79 lines
3.0 KiB
HTML
79 lines
3.0 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<html>
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<head>
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<title>FtpSetCallback</title>
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<link rel="stylesheet" type="text/css" href="doc.css">
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</head>
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<body>
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<h1>FtpSetCallback</h1>
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<p>Establishes a callback function.</p>
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<h2>SYNOPSIS</h2>
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<pre>
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#include <ftplib.h>
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int FtpCallback(FtpCallbackOptions *opt, netbuf *nControl);
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</pre>
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<p>FtpCallbackOptions is declared as follows.</p>
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<pre>
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typedef struct FtpCallbackOptions {
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FtpCallback cbFunc; /* function to call */
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void *cbArg; /* argument to pass to function */
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unsigned int bytesXferred; /* callback if this number of bytes transferred */
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unsigned int idleTime; /* callback if this many milliseconds have elapsed */
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} FtpCallbackOptions;
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</pre>
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<h2>PARAMETERS</h2>
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<dl>
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<dt><b>opt</b></dt>
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<dd>The address of a structure that contains a pointer to the callback
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function and the criteria for calling it.</dd>
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<dt><b>nControl</b></dt>
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<dd>A handle returned by <a href="FtpConnect.html">FtpConnect()</a>
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or <a href="FtpAccess.html">FtpAccess()</a>.</dd>
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</dl>
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<h2>DESCRIPTION</h2>
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<p>FtpSetCallback() establishes a callback functions and tells FTPlib
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when to call it. A data connection inherits the options assigned to
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the control connection it is created from. Callbacks are only called
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on file data connections.</p>
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<p>The fields in FtpCallbackStruct are described below.</p>
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<dl>
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<dt>cbFunc</dt>
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<dd>Specifies the address of a user callback routine.</dd>
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<dt>cbArg</dt>
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<dd>Specifies an argument to pass to the user's callback
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routine.</dd>
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<dt>idleTime</dt>
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<dd>Specifies the socket idle time in milliseconds that triggers
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calling the user's callback routine.</dd>
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<dt>bytesXferred</dt>
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<dd>Specifies the number of bytes to transfer between calls to the
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user's callback routine.</dd>
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</dl>
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<p>The user's callback routine is specified as:</p>
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<pre>
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typedef int (*FtpCallback)(netbuf *nControl, int xfered, void *arg);
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</pre>
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<b>nControl</b> is the data connection in use. <b>xfered</b> specifies
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how many bytes of data have been transferred on the
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connection. <b>arg</b> is the value passed in the FtpCallbackOptions
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field cbArg.
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<p>The user can request to be called back on either of two
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events.</p>
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<p>If the routine should be called when the data socket is idle for
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some period of time, pass the number of milliseconds of inactivity
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that should trigger a callback in the idleTime field.</p>
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<p>If the routine should be called when a certain amount of data has
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been transferred, specify a non-zero value in bytesXferred. This
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value represents the minimum number of bytes to transfer between
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callbacks. When using this option, ftplib keeps track of the number of
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bytes transferred and calls the user once the specified number of
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bytes or more has been transferred. It then resets the count to 0 and
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starts again.</p>
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<p>If the user wishes to continue the transfer, the callback
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routine should return true (non-zero). It can abort the transfer by
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return zero.</p>
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<h2>RETURN VALUE</h2>
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<p>Returns 1 for success or 0 for failure.</p>
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</body>
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</html>
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