ber_printf
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 simplified imple-
mentation 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 ele-
ment. The other routines 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 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). See lber-sockbuf(3) for more details on
the Sockbuf implementation of the sb parameter. If the freeit parame-
ter 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 for-
mats 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 bit-
string. 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 out-
put.
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 ele-
ment 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 sup-
plied. 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.
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-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 2.2.13 2004/06/10 LBER_ENCODE(3)
