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   <H1>[fetchmail] Patch for IMAP idling where idling is unsupported
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    <B>Eric S. Raymond
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    <A HREF="mailto:esr%40thyrsus.com"
       TITLE="[fetchmail] Patch for IMAP idling where idling is unsupported">esr@thyrsus.com
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    <I>Mon, 21 Jul 2003 22:32:31 -0400</I>
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<PRE>Chris Boyle &lt;<A HREF="mailto:fetchmail-friends@cmb.is-a-geek.org">fetchmail-friends@cmb.is-a-geek.org</A>&gt;:
&gt;<i> Here's a patch I've written: where IDLE is unavailable, it uses periodic
</I>&gt;<i> NOOP commands instead (every 28 seconds). Important behavioural change:
</I>&gt;<i> the option &quot;idle&quot; will now always result in *some* form of idle. I think
</I>&gt;<i> I read somewhere that some servers will unilaterally send status updates
</I>&gt;<i> if you just hold the connection open, i.e. NOOPs would be unnecessary,
</I>&gt;<i> but that doesn't seem to be the case anywhere I've tried. In any case,
</I>&gt;<i> this patch copes with updates both as a response to the NOOPs and
</I>&gt;<i> unilaterally sent between them. It functions exactly like normal idling
</I>&gt;<i> (N.B. like normal idling, it is single-folder only), and hopefully
</I>&gt;<i> includes all the appropriate changes to the documentation. Enjoy. :-)
</I>&gt;<i> 
</I>&gt;<i> <A HREF="http://cmb.is-a-geek.org/downloads/fetchmail-6.2.2+noopidle.diff.gz">http://cmb.is-a-geek.org/downloads/fetchmail-6.2.2+noopidle.diff.gz</A>
</I>
Nice work.  This will be in 6.2.4.
-- 
		&lt;a href=&quot;<A HREF="http://www.catb.org/~esr/"">http://www.catb.org/~esr/&quot;</A>&gt;Eric S. Raymond&lt;/a&gt;

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generated by cgit v1.2.3 (git 2.39.1) at 2024-11-30 10:38:59 +0000
nction. If the namespace is used, then a user-defined pointer must be passed as an argument: @verbatim trio_printf("<my_namespace:format>\n", my_data); @endverbatim If the handle is used, then the user-defined specifier must not contain a namespace. Instead the handle must be passed as an argument, followed by a user-defined pointer: @verbatim trio_printf("<format>\n", my_handle, my_data); @endverbatim The two examples above are equivalent. There must be exactly one user-defined pointer per user-defined specifier. This pointer can be used within the callback function with the @ref trio_get_argument getter function (see below). The format string is optional. It can be used within the callback function with the @ref trio_get_format getter function. @b Anonymous @b References Anonymous references are specified by passing NULL as the namespace. The handle must be passed as an argument followed by a user-defined pointer. No namespace can be specified. @verbatim anon_handle = trio_register(callback, NULL); trio_printf("<format>\n", anon_handle, my_data); @endverbatim @b Restrictions @li The length of the namespace string cannot exceed 63 characters. @li The length of the user-defined format string cannot exceed 255 characters. @li User-defined formatting cannot re-define existing specifiers. This restriction was imposed because the existing formatting specifiers have a well-defined behaviour, and any re-definition would apply globally to an application (imagine a third-party library changing the behaviour of a specifier that is crusial to your application). @b CALLBACK @b FUNCTION The callback function will be called if a matching user-defined specifier is found within the formatting string. The callback function takes one input parameter, an opaque reference which is needed by the private functions. It returns an @c int, which is currently ignored. The prototype is @verbatim int (*trio_callback_t)(void *ref); @endverbatim See the Example section for full examples. @b PRINTING @b FUNCTIONS The following printing functions must only be used inside a callback function. These functions will print to the same output medium as the printf function which invoked the callback function. For example, if the user-defined specifier is used in an sprintf function, then these print functions will output their result to the same string. @b Elementary @b Printing There are a number of function to print elementary data types. @li @ref trio_print_int Print a signed integer. For example: @verbatim trio_print_int(42); @endverbatim @li @ref trio_print_uint Print an unsigned integer. @li @ref trio_print_double Print a floating-point number. @li @ref trio_print_string Print a string. For example: @verbatim trio_print_string("Hello World"); trio_print_string(trio_get_format()); @endverbatim @li @ref