ber_alloc_t
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
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 long 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 simplified implemen-
tation of the Basic Encoding Rules of ASN.1. The version of BER these
routines support is the one defined for the LDAP protocol. The encod-
ing rules are the same as BER, except that only definite form lengths
are used, and bitstrings and octet strings are always encoded in primi-
tive form. In addition, these lightweight BER routines restrict tags
and class to fit in a single octet (this means the actual tag must be
less than 31). When a "tag" is specified in the descriptions below, it
refers to the tag, class, and primitive or constructed bit in the first
octet of the encoding. This man page describes the encoding routines
in the lber library. See lber-decode(3) for details on the correspond-
ing decoding routines. Consult lber-types(3) for information about
types, allocators, and deallocators.
Normally, the only routines that need 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 routines 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 element to a socket (or file)
descriptor, once it has been fully encoded (using ber_printf() and
friends). The sb structure contains the descriptor and a BerElement
used for input buffering. Only the sb_sd field is relevant to the
ber_flush() routine.
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 mul-
tiple 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(). It interprets and formats its argu-
ments according to the format string fmt. The format string can con-
tain 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.
{ 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 enumberation 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 ele-
ment. The ber_start_set() routine works similarly. The end of the
sequence or set is marked by the nearest matching call to ber_put_seq()
or ber_put_set(), respectively.
The ber_first_element() routine is used to return the tag and length of
the first element in a set or sequence. It also returns in cookie a
magic cookie parameter that should be passed to subsequent calls to
ber_next_element(), which returns similar information.
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
lber-decode(3) lber-memory(3) lber-types(3) ldap-async(3) ldap-sync(3)
ldap-parse(3)
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.
OpenLDAP 2.0.27-Release 12 May 2000 LBER_ENCODE(3)
