form_fieldtype

Section: Miscellaneous Library Functions (3X)
Updated:
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NAME

form_fieldtype - define validation-field types  

SYNOPSIS

#include <form.h>
FIELDTYPE *new_fieldtype(
    bool (* const field_check)(FIELD *, const void *),
    bool (* const char_check)(int, const void *));
int free_fieldtype(FIELDTYPE *fieldtype);
int set_fieldtype_arg(
    FIELDTYPE *fieldtype,
    void *(* const make_arg)(va_list *),
    void *(* const copy_arg)(const void *),
    void  (* const free_arg)(void *));
int set_fieldtype_choice(
    FIELDTYPE *fieldtype,
    bool (* const next_choice)(FIELD *, const void *),
    bool (* const prev_choice)(FIELD *, const void *));
FIELDTYPE *link_fieldtype(FIELDTYPE *type1,
                          FIELDTYPE *type2);
 

DESCRIPTION

The function new_fieldtype creates a new field type usable for data validation. You supply it with field_check, a predicate to check the validity of an entered data string whenever the user attempts to leave a field. The (FIELD *) argument is passed in so the validation predicate can see the field's buffer, sizes and other attributes; the second argument is an argument-block structure, about which more below.

You also supply new_fieldtype with char_check, a function to validate input characters as they are entered; it will be passed the character to be checked and a pointer to an argument-block structure.

The function free_fieldtype frees the space allocated for a given validation type.

The function set_fieldtype_arg associates three storage-management functions with a field type. The make_arg function is automatically applied to the list of arguments you give set_field_type when attaching validation to a field; its job is to bundle these into an allocated argument-block object which can later be passed to validation predicated. The other two hook arguments should copy and free argument-block structures. They will be used by the forms-driver code. You must supply the make_arg function, the other two are optional, you may supply NULL for them. In this case it is assumed that make_arg does not allocate memory but simply loads the argument into a single scalar value.

The function link_fieldtype creates a new field type from the two given types. They are connected by an logical 'OR'.

The form driver requests REQ_NEXT_CHOICE and REQ_PREV_CHOICE assume that the possible values of a field form an ordered set, and provide the forms user with a way to move through the set. The set_fieldtype_choice function allows forms programmers to define successor and predecessor functions for the field type. These functions take the field pointer and an argument-block structure as arguments.  

RETURN VALUE

The pointer-valued routines return NULL on error. They set errno according to their success:
E_OK
The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_SYSTEM_ERROR
System error occurred, e.g., malloc failure.

The integer-valued routines return one of the following codes on error:

E_OK
The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_CONNECTED
The field is already connected to a form.
E_CURRENT
The field is the current field.
E_SYSTEM_ERROR
System error occurred (see errno).
 

SEE ALSO

curses(3X), form(3X).  

NOTES

The header file <form.h> automatically includes the header file <curses.h>.

All of the (char *) arguments of these functions should actually be (void *). The type has been left uncorrected for strict compatibility with System V.  

PORTABILITY

These routines emulate the System V forms library. They were not supported on Version 7 or BSD versions.  

AUTHORS

Juergen Pfeifer. Manual pages and adaptation for new curses by Eric S. Raymond.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
SEE ALSO
NOTES
PORTABILITY
AUTHORS

This document was created by using the manual pages.
Time: 23:07:20 GMT, May 09, 2009