term% cat index.txt CBT(3X) CBT(3X)
NAME
bopen, bclose, bseek, bfirst, bkey, breclen, bread, bdelete, bwrite -
compressed B-tree subroutines
SYNOPSIS
#include <cbt.h>
bfile *bopen(name, typ) char *name;
void bclose(b) bfile *b;
bseek(b, key) bfile *b; mbuf key;
bfirst(b) bfile *b;
mbuf bkey(b) bfile *b;
breclen(b) bfile *b;
bread(b, key, val) bfile *b; mbuf *key, *val;
bdelete(b, key) bfile *b; mbuf key;
bwrite(b, key, val) bfile *b; mbuf key, val;
DESCRIPTION
These functions manipulate files of key/value records. Such files are
created by cbt(1). To load the functions use ld(1) option -lcbt.
The records occur sorted by their keys, which must be distinct. Both
keys and values are arrays of characters accessed through the data type
`mbuf':
typedef struct {
char *mdata; /* pointer to the data */
short mlen; /* number of bytes in the data */
} mbuf;
Bopen attempts to open a named B-tree, and if successful establishes a
read pointer pointing to the beginning of the file and returns a
pointer to be used in calling the other routines. Typ is 0 for read-
only or 2 for read-write. Bopen returns a descriptor that identifies
the file to the other functions.
Bclose closes a B-tree.
Bseek positions the read pointer of the file to the record whose key is
the first not less than key. The routine returns 1 if key is in the
file, EOF if key is greater than any key in the file, and 0 otherwise.
Bfirst sets the read pointer to the beginning of the file. It has the
same error return as bseek.
Bkey returns the current key. The element mdata of the returned struc‐
ture is 0 on errors, otherwise it points to a critical static buffer.
Breclen returns the length of the value part of the current record.
Bread reads the value at the read pointer into the space pointed to by
val->mdata, places its length in val->mlen, and advances the read
pointer to the record with the next greater key. If key is not 0 the
key of the record is read into the space pointed to by key->mdata and
its length is placed in key->mlen. Bread returns 0 if successful.
Bdelete removes the record with the given key, returning 1 if the
record was found, -1 if there was an error, and 0 otherwise, The read
pointer is left undefined.
Bwrite writes the given value with the given key, returning 0 if there
was no error. An existing record with that key will be replaced. The
read pointer is left undefined.
FILES
The btree name is stored in files name.T and name.F.
SEE ALSO
cbt(1), dbm(3)
DIAGNOSTICS
Routines which return pointers return 0 on errors, routines which re‐
turn integers return -1.
BUGS
The lengths of keys and values are limited.
CBT(3X)