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

LIBRARY

OpenLDAP LBER (liblber, -llber)

SYNOPSIS

#include

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);

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 _s_b parameter. If the _f_r_e_e_i_t parameter is non-zero, the supplied _b_e_r will be freed. If _L_B_E_R___F_L_U_S_H___F_R_E_E___O_N___S_U_C_C_E_S_S is used, the _b_e_r is only freed when successfully flushed, otherwise it is left intact; if _L_B_E_R___F_L_U_S_H___F_R_E_E___O_N___E_R_R_O_R is used, the _b_e_r is only freed when an error occurs, otherwise it is left intact; if _L_B_E_R___F_L_U_S_H___F_R_E_E___A_L_W_A_Y_S is used, the _b_e_r is freed anyway. This function differs from the original ber_flush(3) function, whose behavior corresponds to that indicated for _L_B_E_R___F_L_U_S_H___F_R_E_E___O_N___S_U_C_C_E_S_S. Note that in the future, the behavior of ber_flush(3) with _f_r_e_e_i_t non-zero might change into that of ber_flush2(3) with _f_r_e_e_i_t set to _L_B_E_R___F_L_U_S_H___F_R_E_E___A_L_W_A_Y_S.

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 _b_e_r 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 _b_e_r, a pointer to a BerElement such as returned by ber_alloc_t(). It interprets and formats its arguments according to the format string _f_m_t. 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 _n_u_m to the BER element _b_e_r.

The ber_put_enum() routine writes the enumeration element _n_u_m to the BER element _b_e_r.

The ber_put_boolean() routine writes the boolean value given by _b_o_o_l to the BER element.

The ber_put_bitstring() routine writes _b_l_e_n bits starting at _s_t_r as a bitstring value to the given BER element. Note that _b_l_e_n is the length _i_n _b_i_t_s of the bitstring.

The ber_put_ostring() routine writes _l_e_n bytes starting at _s_t_r 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 header file.

SEE ALSO

lber-decode(3) lber-memory(3) lber-sockbuf(3) lber-types(3)

ACKNOWLEDGEMENTS

OpenLDAP Software is developed and maintained by The OpenLDAP Project . OpenLDAP Software is derived from University of Michigan LDAP 3.3 Release.