message_buffer.h

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/*
 * FreeRTOS Kernel V10.0.0
 * Copyright (C) 2017 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * 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
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 * 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,
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 *
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 * FreeRTOS name, please do so in a fair use way that does not cause confusion.
 *
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/*
 * 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
 
/* Message buffers are built onto of stream buffers. */
#include "stream_buffer.h"
 
#if defined( __cplusplus )
extern "C" {
#endif
 
typedef void * MessageBufferHandle_t;
 
/*-----------------------------------------------------------*/
 
#define xMessageBufferCreate( xBufferSizeBytes ) ( MessageBufferHandle_t ) xStreamBufferGenericCreate( xBufferSizeBytes, ( size_t ) 0, pdTRUE )
 
#define xMessageBufferCreateStatic( xBufferSizeBytes, pucMessageBufferStorageArea, pxStaticMessageBuffer ) ( MessageBufferHandle_t ) xStreamBufferGenericCreateStatic( xBufferSizeBytes, 0, pdTRUE, pucMessageBufferStorageArea, pxStaticMessageBuffer )
 
#define xMessageBufferSend( xMessageBuffer, pvTxData, xDataLengthBytes, xTicksToWait ) xStreamBufferSend( ( StreamBufferHandle_t ) xMessageBuffer, pvTxData, xDataLengthBytes, xTicksToWait )
 
#define xMessageBufferSendFromISR( xMessageBuffer, pvTxData, xDataLengthBytes, pxHigherPriorityTaskWoken ) xStreamBufferSendFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pvTxData, xDataLengthBytes, pxHigherPriorityTaskWoken )
 
#define xMessageBufferReceive( xMessageBuffer, pvRxData, xBufferLengthBytes, xTicksToWait ) xStreamBufferReceive( ( StreamBufferHandle_t ) xMessageBuffer, pvRxData, xBufferLengthBytes, xTicksToWait )
 
 
#define xMessageBufferReceiveFromISR( xMessageBuffer, pvRxData, xBufferLengthBytes, pxHigherPriorityTaskWoken ) xStreamBufferReceiveFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pvRxData, xBufferLengthBytes, pxHigherPriorityTaskWoken )
 
#define vMessageBufferDelete( xMessageBuffer ) vStreamBufferDelete( ( StreamBufferHandle_t ) xMessageBuffer )
 
#define xMessageBufferIsFull( xMessageBuffer ) xStreamBufferIsFull( ( StreamBufferHandle_t ) xMessageBuffer )
 
#define xMessageBufferIsEmpty( xMessageBuffer ) xStreamBufferIsEmpty( ( StreamBufferHandle_t ) xMessageBuffer )
 
#define xMessageBufferReset( xMessageBuffer ) xStreamBufferReset( ( StreamBufferHandle_t ) xMessageBuffer )
 
 
#define xMessageBufferSpaceAvailable( xMessageBuffer ) xStreamBufferSpacesAvailable( ( StreamBufferHandle_t ) xMessageBuffer )
 
#define xMessageBufferSendCompletedFromISR( xMessageBuffer, pxHigherPriorityTaskWoken ) xStreamBufferSendCompletedFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pxHigherPriorityTaskWoken )
 
#define xMessageBufferReceiveCompletedFromISR( xMessageBuffer, pxHigherPriorityTaskWoken ) xStreamBufferReceiveCompletedFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pxHigherPriorityTaskWoken )
 
#if defined( __cplusplus )
} /* extern "C" */
#endif
 
#endif  /* !defined( FREERTOS_MESSAGE_BUFFER_H ) */