m4_comment([$Id: db_set_bt_compare.so,v 10.50 2006/10/26 20:59:24 bostic Exp $])

define(M4PAGELOCAL, dbh_set_bt_compare)
include(m4/m4.seealso)

m4_pf_header(m4_ref(dbh_set_bt_compare),
ifelse(M4API, C_API, [dnl
int
DB-__GT__set_bt_compare(DB *db,
    int (*bt_compare_fcn)(DB *db, const DBT *dbt1, const DBT *dbt2));
])
ifelse(M4API, CXX_API, [dnl
extern "C" {
    typedef int (*bt_compare_fcn_type)(DB *db, const DBT *dbt1, const DBT *dbt2);
};
int
Db::set_bt_compare(bt_compare_fcn_type bt_compare_fcn);
]))

m4_p([dnl
Set the Btree key comparison function.  The comparison function is
called whenever it is necessary to compare a key specified by the
application with a key currently stored in the tree.])

m4_p([dnl
If no comparison function is specified, the keys are compared lexically,
with shorter keys collating before longer keys.])

m4_scope_dbh(dbh_set_bt_compare)

m4_when_dbopen(dbh_set_bt_compare, corrupt)

m4_return(dbh_set_bt_compare, std)

m4_parambegin
m4_param(bt_compare_fcn, [dnl
The m4_arg(bt_compare_fcn) function is the application-specified Btree
comparison function.  The comparison function takes three parameters:
m4_tagbegin
m4_tag(m4_arg(db), [dnl
The m4_arg(db) parameter is the enclosing database handle.])
m4_tag(m4_arg(dbt1), [dnl
The m4_arg(dbt1) parameter is the m4_ref(Dbt) representing the
application supplied key.])
m4_tag(m4_arg(dbt2), [dnl
The m4_arg(dbt2) parameter is the m4_ref(Dbt) representing the
current tree's key.])
m4_tagend])

m4_p([dnl
The m4_arg(bt_compare_fcn) function must return an integer value less
than, equal to, or greater than zero if the first key parameter is
considered to be respectively less than, equal to, or greater than the
second key parameter.  In addition, the comparison function must cause
the keys in the database to be m4_italic(well-ordered).  The comparison
function must correctly handle any key values used by the application
(possibly including zero-length keys).  In addition, when Btree key
prefix comparison is being performed (see m4_ref(dbh_set_bt_prefix) for
more information), the comparison routine may be passed a prefix of any
database key.  The m4_arg(data) and m4_arg(size) fields of the
m4_ref(Dbt) are the only fields that may be used for the purposes of
this comparison, and no particular alignment of the memory to which by
the m4_arg(data) field refers may be assumed.])
m4_paramend

m4_err(dbh_set_bt_compare,
einval, [the method was called after m4_ref(dbh_open) was called])

m4_seealso(Db)
m4_page_footer