ber_alloc_t, ber_flush, ber_flush2, 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 -
OpenLDAP LBER simplified Basic Encoding Rules library routines for encoding
OpenLDAP LBER (liblber, -llber)
#include <lber.h>
BerElement *ber_alloc_t(int options);
int ber_flush(Sockbuf *sb, BerElement *ber, int
freeit);
int ber_flush2(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);
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
ber_alloc_t() to allocate a BER element for encoding,
ber_printf() to do the actual encoding, and
ber_flush2() 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_flush2() 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). 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. If
LBER_FLUSH_FREE_ON_SUCCESS is used, the
ber is only freed when
successfully flushed, otherwise it is left intact; if
LBER_FLUSH_FREE_ON_ERROR is used, the
ber is only freed when an
error occurs, otherwise it is left intact; if
LBER_FLUSH_FREE_ALWAYS is
used, the
ber is freed anyway. This function differs from the original
ber_flush(3) function, whose behavior corresponds to that indicated for
LBER_FLUSH_FREE_ON_SUCCESS. Note that in the future, the behavior of
ber_flush(3) with
freeit non-zero might change into that of
ber_flush2(3) with
freeit set to
LBER_FLUSH_FREE_ALWAYS.
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 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
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 similarly. The end of the
sequence or set is marked by the nearest matching call to
ber_put_seq()
or
ber_put_set(), respectively.
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 */
}
If an error occurs during encoding, generally these routines return -1.
The return values for all of these functions are declared in the <lber.h>
header file.
lber-decode(3),
lber-memory(3),
lber-sockbuf(3),
lber-types(3)
OpenLDAP Software is developed and maintained by The OpenLDAP Project
<
http://www.openldap.org/>.
OpenLDAP Software is derived from the
University of Michigan LDAP 3.3 Release.