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VistaIOGetAttr(3)


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>



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