text: /*
   * 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
   *
   */
  
  /*
   * Stream buffers are used to send a continuous stream of data 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 xStreamBufferSend()) 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 xStreamBufferReceive()) inside a critical section section and set the
   * receive block time to 0.
   *
   */
  
  #ifndef STREAM_BUFFER_H
  #define STREAM_BUFFER_H
  
  #ifndef INC_FREERTOS_H
      #error "include FreeRTOS.h must appear in source files before include stream_buffer.h"
  #endif
  
  /* *INDENT-OFF* */
  #if defined( __cplusplus )
      extern "C" {
  #endif
  /* *INDENT-ON* */
  
  /**
   * Type by which stream buffers are referenced.  For example, a call to
   * xStreamBufferCreate() returns an StreamBufferHandle_t variable that can
   * then be used as a parameter to xStreamBufferSend(), xStreamBufferReceive(),
   * etc.
   */
  struct StreamBufferDef_t;
  typedef struct StreamBufferDef_t * StreamBufferHandle_t;
  
  
  /**
   * message_buffer.h
   *
   * <pre>
   * StreamBufferHandle_t xStreamBufferCreate( size_t xBufferSizeBytes, size_t xTriggerLevelBytes );
   * </pre>
   *
   * Creates a new stream buffer using dynamically allocated memory.  See
   * xStreamBufferCreateStatic() 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 xStreamBufferCreate() to be available.
   *
   * @param xBufferSizeBytes The total number of bytes the stream buffer will be
   * able to hold at any one time.
   *
   * @param xTriggerLevelBytes The number of bytes that must be in the stream
   * buffer before a task that is blocked on the stream buffer to wait for data is
   * moved out of the blocked state.  For example, if a task is blocked on a read
   * of an empty stream buffer that has a trigger level of 1 then the task will be
   * unblocked when a single byte is written to the buffer or the task's block
   * time expires.  As another example, if a task is blocked on a read of an empty
   * stream buffer that has a trigger level of 10 then the task will not be
   * unblocked until the stream buffer contains at least 10 bytes or the task's
   * block time expires.  If a reading task's block time expires before the
   * trigger level is reached then the task will still receive however many bytes
   * are actually available.  Setting a trigger level of 0 will result in a
   * trigger level of 1 being used.  It is not valid to specify a trigger level
   * that is greater than the buffer size.
   *
   * @return If NULL is returned, then the stream buffer cannot be created
   * because there is insufficient heap memory available for FreeRTOS to allocate
   * the stream buffer data structures and storage area.  A non-NULL value being
   * returned indicates that the stream buffer has been created successfully -
   * the returned value should be stored as the handle to the created stream
   * buffer.
   *
   * Example use:
   * <pre>
   *
   * void vAFunction( void )
   * {
   * StreamBufferHandle_t xStreamBuffer;
   * const size_t xStreamBufferSizeBytes = 100, xTriggerLevel = 10;
   *
   *  // Create a stream buffer that can hold 100 bytes.  The memory used to hold
   *  // both the stream buffer structure and the data in the stream buffer is
   *  // allocated dynamically.
   *  xStreamBuffer = xStreamBufferCreate( xStreamBufferSizeBytes, xTriggerLevel );
   *
   *  if( xStreamBuffer == NULL )
   *  {
   *      // There was not enough heap memory space available to create the
   *      // stream buffer.
   *  }
   *  else
   *  {
   *      // The stream buffer was created successfully and can now be used.
   *  }
   * }
   * </pre>
   * \defgroup xStreamBufferCreate xStreamBufferCreate
   * \ingroup StreamBufferManagement
   */
  #define xStreamBufferCreate( xBufferSizeBytes, xTriggerLevelBytes )    xStreamBufferGenericCreate( xBufferSizeBytes, xTriggerLevelBytes, pdFALSE )
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * StreamBufferHandle_t xStreamBufferCreateStatic( size_t xBufferSizeBytes,
   *                                              size_t xTriggerLevelBytes,
   *                                              uint8_t *pucStreamBufferStorageArea,
   *                                              StaticStreamBuffer_t *pxStaticStreamBuffer );
   * </pre>
   * Creates a new stream buffer using statically allocated memory.  See
   * xStreamBufferCreate() for a version that uses dynamically allocated memory.
   *
   * configSUPPORT_STATIC_ALLOCATION must be set to 1 in FreeRTOSConfig.h for
   * xStreamBufferCreateStatic() to be available.
   *
