buffer, blocking for a maximum of 100ms to
* // wait for enough space to be available in the message buffer.
* xBytesSent = xMessageBufferSend( xMessageBuffer, ( void * ) ucArrayToSend, sizeof( ucArrayToSend ), x100ms );
*
* if( xBytesSent != sizeof( ucArrayToSend ) )
* {
* // The call to xMessageBufferSend() times out before there was enough
* // space in the buffer for the data to be written.
* }
*
* // Send the string to the message buffer. Return immediately if there is
* // not enough space in the buffer.
* xBytesSent = xMessageBufferSend( xMessageBuffer, ( void * ) pcStringToSend, strlen( pcStringToSend ), 0 );
*
* if( xBytesSent != strlen( pcStringToSend ) )
* {
* // The string could not be added to the message buffer because there was
* // not enough free space in the buffer.
* }
* }
* @endcode
* \defgroup xMessageBufferSend xMessageBufferSend
* \ingroup MessageBufferManagement
*/
#define xMessageBufferSend( xMessageBuffer, pvTxData, xDataLengthBytes, xTicksToWait ) \
xStreamBufferSend( ( StreamBufferHandle_t ) xMessageBuffer, pvTxData, xDataLengthBytes, xTicksToWait )
/**
* message_buffer.h
*
* @code{c}
* size_t xMessageBufferSendFromISR( MessageBufferHandle_t xMessageBuffer,
* const void *pvTxData,
* size_t xDataLengthBytes,
* BaseType_t *pxHigherPriorityTaskWoken );
* @endcode
*
* Interrupt safe version of the API function that sends a discrete message to
* the message buffer. The message can be any length that fits within the
* buffer's free space, and is copied into the buffer.
*
* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
* implementation (so also the message buffer implementation, as message buffers
* are built on top of stream buffers) assumes there is only one task or
* interrupt that will write to the buffer (the writer), and only one task or
* interrupt that will read from the buffer (the reader). It is safe for the
* writer and reader to be different tasks or interrupts, but, unlike other
* FreeRTOS objects, it is not safe to have multiple different writers or
* multiple different readers. If there are to be multiple different writers
* then the application writer must place each call to a writing API function
* (such as xMessageBufferSend()) inside a critical section and set the send
* block time to 0. Likewise, if there are to be multiple different readers
* then the application writer must place each call to a reading API function
* (such as xMessageBufferRead()) inside a critical section and set the receive
* block time to 0.
*
* Use xMessageBufferSend() to write to a message buffer from a task. Use
* xMessageBufferSendFromISR() to write to a message buffer from an interrupt
* service routine (ISR).
*
* @param xMessageBuffer The handle of the message buffer to which a message is
* being sent.
*
* @param pvTxData A pointer to the message that is to be copied into the
* message buffer.
*
* @param xDataLengthBytes The length of the message. That is, the number of
* bytes to copy from pvTxData into the message buffer. When a message is
* written to the message buffer an additional sizeof( size_t ) bytes are also
* written to store the message's length. sizeof( size_t ) is typically 4 bytes
* on a 32-bit architecture, so on most 32-bit architecture setting
* xDataLengthBytes to 20 will reduce the free space in the message buffer by 24
* bytes (20 bytes of message data and 4 bytes to hold the message length).
*
* @param pxHigherPriorityTaskWoken It is possible that a message buffer will
* have a task blocked on it waiting for data. Calling
* xMessageBufferSendFromISR() can make data available, and so cause a task that
* was waiting for data to leave the Blocked state. If calling
* xMessageBufferSendFromISR() causes a task to leave the Blocked state, and the
* unblocked task has a priority higher than the currently executing task (the
* task that was interrupted), then, internally, xMessageBufferSendFromISR()
* will set *pxHigherPriorityTaskWoken to pdTRUE. If
* xMessageBufferSendFromISR() sets this value to pdTRUE, then normally a
* context switch should be performed before the interrupt is exited. This will
* ensure that the interrupt returns directly to the highest priority Ready
* state task. *pxHigherPriorityTaskWoken should be set to pdFALSE before it
* is passed into the function. See the code example below for an example.
