LBER_ENCODE
NAME
ber_alloc_t, ber_flush, ber_printf, ber_put_int, ber_put_enum, ber_put_ostring, ber_put_string, ber_put_null, ber_put_boolean, ber_put_bitstring, ber_start_seq, ber_start_set, ber_put_seq, ber_put_set - LBER simplified Basic Encoding Rules library routines for encoding
LIBRARY
OpenLDAP LBER (liblber, -llber)
SYNOPSIS
#include <lber.h>
I BerElement *ber_alloc_t(int options );
I int ber_flush(Sockbuf * sb , BerElement * ber , int freeit );
I int ber_printf(BerElement * ber , const char * fmt , ...);
I int ber_put_int(BerElement * ber , ber_int_t num , ber_tag_t tag );
I int ber_put_enum(BerElement * ber , ber_int_t num , ber_tag_t tag );
I int ber_put_ostring(BerElement * ber , const char * str , ber_len_t len , ber_tag_t tag );
I int ber_put_string(BerElement * ber , const char * str , ber_tag_t tag );
I int ber_put_null(BerElement * ber , ber_tag_t tag );
I int ber_put_boolean(BerElement * ber , ber_int_t bool , ber_tag_t tag );
I int ber_put_bitstring(BerElement * ber , const char * str , ber_len_t blen , ber_tag_t tag );
I int ber_start_seq(BerElement * ber , ber_tag_t tag );
I int ber_start_set(BerElement * ber , ber_tag_t tag );
I int ber_put_seq(BerElement * ber );
I int ber_put_set(BerElement * ber );
DESCRIPTION
These routines provide a subroutine interface to a simplified
implementation of the Basic Encoding Rules of ASN.1. The version
of BER these routines support is the one defined for the LDAP
protocol. The encoding rules are the same as BER, except that
only definite form lengths are used, and bitstrings and octet strings
are always encoded in primitive form. This
man page describes the encoding routines in the lber library. See
lber-decode(3)
for details on the corresponding decoding routines. Consult
lber-types(3)
for information about types, allocators, and deallocators.
Normally, the only routines that need to be called by an application
are
R ber_alloc_t ()
to allocate a BER element for encoding,
R ber_printf ()
to do the actual encoding, and
R ber_flush ()
to actually write the element. The other routines are provided for those
applications that need more control than
R ber_printf ()
provides. In
general, these routines return the length of the element encoded, or
-1 if an error occurred.
The
R ber_alloc_t ()
routine is used to allocate a new BER element. It
should be called with an argument of LBER_USE_DER.
The
R ber_flush ()
routine is used to actually write the element to a socket
(or file) descriptor, once it has been fully encoded (using
R ber_printf ()
and friends). See
lber-sockbuf(3)
for more details on the Sockbuf implementation of the
sb parameter.
If the
freeit parameter is non-zero, the supplied
ber will
be freed after its contents have been flushed.
The
R ber_printf ()
routine is used to encode a BER element in much the same way that
sprintf(3)
works. One important difference, though, is
that some state information is kept with the
ber parameter so
that multiple calls can be made to
R ber_printf ()
to append things to the end of the BER element.
R Ber_printf ()
writes to
ber, a pointer to a BerElement such as returned by
R ber_alloc_t ().
It interprets and
formats its arguments according to the format string
fmt.
The format string can contain the following characters:
b
Boolean. An ber_int_t parameter should be supplied. A boolean element
is output.
e
Enumeration. An ber_int_t parameter should be supplied. An
enumeration element is output.
i
Integer. An ber_int_t parameter should be supplied. An integer element
is output.
B
Bitstring. A char * pointer to the start of the bitstring is supplied,
followed by the number of bits in the bitstring. A bitstring element
is output.
n
Null. No parameter is required. A null element is output.
o
Octet string. A char * is supplied, followed by the length of the
string pointed to. An octet string element is output.
O
Octet string. A struct berval * is supplied.
An octet string element is output.
s
Octet string. A null-terminated string is supplied. An octet string
element is output, not including the trailing NULL octet.
t
Tag. A ber_tag_t specifying the tag to give the next element
is provided. This works across calls.
v
Several octet strings. A null-terminated array of char *'s is
supplied. Note that a construct like '{v}' is required to get
an actual SEQUENCE OF octet strings.
V
Several octet strings. A null-terminated array of struct berval *'s
is supplied. Note that a construct like '{V}' is required to get
an actual SEQUENCE OF octet strings.
W
Several octet strings. An array of struct berval's is supplied. The
array is terminated by a struct berval with a NULL bv_val.
Note that a construct like '{W}' is required to get
an actual SEQUENCE OF octet strings.
{
Begin sequence. No parameter is required.
}
End sequence. No parameter is required.
[
Begin set. No parameter is required.
]
End set. No parameter is required.
The
R ber_put_int ()
routine writes the integer element num to the BER element ber.
The
R ber_put_enum ()
routine writes the enumeration element num to the BER element ber.
The
R ber_put_boolean ()
routine writes the boolean value given by bool to the BER element.
The
R ber_put_bitstring ()
routine writes blen bits starting
at str as a bitstring value to the given BER element. Note
that blen is the length in bits of the bitstring.
The
R ber_put_ostring ()
routine writes len bytes starting at
str to the BER element as an octet string.
The
R ber_put_string ()
routine writes the null-terminated string (minus
the terminating '\0') to the BER element as an octet string.
The
R ber_put_null ()
routine writes a NULL element to the BER element.
The
R ber_start_seq ()
routine is used to start a sequence in the BER element. The
R ber_start_set ()
routine works similarly.
The end of the sequence or set is marked by the nearest matching call to
R ber_put_seq ()
or
R ber_put_set (),
respectively.
EXAMPLES
Assuming the following variable declarations, and that the variables
have been assigned appropriately, an lber encoding of
the following ASN.1 object:
AlmostASearchRequest := SEQUENCE {
baseObject DistinguishedName,
scope ENUMERATED {
baseObject (0),
singleLevel (1),
wholeSubtree (2)
},
derefAliases ENUMERATED {
neverDerefaliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
alwaysDerefAliases (3)
},
sizelimit INTEGER (0 .. 65535),
timelimit INTEGER (0 .. 65535),
attrsOnly BOOLEAN,
attributes SEQUENCE OF AttributeType
}
can be achieved like so:
int rc;
ber_int_t scope, ali, size, time, attrsonly;
char *dn, **attrs;
BerElement *ber;
/* ... fill in values ... */
ber = ber_alloc_t( LBER_USE_DER );
if ( ber == NULL ) {
/* error */
}
rc = ber_printf( ber, "{siiiib{v}}", dn, scope, ali,
size, time, attrsonly, attrs );
if( rc == -1 ) {
/* error */
} else {
/* success */
}
ERRORS
If an error occurs during encoding, generally these routines return -1.
NOTES
The return values for all of these functions are declared in the
<lber.h> header file.
SEE ALSO
ACKNOWLEDGEMENTS
OpenLDAP
is developed and maintained by The OpenLDAP Project (http://www.openldap.org/).
OpenLDAP
is derived from University of Michigan LDAP 3.3 Release.