   * @param xBufferSizeBytes The size, in bytes, of the buffer pointed to by the
   * pucStreamBufferStorageArea parameter.
   *
   * @param xTriggerLevelBytes The number of bytes that must be in the stream
   * buffer before a task that is blocked on the stream buffer to wait for data is
   * moved out of the blocked state.  For example, if a task is blocked on a read
   * of an empty stream buffer that has a trigger level of 1 then the task will be
   * unblocked when a single byte is written to the buffer or the task's block
   * time expires.  As another example, if a task is blocked on a read of an empty
   * stream buffer that has a trigger level of 10 then the task will not be
   * unblocked until the stream buffer contains at least 10 bytes or the task's
   * block time expires.  If a reading task's block time expires before the
   * trigger level is reached then the task will still receive however many bytes
   * are actually available.  Setting a trigger level of 0 will result in a
   * trigger level of 1 being used.  It is not valid to specify a trigger level
   * that is greater than the buffer size.
   *
   * @param pucStreamBufferStorageArea Must point to a uint8_t array that is at
   * least xBufferSizeBytes big.  This is the array to which streams are
   * copied when they are written to the stream buffer.
   *
   * @param pxStaticStreamBuffer Must point to a variable of type
   * StaticStreamBuffer_t, which will be used to hold the stream buffer's data
   * structure.
   *
   * @return If the stream buffer is created successfully then a handle to the
   * created stream buffer is returned. If either pucStreamBufferStorageArea or
   * pxStaticstreamBuffer are NULL then NULL is returned.
   *
   * Example use:
   * <pre>
   *
   * // Used to dimension the array used to hold the streams.  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 streams within the stream
   * // buffer.
   * static uint8_t ucStorageBuffer[ STORAGE_SIZE_BYTES ];
   *
   * // The variable used to hold the stream buffer structure.
   * StaticStreamBuffer_t xStreamBufferStruct;
   *
   * void MyFunction( void )
   * {
   * StreamBufferHandle_t xStreamBuffer;
   * const size_t xTriggerLevel = 1;
   *
   *  xStreamBuffer = xStreamBufferCreateStatic( sizeof( ucStorageBuffer ),
   *                                             xTriggerLevel,
   *                                             ucStorageBuffer,
   *                                             &xStreamBufferStruct );
   *
   *  // As neither the pucStreamBufferStorageArea or pxStaticStreamBuffer
   *  // parameters were NULL, xStreamBuffer will not be NULL, and can be used to
   *  // reference the created stream buffer in other stream buffer API calls.
   *
   *  // Other code that uses the stream buffer can go here.
   * }
   *
   * </pre>
   * \defgroup xStreamBufferCreateStatic xStreamBufferCreateStatic
   * \ingroup StreamBufferManagement
   */
  #define xStreamBufferCreateStatic( xBufferSizeBytes, xTriggerLevelBytes, pucStreamBufferStorageArea, pxStaticStreamBuffer ) \
      xStreamBufferGenericCreateStatic( xBufferSizeBytes, xTriggerLevelBytes, pdFALSE, pucStreamBufferStorageArea, pxStaticStreamBuffer )
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * size_t xStreamBufferSend( StreamBufferHandle_t xStreamBuffer,
   *                        const void *pvTxData,
   *                        size_t xDataLengthBytes,
   *                        TickType_t xTicksToWait );
   * </pre>
   *
   * Sends bytes to a stream buffer.  The bytes are copied into the stream 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 xStreamBufferSend()) 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 xStreamBufferReceive()) inside a critical section and set the receive
   * block time to 0.
   *
   * Use xStreamBufferSend() to write to a stream buffer from a task.  Use
   * xStreamBufferSendFromISR() to write to a stream buffer from an interrupt
   * service routine (ISR).
   *
   * @param xStreamBuffer The handle of the stream buffer to which a stream is
   * being sent.
   *
   * @param pvTxData A pointer to the buffer that holds the bytes to be copied
   * into the stream buffer.
   *
   * @param xDataLengthBytes   The maximum number of bytes to copy from pvTxData
   * into the stream buffer.
   *
   * @param xTicksToWait The maximum amount of time the task should remain in the
   * Blocked state to wait for enough space to become available in the stream
   * buffer, should the stream buffer contain too little space to hold the
   * another xDataLengthBytes bytes.  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.  If a task times out