*
* @return The number of bytes actually written to the message buffer. If the
* message buffer didn't have enough free space for the message to be stored
* then 0 is returned, otherwise xDataLengthBytes is returned.
*
* Example use:
* @code{c}
* // A message buffer that has already been created.
* MessageBufferHandle_t xMessageBuffer;
*
* void vAnInterruptServiceRoutine( void )
* {
* size_t xBytesSent;
* char *pcStringToSend = "String to send";
* BaseType_t xHigherPriorityTaskWoken = pdFALSE; // Initialised to pdFALSE.
*
* // Attempt to send the string to the message buffer.
* xBytesSent = xMessageBufferSendFromISR( xMessageBuffer,
* ( void * ) pcStringToSend,
* strlen( pcStringToSend ),
* &xHigherPriorityTaskWoken );
*
* if( xBytesSent != strlen( pcStringToSend ) )
* {
* // The string could not be added to the message buffer because there was
* // not enough free space in the buffer.
* }
*
* // If xHigherPriorityTaskWoken was set to pdTRUE inside
* // xMessageBufferSendFromISR() then a task that has a priority above the
* // priority of the currently executing task was unblocked and a context
* // switch should be performed to ensure the ISR returns to the unblocked
* // task. In most FreeRTOS ports this is done by simply passing
* // xHigherPriorityTaskWoken into portYIELD_FROM_ISR(), which will test the
* // variables value, and perform the context switch if necessary. Check the
* // documentation for the port in use for port specific instructions.
* portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
* }
* @endcode
* \defgroup xMessageBufferSendFromISR xMessageBufferSendFromISR
* \ingroup MessageBufferManagement
*/
#define xMessageBufferSendFromISR( xMessageBuffer, pvTxData, xDataLengthBytes, pxHigherPriorityTaskWoken ) \
xStreamBufferSendFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pvTxData, xDataLengthBytes, pxHigherPriorityTaskWoken )
/**
* message_buffer.h
*
* @code{c}
* size_t xMessageBufferReceive( MessageBufferHandle_t xMessageBuffer,
* void *pvRxData,
* size_t xBufferLengthBytes,
* TickType_t xTicksToWait );
* @endcode
*
* Receives a discrete message from a message buffer. Messages can be of
* variable length and are copied out of the buffer.
*
* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
* implementation (so also the message buffer implementation, as message buffers
* are built on top of stream buffers) assumes there is only one task or
* interrupt that will write to the buffer (the writer), and only one task or
* interrupt that will read from the buffer (the reader). It is safe for the
* writer and reader to be different tasks or interrupts, but, unlike other
* FreeRTOS objects, it is not safe to have multiple different writers or
* multiple different readers. If there are to be multiple different writers
* then the application writer must place each call to a writing API function
* (such as xMessageBufferSend()) inside a critical section and set the send
* block time to 0. Likewise, if there are to be multiple different readers
* then the application writer must place each call to a reading API function
* (such as xMessageBufferRead()) inside a critical section and set the receive
* block time to 0.
*
* Use xMessageBufferReceive() to read from a message buffer from a task. Use
* xMessageBufferReceiveFromISR() to read from a message buffer from an
* interrupt service routine (ISR).
*
* @param xMessageBuffer The handle of the message buffer from which a message
* is being received.
*
* @param pvRxData A pointer to the buffer into which the received message is
* to be copied.
*
* @param xBufferLengthBytes The length of the buffer pointed to by the pvRxData
* parameter. This sets the maximum length of the message that can be received.
* If xBufferLengthBytes is too small to hold the next message then the message
* will be left in the message buffer and 0 will be returned.
*
* @param xTicksToWait The maximum amount of time the task should remain in the
* Blocked state to wait for a message, should the message buffer be empty.
