The following functions are used to compare a given attribute
    value assertion against an LDAP entry. There are four variations.

            int ldap_compare_ext(
                    LDAP                              *ld,
                    const char                        *dn,
                    const char                        *attr,
                    const struct berval               *bvalue
                    LDAPControl                       **serverctrls,
                    LDAPControl                       **clientctrls,
                    int                               *msgidp
            );

            int ldap_compare_ext_s(
                    LDAP                              *ld,
                    const char                        *dn,
                    const char                        *attr,
                    const struct berval               *bvalue,
                    LDAPControl                       **serverctrls,
                    LDAPControl                       **clientctrls
            );

            int ldap_compare(
                    LDAP                              *ld,
                    const char                        *dn,
                    const char                        *attr,
                    const char                        *value
            );

            int ldap_compare_s(
                    LDAP                              *ld,
                    const char                        *dn,
                    const char                        *attr,
                    const char                        *value
            );

    Parameters are as follows:

    ld             The session handle.
    dn             The name of the entry to compare against.
    attr           The attribute to compare against.
    bvalue         The attribute value to compare against those found
                   in the given entry. This parameter is used in the
                   extended functions and is a pointer to a struct
                   berval so it is possible to compare binary values.
    value          A string attribute value to compare against,
                   used by the ldap_compare() and ldap_compare_s()
                   functions. Use ldap_compare_ext() or ldap_compare_
                   ext_s() if you need to compare binary values.
    serverctrls    List of LDAP server controls.
    clientctrls    List of client controls.
    msgidp         This result parameter will be set to the message
                   id of the request if the ldap_compare_ext() call
                   succeeds.

    The ldap_compare_ext() function initiates an asynchronous compare
    operation and returns either the constant LDAP_SUCCESS if the
    request was successfully sent, or another LDAP error code if not.
    See Errors for more information about possible errors and how
    to interpret them. If successful, ldap_compare_ext() places the
    message id of the request in *msgidp. A subsequent call to ldap_
    result() can be used to obtain the result of the compare.

    Similar to ldap_compare_ext(), the ldap_compare()  function
    initiates an asynchronous compare operation and returns the
    message id of the operation initiated. As for ldap_compare_ext(),
    a subsequent call to ldap_result() can be used to obtain the
    result of the compare. In case of error, ldap_compare() will
    return -1, setting the session error parameters in the LDAP
    structure appropriately.

    The synchronous ldap_compare_ext_s() and ldap_compare_s()
    functions both return the result of the operation, either
    the constants LDAP_COMPARE_TRUE or LDAP_COMPARE_FALSE if the
    operation was successful, or another LDAP error code if it was
    not. See Errors for more information about possible errors and
    how to interpret them.

    The ldap_compare_ext() and ldap_compare_ext_s()  functions
    support LDAPv3 server controls and client controls.