   * before it can write all xDataLengthBytes into the buffer it will still write
   * as many bytes as possible.  A task does not use any CPU time when it is in
   * the blocked state.
   *
   * @return The number of bytes written to the stream buffer.  If a task times
   * out before it can write all xDataLengthBytes into the buffer it will still
   * write as many bytes as possible.
   *
   * Example use:
   * <pre>
   * void vAFunction( StreamBufferHandle_t xStreamBuffer )
   * {
   * 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 stream buffer, blocking for a maximum of 100ms to
   *  // wait for enough space to be available in the stream buffer.
   *  xBytesSent = xStreamBufferSend( xStreamBuffer, ( void * ) ucArrayToSend, sizeof( ucArrayToSend ), x100ms );
   *
   *  if( xBytesSent != sizeof( ucArrayToSend ) )
   *  {
   *      // The call to xStreamBufferSend() times out before there was enough
   *      // space in the buffer for the data to be written, but it did
   *      // successfully write xBytesSent bytes.
   *  }
   *
   *  // Send the string to the stream buffer.  Return immediately if there is not
   *  // enough space in the buffer.
   *  xBytesSent = xStreamBufferSend( xStreamBuffer, ( void * ) pcStringToSend, strlen( pcStringToSend ), 0 );
   *
   *  if( xBytesSent != strlen( pcStringToSend ) )
   *  {
   *      // The entire string could not be added to the stream buffer because
   *      // there was not enough free space in the buffer, but xBytesSent bytes
   *      // were sent.  Could try again to send the remaining bytes.
   *  }
   * }
   * </pre>
   * \defgroup xStreamBufferSend xStreamBufferSend
   * \ingroup StreamBufferManagement
   */
  size_t xStreamBufferSend( StreamBufferHandle_t xStreamBuffer,
                            const void * pvTxData,
                            size_t xDataLengthBytes,
                            TickType_t xTicksToWait ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * size_t xStreamBufferSendFromISR( StreamBufferHandle_t xStreamBuffer,
   *                               const void *pvTxData,
   *                               size_t xDataLengthBytes,
   *                               BaseType_t *pxHigherPriorityTaskWoken );
   * </pre>
   *
   * Interrupt safe version of the API function that sends a stream of bytes to
   * the stream 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 xStreamBufferSend()) 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 xStreamBufferReceive()) inside a critical section and set the receive
   * block time to 0.
   *
   * Use xStreamBufferSend() to write to a stream buffer from a task.  Use
   * xStreamBufferSendFromISR() to write to a stream buffer from an interrupt
   * service routine (ISR).
   *
   * @param xStreamBuffer The handle of the stream buffer to which a stream is
   * being sent.
   *
   * @param pvTxData A pointer to the data that is to be copied into the stream
   * buffer.
   *
   * @param xDataLengthBytes The maximum number of bytes to copy from pvTxData
   * into the stream buffer.
   *
   * @param pxHigherPriorityTaskWoken  It is possible that a stream buffer will
   * have a task blocked on it waiting for data.  Calling
   * xStreamBufferSendFromISR() can make data available, and so cause a task that
   * was waiting for data to leave the Blocked state.  If calling
   * xStreamBufferSendFromISR() 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, xStreamBufferSendFromISR()
   * will set *pxHigherPriorityTaskWoken to pdTRUE.  If
   * xStreamBufferSendFromISR() 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 example code below for an example.
   *
   * @return The number of bytes actually written to the stream buffer, which will
   * be less than xDataLengthBytes if the stream buffer didn't have enough free
   * space for all the bytes to be written.
   *
   * Example use:
   * <pre>
   * // A stream buffer that has already been created.
   * StreamBufferHandle_t xStreamBuffer;
   *
   * 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 stream buffer.
   *  xBytesSent = xStreamBufferSendFromISR( xStreamBuffer,
   *                                         ( void * ) pcStringToSend,
   *                                         strlen( pcStringToSend ),
   *                                         &xHigherPriorityTaskWoken );
   *
   *  if( xBytesSent != strlen( pcStringToSend ) )
   *  {
   *      // There was not enough free space in the stream buffer for the entire
   *      // string to be written, ut xBytesSent bytes were written.
   *  }
   *
   *  // If xHigherPriorityTaskWoken was set to pdTRUE inside