* xMessageBufferReceive() will return immediately if xTicksToWait is zero and
* the message buffer is empty. The block time is specified in tick periods, so
* the absolute time it represents is dependent on the tick frequency. The
* macro pdMS_TO_TICKS() can be used to convert a time specified in milliseconds
* into a time specified in ticks. Setting xTicksToWait to portMAX_DELAY will
* cause the task to wait indefinitely (without timing out), provided
* INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h. Tasks do not use any
* CPU time when they are in the Blocked state.
*
* @return The length, in bytes, of the message read from the message buffer, if
* any. If xMessageBufferReceive() times out before a message became available
* then zero is returned. If the length of the message is greater than
* xBufferLengthBytes then the message will be left in the message buffer and
* zero is returned.
*
* Example use:
* @code{c}
* void vAFunction( MessageBuffer_t xMessageBuffer )
* {
* uint8_t ucRxData[ 20 ];
* size_t xReceivedBytes;
* const TickType_t xBlockTime = pdMS_TO_TICKS( 20 );
*
* // Receive the next message from the message buffer. Wait in the Blocked
* // state (so not using any CPU processing time) for a maximum of 100ms for
* // a message to become available.
* xReceivedBytes = xMessageBufferReceive( xMessageBuffer,
* ( void * ) ucRxData,
* sizeof( ucRxData ),
* xBlockTime );
*
* if( xReceivedBytes > 0 )
* {
* // A ucRxData contains a message that is xReceivedBytes long. Process
* // the message here....
* }
* }
* @endcode
* \defgroup xMessageBufferReceive xMessageBufferReceive
* \ingroup MessageBufferManagement
*/
#define xMessageBufferReceive( xMessageBuffer, pvRxData, xBufferLengthBytes, xTicksToWait ) \
xStreamBufferReceive( ( StreamBufferHandle_t ) xMessageBuffer, pvRxData, xBufferLengthBytes, xTicksToWait )
/**
* message_buffer.h
*
* @code{c}
* size_t xMessageBufferReceiveFromISR( MessageBufferHandle_t xMessageBuffer,
* void *pvRxData,
* size_t xBufferLengthBytes,
* BaseType_t *pxHigherPriorityTaskWoken );
* @endcode
*
* An interrupt safe version of the API function that receives a discrete
* message from a message buffer. Messages can be of variable length and are
* copied out of the buffer.
*
* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
* implementation (so also the message buffer implementation, as message buffers
* are built on top of stream buffers) assumes there is only one task or
* interrupt that will write to the buffer (the writer), and only one task or
* interrupt that will read from the buffer (the reader). It is safe for the
* writer and reader to be different tasks or interrupts, but, unlike other
* FreeRTOS objects, it is not safe to have multiple different writers or
* multiple different readers. If there are to be multiple different writers
* then the application writer must place each call to a writing API function
* (such as xMessageBufferSend()) inside a critical section and set the send
* block time to 0. Likewise, if there are to be multiple different readers
* then the application writer must place each call to a reading API function
* (such as xMessageBufferRead()) inside a critical section and set the receive
* block time to 0.
*
* Use xMessageBufferReceive() to read from a message buffer from a task. Use
* xMessageBufferReceiveFromISR() to read from a message buffer from an
* interrupt service routine (ISR).
*
* @param xMessageBuffer The handle of the message buffer from which a message
* is being received.
*
* @param pvRxData A pointer to the buffer into which the received message is
* to be copied.
*
* @param xBufferLengthBytes The length of the buffer pointed to by the pvRxData
* parameter. This sets the maximum length of the message that can be received.
* If xBufferLengthBytes is too small to hold the next message then the message
* will be left in the message buffer and 0 will be returned.
