bend_initresult (*bend_init)(bend_initrequest *r);
    

This handler is called once for each new connection request, after a new process/thread has been created, and an Initialize Request has been received from the client. The pointer to the bend_init handler is passed in the call to statserv_start.

This handler is also called when operating in SRU mode - when a connection has been made (even though SRU does not offer this service).

Unlike previous versions of YAZ, the bend_init also serves as a handler that defines the Z39.50 services that the backend wish to support. Pointers to all service handlers, including search - and fetch must be specified here in this handler.

The request - and result structures are defined as

typedef struct bend_initrequest
{
    /** \brief user/name/password to be read */
    Z_IdAuthentication *auth; 
    /** \brief encoding stream (for results) */
    ODR stream;
    /** \brief printing stream */
    ODR print;
    /** \brief decoding stream (use stream for results) */
    ODR decode; 
    /** \brief reference ID */
    Z_ReferenceId *referenceId;
    /** \brief peer address of client */
    char *peer_name;           
    
    /** \brief character set and language negotiation 

    see include/yaz/z-charneg.h 
    */
    Z_CharSetandLanguageNegotiation *charneg_request;

    /** \brief character negotiation response */
    Z_External *charneg_response;

    /** \brief character set (encoding) for query terms 
        
    This is NULL by default. It should be set to the native character
    set that the backend assumes for query terms */
    char *query_charset;      

    /** \brief whehter query_charset also applies to recors 
    
    Is 0 (No) by default. Set to 1 (yes) if records is in the same
    character set as queries. If in doubt, use 0 (No).
    */
    int records_in_same_charset;

    char *implementation_id;
    char *implementation_name;
    char *implementation_version;

    /** \brief Z39.50 sort handler */
    int (*bend_sort)(void *handle, bend_sort_rr *rr);
    /** \brief SRU/Z39.50 search handler */
    int (*bend_search)(void *handle, bend_search_rr *rr);
    /** \brief SRU/Z39.50 fetch handler */
    int (*bend_fetch)(void *handle, bend_fetch_rr *rr);
    /** \brief SRU/Z39.50 present handler */
    int (*bend_present)(void *handle, bend_present_rr *rr);
    /** \brief Z39.50 extended services handler */
    int (*bend_esrequest) (void *handle, bend_esrequest_rr *rr);
    /** \brief Z39.50 delete result set handler */
    int (*bend_delete)(void *handle, bend_delete_rr *rr);
    /** \brief Z39.50 scan handler */
    int (*bend_scan)(void *handle, bend_scan_rr *rr);
    /** \brief Z39.50 segment facility handler */
    int (*bend_segment)(void *handle, bend_segment_rr *rr);
    /** \brief SRU explain handler */
    int (*bend_explain)(void *handle, bend_explain_rr *rr);
    /** \brief SRU scan handler */
    int (*bend_srw_scan)(void *handle, bend_scan_rr *rr);
    /** \brief SRU record update handler */
    int (*bend_srw_update)(void *handle, bend_update_rr *rr);

    /** \brief whether named result sets are supported (0=disable, 1=enable) */
    int named_result_sets;
} bend_initrequest;

typedef struct bend_initresult
{
    int errcode;               /* 0==OK */
    char *errstring;           /* system error string or NULL */
    void *handle;              /* private handle to the backend module */
} bend_initresult;
    

In general, the server frontend expects that the bend_*result pointer that you return is valid at least until the next call to a bend_* function. This applies to all of the functions described herein. The parameter structure passed to you in the call belongs to the server frontend, and you should not make assumptions about its contents after the current function call has completed. In other words, if you want to retain any of the contents of a request structure, you should copy them.

The errcode should be zero if the initialization of the backend went well. Any other value will be interpreted as an error. The errstring isn't used in the current version, but one option would be to stick it in the initResponse as a VisibleString. The handle is the most important parameter. It should be set to some value that uniquely identifies the current session to the backend implementation. It is used by the frontend server in any future calls to a backend function. The typical use is to set it to point to a dynamically allocated state structure that is private to your backend module.

The auth member holds the authentication information part of the Z39.50 Initialize Request. Interpret this if your serves requires authentication.

The members peer_name, implementation_id, implementation_name and implementation_version holds DNS of client, ID of implementor, name of client (Z39.50) implementation - and version.

The bend_ - members are set to NULL when bend_init is called. Modify the pointers by setting them to point to backend functions.

We now describe the handlers that are required to support search - and retrieve. You must support two functions - one for search - and one for fetch (retrieval of one record). If desirable you can provide a third handler which is called when a present request is received which allows you to optimize retrieval of multiple-records.

int (*bend_search) (void *handle, bend_search_rr *rr);

typedef struct {
    char *setname;             /* name to give to this set */
    int replace_set;           /* replace set, if it already exists */
    int num_bases;             /* number of databases in list */
    char **basenames;          /* databases to search */
    Z_ReferenceId *referenceId;/* reference ID */
    Z_Query *query;            /* query structure */
    ODR stream;                /* encode stream */
    ODR decode;                /* decode stream */
    ODR print;                 /* print stream */

    bend_request request;
    bend_association association;
    int *fd;
    int hits;                  /* number of hits */
    int errcode;               /* 0==OK */
    char *errstring;           /* system error string or NULL */
    Z_OtherInformation *search_info; /* additional search info */
    char *srw_sortKeys;        /* holds SRU/SRW sortKeys info */
    char *srw_setname;         /* holds SRU/SRW generated resultsetID */
    int *srw_setnameIdleTime;  /* holds SRU/SRW life-time */
    int estimated_hit_count;   /* if hit count is estimated