NAME¶
VistaIOGetAttr, VistaIOGetAttrValue - fetch an attribute's value
SYNOPSIS¶
VistaIOGetAttrResult VistaIOGetAttr ( list, name, dict, repn, value)
VistaIOAttrList list;
VistaIOStringConst name;
VistaIODictEntry * dict;
VistaIORepnKind repn;
VistaIOPointer value;
typedef enum { VistaIOAttrFound, VistaIOAttrMissing, VistaIOAttrBadValue } VistaIOGetAttrResult;
VistaIOBoolean VistaIOGetAttrValue ( posn, dict, repn, value)
VistaIOAttrListPosn * posn;
VistaIODictEntry * dict;
VistaIORepnKind repn;
VistaIOPointer value;
ARGUMENTS¶
- list
- Specifies the list of attributes to be searched by name for the desired
attribute.
- name
- Specifies the name of the desired attribute.
- posn
- Specifies the position of the desired attribute within its attribute
list.
- dict
- May specify a dictionary to be used in recognizing a keyword stored as the
attribute's value, or it may be NULL
- repn
- Specifies the representation in which the attribute value is to be
returned.
- value
- Specifies a location at which the attribute value is be returned.
DESCRIPTION¶
These routines both return an attribute's value, but they differ in how the
attribute is identified:
- •
- VistaIOGetAttr fetches the value of the first attribute with the
name name in the list list.
- •
- VistaIOGetAttrValue fetches the value of the attribute whose
position within an attribute list is posn.
If a dictionary,
dict, has been provided and the attribute's value is
stored as a character string, the routine determines whether the string is a
keyword defined in the dictionary. If so, it uses the value associated with
that keyword rather than the attribute's original value. (See the
VistaIOdictionary(3) manual page.)
The value obtained directly from the attribute, or indirectly via the
dictionary, is converted to the representation
repn and then stored at
the location pointed to by
value. The
repn argument may have any
VistaIORepnKind value (any of the values returned by
VistaIORegisterType(3). However, an attribute value that is a string
can only be returned as a string or a number, and other attribute values can
only be returned in the representation with which they are stored. (The
VistaIOGetAttrRepn(3) macro can be used to determine an attribute
value's representation.)
If
repn calls for a number to be returned, the caller receives a copy of
the value stored with the attribute. If, on the other hand, it calls for a
string, attribute list, pointer, image, edge set, etc. to be returned, the
caller receives a pointer to the same value as that stored with the attribute.
RETURN VALUES¶
If the specified attribute is not found,
VistaIOGetAttr returns
VistaIOAttrMissing. If it is found but its value cannot be converted to
the desired representation,
VistaIOGetAttr returns
VistaIOAttrBadValue. Otherwise,
VistaIOGetAttr is successful and
it returns
VistaIOAttrFound, having stored the attribute's value at *
value.
VistaIOGetAttrValue returns
TRUE if it is
successfully returning the attribute's value at *
value, and
FALSE if the value cannot be converted to the desired
representation.
EXAMPLES¶
The following code fragment prints the name of an image:
VistaIOImage image;
VistaIOStringConst name;
if (VistaIOGetAttr (VistaIOImageAttrList (image), VistaIONameAttr, NULL,
VistaIOStringRepn, (VistaIOPointer) & name) == VistaIOAttrFound)
printf ("Name: %s\n", name);
SEE ALSO¶
VistaIOExtractAttr(3),
VistaIOSetAttr(3),
VistaIOSetAttrValue(3),
VistaIOattribute(3),
VistaIOdictionary(3),
NOTES¶
VistaIOGetAttr is meant for use with attribute lists representing sets,
in which each attribute name occurs at most once. If
list contains
multiple attributes named
name, only the first is located and returned.
The
value argument must point to sufficient storage to contain a value of
the representation requested. Neither the routine nor the C compiler can
automatically check that this is so.
AUTHOR¶
Art Pope <pope@cs.ubc.ca>
Adaption to vistaio: Gert Wollny <gw.fossdev@gmail.com>