*
* @param pxHigherPriorityTaskWoken It is possible that a message buffer will
* have a task blocked on it waiting for space to become available. Calling
* xMessageBufferReceiveFromISR() can make space available, and so cause a task
* that is waiting for space to leave the Blocked state. If calling
* xMessageBufferReceiveFromISR() causes a task to leave the Blocked state, and
* the unblocked task has a priority higher than the currently executing task
* (the task that was interrupted), then, internally,
* xMessageBufferReceiveFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE.
* If xMessageBufferReceiveFromISR() sets this value to pdTRUE, then normally a
* context switch should be performed before the interrupt is exited. That will
* ensure the interrupt returns directly to the highest priority Ready state
* task. *pxHigherPriorityTaskWoken should be set to pdFALSE before it is
* passed into the function. See the code example below for an example.
*
* @return The length, in bytes, of the message read from the message buffer, if
* any.
*
* Example use:
* @code{c}
* // A message buffer that has already been created.
* MessageBuffer_t xMessageBuffer;
*
* void vAnInterruptServiceRoutine( void )
* {
* uint8_t ucRxData[ 20 ];
* size_t xReceivedBytes;
* BaseType_t xHigherPriorityTaskWoken = pdFALSE; // Initialised to pdFALSE.
*
* // Receive the next message from the message buffer.
* xReceivedBytes = xMessageBufferReceiveFromISR( xMessageBuffer,
* ( void * ) ucRxData,
* sizeof( ucRxData ),
* &xHigherPriorityTaskWoken );
*
* if( xReceivedBytes > 0 )
* {
* // A ucRxData contains a message that is xReceivedBytes long. Process
* // the message here....
* }
*
* // If xHigherPriorityTaskWoken was set to pdTRUE inside
* // xMessageBufferReceiveFromISR() then a task that has a priority above the
* // priority of the currently executing task was unblocked and a context
* // switch should be performed to ensure the ISR returns to the unblocked
* // task. In most FreeRTOS ports this is done by simply passing
* // xHigherPriorityTaskWoken into portYIELD_FROM_ISR(), which will test the
* // variables value, and perform the context switch if necessary. Check the
* // documentation for the port in use for port specific instructions.
* portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
* }
* @endcode
* \defgroup xMessageBufferReceiveFromISR xMessageBufferReceiveFromISR
* \ingroup MessageBufferManagement
*/
#define xMessageBufferReceiveFromISR( xMessageBuffer, pvRxData, xBufferLengthBytes, pxHigherPriorityTaskWoken ) \
xStreamBufferReceiveFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pvRxData, xBufferLengthBytes, pxHigherPriorityTaskWoken )
/**
* message_buffer.h
*
* @code{c}
* void vMessageBufferDelete( MessageBufferHandle_t xMessageBuffer );
* @endcode
*
* Deletes a message buffer that was previously created using a call to
* xMessageBufferCreate() or xMessageBufferCreateStatic(). If the message
* buffer was created using dynamic memory (that is, by xMessageBufferCreate()),
* then the allocated memory is freed.
*
* A message buffer handle must not be used after the message buffer has been
* deleted.
*
* @param xMessageBuffer The handle of the message buffer to be deleted.
*
*/
#define vMessageBufferDelete( xMessageBuffer ) \
vStreamBufferDelete( ( StreamBufferHandle_t ) xMessageBuffer )
/**
* message_buffer.h
* @code{c}
* BaseType_t xMessageBufferIsFull( MessageBufferHandle_t xMessageBuffer );
* @endcode
*
* Tests to see if a message buffer is full. A message buffer is full if it
* cannot accept any more messages, of any size, until space is made available
* by a message being removed from the message buffer.
*
* @param xMessageBuffer The handle of the message buffer being queried.
*
* @return If the message buffer referenced by xMessageBuffer is full then
* pdTRUE is returned. Otherwise pdFALSE is returned.
