lber-encode(3)
LBER_ENCODE(3) C LIBRARY FUNCTIONS 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
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
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
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LBER_ENCODE(3) C LIBRARY FUNCTIONS LBER_ENCODE(3)
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 rou-
tines 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 ele-
ment. 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 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 sup-
plied. 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 out-
put.
n Null. No parameter is required. A null element is
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LBER_ENCODE(3) C LIBRARY FUNCTIONS LBER_ENCODE(3)
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 con-
struct 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.
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LBER_ENCODE(3) C LIBRARY FUNCTIONS LBER_ENCODE(3)
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 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 ) {
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LBER_ENCODE(3) C LIBRARY FUNCTIONS LBER_ENCODE(3)
/* 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-sockbuf(3), lber-
types(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 LDVERSION Last change: RELEASEDATE 5
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