m4_comment([$Id: dbc_get.so,v 11.22 2004/12/02 18:21:08 bostic Exp $])

define(M4PAGELOCAL,)
include(tcl/m4.tcl)

m4_tcl_header(db get, m4_tcl_dbc_get, [dnl
dbc get
	m4_tcl_arg([-current])
	m4_tcl_arg([-first])
	m4_tcl_arg([-get_recno])
	m4_tcl_arg([-join_item])
	m4_tcl_arg([-last])
	m4_tcl_arg([-next])
	m4_tcl_arg([-nextdup])
	m4_tcl_arg([-nextnodup])
	m4_tcl_arg([-partial {offset length}])
	m4_tcl_arg([-prev])
	m4_tcl_arg([-prevnodup])
	m4_tcl_arg([-rmw])

dbc get
	m4_tcl_arg([-partial {offset length}])
	m4_tcl_arg([-rmw])
	m4_tcl_arg([-set])
	m4_tcl_arg([-set_range])
	m4_tcl_arg([-set_recno])
	key
dbc get
	-get_both
	m4_tcl_arg([-partial {offset length}])
	m4_tcl_arg([-rmw])
	key data
])

m4_p([dnl
The m4_tcl_dbc_get command returns a list of {key value} pairs, except in
the case of the m4_arg(-get_recno) and m4_arg(-join_item) options.  In
the case of the m4_arg(-get_recno) option, m4_tcl_dbc_get returns a list
of the record number.  In the case of the m4_arg(-join_item) option,
m4_tcl_dbc_get returns a list containing the joined key.])

m4_p([dnl
The options are as follows:])

m4_tagbegin

m4_tag([-current], [dnl
Return the key/data pair to which the cursor currently refers.
m4_p([dnl
If the cursor key/data pair was deleted, m4_tcl_dbc_get will return an
empty list.])])

m4_tag([-first], [dnl
The cursor is set to refer to the first key/data pair of the database, and
that pair is returned. In the presence of duplicate key values, the first
data item in the set of duplicates is returned.
m4_p([dnl
If the database is a Queue or Recno database, m4_tcl_dbc_get using the
m4_arg(-first) option will skip any keys that exist but were never
explicitly created by the application, or were created and later deleted.])
m4_p([dnl
If the database is empty, m4_tcl_dbc_get will return an empty list.])])

m4_tag([-last], [dnl
The cursor is set to refer to the last key/data pair of the database, and
that pair is returned. In the presence of duplicate key values, the last
data item in the set of duplicates is returned.
m4_p([dnl
If the database is a Queue or Recno database, m4_tcl_dbc_get using the
m4_arg(-last) option will skip any keys that exist but were never
explicitly created by the application, or were created and later deleted.])
m4_p([dnl
If the database is empty, m4_tcl_dbc_get will return an empty list.])])

m4_tag([-next], [dnl
If the cursor is not yet initialized, the m4_arg(-next) option is
identical to m4_arg(-first).
m4_p([dnl
Otherwise, the cursor is moved to the next key/data pair of the database,
and that pair is returned. In the presence of duplicate key values, the
value of the key may not change.])
m4_p([dnl
If the database is a Queue or Recno database, m4_tcl_dbc_get using the
m4_arg(-next) option will skip any keys that exist but were never
explicitly created by the application, or were created and later deleted.])
m4_p([dnl
If the cursor is already on the last record in the database, m4_tcl_dbc_get
will return an empty list.])])

m4_tag([-nextdup], [dnl
If the next key/data pair of the database is a duplicate record for the
current key/data pair, the cursor is moved to the next key/data pair of the
database, and that pair is returned. Otherwise, m4_tcl_dbc_get will return
an empty list.])

m4_tag([-nextnodup], [dnl
If the cursor is not yet initialized, the m4_arg(-nextnodup) option is
identical to m4_arg(-first).
m4_p([dnl
Otherwise, the cursor is moved to the next non-duplicate
key/data pair of the database, and that pair is returned.])
m4_p([dnl
If no non-duplicate key/data pairs occur after the cursor
position in the database, m4_tcl_dbc_get will return an empty list.])])

