form_fieldtype - define validation-field types

NAME  SYNOPSIS  DESCRIPTION  new_fieldtype  free_fieldtype  set_fieldtype_arg  set_fieldtype_choice  link_fieldtype  RETURN VALUE  PORTABILITY  AUTHORS  SEE ALSO 

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

new_fieldtype

The function new_fieldtype creates a new field type usable for data validation. Its parameters are function pointers:
field_check

This function checks the validity of an entered data string whenever the user attempts to leave a field. It has two arguments:

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.

char_check

This function validates input characters as they are entered. The form library passes it the character to be checked and a pointer to an argument-block structure.

free_fieldtype

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

set_fieldtype_arg

The function set_fieldtype_arg associates three storage-management functions with a field type:
make_arg

This function is automatically applied to the list of arguments you give set_field_type when attaching validation to a field. It stores the arguments in an allocated argument-block object which is used when validating input.

copy_arg

This function may be used by applications to copy argument-blocks.

free_arg

Frees an argument-block structure.

You must supply the make_arg function. The other two are optional: you may supply NULL for them. In this case, the form library assumes that make_arg does not allocate memory but simply loads the argument into a single scalar value.

set_fieldtype_choice

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.

link_fieldtype

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

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(3)).

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.

SEE ALSO

curses(3X), form(3X), form_field_validation(3X)


Updated 2024-01-29 - jenkler.se | uex.se