xStreamBufferCreateStatic macro

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. Example use:

{c}
 // 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.
 }
 

Syntax

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Summary

Declaration

from stream_buffer.h:247

#define xStreamBufferCreateStatic( xBufferSizeBytes, xTriggerLevelBytes, pucStreamBufferStorageArea, pxStaticStreamBuffer ) \ xStreamBufferGenericCreateStatic( ( xBufferSizeBytes ), ( xTriggerLevelBytes ), pdFALSE, ( pucStreamBufferStorageArea ), ( pxStaticStreamBuffer ), NULL, NULL )

Arguments

Argument

Description

xBufferSizeBytes

The size, in bytes, of the buffer pointed to by the pucStreamBufferStorageArea parameter.

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.

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.

pxStaticStreamBuffer

Must point to a variable of type StaticStreamBuffer_t, which will be used to hold the stream buffer's data structure.

Return value

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.

References

Code

Location

#define xStreamBufferCreateStatic( xBufferSizeBytes, xTriggerLevelBytes, pucStreamBufferStorageArea, pxStaticStreamBuffer ) \

stream_buffer.h:247

xStreamBuffer = xStreamBufferCreateStatic( xBufferSizeBytes, xTriggerLevelBytes, pucStreamBufferStorageArea, pxStaticStreamBuffer );

idf_additions.c:364

xStreamBufferCreateStatic macro

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