   *  // xStreamBufferSendFromISR() 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 taskYIELD_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.
   *  taskYIELD_FROM_ISR( xHigherPriorityTaskWoken );
   * }
   * </pre>
   * \defgroup xStreamBufferSendFromISR xStreamBufferSendFromISR
   * \ingroup StreamBufferManagement
   */
  size_t xStreamBufferSendFromISR( StreamBufferHandle_t xStreamBuffer,
                                   const void * pvTxData,
                                   size_t xDataLengthBytes,
                                   BaseType_t * const pxHigherPriorityTaskWoken ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * size_t xStreamBufferReceive( StreamBufferHandle_t xStreamBuffer,
   *                           void *pvRxData,
   *                           size_t xBufferLengthBytes,
   *                           TickType_t xTicksToWait );
   * </pre>
   *
   * Receives bytes from a stream 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 xStreamBufferSend()) 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 xStreamBufferReceive()) inside a critical section and set the receive
   * block time to 0.
   *
   * Use xStreamBufferReceive() to read from a stream buffer from a task.  Use
   * xStreamBufferReceiveFromISR() to read from a stream buffer from an
   * interrupt service routine (ISR).
   *
   * @param xStreamBuffer The handle of the stream buffer from which bytes are to
   * be received.
   *
   * @param pvRxData A pointer to the buffer into which the received bytes will be
   * copied.
   *
   * @param xBufferLengthBytes The length of the buffer pointed to by the
   * pvRxData parameter.  This sets the maximum number of bytes to receive in one
   * call.  xStreamBufferReceive will return as many bytes as possible up to a
   * maximum set by xBufferLengthBytes.
   *
   * @param xTicksToWait The maximum amount of time the task should remain in the
   * Blocked state to wait for data to become available if the stream buffer is
   * empty.  xStreamBufferReceive() will return immediately 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.  A task does not use any CPU time when it is in the
   * Blocked state.
   *
   * @return The number of bytes actually read from the stream buffer, which will
   * be less than xBufferLengthBytes if the call to xStreamBufferReceive() timed
   * out before xBufferLengthBytes were available.
   *
   * Example use:
   * <pre>
   * void vAFunction( StreamBuffer_t xStreamBuffer )
   * {
   * uint8_t ucRxData[ 20 ];
   * size_t xReceivedBytes;
   * const TickType_t xBlockTime = pdMS_TO_TICKS( 20 );
   *
   *  // Receive up to another sizeof( ucRxData ) bytes from the stream buffer.
   *  // Wait in the Blocked state (so not using any CPU processing time) for a
   *  // maximum of 100ms for the full sizeof( ucRxData ) number of bytes to be
   *  // available.
   *  xReceivedBytes = xStreamBufferReceive( xStreamBuffer,
   *                                         ( void * ) ucRxData,
   *                                         sizeof( ucRxData ),
   *                                         xBlockTime );
   *
   *  if( xReceivedBytes > 0 )
   *  {
   *      // A ucRxData contains another xRecievedBytes bytes of data, which can
   *      // be processed here....
   *  }
   * }
   * </pre>
   * \defgroup xStreamBufferReceive xStreamBufferReceive
   * \ingroup StreamBufferManagement
   */
  size_t xStreamBufferReceive( StreamBufferHandle_t xStreamBuffer,
                               void * pvRxData,
                               size_t xBufferLengthBytes,
                               TickType_t xTicksToWait ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * size_t xStreamBufferReceiveFromISR( StreamBufferHandle_t xStreamBuffer,
   *                                  void *pvRxData,
   *                                  size_t xBufferLengthBytes,
   *                                  BaseType_t *pxHigherPriorityTaskWoken );
   * </pre>
   *
   * An interrupt safe version of the API function that receives bytes from a
   * stream buffer.
   *
   * Use xStreamBufferReceive() to read bytes from a stream buffer from a task.
   * Use xStreamBufferReceiveFromISR() to read bytes from a stream buffer from an
   * interrupt service routine (ISR).
   *
   * @param xStreamBuffer The handle of the stream buffer from which a stream
   * is being received.
   *
   * @param pvRxData A pointer to the buffer into which the received bytes are
   * copied.
   *
   * @param xBufferLengthBytes The length of the buffer pointed to by the
   * pvRxData parameter.  This sets the maximum number of bytes to receive in one
