V10/man/man3/cbt.3

.TH CBT 3X
.CT 2 data_man
.SH NAME
bopen, bclose, bseek, bfirst, bkey, breclen, bread,
bdelete, bwrite \(mi compressed B-tree subroutines
.SH SYNOPSIS
.nf
.PP
.B #include <cbt.h>
.PP
.B "bfile *bopen(name, typ) char *name;"
.PP
.B "void bclose(b) bfile *b;"
.PP
.B "bseek(b, key) bfile *b; mbuf key;"
.PP
.B "bfirst(b) bfile *b;"
.PP
.B "mbuf bkey(b) bfile *b;"
.PP
.B "breclen(b) bfile *b;"
.PP
.B "bread(b, key, val) bfile *b; mbuf *key, *val;"
.PP
.B "bdelete(b, key) bfile *b; mbuf key;"
.PP
.B "bwrite(b, key, val) bfile *b; mbuf key, val;"
.fi
.SH DESCRIPTION
These functions manipulate
files of key/value records.
Such files are created by
.BR "cbt creat" ;
see
.IR cbt (1).
To load the functions use the
.IR ld (1)
option
.BR \-lcbt .
.PP
The records occur sorted
(increasing lexicographical order) by their keys,
which must be distinct.
Both keys and values are arrays of characters accessed through
the structure
.EX
.ta 8n +15n
.nf
\fLtypedef struct {
	\fLchar *mdata;\fR	address of data bytes
	\fLshort mlen;\fP	number of data bytes
\fL} mbuf;\fR
.fi
.EE
.PP
.I "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.
.I Typ
is 0 for read-only or 2 for read-write.
.I Bopen
returns a descriptor that identifies the file to the other functions.
.PP
.I "Bclose"
closes a B-tree.
.PP
.I "Bseek"
positions the read pointer of the file
to the record whose key is
the first not less than
.IR key .
The routine returns 1 if
.I key
is in the file,
.B EOF
if
.I key
is greater
than any key in the file,
and 0 otherwise.
.PP
.I "Bfirst"
sets the read pointer to the beginning of the file.
It has the same error return as
.BR bseek .
.PP
.I "Bkey"
returns the current key.
The element
.I mdata
of the returned structure
is 0
on errors,
otherwise it points to a static buffer.
.PP
.I "Breclen"
returns the length of the value part of the current record.
.PP
.I "Bread"
reads the value at the read pointer into the space
pointed to by
.B val->mdata,
places its length in
.LR val->mlen ,
and advances the read pointer
to the record with the next greater key.
If
.I key
is not 0
the key of the record is read into the
space pointed to by
.B key->mdata
and its length is placed in
.BR key->mlen .
.I Bread
returns 0
if successful.
.PP
.I "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.
.PP
.I "Bwrite"
writes the given value with the given key.
An existing record with that key will be replaced.
The read pointer is left undefined.
.SH FILES
.F \fIname\fP.T
.br
.F \fIname\fP.F
.SH SEE ALSO
.IR cbt (1), 
.IR dbm (3)
.SH DIAGNOSTICS
Routines which return pointers return 0
on errors,
routines which return integers return \-1.
.SH BUGS
The length of any key is limited to 255.
.br
The
.B mbuf
arguments are passed inconsistently to the routines,
sometimes by value and sometimes by reference.
.br
.I Cbt
files are not directly portable between big-endian and
little-endian machines.