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<div class="title">xStreamBufferCreate</div> </div>
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<p><a class="el" href="message__buffer_8h.html">message_buffer.h</a></p>
<pre>
StreamBufferHandle_t <a class="el" href="stream__buffer_8h.html#a39aa4dd8b83e2df7ded291f863fb5fed">xStreamBufferCreate( size_t xBufferSizeBytes, size_t xTriggerLevelBytes )</a>;
</pre><p>Creates a new stream buffer using dynamically allocated memory. See <a class="el" href="stream__buffer_8h.html#a3c248575ac1b83801db605b32a118f77">xStreamBufferCreateStatic()</a> for a version that uses statically allocated memory (memory that is allocated at compile time).</p>
<p>configSUPPORT_DYNAMIC_ALLOCATION must be set to 1 or left undefined in <a class="el" href="_free_r_t_o_s_config_8h.html">FreeRTOSConfig.h</a> for <a class="el" href="stream__buffer_8h.html#a39aa4dd8b83e2df7ded291f863fb5fed">xStreamBufferCreate()</a> to be available.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">xBufferSizeBytes</td><td>The total number of bytes the stream buffer will be able to hold at any one time.</td></tr>
<tr><td class="paramname">xTriggerLevelBytes</td><td>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.</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>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.</dd></dl>
<p>Example use: </p><pre></pre><pre>void vAFunction( void )
{
StreamBufferHandle_t xStreamBuffer;
const size_t xStreamBufferSizeBytes = 100, xTriggerLevel = 10;</pre><pre> // 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 = <a class="el" href="stream__buffer_8h.html#a39aa4dd8b83e2df7ded291f863fb5fed">xStreamBufferCreate( xStreamBufferSizeBytes, xTriggerLevel )</a>;</pre><pre> 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.
}
}
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