   * call.  xStreamBufferReceive will return as many bytes as possible up to a
   * maximum set by xBufferLengthBytes.
   *
   * @param pxHigherPriorityTaskWoken  It is possible that a stream buffer will
   * have a task blocked on it waiting for space to become available.  Calling
   * xStreamBufferReceiveFromISR() can make space available, and so cause a task
   * that is waiting for space to leave the Blocked state.  If calling
   * xStreamBufferReceiveFromISR() 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,
   * xStreamBufferReceiveFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE.
   * If xStreamBufferReceiveFromISR() 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 number of bytes read from the stream buffer, if any.
   *
   * Example use:
   * <pre>
   * // A stream buffer that has already been created.
   * StreamBuffer_t xStreamBuffer;
   *
   * void vAnInterruptServiceRoutine( void )
   * {
   * uint8_t ucRxData[ 20 ];
   * size_t xReceivedBytes;
   * BaseType_t xHigherPriorityTaskWoken = pdFALSE;  // Initialised to pdFALSE.
   *
   *  // Receive the next stream from the stream buffer.
   *  xReceivedBytes = xStreamBufferReceiveFromISR( xStreamBuffer,
   *                                                ( void * ) ucRxData,
   *                                                sizeof( ucRxData ),
   *                                                &xHigherPriorityTaskWoken );
   *
   *  if( xReceivedBytes > 0 )
   *  {
   *      // ucRxData contains xReceivedBytes read from the stream buffer.
   *      // Process the stream here....
   *  }
   *
   *  // If xHigherPriorityTaskWoken was set to pdTRUE inside
   *  // xStreamBufferReceiveFromISR() 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 taskYIELD_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.
   *  taskYIELD_FROM_ISR( xHigherPriorityTaskWoken );
   * }
   * </pre>
   * \defgroup xStreamBufferReceiveFromISR xStreamBufferReceiveFromISR
   * \ingroup StreamBufferManagement
   */
  size_t xStreamBufferReceiveFromISR( StreamBufferHandle_t xStreamBuffer,
                                      void * pvRxData,
                                      size_t xBufferLengthBytes,
                                      BaseType_t * const pxHigherPriorityTaskWoken ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * void vStreamBufferDelete( StreamBufferHandle_t xStreamBuffer );
   * </pre>
   *
   * Deletes a stream buffer that was previously created using a call to
   * xStreamBufferCreate() or xStreamBufferCreateStatic().  If the stream
   * buffer was created using dynamic memory (that is, by xStreamBufferCreate()),
   * then the allocated memory is freed.
   *
   * A stream buffer handle must not be used after the stream buffer has been
   * deleted.
   *
   * @param xStreamBuffer The handle of the stream buffer to be deleted.
   *
   * \defgroup vStreamBufferDelete vStreamBufferDelete
   * \ingroup StreamBufferManagement
   */
  void vStreamBufferDelete( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * BaseType_t xStreamBufferIsFull( StreamBufferHandle_t xStreamBuffer );
   * </pre>
   *
   * Queries a stream buffer to see if it is full.  A stream buffer is full if it
   * does not have any free space, and therefore cannot accept any more data.
   *
   * @param xStreamBuffer The handle of the stream buffer being queried.
   *
   * @return If the stream buffer is full then pdTRUE is returned.  Otherwise
   * pdFALSE is returned.
   *
   * \defgroup xStreamBufferIsFull xStreamBufferIsFull
   * \ingroup StreamBufferManagement
   */
  BaseType_t xStreamBufferIsFull( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * BaseType_t xStreamBufferIsEmpty( StreamBufferHandle_t xStreamBuffer );
   * </pre>
   *
   * Queries a stream buffer to see if it is empty.  A stream buffer is empty if
   * it does not contain any data.
   *
   * @param xStreamBuffer The handle of the stream buffer being queried.
   *
   * @return If the stream buffer is empty then pdTRUE is returned.  Otherwise
   * pdFALSE is returned.
   *
   * \defgroup xStreamBufferIsEmpty xStreamBufferIsEmpty
   * \ingroup StreamBufferManagement
   */
  BaseType_t xStreamBufferIsEmpty( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * BaseType_t xStreamBufferReset( StreamBufferHandle_t xStreamBuffer );
   * </pre>
   *
   * Resets a stream buffer to its initial, empty, state.  Any data that was in
   * the stream buffer is discarded.  A stream buffer can only be reset if there
   * are no tasks blocked waiting to either send to or receive from the stream
   * buffer.
   *
   * @param xStreamBuffer The handle of the stream buffer being reset.
   *
