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.
