#include "btree.h"
int btselp(BTA* btact, char* key, char* data, int dsize, int* rsize);
The btselp function locates and returns
the previous key and data record in the file associated with
the btact context pointer. Before
using btselp, a call to btsel or btpos must be made
to initialise the position within the B Tree. Calls to btseln may be
freely intermingled with calls to btselp.
Both key and
data are character pointers. The
dsize parameter must contain the
maximum number of bytes to be returned. The caller should
ensure that the data pointer refers to
an area of memory of at least dsize
bytes. The actual number of bytes returned is returned in
rsize. Even if the data record
contains more than dsize bytes, only
dsize bytes will be returned. If the
data record is successfully retrieved (even partially),
btselp returns zero.
If no previous key exists, btselp will return
the error code QNOKEY.
An application program can determine the number of bytes
occupied by a data record through the btrecs function.
A non-zero return from btseln indicates
an error occurred.
