Function : Basic Encoding Rules

ber_scanf - Used to decode a BerElement

#include <lber.h>
ber_tag_t LNVARARGS ber_scanf(

    BerElement *ber,
    const char *fmt,
    <Any 'C' type>  optional_var1, ...);

Description :

The ber_scanf() function is used to decode a BER element in much the same way that scanf() works. One important difference, though, is that some state information is kept with the ber argument so that multiple calls can be made to ber_scanf() to sequentially read from the BER element. It reads from ber, a pointer to a BerElement, interprets the bytes according to the format string fmt, and stores the results in its additional arguments. The format string contains conversion specifications which are used to direct the interpretation of the BER element. The format string can contain the following characters.

'a' Octet string.
A char ** argument must be supplied. Memory is allocated, filled with the contents of the octet string, zero-terminated, and the pointer to the string is stored in the argument. The returned value should be freed using ldap_memfree. The tag of the element must indicate the primitive form (constructed strings are not supported) but is otherwise ignored and discarded during the decoding.
This format cannot be used with octet strings which could contain null bytes.

'O' Octet string.
A struct berval ** argument must be supplied, which upon return points to an allocated struct berval containing the octet string and its length.
ber_bvfree() SHOULD be called to free the allocated memory. The tag of the element must indicate the primitive form (constructed strings are not supported) but is otherwise ignored during the decoding.

'b' Boolean.
A pointer to a ber_int_t must be supplied. The ber_int_t value stored will be 0 for FALSE or nonzero for TRUE. The tag of the element must indicate the primitive form but is otherwise ignored during the decoding.

'e' Enumerated.
A pointer to a ber_int_t must be supplied. The enumerated value stored will be in host byte order. The tag of the element must indicate the primitive form but is otherwise ignored during the decoding. ber_scanf() will return an error if the value of the enumerated value cannot be stored in a ber_int_t.

'i' Integer.
A pointer to a ber_int_t must be supplied. The ber_int_t value stored will be in host byte order. The tag of the element must indicate the primitive form but is otherwise ignored during the decoding. ber_scanf() will return an error if the integer cannot be stored in a ber_int_t.

'B' Bitstring.
A char ** argument must be supplied which will point to the allocated bits, followed by a ber_len_t * argument, which will point to the length (in bits) of the bitstring returned. ldap_memfree should be called to free the bitstring.
The tag of the element must indicate the primitive form (constructed bit- strings are not supported) but is otherwise ignored during the decoding.

'n' Null.
No argument is needed. The element is verified to have a zero-length value and is skipped. The tag is ignored.

't' Tag.
A pointer to a ber_tag_t must be supplied. The ber_tag_t value stored will be the tag of the next element in the BerElement ber, represented so it can be written using the 't' format of ber_printf(). The decoding position within the ber argument is unchanged by this; that is, the fact that the tag has been retrieved does not affect future use of ber.

'v' Several octet strings.
A char *** argument must be supplied, which upon return points to an allocated NULL-terminated array of char *'s containing the octet strings. NULL is stored if the sequence is empty. ldap_memfree should be called to free each element of the array and the array itself. The tag of the sequence and of the octet strings are ignored.

'V' Several octet strings (which could contain null bytes).
A struct berval *** must be supplied, which upon return points to a allocated NULL-terminated array of struct berval *'s containing the octet strings and their lengths. NULL is stored if the sequence is empty. ber_bvecfree() can be called to free the allocated memory. The tag of the sequence and of the octet strings are ignored.

'x' Skip element.
The next element is skipped. No argument is needed.

'{' Begin sequence.
No argument is needed. The initial sequence tag and length are skipped.

'}' End sequence.
No argument is needed.

'[' Begin set.
No argument is needed. The initial set tag and length are skipped.

']' End set.
No argument is needed.

Implemented as a macro:

define ber_scanf ND_ber_scanf

Parameters : Input : ber - A pointer to a BerElement returned by ber_init().

fmt - Routine interprets the bytes according to this format string.

Output : (routine) - A ber_tag_t structure.

Routine returns LBER_ERROR on error, and a different value on success. If an error occurred, the values of all the result parameters are undefined.

optional_var1, ... - Routine stores its results in these optional arguments.