Tribblix: manual page: ber

BER_ENCODE(3LDAP) LDAP Library Functions BER_ENCODE(3LDAP)

NAME

ber_encode, ber_alloc, ber_printf, ber_put_int, 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 - simplified
Basic Encoding Rules library encoding functions

SYNOPSIS

cc[ flag... ] file... -lldap[ library... ]
#include <lber.h>

BerElement *ber_alloc();

ber_printf(BerElement *ber, char **fmt[, arg... ]);

ber_put_int(BerElement *ber, long num, char tag);

ber_put_ostring(BerElement *ber, char **str, unsigned long len,
char tag);

ber_put_string(BerElement *ber, char **str, char tag);

ber_put_null(BerElement *ber, char tag);

ber_put_boolean(BerElement *ber, int bool, char tag);

ber_put_bitstring(BerElement *ber, char *str, int blen, char tag);

ber_start_seq(BerElement *ber, char tag);

ber_start_set(BerElement *ber, char tag);

ber_put_seq(BerElement *ber);

ber_put_set(BerElement *ber);

DESCRIPTION

These functions provide a subfunction interface to a simplified
implementation of the Basic Encoding Rules of ASN.1. The version of
BER these functions 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. In addition, these lightweight BER
functions 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 functions in the lber library. See
ber_decode(3LDAP) for details on the corresponding decoding
functions.

Normally, the only functions that need be called by an application
are ber_alloc(), to allocate a BER element, and ber_printf() to do
the actual encoding. The other functions are provided for those
applications that need more control than ber_printf() provides. In
general, these functions return the length of the element encoded, or
-1 if an error occurred.

The ber_alloc() function is used to allocate a new BER element.

The ber_printf() function is used to encode a BER element in much
the same way that sprintf(3C) 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(). It
interprets and formats its arguments according to the format string
fmt. The format string can contain the following characters:

b
Boolean. An integer parameter should be supplied. A boolean
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.

i
Integer. An integer parameter should be supplied. An integer
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. An int specifying the tag to give the next element is
provided. This works across calls.

v
Several octet strings. A null-terminated array of char * 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() function writes the integer element num to the BER
element ber.

The ber_put_boolean() function writes the boolean value given by
bool to the BER element.

The ber_put_bitstring() function 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() function writes len bytes starting at str to
the BER element as an octet string.

The ber_put_string() function writes the null-terminated string
(minus the terminating '') to the BER element as an octet string.

The ber_put_null() function writes a NULL element to the BER
element.

The ber_start_seq() function is used to start a sequence in the BER
element. The ber_start_set() function 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() function 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

Example 1: Assuming the following variable declarations, and that the

variables have been assigned appropriately, an BER 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 (3N)
},
sizelimit INTEGER (0 .. 65535),
timelimit INTEGER (0 .. 65535),
attrsOnly BOOLEAN,
attributes SEQUENCE OF AttributeType
}

can be achieved like so:

int scope, ali, size, time, attrsonly;
char *dn, **attrs;

/* ... fill in values ... */
if ( (ber = ber_alloc()) == NULLBER )
/* error */

if ( ber_printf( ber, "{siiiib{v}}", dn, scope, ali,
size, time, attrsonly, attrs ) == -1 )
/* error */
else
/* success */

RETURN VALUES

If an error occurs during encoding, ber_alloc() returns NULL; other
functions generally return -1.

ATTRIBUTES

NOTES

The return values for all of these functions are declared in
<lber.h>.

October 6, 2008 BER_ENCODE(3LDAP)