   * @return If the stream buffer is reset then pdPASS is returned.  If there was
   * a task blocked waiting to send to or read from the stream buffer then the
   * stream buffer is not reset and pdFAIL is returned.
   *
   * \defgroup xStreamBufferReset xStreamBufferReset
   * \ingroup StreamBufferManagement
   */
  BaseType_t xStreamBufferReset( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * size_t xStreamBufferSpacesAvailable( StreamBufferHandle_t xStreamBuffer );
   * </pre>
   *
   * Queries a stream buffer to see how much free space it contains, which is
   * equal to the amount of data that can be sent to the stream buffer before it
   * is full.
   *
   * @param xStreamBuffer The handle of the stream buffer being queried.
   *
   * @return The number of bytes that can be written to the stream buffer before
   * the stream buffer would be full.
   *
   * \defgroup xStreamBufferSpacesAvailable xStreamBufferSpacesAvailable
   * \ingroup StreamBufferManagement
   */
  size_t xStreamBufferSpacesAvailable( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * size_t xStreamBufferBytesAvailable( StreamBufferHandle_t xStreamBuffer );
   * </pre>
   *
   * Queries a stream buffer to see how much data it contains, which is equal to
   * the number of bytes that can be read from the stream buffer before the stream
   * buffer would be empty.
   *
   * @param xStreamBuffer The handle of the stream buffer being queried.
   *
   * @return The number of bytes that can be read from the stream buffer before
   * the stream buffer would be empty.
   *
   * \defgroup xStreamBufferBytesAvailable xStreamBufferBytesAvailable
   * \ingroup StreamBufferManagement
   */
  size_t xStreamBufferBytesAvailable( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * BaseType_t xStreamBufferSetTriggerLevel( StreamBufferHandle_t xStreamBuffer, size_t xTriggerLevel );
   * </pre>
   *
   * A stream buffer's trigger level is the number of bytes that must be in the
   * stream buffer before a task that is blocked on the stream buffer to
   * wait for data is moved out of the blocked state.  For example, if a task is
   * blocked on a read of an empty stream buffer that has a trigger level of 1
   * then the task will be unblocked when a single byte is written to the buffer
   * or the task's block time expires.  As another example, if a task is blocked
   * on a read of an empty stream buffer that has a trigger level of 10 then the
   * task will not be unblocked until the stream buffer contains at least 10 bytes
   * or the task's block time expires.  If a reading task's block time expires
   * before the trigger level is reached then the task will still receive however
   * many bytes are actually available.  Setting a trigger level of 0 will result
   * in a trigger level of 1 being used.  It is not valid to specify a trigger
   * level that is greater than the buffer size.
   *
   * A trigger level is set when the stream buffer is created, and can be modified
   * using xStreamBufferSetTriggerLevel().
   *
   * @param xStreamBuffer The handle of the stream buffer being updated.
   *
   * @param xTriggerLevel The new trigger level for the stream buffer.
   *
   * @return If xTriggerLevel was less than or equal to the stream buffer's length
   * then the trigger level will be updated and pdTRUE is returned.  Otherwise
   * pdFALSE is returned.
   *
   * \defgroup xStreamBufferSetTriggerLevel xStreamBufferSetTriggerLevel
   * \ingroup StreamBufferManagement
   */
  BaseType_t xStreamBufferSetTriggerLevel( StreamBufferHandle_t xStreamBuffer,
                                           size_t xTriggerLevel ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * BaseType_t xStreamBufferSendCompletedFromISR( StreamBufferHandle_t xStreamBuffer, BaseType_t *pxHigherPriorityTaskWoken );
   * </pre>
   *
   * 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.  xStreamBufferSendCompletedFromISR() 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 xStreamBuffer The handle of the stream buffer to which data was
   * written.
   *
   * @param pxHigherPriorityTaskWoken *pxHigherPriorityTaskWoken should be
   * initialised to pdFALSE before it is passed into
   * xStreamBufferSendCompletedFromISR().  If calling
   * xStreamBufferSendCompletedFromISR() 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 xStreamBufferSendCompletedFromISR xStreamBufferSendCompletedFromISR
   * \ingroup StreamBufferManagement
   */
  BaseType_t xStreamBufferSendCompletedFromISR( StreamBufferHandle_t xStreamBuffer,
                                                BaseType_t * pxHigherPriorityTaskWoken ) PRIVILEGED_FUNCTION;
  
