XrmGetResource(3X11) XLIB FUNCTIONS 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
size) allocated for list_return.
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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 destina-
tion (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 destina-
tion (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 repre-
sentation, 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 XrmQGetRe-
source 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
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order and uses the same algorithm as XrmGetResource for
determining precedence. If list_return was large enough
for the search list, XrmQGetSearchList returns True; oth-
erwise, 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 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 qual-
ified 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 aster-
isk (*) 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 the character ``?'') 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 com-
ponent at a time. At each level, the corresponding
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XrmGetResource(3X11) XLIB FUNCTIONS XrmGetResource(3X11)
component and/or binding of each matching entry is deter-
mined, and these matching components and bindings are com-
pared 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 prece-
dence 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 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.
SEE ALSOXrmInitialize(3X11), XrmMergeDatabases(3X11), XrmPutRe-
source(3X11), XrmUniqueQuark(3X11)
Xlib - C Language X Interface
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