*/
#define xMessageBufferIsFull( xMessageBuffer ) \
xStreamBufferIsFull( ( StreamBufferHandle_t ) xMessageBuffer )
/**
* message_buffer.h
* @code{c}
* BaseType_t xMessageBufferIsEmpty( MessageBufferHandle_t xMessageBuffer );
* @endcode
*
* Tests to see if a message buffer is empty (does not contain any messages).
*
* @param xMessageBuffer The handle of the message buffer being queried.
*
* @return If the message buffer referenced by xMessageBuffer is empty then
* pdTRUE is returned. Otherwise pdFALSE is returned.
*
*/
#define xMessageBufferIsEmpty( xMessageBuffer ) \
xStreamBufferIsEmpty( ( StreamBufferHandle_t ) xMessageBuffer )
/**
* message_buffer.h
* @code{c}
* BaseType_t xMessageBufferReset( MessageBufferHandle_t xMessageBuffer );
* @endcode
*
* Resets a message buffer to its initial empty state, discarding any message it
* contained.
*
* A message buffer can only be reset if there are no tasks blocked on it.
*
* @param xMessageBuffer The handle of the message buffer being reset.
*
* @return If the message buffer was reset then pdPASS is returned. If the
* message buffer could not be reset because either there was a task blocked on
* the message queue to wait for space to become available, or to wait for a
* a message to be available, then pdFAIL is returned.
*
* \defgroup xMessageBufferReset xMessageBufferReset
* \ingroup MessageBufferManagement
*/
#define xMessageBufferReset( xMessageBuffer ) \
xStreamBufferReset( ( StreamBufferHandle_t ) xMessageBuffer )
/**
* message_buffer.h
* @code{c}
* size_t xMessageBufferSpaceAvailable( MessageBufferHandle_t xMessageBuffer );
* @endcode
* Returns the number of bytes of free space in the message buffer.
*
* @param xMessageBuffer The handle of the message buffer being queried.
*
* @return The number of bytes that can be written to the message buffer before
* the message buffer would be full. When a message is written to the message
* buffer an additional sizeof( size_t ) bytes are also written to store the
* message's length. sizeof( size_t ) is typically 4 bytes on a 32-bit
* architecture, so if xMessageBufferSpacesAvailable() returns 10, then the size
* of the largest message that can be written to the message buffer is 6 bytes.
*
* \defgroup xMessageBufferSpaceAvailable xMessageBufferSpaceAvailable
* \ingroup MessageBufferManagement
*/
#define xMessageBufferSpaceAvailable( xMessageBuffer ) \
xStreamBufferSpacesAvailable( ( StreamBufferHandle_t ) xMessageBuffer )
#define xMessageBufferSpacesAvailable( xMessageBuffer ) \
xStreamBufferSpacesAvailable( ( StreamBufferHandle_t ) xMessageBuffer ) /* Corrects typo in original macro name. */
/**
* message_buffer.h
* @code{c}
* size_t xMessageBufferNextLengthBytes( MessageBufferHandle_t xMessageBuffer );
* @endcode
* Returns the length (in bytes) of the next message in a message buffer.
* Useful if xMessageBufferReceive() returned 0 because the size of the buffer
* passed into xMessageBufferReceive() was too small to hold the next message.
*
* @param xMessageBuffer The handle of the message buffer being queried.
*
* @return The length (in bytes) of the next message in the message buffer, or 0
* if the message buffer is empty.
*
* \defgroup xMessageBufferNextLengthBytes xMessageBufferNextLengthBytes
* \ingroup MessageBufferManagement
*/
#define xMessageBufferNextLengthBytes( xMessageBuffer ) \
xStreamBufferNextMessageLengthBytes( ( StreamBufferHandle_t ) xMessageBuffer ) PRIVILEGED_FUNCTION;
/**
* message_buffer.h
*
* @code{c}
* BaseType_t xMessageBufferSendCompletedFromISR( MessageBufferHandle_t xMessageBuffer, BaseType_t *pxHigherPriorityTaskWoken );
* @endcode
*
* For advanced users only.