  /**
   * stream_buffer.h
   *
   * <pre>
   * BaseType_t xStreamBufferReceiveCompletedFromISR( StreamBufferHandle_t xStreamBuffer, BaseType_t *pxHigherPriorityTaskWoken );
   * </pre>
   *
   * 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.  xStreamBufferReceiveCompletedFromISR()
   * 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 xStreamBuffer The handle of the stream buffer from which data was
   * read.
   *
   * @param pxHigherPriorityTaskWoken *pxHigherPriorityTaskWoken should be
   * initialised to pdFALSE before it is passed into
   * xStreamBufferReceiveCompletedFromISR().  If calling
   * xStreamBufferReceiveCompletedFromISR() 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 xStreamBufferReceiveCompletedFromISR xStreamBufferReceiveCompletedFromISR
   * \ingroup StreamBufferManagement
   */
  BaseType_t xStreamBufferReceiveCompletedFromISR( StreamBufferHandle_t xStreamBuffer,
                                                   BaseType_t * pxHigherPriorityTaskWoken ) PRIVILEGED_FUNCTION;
  
  /* Functions below here are not part of the public API. */
  StreamBufferHandle_t xStreamBufferGenericCreate( size_t xBufferSizeBytes,
                                                   size_t xTriggerLevelBytes,
                                                   BaseType_t xIsMessageBuffer ) PRIVILEGED_FUNCTION;
  
  StreamBufferHandle_t xStreamBufferGenericCreateStatic( size_t xBufferSizeBytes,
                                                         size_t xTriggerLevelBytes,
                                                         BaseType_t xIsMessageBuffer,
                                                         uint8_t * const pucStreamBufferStorageArea,
                                                         StaticStreamBuffer_t * const pxStaticStreamBuffer ) PRIVILEGED_FUNCTION;
  
  size_t xStreamBufferNextMessageLengthBytes( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
  
  #if ( configUSE_TRACE_FACILITY == 1 )
      void vStreamBufferSetStreamBufferNumber( StreamBufferHandle_t xStreamBuffer,
                                               UBaseType_t uxStreamBufferNumber ) PRIVILEGED_FUNCTION;
      UBaseType_t uxStreamBufferGetStreamBufferNumber( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
      uint8_t ucStreamBufferGetStreamBufferType( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
  #endif
  
  /* *INDENT-OFF* */
  #if defined( __cplusplus )
      }
  #endif
  /* *INDENT-ON* */
  
  #endif /* !defined( STREAM_BUFFER_H ) */
  