OpenLDAP LBER библиотечные подпрограммы базовых правил кодирования (OpenLDAP LBER simplified Basic Encoding Rules library routines for encoding)
Дубль
(статьи:
ber_alloc_t - OpenLDAP LBER библиотечные подпрограммы базовых правил кодирования )
Имя (Name)
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
Библиотека (Library)
OpenLDAP LBER (liblber, -llber)
Синопсис (Synopsis)
#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);
Описание (Description)
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.
Примеры (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 */
}
Ошибки (Error)
If an error occurs during encoding, generally these routines
return -1.
Примечание (Note)
The return values for all of these functions are declared in the
<lber.h> header file.
Смотри также (See also)
lber-decode(3), lber-memory(3), lber-sockbuf(3), lber-types(3)
