XrmGetResource(3)

NAME

       XrmGetResource, XrmQGetResource, XrmQGetSearchList, XrmQGetSearchRe-
       source - retrieve database resources and search lists

SYNTAX

       Bool XrmGetResource(XrmDatabase database, char *str_name, char
              *str_class, char **str_type_return, XrmValue *value_return);

       Bool XrmQGetResource(XrmDatabase database, XrmNameList quark_name, Xrm-
              ClassList quark_class, XrmRepresentation *quark_type_return,
              XrmValue *value_return);

       typedef XrmHashTable *XrmSearchList;

              Bool XrmQGetSearchList(XrmDatabase database, XrmNameList names,
              XrmClassList classes, XrmSearchList list_return, int
              list_length);

       Bool XrmQGetSearchResource(XrmSearchList list, XrmName name, XrmClass
              class, XrmRepresentation *type_return, XrmValue *value_return);

ARGUMENTS

       class     Specifies the resource class.

       classes   Specifies a list of resource classes.

       database  Specifies the database that is to be used.

       list      Specifies the search list returned by XrmQGetSearchList.

       list_length
                 Specifies the number of entries (not the byte size) allocated
                 for list_return.

       list_return
                 Returns a search list for further use.

       name      Specifies the resource name.

       names     Specifies a list of resource names.

       quark_class
                 Specifies the fully qualified class of the value being
                 retrieved (as a quark).

       quark_name
                 Specifies the fully qualified name of the value being
                 retrieved (as a quark).

       quark_type_return
                 Returns the representation type of the destination (as a
                 quark).

       str_class Specifies the fully qualified class of the value being
                 retrieved (as a string).

       str_name  Specifies the fully qualified name of the value being
                 retrieved (as a string).

       str_type_return
                 Returns the representation type of the destination (as a
                 string).

       type_return
                 Returns data representation type.

       value_return
                 Returns the value in the database.

DESCRIPTION

       The XrmGetResource and XrmQGetResource functions retrieve a resource
       from the specified database.  Both take a fully qualified name/class
       pair, a destination resource representation, and the address of a value
       (size/address pair).  The value and returned type point into database
       memory; therefore, you must not modify the data.

       The database only frees or overwrites entries on XrmPutResource,
       XrmQPutResource, or XrmMergeDatabases.  A client that is not storing
       new values into the database or is not merging the database should be
       safe using the address passed back at any time until it exits.  If a
       resource was found, both XrmGetResource and XrmQGetResource return
       True; otherwise, they return False.

       The XrmQGetSearchList function takes a list of names and classes and
       returns a list of database levels where a match might occur.  The
       returned list is in best-to-worst order and uses the same algorithm as
       XrmGetResource for determining precedence.  If list_return was large
       enough for the search list, XrmQGetSearchList returns True; otherwise,
       it returns False.

       The size of the search list that the caller must allocate is dependent
       upon the number of levels and wildcards in the resource specifiers that
       are stored in the database.  The worst case length is %3 sup n%, where
       n is the number of name or class components in names or classes.

       When using XrmQGetSearchList followed by multiple probes for resources
       with a common name and class prefix, only the common prefix should be
       specified in the name and class list to XrmQGetSearchList.

       The XrmQGetSearchResource function searches the specified database lev-
       els for the resource that is fully identified by the specified name and
       class.  The search stops with the first match.  XrmQGetSearchResource
       returns True if the resource was found; otherwise, it returns False.

       A call to XrmQGetSearchList with a name and class list containing all
       but the last component of a resource name followed by a call to
       XrmQGetSearchResource with the last component name and class returns
       the same database entry as XrmGetResource and XrmQGetResource with the
       fully qualified name and class.

MATCHING RULES

       The algorithm for determining which resource database entry matches a
       given query is the heart of the resource manager.  All queries must
       fully specify the name and class of the desired resource (use of the
       characters ``*'' and ``?'' are not permitted).  The library supports up
       to 100 components in a full name or class.  Resources are stored in the
       database with only partially specified names and classes, using pattern
       matching constructs.  An asterisk (*) is a loose binding and is used to
       represent any number of intervening components, including none.  A
       period (.) is a tight binding and is used to separate immediately adja-
       cent components.  A question mark (?) is used to match any single com-
       ponent name or class.  A database entry cannot end in a loose binding;
       the final component (which cannot be the character ``?'') must be spec-
       ified.  The lookup algorithm searches the database for the entry that
       most closely matches (is most specific for) the full name and class
       being queried.  When more than one database entry matches the full name
       and class, precedence rules are used to select just one.

       The full name and class are scanned from left to right (from highest
       level in the hierarchy to lowest), one component at a time.  At each
       level, the corresponding component and/or binding of each matching
       entry is determined, and these matching components and bindings are
       compared according to precedence rules.  Each of the rules is applied
       at each level before moving to the next level, until a rule selects a
       single entry over all others.  The rules, in order of precedence, are:

       1.   An entry that contains a matching component (whether name, class,
            or the character ``?'')  takes precedence over entries that elide
            the level (that is, entries that match the level in a loose bind-
            ing).

       2.   An entry with a matching name takes precedence over both entries
            with a matching class and entries that match using the character
            ``?''.  An entry with a matching class takes precedence over
            entries that match using the character ``?''.

       3.   An entry preceded by a tight binding takes precedence over entries
            preceded by a loose binding.

XrmGetResource(3)

NAME

SYNTAX

ARGUMENTS

DESCRIPTION

MATCHING RULES

SEE ALSO