Document revision date: 30 March 2001

The ldap_first_message() and ldap_next_message() functions are used to step through the list of messages in a result chain returned by ldap_result() . For search operations, the result chain may actually include referral messages, entry messages, and result messages. The ldap_count_messages() function is used to count the number of messages returned. The ldap_msgtype() function can be used to distinguish between the different message types.

LDAPMessage *ldap_first_message( LDAP *ld, LDAPMessage *res ); LDAPMessage *ldap_next_message ( LDAP *ld, LDAPMesage *msg ); int ldap_count_messages( LDAP *ld, LDAPMessage *res );

Parameters are as follows:

ld	The session handle.
res	The result chain, as obtained by a call to one of the synchronous search functions or ldap_result() .
msg	The message returned by a previous call to ldap_first_message() or ldap_next_message() .

The ldap_first_message() and ldap_next_message() functions will return NULL when no more messages exist in the result set to be returned. NULL is also returned if an error occurs while stepping through the entries, in which case the error parameters in the session handle ld will be set to indicate the error.

The ldap_count_messages() function returns the number of messages contained in a chain of results. It can also be used to count the number of messages that remain in a chain if called with a message, entry, or reference returned by ldap_first_message() , ldap_next_message() , ldap_first_entry() , ldap_next_entry() , ldap_first_reference() , ldap_next_reference() .

12.19 Parsing Search Results

The following calls are used to parse the entries and references returned by ldap_search() . These results are returned in an opaque structure that should only be accessed by calling the functions. Functions are provided to step through the entries and references returned, step through the attributes of an entry, retrieve the name of an entry, and retrieve the values associated with a given attribute in an entry.

12.19.1 Stepping Through a List of Entries

The ldap_first_entry() and ldap_next_entry() functions are used to step through and retrieve the list of entries from a search result chain. The ldap_first_reference() and ldap_next_reference() functions are used to step through and retrieve the list of continuation references from a search result chain. The ldap_count_entries() function is used to count the number of entries returned. The ldap_count_references() function is used to count the number of references returned.

LDAPMessage *ldap_first_entry( LDAP *ld, LDAPMessage *res ); LDAPMessage *ldap_next_entry( LDAP *ld, LDAPMessage *entry ); LDAPMessage *ldap_first_reference( LDAP *ld, LDAPMessage *res ); LDAPMessage *ldap_next_reference( LDAP *ld, LDAPMessage *ref ); int ldap_count_entries( LDAP *ld, LDAPMessage *res ); int ldap_count_references( LDAP *ld, LDAPMessage *res );

Parameters are as follows:

ld	The session handle.
res	The search result, as obtained by a call to one of the synchronous search functions or ldap_result() .
entry	The entry returned by a previous call to ldap_first_entry() or ldap_next_entry() .

The ldap_first_entry() and ldap_next_entry() functions will return NULL when no more entries or references exist in the result set to be returned. NULL is also returned if an error occurs while stepping through the entries, in which case the error parameters in the session handle ld will be set to indicate the error.

The ldap_count_entries() function returns the number of entries contained in a chain of entries. It can also be used to count the number of entries that remain in a chain if called with a message, entry or reference returned by ldap_first_message() , ldap_next_message() , ldap_first_entry() , ldap_next_entry() , ldap_first_reference() , ldap_next_reference() .

The ldap_count_references() function returns the number of references contained in a chain of search results. It can also be used to count the number of references that remain in a chain.

12.19.2 Stepping Through the Attributes of an Entry

The ldap_first_attribute() and ldap_next_attribute() calls are used to step through the list of attribute types returned with an entry.

char *ldap_first_attribute( LDAP *ld, LDAPMessage *entry, BerElement **ptr ); char *ldap_next_attribute( LDAP *ld, LDAPMessage *entry, BerElement *ptr ); void ldap_memfree( char *mem );

Parameters are as follows:

ld	The session handle.
entry	The entry whose attributes are to be stepped through, as returned by ldap_first_entry() or ldap_next_entry() .
ptr	In ldap_first_attribute() , the address of a pointer used internally to keep track of the current position in the entry. In ldap_next_attribute() , the pointer returned by a previous call to ldap_first_attribute() .
mem	A pointer to memory allocated by the LDAP library, such as the attribute type names returned by ldap_first_attribute() and ldap_next_attribute() , or the DN returned by ldap_get_dn() .

