Why not adopt me?
NAME
CodeBase - Perl module for accessing dBASE files
ABSTRACT
The CodeBase module provides a Perl 5 class for accessing dBASE files. It is a development of an earlier unpublished Perl 4 extension.
SYNOPSIS
Programs using the CodeBase module must include the line:
use CodeBase;
The functions that the module provides are listed below, grouped according to type of function.
File manipulation functions
$fh = CodeBase::open($filename, @options);
$fh = CodeBase::create($filename, @fielddefs);
$fh->DESTROY();
File information functions
$n_recs = $fh->reccount();
$recsize = $fh->recsize();
$n_fields = $fh->fldcount();
@names = $fh->names();
$type = $fh->type($fieldname);
@fieldinfo = $fh->fieldinfo();
Navigation functions
$recno = $fh->recno();
$fh->goto($recno);
$fh->skip($n_recs);
$fh->bof();
$fh->eof();
Record manipulation functions
@values = $fh->fields();
$value = $fh->field($fieldname);
$fh->set_field($fieldname, $value);
$fh->new_record(@values);
$fh->replace_record(@values);
$fh->deleted();
$fh->delete_record($recno);
$fh->flush($tries);
$fh->pack($compress_memo);
$fh->lock($what, $tries);
$fh->unlock();
Index manipulation functions
$n_tags = $fh->tag_count();
@tags = $fh->tags();
@taginfo = $fh->taginfo($index_name);
$fh->open_index($name);
$fh->create_index($name, $taginfo);
$fh->reindex();
$fh->set_tag();
$fh->seek($key);
$q = $fh->prepare_query($expr [, $sortexpr [, $desc]]);
$q->execute;
$q->next([$skip]);
Miscellaneous functions
CodeBase::option(@options);
$errno = CodeBase::errno();
$errmsg = CodeBase::errmsg($errno);
$version = CodeBase::libversion;
$dbtype = CodeBase::dbtype;
DESCRIPTION
Each function provided by the CodeBase module is described below. The module uses the CodeBase library from Sequiter Software Inc., which is a C library providing database management functions for dBASE files.
File manipulation functions
Existing dBASE files can be opened with open()
and new files created with create()
. Files are implicit closed by the DESTROY
method, which is called when all references to the internal file handle go out of scope.
- open FILENAME [, OPTION-KEYWORD ...]
-
Opens the named dBASE file and returns a file handle which can be used in other CodeBase functions. The filename should omit the
.dbf
extension. The following options keywords are recognized:"readonly"
,"noindex"
or"exclusive"
("ro"
is a synonym for"readonly"
and"x"
is a synonym for"exclusive"
). Option keywords are case-insensitive. For example to open the filebooks.dbf
in read-only mode, without opening the production index:$fh = CodeBase::open("books", "readonly", "noindex");
- create FILENAME, FIELD-DEFS =item create FILENAME, FIELD-DEF-ARRAY, INDEX-TAG
-
Creates a new dBASE file using the field definitions specified and returns a file that can be used in other CodeBase functions. The field definitions consist of an array of alternating pairs of field name and field type.
@field_defs = ( "F1" => "C10", "F2" => "N4" ); $fh = CodeBase::create("test", @field_defs);
The field types are as follows:
Type Code Length Decimals ------------------------------------------- Character C 1 to 65533 0 Date D 8 0 F.P. F 1 to 19 0 to len - 2 Logical L 1 0 Memo M 10 0 Numeric N 1 to 19 0 to len - 2
Note:
create
does not create a production index file -- usecreate_index
with an empty filename. The facility to create a production index at the same time that a database is created may be added later. Field and tag information arguments would then be specified as references. - DESTROY FILEHANDLE
-
The DESTROY function is not normally called explicitly. It is invoked automatically when all copies of the file handle generated by
open()
orcreate()
go out of scope. For example:{ my($fh2); { $fh1 = CodeBase::open("test"); $fh2 = $fh1; } # $fh1 is destroyed here, but $fh2 contains a copy of the file # handle so CodeBase::DESTROY is not called yet. } # $fh2 is destroyed as it goes out of scope, so CodeBase::DESTROY # is invoked.
