MirBSD manpage: recno(3)

RECNO(3)                   BSD Programmer's Manual                    RECNO(3)


     recno - record number database access method


     #include <sys/types.h>
     #include <db.h>


     The dbopen() routine is the library interface to database files. One of
     the supported file formats is record number files. The general descrip-
     tion of the database access methods is in dbopen(3). This manual page
     describes only the recno specific information.

     The record number data structure is either variable or fixed-length
     records stored in a flat-file format, accessed by the logical record
     number. The existence of record number five implies the existence of
     records one through four, and the deletion of record number one causes
     record number five to be renumbered to record number four, as well as the
     cursor, if positioned after record number one, to shift down one record.

     The recno access method specific data structure provided to dbopen() is
     defined in the <db.h> include file as follows:

           typedef struct {
                   unsigned long   flags;
                   unsigned int    cachesize;
                   unsigned int    psize;
                   int             lorder;
                   size_t          reclen;
                   unsigned char   bval;
                   char            *bfname;
           } RECNOINFO;

     The elements of this structure are defined as follows:

     flags   The flag value is specified by OR'ing any of the following

             R_FIXEDLEN  The records are fixed-length, not byte delimited. The
                         structure element reclen specifies the length of the
                         record, and the structure element bval is used as the
                         pad character. Any records, inserted into the data-
                         base, that are less than reclen bytes long are au-
                         tomatically padded.

             R_NOKEY     In the interface specified by dbopen(), the sequen-
                         tial record retrieval fills in both the caller's key
                         and data structures. If the R_NOKEY flag is speci-
                         fied, the cursor routines are not required to fill in
                         the key structure. This permits applications to re-
                         trieve records at the end of files without reading
                         all of the intervening records.

             R_SNAPSHOT  This flag requires that a snapshot of the file be
                         taken when dbopen() is called, instead of permitting
                         any unmodified records to be read from the original

             A suggested maximum size, in bytes, of the memory cache. This
             value is only advisory, and the access method will allocate more
             memory rather than fail. If cachesize is 0 (no size is specified)
             a default cache is used.

     psize   The recno access method stores the in-memory copies of its
             records in a btree. This value is the size (in bytes) of the
             pages used for nodes in that tree. If psize is 0 (no page size is
             specified) a page size is chosen based on the underlying filesys-
             tem I/O block size. See btree(3) for more information.

     lorder  The byte order for integers in the stored database metadata. The
             number should represent the order as an integer; for example, big
             endian order would be the number 4,321. If lorder is 0 (no order
             is specified) the current host order is used.

     reclen  The length of a fixed-length record.

     bval    The delimiting byte to be used to mark the end of a record for
             variable-length records, and the pad character for fixed-length
             records. If no value is specified, newlines ('\n') are used to
             mark the end of variable-length records and fixed-length records
             are padded with spaces.

     bfname  The recno access method stores the in-memory copies of its
             records in a btree. If bfname is non-NULL, it specifies the name
             of the btree(3) file, as if specified as the file name for a
             dbopen(3) of a btree(3) file.

             The data part of the key/data pair used by the recno access
             method is the same as other access methods. The key is different.
             The data field of the key should be a pointer to a memory loca-
             tion of type recno_t, as defined in the <db.h> include file. This
             type is normally the largest unsigned integral type available to
             the implementation. The size field of the key should be the size
             of that type.

             Because there can be no meta-data associated with the underlying
             recno access method files, any changes made to the default values
             (e.g., fixed record length or byte separator value) must be ex-
             plicitly specified each time the file is opened.

             In the interface specified by dbopen(), using the put interface
             to create a new record will cause the creation of multiple, empty
             records if the record number is more than one greater than the
             largest record currently in the database.


     The recno access method routines may fail and set errno for any of the
     errors specified for the library routine dbopen(3), or the following:

     [EINVAL]  An attempt was made to add a record to a fixed-length database
               that was too large to fit.


     btree(3), dbopen(3), hash(3), mpool(3)

     Michael Stonebraker, Heidi Stettner, Joseph Kalash, Antonin Guttman, and
     Nadene Lynn, "Document Processing in a Relational Database System",
     Memorandum No. UCB/ERL M82/32, May 1982.


     Only big and little endian byte order is supported.

MirBSD #10-current             August 18, 1994                               1

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