NAME
XrmGetResource, XrmQGetResource, XrmQGetSearchList, XrmQGetSearchResource -
retrieve database resources and search lists
SYNTAX
#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);
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.
- 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.
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.
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 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.
SEE ALSO
XrmInitialize(3), XrmMergeDatabases(3), XrmPutResource(3), XrmUniqueQuark(3)
Xlib - C Language X Interface