Navigation functions
- recno
-
Returns the current record number. It is equivalent to the dBASE
RECNO()
function.$recno = $fh->recno
If the file has just been opened, created or packed there is no current record number and
recno()
will returnundef
. - goto RECNO
-
Positions the current record of the database file to the specified record. It is equivalent to the dBASE
GOTO
statement.$fh->goto($recno);
The record number for
CodeBase::goto
should be an integer between 1 andCodeBase::reccount
. It can also take one of the keywords:"TOP"
or"BOTTOM"
. The keywords"START"
and"FIRST"
are accepted as synonyms for"TOP"
, and"END"
and"LAST"
as synonyms for"BOTTOM"
. Only the first character of a keyword is significant and case is not significant.Normally
goto
returns 1 to signify success; if an error occurs it returnsundef
. The error code can then be retrieved witherrno
. - skip N_RECORDS
-
Skips forwards or backwards in the database file by the specified number of fields. It is equivalent to the dBASE
SKIP
statement. The number of fields defaults to one.$fh->skip($n_records);
Normally
skip
returns the new record number; if an error occurs it returnsundef
. The error code can then be retrieved witherrno
. - bof
-
Returns a boolean value indicating whether the current record is positioned before the first record. It is equivalent to the dBASE
BOF()
function.if ($fh->bof()) ...
- eof
-
Returns a boolean value indicating whether the current record is positioned at the end of the file. It is equivalent to the dBASE
EOF()
function.while (!$fh->eof()) ...
Record handling functions
- reccount
-
Returns the number of records in the database file. It is equivalent to the dBASE
RECCOUNT()
function.$n_recs = $fh->reccount();
- recsize
-
Returns the size in bytes of records in the database file (including the deletion flag). It is equivalent to the dBASE
RECWIDTH()
function.$recsize = $fh->recsize();
- fldcount
-
Returns the number of fields per record for the database file.
$n_fields = $fh->fldcount();
It is equivalent to the dBASE
FLDCOUNT()
function. - names
-
Returns the field names as an array.
@names = $fh->names();
- type FIELD
-
Returns the type of the named field as a string.
$type = $fh->type("field1");
- fieldinfo [NAMES]
-
Returns an array containing information about the specified fields or about all fields if no fields are specified. For example if the database open on
$fh
contains, amongst others, the fieldsfield1
andfield2
as a 12 character field and a 10 byte numeric field with 3 decimal places respectively then:@names = ("field1, "field2"); $fh->fieldinfo(@names);
would return an array containing the values:
("field1", "C12", "field2", "N10.3")
This is a shortcut function. The same information can be built up by using
names
andtype
:foreach $name ($fh->names) { push(@results, ($name, $fh->type($name))); }
- values [NAMES]
-
Returns an array containing the values of each of the specified fields, or of all fields if no field names are specified.
@values = $fh->values("field1", "field3");
- field NAME
-
Returns the value of the named field.
$value = $fh->field("field1");
- set_field NAME, VALUE
-
Sets the value of the named field to the specified value.
$fh->set_field("field1", $value);
If the field is a date field the value should be formatted in dBASE date format (e.g.
"YYYYMMDD"
) or should be one of the keywords"YESTERDAY"
,"TODAY"
or"TOMORROW"
(the keywords are not case sensitive) or may be a number of days to the current date specified as+num
or-num
. For example to set a date field to a week's time:$fh->set_field("date", "+7");
- new_record VALUES
-
Creates a new record using the values specified.
VALUES
may be an array of field values:$fh->new_record({ firstname => "Fred", surname => "Bloggs" });
or a reference to a hash, the keys of which are the field names:
$fh->new_record("Bloggs", "Fred");
If the values are supplied as an array, a value must be supplied for each field. If the values are supplied as a hash unspecified fields are filled with blanks. Excess array values or hash keys that are not names of fields are simply ignored. The handling of date fields is as described under
set_field
. - replace_record VALUES
-
Replaces the fields of the current record with the values specified. As with
new_record
VALUES
may be an array of field values:$fh->replace_record("Bloggs", "Fred");
or a reference to a hash, the keys of which are the field names.
$fh->replace_record({ firstname => "Fred", surname => "Bloggs" });
In the former case a value must be supplied for each field, while in the latter case unspecified fields are unchanged. Excess values or hash keys that are not names of fields are ignored. The handling of date fields is as described under
set_field
. - deleted
-
Returns a boolean value indicating whether the current record is deleted.
if ($fh->deleted()) ...
This function is equivalent to the dBASE
DELETED()
function. - delete_record [RECNO]
-
Deletes the record specified or the current record if called without a record number.
$fh->delete_record($recno);
- recall_record [RECNO]
-
Recalls the record specified or the current record if called without a record number. (Not yet implemented).
