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<html><head><!- Copyright (c) Go Ahead Software Inc., 1995-2000. All Rights Reserved. -><title>ringqOpen -- basic</title><link rel="stylesheet" href="../../../style/doc.css" type="text/css"></head><body> <table width="550"> <tr><td><table border=0 width=100% cellspacing=0 cellpadding=0 CLASS="apiTitle"><tr> <td class="titleLeft" align=left width="33%"><b> ringqOpen</b></td><td class="titleCenter" align=center width="33%"><b> basic</b></td><td class="titleRight" align=right width="33%"><B> EMF</B></td></tr></table><hr><h2>Synopsis</h2><p>Create a new ring queue for dynamic strings.</p><h2>Prototype</h2><pre> #include "uemf.h" int <b>ringqOpen</b>(ringq_t *rq, int increment, int maxsize); </pre><h2>Parameters</h2><table width=100% BORDER="0" CELLPADDING="0" CELLSPACING="0"> <tr> <td width="9%">rq</td><td width="91%">Pointer to a ringq_t struct that receives the new ring queue.</td></tr> <tr> <td width="9%">increment</td><td width="91%">The amount to increase the size of the ringq should it need to grow.</td></tr> <tr> <td width="9%">maxsize</td><td width="91%">The upper limit beyond which the queue must not grow.</td></tr></table><h2>Description</h2><p> A ring queue allows maximum utilization of memory for data storage and is ideal for input/output buffering. This module provides a highly efficient implementation and a vehicle for dynamic strings. </p><p> <b>Caution</b>: This is a public implementation and callers have full access to the queue structure and pointers. Change this module very carefully. </p><p>This module follows the open/close model.</p><p>Operation of a ringq where rq is a pointer to a ringq:</p><p>rq->buflen contains the size of the buffer.<br>rq->buf will point to the start of the buffer.<br>rq->servp will point to the first (un-consumed) data byte.<br> rq->endp will point to the next free location to which new data is added.<br>rq->endbuf will point to one past the end of the buffer.</p><p> E.g.: If the ringq contains the data "abcdef", it might look like: </p><pre>+-------------------------------------------------------------------+ | | | | | | | | a | b | c | d | e | f | | | | |+-------------------------------------------------------------------+ ^ ^ ^ ^ | | | | rq->buf rq->servp rq->endp rq->enduf</pre><p> The queue is empty when servp == endp. This means that the queue will hold at most rq->buflen -1 bytes. It is the filler's responsibility to ensure that the ringq is never filled such that servp == endp. </p><p> It is the filler's 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. </p><h2>Return Value</h2><p> 0 on success, -1 on error.</p><h2>Example</h2><pre>if (ringqOpen(&p.tagbuf, XML_INC, XML_MAX) < 0) { return -1;}</pre><h2>Stability Classification</h2><p>Evolving.</p><h2></h2><h2></h2><h2>See Also</h2><p><a href="ringqPutBlk.htm">ringqPutBlk</a>,<a href="ringqPutStr.htm">ringqPutStr</a></p></td></tr></table></body></html>⌨️ 快捷键说明
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