trio_print_pointer Print a pointer. @b Formatted @b Printing The functions @ref trio_print_ref, @ref trio_vprint_ref, and @ref trio_printv_ref outputs a formatted string just like its printf equivalents. @verbatim trio_print_ref(ref, "There are %d towels\n", 42); trio_print_ref(ref, "%<recursive>\n", recursive_writer, trio_get_argument()); @endverbatim @b GETTER @b AND @b SETTER @b FUNCTIONS The following getter and setter functions must only be used inside a callback function. They can either operate on the modifiers or on special data. @b Modifiers The value of a modifier, or a boolean indication of its presence or absence, can be found or set with the getter and setter functions. The generic prototypes of the these getter and setter functions are @verbatim int trio_get_???(void *ref); void trio_set_???(void *ref, int); @endverbatim where @c ??? refers to a modifier. For example, to get the width of the user-defined specifier use @verbatim int width = trio_get_width(ref); @endverbatim @b Special @b Data Consider the following user-defined specifier, in its two possible referencing presentations. @verbatim trio_printf("%<format>\n", namespace_writer, argument); trio_printf("%<namespace:format>\n", argument); @endverbatim @ref trio_get_format will get the @p format string, and @ref trio_get_argument} will get the @p argument parameter. There are no associated setter functions. @b EXAMPLES The following examples show various types of user-defined specifiers. Although each specifier is demonstrated in isolation, they can all co-exist within the same application. @b Time @b Example Print the time in the format "HOUR:MINUTE:SECOND" if "time" is specified inside the user-defined specifier. @verbatim static int time_writer(void *ref) { const char *format; time_t *data; char buffer[256]; format = trio_get_format(ref); if ((format) && (strcmp(format, "time") == 0)) { data = trio_get_argument(ref); if (data == NULL) return -1; strftime(buffer, sizeof(buffer), "%H:%M:%S", localtime(data)); trio_print_string(ref, buffer); } return 0; } @endverbatim @verbatim int main(void) { void *handle; time_t now = time(NULL); handle = trio_register(time_print, "my_time"); trio_printf("%<time>\n", handle, &now); trio_printf("%<my_time:time>\n", &now); trio_unregister(handle); return 0; } @endverbatim @b Complex @b Numbers @b Example Consider a complex number consisting of a real part, re, and an imaginary part, im. @verbatim struct Complex { double re; double im; }; @endverbatim This example can print such a complex number in one of two formats. The default format is "re + i im". If the alternative modifier is used, then the format is "r exp(i theta)", where r is the length of the complex vector (re, im) and theta is its angle. @verbatim static int complex_print(void *ref) { struct Complex *data; const char *format; data = (struct Complex *)trio_get_argument(ref); if (data) { format = trio_get_format(ref); if (trio_get_alternative(ref)) { double r, theta; r = sqrt(pow(data->re, 2) + pow(data->im, 2)); theta = acos(data->re / r); trio_print_ref(ref, "%#f exp(i %#f)", r, theta); } else { trio_print_ref(ref, "%#f + i %#f", data->re, data->im); } } return 0; } @endverbatim @verbatim int main(void) { void *handle; handle = trio_register(complex_print, "complex"); /* Normal format. With handle and the with namespace */ trio_printf("%<>\n", handle, &complex); trio_printf("%<complex:>\n", &complex); /* In exponential notation */ trio_printf("%#<>\n", handle, &complex); trio_printf("%#<complex:unused data>\n", &complex); trio_unregister(handle); return 0; } @endverbatim @b RETURN @b VALUES @ref trio_register returns a handle, or NULL if an error occured. @b SEE @b ALSO @ref trio_printf @b NOTES User-defined specifiers, @ref trio_register, and @ref trio_unregister are not thread-safe. In multi-threaded applications they must be guarded by mutexes. Trio provides two special callback functions, called ":enter" and ":leave", which are invoked every time a thread-unsafe operation is attempted. As the thread model is determined by the application, these callback functions must be implemented by the application. The following callback functions are for demonstration-purposes only. Replace their bodies with locking and unlocking of a mutex to achieve thread-safety. @verbatim static int enter_region(void *ref) { fprintf(stderr, "Enter Region\n"); return 1; } static int leave_region(void *ref) { fprintf(stderr, "Leave Region\n"); return 1; } @endverbatim These two callbacks must be registered before other callbacks are registered. @verbatim trio_register(enter_region, ":enter"); trio_register(leave_region, ":leave"); another_handle = trio_register(another_callback, NULL); @endverbatim */
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