LBER_ENCODE(3)LBER_ENCODE(3)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>
BerElement *ber_alloc_t(int options);
int ber_flush(Sockbuf *sb, BerElement *ber, int freeit);
int ber_printf(BerElement *ber, const char *fmt, ...);
int ber_put_int(BerElement *ber, ber_int_t num, ber_tag_t
tag);
int ber_put_enum(BerElement *ber, ber_int_t num, ber_tag_t
tag);
int ber_put_ostring(BerElement *ber, const char *str,
ber_len_t len, ber_tag_t tag);
int ber_put_string(BerElement *ber, const char *str,
ber_tag_t tag);
int ber_put_null(BerElement *ber, ber_tag_t tag);
int ber_put_boolean(BerElement *ber, ber_int_t bool,
ber_tag_t tag);
int ber_put_bitstring(BerElement *ber, const char *str,
ber_len_t blen, ber_tag_t tag);
int ber_start_seq(BerElement *ber, ber_tag_t tag);
int ber_start_set(BerElement *ber, ber_tag_t tag);
int ber_put_seq(BerElement *ber);
int ber_put_set(BerElement *ber);
DESCRIPTION
These routines provide a subroutine interface to a simpli-
fied 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 ber_alloc_t() to allocate a BER element
for encoding, ber_printf() to do the actual encoding, and
ber_flush() to actually write the element. The other rou-
tines are provided for those applications that need more
control than ber_printf() provides. In general, these
routines return the length of the element encoded, or -1
if an error occurred.
The ber_alloc_t() routine is used to allocate a new BER
element. It should be called with an argument of
LBER_USE_DER.
The ber_flush() routine is used to actually write the ele-
ment to a socket (or file) descriptor, once it has been
fully encoded (using 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 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 ber_printf() to append things to the end of the BER
element. Ber_printf() writes to ber, a pointer to a
BerElement such as returned by ber_alloc_t(). It inter-
prets 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 sup-
plied. 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 sup-
plied. 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 sup-
plied. 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 ber_put_int() routine writes the integer element num
to the BER element ber.
The ber_put_enum() routine writes the enumeration element
num to the BER element ber.
The ber_put_boolean() routine writes the boolean value
given by bool to the BER element.
The 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 ber_put_ostring() routine writes len bytes starting at
str to the BER element as an octet string.
The ber_put_string() routine writes the null-terminated
string (minus the terminating ' ') to the BER element as
an octet string.
The ber_put_null() routine writes a NULL element to the
BER element.
The ber_start_seq() routine is used to start a sequence in
the BER element. The ber_start_set() routine works simi-
larly. The end of the sequence or set is marked by the
nearest matching call to ber_put_seq() or ber_put_set(),
respectively.
EXAMPLES
Assuming the following variable declarations, and that the
variables have been assigned appropriately, an lber encod-
ing 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 rou-
tines return -1.
NOTES
The return values for all of these functions are declared
in the <lber.h> header file.
SEE ALSOlber-decode(3), lber-memory(3), lber-sockbuf(3), lber-
types(3)ACKNOWLEDGEMENTS
OpenLDAP is developed and maintained by The OpenLDAP Pro-
ject (http://www.openldap.org/). OpenLDAP is derived from
University of Michigan LDAP 3.3 Release.
OpenLDAP LDVERSION RELEASEDATE LBER_ENCODE(3)
