XrmGetResource(XS) X Version 11 (Release 5) XrmGetResource(XS)
6 January 1993
Name
XrmGetResource - retrieve database resources and search lists
Syntax
Bool XrmGetResource(database, str_name, str_class, str_type_return,
value_return)
XrmDatabase database;
char *str_name;
char *str_class;
char **str_type_return;
XrmValue *value_return;
Bool XrmQGetResource(database, quark_name, quark_class, quark_type_return,
value_return)
XrmDatabase database;
XrmNameList quark_name;
XrmClassList quark_class;
XrmRepresentation *quark_type_return;
XrmValue *value_return;
typedef XrmHashTable *XrmSearchList;
Bool XrmQGetSearchList(database, names, classes, list_return, list_length)
XrmDatabase database;
XrmNameList names;
XrmClassList classes;
XrmSearchList list_return;
int list_length;
Bool XrmQGetSearchResource(list, name, class, type_return, value_return)
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.
listlength Specifies the number of entries (not the byte size) allo-
cated for listreturn.
listreturn Returns a search list for further use.
name Specifies the resource name.
names Specifies a list of resource names.
quarkclass Specifies the fully qualified class of the value being
retrieved (as a quark).
quarkname Specifies the fully qualified name of the value being
retrieved (as a quark).
quarktypereturn
Returns the representation type of the destination (as a
quark).
strclass Specifies the fully qualified class of the value being
retrieved (as a string).
strname Specifies the fully qualified name of the value being
retrieved (as a string).
strtypereturn
Returns the representation type of the destination (as a
string).
typereturn Returns data representation type.
valuereturn 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, XrmQPu-
tResource, 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 listreturn 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 3n, 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 levels
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 XrmQGetSear-
chResource with the last component name and class returns the same data-
base 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 ``*'' 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 par-
tially 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 adjacent components. A question mark
(?) is used to match any single component name or class. A database
entry cannot end in a loose binding; the final component (which cannot be
``?'') must be specified. 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
``?'') takes precedence over entries that elide the level (that is,
entries that match the level in a loose binding).
2. An entry with a matching name takes precedence over both entries with
a matching class and entries that match using ``?''. An entry with a
matching class takes precedence over entries that match using ``?''.
3. An entry preceded by a tight binding takes precedence over entries
preceded by a loose binding.
See also
XrmInitialize(XS), XrmMergeDatabases(XS), XrmPutResource(XS),
XrmUniqueQuark(XS)
Xlib - C Language X Interface