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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<a class="qindex" href="index.html">Main Page</a> <a class="qindex" href="modules.html">Modules</a> </center>
<hr><h1>User-defined Formatted Printing Functions.</h1>Functions for using customized formatting specifiers.
<a href="#_details">More...</a><table border=0 cellpadding=0 cellspacing=0>
<tr><td colspan=2><br><h2>Functions</h2></td></tr>
<tr><td nowrap align=right valign=top>trio_pointer_t </td><td valign=bottom><a class="el" href="group___user_defined.html#a0">trio_register</a> (trio_callback_t callback, const char *name)</td></tr>
<tr><td> </td><td><font size=-1><em>Register new user-defined specifier.</em> <a href="#a0">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>void </td><td valign=bottom><a class="el" href="group___user_defined.html#a1">trio_unregister</a> (trio_pointer_t handle)</td></tr>
<tr><td> </td><td><font size=-1><em>Unregister an existing user-defined specifier.</em> <a href="#a1">More...</a><em></em></font><br><br></td></tr>
</table>
<hr><a name="_details"></a><h2>Detailed Description</h2>
Functions for using customized formatting specifiers.
<p>
<b>SYNOPSIS</b>
<p>
<div class="fragment"><pre>
cc ... -ltrio -lm
#include <trio.h>
#include <triop.h>
</pre></div>
<p>
<b>DESCRIPTION</b>
<p>
This documentation is incomplete.
<p>
<b>User-defined</b> <b>Specifier</b>
<p>
The user-defined specifier consists of a start character (\074 = '<'), an optional namespace string followed by a namespace separator (\072 = ':'), a format string, and an end character (\076 = '>').
<p>
The namespace string can consist of alphanumeric characters, and is used to define a named reference (see below). The namespace is case-sensitive. If no namespace is specified, then we use an unnamed reference (see below).
<p>
The format can consist of any character except the end character ('>'), the namespace separator (':'), and the nil character (\000).
<p>
Any modifier can be used together with the user-defined specifier.
<p>
<b>Registering</b>
<p>
A user-defined specifier must be registered before it can be used. Unregistered user-defined specifiers are ignored. The <a class="el" href="group___user_defined.html#a0">trio_register</a> function is used to register a user-defined specifier. It takes two argument, a callback function and a namespace, and it returns a handle. The handle must be used to unregister the specifier later.
<p>
The following example registers a user-define specifier with the "my_namespace" namespace:
<p>
<div class="fragment"><pre>
my_handle = trio_register(my_callback, "my_namespace");
</pre></div>
<p>
There can only be one user-defined specifier with a given namespace. There can be an unlimited number (subject to maximum length of the namespace) of different user-defined specifiers.
<p>
Passing NULL as the namespace argument results in an anonymous reference. There can be an unlimited number of anonymous references.
<p>
<b>REFERENCES</b>
<p>
There are two ways that a registered callback can be called. Either the user-defined specifier must contain the registered namespace in the format string, or the handle is passed as an argument to the formatted printing function.
<p>
If the namespace is used, then a user-defined pointer must be passed as an argument:
<p>
<div class="fragment"><pre>
trio_printf("<my_namespace:format>\n", my_data);
</pre></div>
<p>
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:
<p>
<div class="fragment"><pre>
trio_printf("<format>\n", my_handle, my_data);
</pre></div>
<p>
The two examples above are equivalent.
<p>
There must be exactly one user-defined pointer per user-defined specifier. This pointer can be used within the callback function with the trio_get_argument getter function (see below).
<p>
The format string is optional. It can be used within the callback function with the trio_get_format getter function.
<p>
<b>Anonymous</b> <b>References</b> Anonymous references are specified by passing NULL as the namespace.
<p>
The handle must be passed as an argument followed by a user-defined pointer. No namespace can be specified.
<p>
<div class="fragment"><pre>
anon_handle = trio_register(callback, NULL);
trio_printf("<format>\n", anon_handle, my_data);
</pre></div>
<p>
<b>Restrictions</b>
<p>
<ul>
<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).</ul>
<b>CALLBACK</b> <b>FUNCTION</b>
<p>
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 <code>int</code>, which is currently ignored. The prototype is
<p>
<div class="fragment"><pre>
int (*trio_callback_t)(void *ref);
</pre></div>
<p>
See the Example section for full examples.
<p>
<b>PRINTING</b> <b>FUNCTIONS</b>
<p>
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.
<p>
<b>Elementary</b> <b>Printing</b>
<p>
There are a number of function to print elementary data types.
<p>
<ul>
<li> trio_print_int Print a signed integer. For example: <div class="fragment"><pre>
trio_print_int(42);
</pre></div> <li> trio_print_uint Print an unsigned integer. <li> trio_print_double Print a floating-point number. <li> trio_print_string Print a string. For example: <div class="fragment"><pre>
trio_print_string("Hello World");
trio_print_string(trio_get_format());
</pre></div> <li> trio_print_pointer Print a pointer.</ul>
<b>Formatted</b> <b>Printing</b>
<p>
The functions trio_print_ref, trio_vprint_ref, and trio_printv_ref outputs a formatted string just like its printf equivalents.
<p>
<div class="fragment"><pre>
trio_print_ref(ref, "There are %d towels\n", 42);
trio_print_ref(ref, "%<recursive>\n", recursive_writer, trio_get_argument());
</pre></div>
<p>
<b>GETTER</b> <b>AND</b> <b>SETTER</b> <b>FUNCTIONS</b>
<p>
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.