m4_tag([-prev], [dnl
If the cursor is not yet initialized, m4_arg(-prev) is identical to
m4_arg(-last).
m4_p([dnl
Otherwise, the cursor is moved to the previous key/data pair of the
database, and that pair is returned. In the presence of duplicate key
values, the value of the key may not change.])
m4_p([dnl
If the database is a Queue or Recno database, m4_tcl_dbc_get using the
m4_arg(-prev) flag will skip any keys that exist but were never explicitly
created by the application, or were created and later deleted.])
m4_p([dnl
If the cursor is already on the first record in the database,
m4_tcl_dbc_get will return an empty list.])])

m4_tag([-prevnodup], [dnl
If the cursor is not yet initialized, the m4_arg(-prevnodup) option is
identical to m4_arg(-last).
m4_p([dnl
Otherwise, the cursor is moved to the previous non-duplicate
key/data pair of the database, and that pair is returned.])
m4_p([dnl
If no non-duplicate key/data pairs occur before the cursor
position in the database, m4_tcl_dbc_get will return an empty list.])])

m4_tag([-set], [dnl
Move the cursor to the specified key/data pair of the database, and return
the datum associated with the given key.
m4_p([dnl
In the presence of duplicate key values, m4_tcl_dbc_get will return the
first data item for the given key.])
m4_p([dnl
If the database is a Queue or Recno database and the requested key exists,
but was never explicitly created by the application or was later deleted,
m4_tcl_dbc_get will return an empty list.])
m4_p([dnl
If no matching keys are found, m4_tcl_dbc_get will return an empty list.])])

m4_tag([-set_range], [dnl
The m4_arg(-set_range) option is identical to the m4_arg(-set) option,
except that the key is returned as well as the data item, and, in the case
of the Btree access method, the returned key/data pair is the smallest
key greater than or equal to the specified key (as determined by the
comparison function), permitting partial key matches and range searches.])

m4_tag([-get_both], [dnl
The m4_arg(-get_both) option is identical to the m4_arg(-set) option,
except that both the key and the data arguments must be matched by the
key and data item in the database.
m4_p([dnl
For m4_arg(-get_both) to be specified, the underlying database must be of
type Btree or Hash.])])

m4_tag([-set_recno], [dnl
Move the cursor to the specific numbered record of the database, and
return the associated key/data pair. The key
must be a record number.
m4_p([dnl
For the m4_arg(-set_recno) option to be specified, the underlying database
must be of type Btree, and it must have been created with the m4_arg(-recnum)
option.])])

m4_tag([-get_recno], [dnl
Return a list of the record number associated with the current cursor
position.  No key argument should be specified.
m4_p([dnl
For m4_arg(-get_recno) to be specified, the underlying database must be
of type Btree, and it must have been created with the m4_arg(-recnum)
option.])])

m4_tag([-join_item], [dnl
Do not use the data value found in all the cursors as a lookup key for
the primary database, but simply return it in the key parameter instead.
The data parameter is left unchanged.
m4_p([dnl
For m4_arg(-join_item) to be specified, the cursor must have been created
by the m4_tcl_db_join command.])])

m4_tag([-partial {offset length}], [dnl
The m4_arg(dlen) bytes starting m4_arg(doff) bytes from the beginning
of the retrieved data record are returned as if they comprised the
entire record.  If any or all of the specified bytes do not exist in
the record, the command is successful and any existing bytes are
returned.])

m4_tag([-rmw], [dnl
Acquire write locks instead of read locks when doing the retrieval. Setting
this flag may decrease the likelihood of deadlock during a read-modify-write
cycle by immediately acquiring the write lock during the read part of the
cycle so that another thread of control acquiring a read lock for the same
item, in its own read-modify-write cycle, will not result in deadlock.])

m4_tagend

m4_p([dnl
If a key is specified, and if the underlying database is a Queue or
Recno database, the given key will be interpreted by Tcl as an integer.
For all other database types, the key is interpreted by Tcl as a byte
array, unless indicated by a given option.])

m4_p([dnl
In the normal error case of attempting to retrieve a key that does not
exist an empty list is returned.])

m4_tcl_ret_error

m4_page_footer