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IRIX Base Documentation 1998 November
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IRIX 6.5.2 Base Documentation November 1998.img
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recno.z
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recno
Wrap
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1998-10-20
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8KB
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199 lines
RRRREEEECCCCNNNNOOOO((((3333)))) UUUUNNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((AAAAuuuugggguuuusssstttt 11118888,,,, 1111999999994444)))) RRRREEEECCCCNNNNOOOO((((3333))))
NNNNAAAAMMMMEEEE
recno - record number database access method
SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
####iiiinnnncccclllluuuuddddeeee <<<<ssssyyyyssss////ttttyyyyppppeeeessss....hhhh>>>>
####iiiinnnncccclllluuuuddddeeee <<<<ddddbbbb....hhhh>>>>
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
The routine _d_b_o_p_e_n is the library interface to database
files. One of the supported file formats is record number
files. The general description of the database access
methods is in _d_b_o_p_e_n(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
_d_b_o_p_e_n is defined in the <db.h> include file as follows:
typedef struct {
u_long flags;
u_int cachesize;
u_int psize;
int lorder;
size_t reclen;
u_char bval;
char *bfname;
} RECNOINFO;
The elements of this structure are defined as follows:
flags
The flag value is specified by _o_r'ing any of the
following values:
R_FIXEDLEN
The records are fixed-length, not byte delimited.
The structure element _r_e_c_l_e_n specifies the length
of the record, and the structure element _b_v_a_l is
used as the pad character. Any records, inserted
into the database, that are less than _r_e_c_l_e_n bytes
long are automatically padded.
R_NOKEY
In the interface specified by _d_b_o_p_e_n, the
Page 1 (printed 4/30/98)
RRRREEEECCCCNNNNOOOO((((3333)))) UUUUNNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((AAAAuuuugggguuuusssstttt 11118888,,,, 1111999999994444)))) RRRREEEECCCCNNNNOOOO((((3333))))
sequential record retrieval fills in both the
caller's key and data structures. If the R_NOKEY
flag is specified, the _c_u_r_s_o_r routines are not
required to fill in the key structure. This
permits applications to retrieve 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 _d_b_o_p_e_n is called, instead of permitting
any unmodified records to be read from the
original file.
cachesize
A suggested maximum size, in bytes, of the memory
cache. This value is oooonnnnllllyyyy advisory, and the access
method will allocate more memory rather than fail. If
_c_a_c_h_e_s_i_z_e 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
_p_s_i_z_e is 0 (no page size is specified) a page size is
chosen based on the underlying file system I/O block
size. See _b_t_r_e_e(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 _l_o_r_d_e_r 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 file, as if specified
as the file name for a dbopen of a btree file.
Page 2 (printed 4/30/98)
RRRREEEECCCCNNNNOOOO((((3333)))) UUUUNNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((AAAAuuuugggguuuusssstttt 11118888,,,, 1111999999994444)))) RRRREEEECCCCNNNNOOOO((((3333))))
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 _d_a_t_a field of the key should be a pointer to
a memory location of type _r_e_c_n_o__t, as defined in the <db.h>
include file. This type is normally the largest unsigned
integral type available to the implementation. The _s_i_z_e
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 explicitly specified each time the
file is opened.
In the interface specified by _d_b_o_p_e_n, using the _p_u_t
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.
EEEERRRRRRRROOOORRRRSSSS
The _r_e_c_n_o access method routines may fail and set _e_r_r_n_o for
any of the errors specified for the library routine
_d_b_o_p_e_n(3) or the following:
[EINVAL]
An attempt was made to add a record to a fixed-length
database that was too large to fit.
SSSSEEEEEEEE AAAALLLLSSSSOOOO
_b_t_r_e_e(3) _d_b_o_p_e_n(3), _h_a_s_h(3), _m_p_o_o_l(3),
_D_o_c_u_m_e_n_t _P_r_o_c_e_s_s_i_n_g _i_n _a _R_e_l_a_t_i_o_n_a_l _D_a_t_a_b_a_s_e _S_y_s_t_e_m, Michael
Stonebraker, Heidi Stettner, Joseph Kalash, Antonin Guttman,
Nadene Lynn, Memorandum No. UCB/ERL M82/32, May 1982.
BBBBUUUUGGGGSSSS
Only big and little endian byte order is supported.
Page 3 (printed 4/30/98)