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>