NAME

XrmGetResource, XrmQGetResource, XrmQGetSearchList, XrmQGetSearchResource - retrieve database resources and search lists

SYNTAX

Bool XrmGetResource(XrmDatabase _d_a_t_a_b_a_s_e, char *_s_t_r___n_a_m_e, char *_s_t_r___c_l_a_s_s, char **_s_t_r___t_y_p_e___r_e_t_u_r_n, XrmValue *_v_a_l_u_e___r_e_t_u_r_n); Bool XrmQGetResource(XrmDatabase _d_a_t_a_b_a_s_e, XrmNameList _q_u_a_r_k___n_a_m_e, XrmClassList _q_u_a_r_k___c_l_a_s_s, XrmRepresentation *_q_u_a_r_k___t_y_p_e___r_e_t_u_r_n, XrmValue *_v_a_l_u_e___r_e_t_u_r_n); typedef XrmHashTable *XrmSearchList;

Bool XrmQGetSearchList(XrmDatabase _d_a_t_a_b_a_s_e, XrmNameList _n_a_m_e_s, XrmClassList _c_l_a_s_s_e_s, XrmSearchList _l_i_s_t___r_e_t_u_r_n, int _l_i_s_t___l_e_n_g_t_h); Bool XrmQGetSearchResource(XrmSearchList _l_i_s_t, XrmName _n_a_m_e, XrmClass _c_l_a_s_s, XrmRepresentation *_t_y_p_e___r_e_t_u_r_n, XrmValue *_v_a_l_u_e___r_e_t_u_r_n);

ARGUMENTS

_c_l_a_s_s Specifies the resource class.
_c_l_a_s_s_e_s Specifies a list of resource classes.
_d_a_t_a_b_a_s_e Specifies the database that is to be used.
_l_i_s_t Specifies the search list returned by
_X_r_m_Q_G_e_t_S_e_a_r_c_h_L_i_s_t.
_l_i_s_t___l_e_n_g_t_h Specifies the number of entries (not the byte size) allocated for list_return.
_l_i_s_t___r_e_t_u_r_n Returns a search list for further use.
_n_a_m_e Specifies the resource name.
_n_a_m_e_s Specifies a list of resource names.
_q_u_a_r_k___c_l_a_s_s Specifies the fully qualified class of the value being retrieved (as a quark).
_q_u_a_r_k___n_a_m_e Specifies the fully qualified name of the value being retrieved (as a quark).
_q_u_a_r_k___t_y_p_e___r_e_t_u_r_n Returns the representation type of the destination (as a quark).
_s_t_r___c_l_a_s_s Specifies the fully qualified class of the value being retrieved (as a string).
_s_t_r___n_a_m_e Specifies the fully qualified name of the value being retrieved (as a string).
_s_t_r___t_y_p_e___r_e_t_u_r_n Returns the representation type of the destination (as a string).
_t_y_p_e___r_e_t_u_r_n Returns data representation type.
_v_a_l_u_e___r_e_t_u_r_n Returns the value in the database.

DESCRIPTION

The _X_r_m_G_e_t_R_e_s_o_u_r_c_e and _X_r_m_Q_G_e_t_R_e_s_o_u_r_c_e 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 _X_r_m_P_u_t_R_e_s_o_u_r_c_e, _X_r_m_Q_P_u_t_R_e_s_o_u_r_c_e, or _X_r_m_M_e_r_g_e_D_a_t_a_b_a_s_e_s. 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 _X_r_m_G_e_t_R_e_s_o_u_r_c_e and _X_r_m_Q_G_e_t_R_e_s_o_u_r_c_e return _T_r_u_e; otherwise, they return _F_a_l_s_e.

The _X_r_m_Q_G_e_t_S_e_a_r_c_h_L_i_s_t 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 _X_r_m_G_e_t_R_e_s_o_u_r_c_e for determining precedence. If list_return was large enough for the search list, _X_r_m_Q_G_e_t_S_e_a_r_c_h_L_i_s_t returns _T_r_u_e; otherwise, it returns _F_a_l_s_e.

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 _X_r_m_Q_G_e_t_S_e_a_r_c_h_L_i_s_t 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 _X_r_m_Q_G_e_t_S_e_a_r_c_h_L_i_s_t.

The _X_r_m_Q_G_e_t_S_e_a_r_c_h_R_e_s_o_u_r_c_e 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. _X_r_m_Q_G_e_t_S_e_a_r_c_h_R_e_s_o_u_r_c_e returns _T_r_u_e if the resource was found; otherwise, it returns _F_a_l_s_e.

A call to _X_r_m_Q_G_e_t_S_e_a_r_c_h_L_i_s_t with a name and class list containing all but the last component of a resource name followed by a call to _X_r_m_Q_G_e_t_S_e_a_r_c_h_R_e_s_o_u_r_c_e with the last component name and class returns the same database entry as _X_r_m_G_e_t_R_e_s_o_u_r_c_e and _X_r_m_Q_G_e_t_R_e_s_o_u_r_c_e 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(3X11), XrmMergeDatabases(3X11), XrmPutResource(3X11), XrmUniqueQuark(3X11)
_X_l_i_b _- _C _L_a_n_g_u_a_g_e _X _I_n_t_e_r_f_a_c_e