XrmGetResource, XrmQGetResource, XrmQGetSearchList, XrmQGetSearchResource -
retrieve database resources and search lists
#include <X11/Xresource.h>
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, XrmNameList
names, XrmClassList classes, XrmSearchList list_return,
int list_length);
Bool XrmQGetSearchResource(XrmSearchList list, XrmName
name, XrmClass class, XrmRepresentation *type_return,
XrmValue *value_return);
- 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.
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 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.
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 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 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 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.
XrmInitialize(3), XrmMergeDatabases(3), XrmPutResource(3), XrmUniqueQuark(3)
Xlib - C Language X Interface