The ldap_first_attribute() and ldap_next_attribute() functions will return NULL when the end of the attributes is reached, or if there is an error, in which case the error parameters in the session handle ld will be set to indicate the error.

Both functions return a pointer to an allocated buffer containing the current attribute name. This should be freed when no longer in use by calling ldap_memfree() .

The ldap_first_attribute() function will allocate and return in ptr a pointer to a BerElement used to keep track of the current position. This pointer should be passed in subsequent calls to ldap_next_attribute() to step through the entry's attributes. After a set of calls to ldap_first_attribute() and ldap_next_attribute() , if ptr is non-NULL, it should be freed by calling ber_free(ptr, 0) . Note that it is very important to pass the second parameter as 0 (zero) in this call, since the buffer associated with the BerElement does not point to separately allocated memory.

The attribute type names returned are suitable for passing in a call to ldap_get_values() to retrieve the associated values.

12.19.3 Retrieving the Values of an Attribute

The ldap_get_values() and ldap_get_values_len() functions are used to retrieve the values of a given attribute from an entry. The ldap_count_values() and ldap_count_values_len() functions are used to count the returned values. The ldap_value_free() and ldap_value_free_len() functions are used to free the values.

char **ldap_get_values( LDAP *ld, LDAPMessage *entry, char *attr ); struct berval **ldap_get_values_len( LDAP *ld, LDAPMessage *entry, char *attr ); int ldap_count_values( char **vals ) int ldap_count_values_len( struct berval **vals ); void ldap_value_free( char **vals ); void ldap_value_free_len( struct berval **vals );

Parameters are as follows:

ld	The session handle.
entry	The entry from which to retrieve values, as returned by ldap_first_entry() or ldap_next_entry() .
attr	The attribute whose values are to be retrieved, as returned by ldap_first_attribute() or ldap_next_attribute() , or a caller- supplied string (for example, "mail").
vals	The values returned by a previous call to ldap_get_values() or ldap_get_values_len() .

Two forms of the various calls are provided. The first form is only suitable for use with non-binary character string data. The second _len form is used with any kind of data.

The ldap_get_values() and ldap_get_values_len() functions return NULL if no values are found for attr or if an error occurs.

The ldap_count_values() and ldap_count_values_len() functions return -1 if an error occurs such as the vals parameter being invalid.

Note that the values returned are dynamically allocated and should be freed by calling either ldap_value_free() or ldap_value_free_len() when no longer in use.

12.19.4 Retrieving the Name of an Entry

The ldap_get_dn() function is used to retrieve the name of an entry. The ldap_explode_dn() and ldap_explode_rdn() functions are used to break up a name into its component parts. The ldap_dn2ufn() function is used to convert the name into a more user-friendly format.

char *ldap_get_dn( LDAP *ld, LDAPMessage *entry ); char **ldap_explode_dn( const char *dn, int notypes ); char **ldap_explode_rdn( const char *rdn, int notypes ); char *ldap_dn2ufn( const char *dn );

Parameters are as follows:

ld	The session handle.
entry	The entry whose name is to be retrieved, as returned by ldap_first_entry() or ldap_next_entry() .
dn	The dn to explode, such as returned by ldap_get_dn() .
rdn	The rdn to explode, such as returned in the components of the array returned by ldap_explode_dn() .
notypes	A boolean parameter, if non-zero indicating that the DN or RDN components should have their type information stripped off (i.e., "cn=Babs" would become "Babs").

The ldap_get_dn() function will return NULL if there is some error parsing the dn, setting error parameters in the session handle ld to indicate the error. It returns a pointer to newly allocated space that the caller should free by calling ldap_memfree() when it is no longer in use.

The ldap_explode_dn() function returns a NULL-terminated char * array containing the RDN components of the DN supplied, with or without types as indicated by the notypes parameter. The components are returned in the order they appear in the dn. The array returned should be freed when it is no longer in use by calling ldap_value_free() .

The ldap_explode_rdn() function returns a NULL-terminated char * array containing the components of the RDN supplied, with or without types as indicated by the notypes parameter. The components are returned in the order they appear in the rdn. The array returned should be freed when it is no longer in use by calling ldap_value_free() .

