XrmGetResource(3X11) XLIB FUNCTIONS XrmGetResource(3X11)
NAME
XrmGetResource, XrmQGetResource, XrmQGetSearchList, XrmQGet-
SearchResource - 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, XrmClassList quark_class, XrmRepresentation
*quark_type_return, XrmValue *value_return);
typedef XrmHashTable *XrmSearchList;
Bool XrmQGetSearchList(XrmDatabase database, XrmNameL-
ist 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 XrmQGetSear-
chList.
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).
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XrmGetResource(3X11) XLIB FUNCTIONS XrmGetResource(3X11)
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 represen-
tation, and the address of a value (size/address pair). The
value and returned type point into database memory; there-
fore, you must not modify the data.
The database only frees or overwrites entries on XrmPu-
tResource, 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; other-
wise, 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
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XrmGetResource(3X11) XLIB FUNCTIONS XrmGetResource(3X11)
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 con-
taining all but the last component of a resource name fol-
lowed by a call to XrmQGetSearchResource with the last com-
ponent 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 pat-
tern matching constructs. An asterisk (*) is a loose binding
and is used to represent any number of intervening com-
ponents, including none. A period (.) is a tight binding and
is used to separate immediately adjacent components. A ques-
tion 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 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 sin-
gle entry over all others. The rules, in order of pre-
cedence, 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 binding).
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XrmGetResource(3X11) XLIB FUNCTIONS XrmGetResource(3X11)
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 match-
ing 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 ALSO
XrmInitialize(3X11), XrmMergeDatabases(3X11),
XrmPutResource(3X11), XrmUniqueQuark(3X11)
Xlib - C Language X Interface
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