From 13c27199231cbc2cc83969ada741b95be1cca4d3 Mon Sep 17 00:00:00 2001 From: Matthias Andree Date: Wed, 10 Nov 2004 19:04:29 +0000 Subject: Import Trio 1.10 into fetchmail's trunk. svn path=/trunk/; revision=3995 --- trio/html/group___user_defined.html | 379 ++++++++++++++++++++++++++++++++++++ 1 file changed, 379 insertions(+) create mode 100644 trio/html/group___user_defined.html (limited to 'trio/html/group___user_defined.html') diff --git a/trio/html/group___user_defined.html b/trio/html/group___user_defined.html new file mode 100644 index 00000000..b2507275 --- /dev/null +++ b/trio/html/group___user_defined.html @@ -0,0 +1,379 @@ + + + + + TRIO + + + + + +Main Page Modules +

User-defined Formatted Printing Functions.

Functions for using customized formatting specifiers. +More... + + + + + +

Functions
trio_pointer_t	trio_register (trio_callback_t callback, const char *name)
	Register new user-defined specifier. More...
void	trio_unregister (trio_pointer_t handle)
	Unregister an existing user-defined specifier. More...

Detailed Description

+Functions for using customized formatting specifiers. +

+SYNOPSIS +

+cc ... -ltrio -lm
+
+#include <trio.h>
+#include <triop.h>
+

+DESCRIPTION +

+This documentation is incomplete. +

+User-defined Specifier +

+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 = '>'). +

+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). +

+The format can consist of any character except the end character ('>'), the namespace separator (':'), and the nil character (\000). +

+Any modifier can be used together with the user-defined specifier. +

+Registering +

+A user-defined specifier must be registered before it can be used. Unregistered user-defined specifiers are ignored. The trio_register 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. +

+The following example registers a user-define specifier with the "my_namespace" namespace: +

+  my_handle = trio_register(my_callback, "my_namespace");
+

+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. +

+Passing NULL as the namespace argument results in an anonymous reference. There can be an unlimited number of anonymous references. +

+REFERENCES +

+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. +

+If the namespace is used, then a user-defined pointer must be passed as an argument: +

+  trio_printf("<my_namespace:format>\n", my_data);
+

+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: +

+  trio_printf("<format>\n", my_handle, my_data);
+

+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 trio_get_argument getter function (see below). +

+The format string is optional. It can be used within the callback function with the trio_get_format getter function. +

+Anonymous 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. +

+  anon_handle = trio_register(callback, NULL);
+  trio_printf("<format>\n", anon_handle, my_data);
+

+Restrictions +

The length of the namespace string cannot exceed 63 characters.
The length of the user-defined format string cannot exceed 255 characters.
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).

+CALLBACK 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 int, which is currently ignored. The prototype is +

+  int (*trio_callback_t)(void *ref);
+

+See the Example section for full examples. +

+PRINTING 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. +

+Elementary Printing +

+There are a number of function to print elementary data types. +

trio_print_int Print a signed integer. For example:
```
+  trio_print_int(42);
+
```
trio_print_uint Print an unsigned integer.
trio_print_double Print a floating-point number.

trio_print_string Print a string. For example:

+  trio_print_string("Hello World");
+  trio_print_string(trio_get_format());
+

trio_print_pointer Print a pointer.

+Formatted Printing +

+The functions trio_print_ref, trio_vprint_ref, and trio_printv_ref outputs a formatted string just like its printf equivalents. +

+  trio_print_ref(ref, "There are %d towels\n", 42);
+  trio_print_ref(ref, "%<recursive>\n", recursive_writer, trio_get_argument());
+

+GETTER AND SETTER 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. +

+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 +

+  int  trio_get_???(void *ref);
+  void trio_set_???(void *ref, int);
+

+where ??? refers to a modifier. For example, to get the width of the user-defined specifier use +

+  int width = trio_get_width(ref);
+

+Special Data +

+Consider the following user-defined specifier, in its two possible referencing presentations. +

+  trio_printf("%<format>\n", namespace_writer, argument);
+  trio_printf("%<namespace:format>\n", argument);
+

+trio_get_format will get the format string, and trio_get_argument} will get the argument parameter. There are no associated setter functions. +

+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. +

+Time Example +

+Print the time in the format "HOUR:MINUTE:SECOND" if "time" is specified inside the user-defined specifier. +

+  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;
+  }
+

+  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;
+  }
+

+Complex Numbers Example +

+Consider a complex number consisting of a real part, re, and an imaginary part, im. +

+  struct Complex {
+    double re;
+    double im;
+  };
+

+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. +

+  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;
+  }
+

+  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;
+  }
+

+RETURN VALUES +

+trio_register returns a handle, or NULL if an error occured. +

+SEE ALSO +

+trio_printf +

+NOTES +

+User-defined specifiers, trio_register, and 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.

+  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;
+  }
+

These two callbacks must be registered before other callbacks are registered.

+  trio_register(enter_region, ":enter");
+  trio_register(leave_region, ":leave");
+
+  another_handle = trio_register(another_callback, NULL);
+

Function Documentation

+ + + + +
+ + + + + + + + + + + + + + + + + + + +
trio_pointer_t trio_register ( trio_callback_t callback,
const char * name
)
+
+ + + + + +
+ + + +
+Register new user-defined specifier. +
+
+Parameters:
+ + + +
callback +
name +
+
+Returns:
+Handle.

+

+ + + + +
+ + + + + + + + + + +
void trio_unregister ( trio_pointer_t handle )
+
+ + + + + +
+ + + +
+Unregister an existing user-defined specifier. +
+
+Parameters:
+ + +
handle +
+

+