The ldap_dn2ufn() function converts the DN into the user friendly format. The UFN returned is newly allocated space that should be freed by a call to ldap_memfree() when no longer in use.

12.19.5 Retrieving Controls from an Entry

The ldap_get_entry_controls() function is used to extract LDAP controls from an entry.

int ldap_get_entry_controls( LDAP *ld, LDAPMessage *entry, LDAPControl ***serverctrlsp );

Parameters are as follows:

ld	The session handle.
entry	The entry to extract controls from, as returned by ldap_first_entry() or ldap_next_entry() .
serverctrlsp	This result parameter will be filled in with an allocated array of controls copied out of entry. The control array should be freed by calling ldap_controls_free() . If serverctrlsp is NULL, no controls are returned.

The ldap_get_entry_controls() function returns an LDAP error code that indicates whether the reference could be successfully parsed (LDAP_SUCCESS if all goes well).

12.19.6 Parsing References

The ldap_parse_reference() function is used to extract referrals and controls from a SearchResultReference message.

int ldap_parse_reference( LDAP *ld, LDAPMessage *ref, char ***referralsp, LDAPControl ***serverctrlsp, int freeit );

Parameters are as follows:

ld	The session handle.
ref	The reference to parse, as returned by ldap_result() , ldap_first_reference() , or ldap_next_reference() .
referralsp	This result parameter will be filled in with an allocated array of character strings. The elements of the array are the referrals (typically LDAP URLs) contained in ref. The array should be freed when no longer in used by calling ldap_value_free() . If referralsp is NULL, the referral URLs are not returned.
serverctrlsp	This result parameter will be filled in with an allocated array of controls copied out of ref. The control array should be freed by calling ldap_controls_free() . If serverctrlsp is NULL, no controls are returned.
freeit	A boolean that determines whether the ref parameter is disposed of or not. Pass any non-zero value to have these functions free res after extracting the requested information. This is provided as a convenience; you can also use ldap_msgfree() to free the result later.

The ldap_parse_reference() function returns an LDAP error code that indicates whether the reference could be successfully parsed (LDAP_SUCCESS if all goes well).

12.20 Encoded ASN.1 Value Manipulation

This section describes functions that may be used to encode and decode BER-encoded ASN.1 values, which are often used inside of control and extension values.

The following additional integral types are defined for use in manipulation of BER encoded ASN.1 values:

typedef unsigned long ber_tag_t; /* for BER tags */ typedef long ber_int_t; /* for BER ints, enums, and Booleans */

With the exceptions of two new functions, ber_flatten() and ber_init() , these functions are compatible with the University of Michigan LDAP 3.3 implementation of BER.

typedef struct berval { ber_len_t bv_len; char *bv_val; } BerValue;

A struct berval contains a sequence of bytes and an indication of its length. The bv_val is not null terminated. A bv_len must always be a nonnegative number. Applications may allocate their own berval structures.

typedef struct berelement { /* opaque */ } BerElement;

The BerElement structure contains not only a copy of the encoded value, but also state information used in encoding or decoding. Applications cannot allocate their own BerElement structures. The internal state is neither thread-specific nor locked, so two threads should not manipulate the same BerElement value simultaneously.

A single BerElement value cannot be used for both encoding and decoding.

void ber_bvfree( struct berval *bv );

The ber_bvfree() function frees a berval returned from this API. Both the bv->bv_val string and the berval itself are freed. Applications should not use ber_bvfree() with bervals which the application has allocated.

void ber_bvecfree ( struct berval **bv );

The ber_bvecfree() function frees an array of bervals returned from this API. Each of the bervals in the array are freed using ber_bvfree() , then the array itself is freed.

struct berval *ber_bvdup (struct berval *bv );

The ber_bvdup() function returns a copy of a berval. The bv_val field in the returned berval points to a different area of memory as the bv_val field in the argument berval. The null pointer is returned on error (for example, out of memory).

void ber_free ( BerElement *ber, int fbuf );

The ber_free() function frees a BerElement which is returned from the API calls ber_alloc_t() or ber_init() . Each BerElement must be freed by the caller. The second argument fbuf should always be set to 1 to ensure that the internal buffer used by the BER functions is freed as well as the BerElement container itself.

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