📄 ringqopen.htm
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<title>ringqOpen -- basic</title>
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<td class=title-left><b> ringqOpen</b></td>
<td class=title-center><b> basic</b></td>
<td class=title-right><B> EMF</B></td>
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<h2>Synopsis</h2>
<p>Create a new ring queue for dynamic strings</p>
<h2>Prototype</h2>
<pre>
int <b>ringqOpen</b>(ringq_t *rq, int increment, int maxsize);
</pre>
<h2>Parameters</h2>
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<td width=40>rq</td>
<td>Pointer to a ringq_t struct that receives the new ring queue</td>
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<td width=40>increment</td>
<td>The amount to increase the size of the ringq should it need to grow</td>
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<td width=40>maxsize</td>
<td>The upper limit beyond which the queue must not grow</td>
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<h2>Description</h2>
<p><pre>
A ring queue allows maximum utilization of memory for data storage and is
ideal for input/output buffering. This module provides a highly effecient
implementation and a vehicle for dynamic strings.
WARNING: This is a public implementation and callers have full access to
the queue structure and pointers. Change this module very carefully.
This module follows the open/close model.
Operation of a ringq where rq is a pointer to a ringq :
rq->buflen contains the size of the buffer.
rq->buf will point to the start of the buffer.
rq->servp will point to the first (un-consumed) data byte.
rq->endp will point to the next free location to which new data is added
rq->endbuf will point to one past the end of the buffer.
Eg. If the ringq contains the data "abcdef", it might look like :
+-------------------------------------------------------------------+
| | | | | | | | a | b | c | d | e | f | | | | |
+-------------------------------------------------------------------+
^ ^ ^ ^
| | | |
rq->buf rq->servp rq->endp rq->enduf
The queue is empty when servp == endp. This means that the queue will hold
at most rq->buflen -1 bytes. It is the fillers responsibility to ensure
the ringq is never filled such that servp == endp.
It is the fillers responsibility to "wrap" the endp back to point to
rq->buf when the pointer steps past the end. Correspondingly it is the
consumers responsibility to "wrap" the servp when it steps to rq->endbuf.
The ringqPutc and ringqGetc routines will do this automatically.
</pre></p>
<h2>Return Value</h2>
<p>
0 on success, -1 on error.
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<h2>Example</h2>
<pre>
</pre>
<h2>See Also</h2>
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<a href="ringqPutBlk.htm">ringqPutBlk</a>,
<a href="ringqPutStr.htm">ringqPutStr</a>,
<a href="ringqPutc.htm">ringqPutc</a>
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