*
* The sbSEND_COMPLETED() macro is called from within the FreeRTOS APIs when
* data is sent to a message buffer or stream buffer. If there was a task that
* was blocked on the message or stream buffer waiting for data to arrive then
* the sbSEND_COMPLETED() macro sends a notification to the task to remove it
* from the Blocked state. xMessageBufferSendCompletedFromISR() does the same
* thing. It is provided to enable application writers to implement their own
* version of sbSEND_COMPLETED(), and MUST NOT BE USED AT ANY OTHER TIME.
*
* See the example implemented in FreeRTOS/Demo/Minimal/MessageBufferAMP.c for
* additional information.
*
* @param xMessageBuffer The handle of the stream buffer to which data was
* written.
*
* @param pxHigherPriorityTaskWoken *pxHigherPriorityTaskWoken should be
* initialised to pdFALSE before it is passed into
* xMessageBufferSendCompletedFromISR(). If calling
* xMessageBufferSendCompletedFromISR() removes a task from the Blocked state,
* and the task has a priority above the priority of the currently running task,
* then *pxHigherPriorityTaskWoken will get set to pdTRUE indicating that a
* context switch should be performed before exiting the ISR.
*
* @return If a task was removed from the Blocked state then pdTRUE is returned.
* Otherwise pdFALSE is returned.
*
* \defgroup xMessageBufferSendCompletedFromISR xMessageBufferSendCompletedFromISR
* \ingroup StreamBufferManagement
*/
#define xMessageBufferSendCompletedFromISR( xMessageBuffer, pxHigherPriorityTaskWoken ) \
xStreamBufferSendCompletedFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pxHigherPriorityTaskWoken )
/**
* message_buffer.h
*
* @code{c}
* BaseType_t xMessageBufferReceiveCompletedFromISR( MessageBufferHandle_t xMessageBuffer, BaseType_t *pxHigherPriorityTaskWoken );
* @endcode
*
* For advanced users only.
*
* The sbRECEIVE_COMPLETED() macro is called from within the FreeRTOS APIs when
* data is read out of a message buffer or stream buffer. If there was a task
* that was blocked on the message or stream buffer waiting for data to arrive
* then the sbRECEIVE_COMPLETED() macro sends a notification to the task to
* remove it from the Blocked state. xMessageBufferReceiveCompletedFromISR()
* does the same thing. It is provided to enable application writers to
* implement their own version of sbRECEIVE_COMPLETED(), and MUST NOT BE USED AT
* ANY OTHER TIME.
*
* See the example implemented in FreeRTOS/Demo/Minimal/MessageBufferAMP.c for
* additional information.
*
* @param xMessageBuffer The handle of the stream buffer from which data was
* read.
*
* @param pxHigherPriorityTaskWoken *pxHigherPriorityTaskWoken should be
* initialised to pdFALSE before it is passed into
* xMessageBufferReceiveCompletedFromISR(). If calling
* xMessageBufferReceiveCompletedFromISR() removes a task from the Blocked state,
* and the task has a priority above the priority of the currently running task,
* then *pxHigherPriorityTaskWoken will get set to pdTRUE indicating that a
* context switch should be performed before exiting the ISR.
*
* @return If a task was removed from the Blocked state then pdTRUE is returned.
* Otherwise pdFALSE is returned.
*
* \defgroup xMessageBufferReceiveCompletedFromISR xMessageBufferReceiveCompletedFromISR
* \ingroup StreamBufferManagement
*/
#define xMessageBufferReceiveCompletedFromISR( xMessageBuffer, pxHigherPriorityTaskWoken ) \
xStreamBufferReceiveCompletedFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pxHigherPriorityTaskWoken )
/* *INDENT-OFF* */
#if defined( __cplusplus )
} /* extern "C" */
#endif
/* *INDENT-ON* */
#endif /* !defined( FREERTOS_MESSAGE_BUFFER_H ) */
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