X Version 11 (Release 5) XrmGetResource(3X11)
NAME
XrmGetResource, XrmQGetResource, XrmQGetSearchList,
XrmQGetSearchResource - 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.
list_length
Specifies the number of entries (not the byte
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X Version 11 (Release 5) XrmGetResource(3X11)
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.
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X Version 11 (Release 5) XrmGetResource(3X11)
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 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 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 "*" 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 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.
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X Version 11 (Release 5) XrmGetResource(3X11)
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(3X11), XrmMergeDatabases(3X11),
XrmPutResource(3X11), XrmUniqueQuark(3X11)
Xlib - C Language X Interface
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