<p>
<b>Modifiers</b>
<p>
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
<p>
<div class="fragment"><pre>
int trio_get_???(void *ref);
void trio_set_???(void *ref, int);
</pre></div>
<p>
where ??? <code>refers</code> to a modifier. For example, to get the width of the user-defined specifier use
<p>
<div class="fragment"><pre>
int width = trio_get_width(ref);
</pre></div>
<p>
<b>Special</b> <b>Data</b>
<p>
Consider the following user-defined specifier, in its two possible referencing presentations.
<p>
<div class="fragment"><pre>
trio_printf("%<format>\n", namespace_writer, argument);
trio_printf("%<namespace:format>\n", argument);
</pre></div>
<p>
trio_get_format will get the <code>format</code> string, and trio_get_argument} will get the <code>argument</code> parameter. There are no associated setter functions.
<p>
<b>EXAMPLES</b>
<p>
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.
<p>
<b>Time</b> <b>Example</b>
<p>
Print the time in the format "HOUR:MINUTE:SECOND" if "time" is specified inside the user-defined specifier.
<p>
<div class="fragment"><pre>
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;
}
</pre></div>
<p>
<div class="fragment"><pre>
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;
}
</pre></div>
<p>
<b>Complex</b> <b>Numbers</b> <b>Example</b>
<p>
Consider a complex number consisting of a real part, re, and an imaginary part, im.
<p>
<div class="fragment"><pre>
struct Complex {
double re;
double im;
};
</pre></div>
<p>
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.
<p>
<div class="fragment"><pre>
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;
}
</pre></div>
<p>
<div class="fragment"><pre>
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;
}
</pre></div>
<p>
<b>RETURN</b> <b>VALUES</b>
<p>
<a class="el" href="group___user_defined.html#a0">trio_register</a> returns a handle, or NULL if an error occured.
<p>
<b>SEE</b> <b>ALSO</b>
<p>
<a class="el" href="group___printf.html#a0">trio_printf</a>
<p>
<b>NOTES</b>
<p>
User-defined specifiers, <a class="el" href="group___user_defined.html#a0">trio_register</a>, and <a class="el" href="group___user_defined.html#a1">trio_unregister</a> 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.
<p>
The following callback functions are for demonstration-purposes only. Replace their bodies with locking and unlocking of a mutex to achieve thread-safety. <div class="fragment"><pre>
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;
}
</pre></div> These two callbacks must be registered before other callbacks are registered. <div class="fragment"><pre>
trio_register(enter_region, ":enter");
trio_register(leave_region, ":leave");
another_handle = trio_register(another_callback, NULL);
</pre></div> <hr><h2>Function Documentation</h2>
<a name="a0" doxytag="trio.c::trio_register"></a><p>
<table width="100%" cellpadding="2" cellspacing="0" border="0">
<tr>
<td class="md">
<table cellpadding="0" cellspacing="0" border="0">
<tr>
<td class="md" nowrap valign="top"> trio_pointer_t trio_register </td>
<td class="md" valign="top">( </td>
<td class="md" nowrap valign="top">trio_callback_t </td>
<td class="mdname" nowrap> <em>callback</em>, </td>
</tr>
<tr>
<td></td>
<td></td>
<td class="md" nowrap>const char * </td>
<td class="mdname" nowrap> <em>name</em></td>
</tr>
<tr>
<td></td>
<td class="md">) </td>
<td class="md" colspan="2"></td>
</tr>
</table>
</td>
</tr>
</table>
<table cellspacing=5 cellpadding=0 border=0>
<tr>
<td>
</td>
<td>
<p>
Register new user-defined specifier.
<p>
<dl compact><dt><b>
Parameters: </b><dd>
<table border=0 cellspacing=2 cellpadding=0>
<tr><td valign=top><em>callback</em> </td><td>
</td></tr>
<tr><td valign=top><em>name</em> </td><td>
</td></tr>
</table>
</dl><dl compact><dt><b>
Returns: </b><dd>
Handle. </dl> </td>
</tr>
</table>
<a name="a1" doxytag="trio.c::trio_unregister"></a><p>
<table width="100%" cellpadding="2" cellspacing="0" border="0">
<tr>
<td class="md">
<table cellpadding="0" cellspacing="0" border="0">
<tr>
<td class="md" nowrap valign="top"> void trio_unregister </td>
<td class="md" valign="top">( </td>
<td class="md" nowrap valign="top">trio_pointer_t </td>
<td class="mdname1" valign="top" nowrap> <em>handle</em> </td>
<td class="md" valign="top">) </td>
<td class="md" nowrap></td>
</tr>
</table>
</td>
</tr>
</table>
<table cellspacing=5 cellpadding=0 border=0>
<tr>
<td>
</td>
<td>
<p>
Unregister an existing user-defined specifier.
<p>
<dl compact><dt><b>
Parameters: </b><dd>
<table border=0 cellspacing=2 cellpadding=0>
<tr><td valign=top><em>handle</em> </td><td>
</td></tr>
</table>
</dl> </td>
</tr>
</table>
<HR>
<center class="copyright">Copyright (C) 2001 Bjørn Reese and Daniel Stenberg.</center>
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