- flush [TRIES]
-
Flushes to file any outstanding changes (made by
set_field()
. Records need to be locked while changes are written.TRIES
is the number of attempts that should be made to aquire the lock. Subsequent attempts are made with a one second interval. - pack COMPRESS-MEMO-FLAG
-
Packs the database file removing deleted records. If flag parameter is specified as true then memo fields are compressed at the same time:
$fh->pack(1);
- lock WHAT [, TRIES]
-
Locks the specified record or the whole file.
WHAT
should either be"FILE"
or a record number (the current record can be referred to as"."
.TRIES
is the number of attempts that should be made to aquire the lock. Subsequent attempts are made with a one second interval. - unlock
-
Removes any existing locks on the file.
Index Handling Functions
A production index file is automatically opened when a database file is opened, if it exists unless the noindex
option is specified. An index file can be opened with the open_index
method.
- tagcount
-
Returns the number of index tags.
$n_tags = $fh->tagcount();
-
Returns an array containing the names of all the tags associated with the database file.
@tags = $fh->tags();
- set_tag TAG
-
Sets the current index tag to the named tag. If no tag is specified the currently selected tag is deselected.
$fh->set_tag("TAG1") || die "Cannot set index tag.\n";
- taginfo
-
Returns an array containing information about tags. Each element of the array is a reference to a hash containing attributes of the tag. The attributes are
name
,expression
,filter
,order
andduplicates
.This array is suitable for passing to
create_index
, for example for copying the index structure of a file:@taginfo = $fh1->taginfo; $fh2->create_index(undef, \@taginfo);
- create_index NAME, TAGINFO
-
Creates a new index file. The index file name is specified by
NAME
and should not include the.mdx
extension. IfNAME
is specified asundef
or""
a production index is created.The new index file will contain the tags specified in the
TAGINFO
argument: an array passed by reference, each element of which is a hash containing attributes of the particular tag. Valid attributes are:name
,expression
,filter
,duplicates
andorder
.For example to create a production index with three tags:
$fh->create_index( undef, [ { name => "TAG1", expression => "F1", duplicates => "KEEP" }, { name => "TAG2", expression => "F2", order => "DESCENDING" }, { name => "TAG3", expression => "UPPER(F3)" } ] );
- open_index [ NAME ]
-
Opens the specified index file. The name should not include the
.mdx
extension. If the name is not specified then the production index is opened. - seek VALUE
-
Seeks in the currently selected index tag for a match for the specified value. Returns 1 if a match is found otherwise the undefined value is returned and the error code can be retrieved with
CodeBase::errno
.The search value must be formatted correctly for the index, for example if an index is generted on
STR(F1)
, whereF1
is a numeric field of width 6, the value be formatted as a right aligned 6-character integer:$fh->seek(" 42");
For string valued index keys a search value shorter than the tag expression length will be matched on the initial substring, e.g.
"FRED"
would match"FREDERICK"
.
Query functions
The query functions interface to the CodeBase Relate/Query module. The interface is currently incomplete. All that is provided is the facility to query a single file.
A query is prepared (in a similar manner to the Perl DBI query) and then executed and the result set stepped through. The functions are:
$q = $fh->prepare_query($expr [, $sortexpr [, $desc]]);
$q->execute;
$q->next([$skip]);
An example of the usage would be:
$q = $fh->prepare_query('AGE >= 18 .AND. AGE <= 65', 'AGE', 1);
$q->execute;
while (my $r = $q->next) {
@fields = $r->values;
# do some processing.
}
I intend to allow more complex queries to be built up in a Perl-ish manner, but I haven't come up with an interface yet.
Miscellaneous functions
- CodeBase::option OPTIONS
-
Sets configuration options for the CodeBase module. The only option currently offered is
trace
. Setting this to a non-zero value enables the output of tracing, which can be helpful in debugging.# Enable tracing CodeBase::option("trace=1"); # Disable tracing CodeBase::option("trace=0");
- CodeBase::errno
-
Returns the error code for the last operation.
- CodeBase::errmsg ERRNO
-
Returns an explanatory string for the error code
ERRNO
- CodeBase::libversion
-
Returns the version of the CodeBase library that the module was compiled and linked against.
- CodeBase::dbformat
-
Returns the XBase file format that the library and module were compiled for. This will be one of "dBASE IV", "FoxPro" or "Clipper".
ERRORS
Functions return a value on success and undef
on error. The error code can be determined by calling CodeBase::errno
, and the equivalent error message by calling CodeBase::errmsg
.
A number of variables are defined as symbolic names for the CodeBase error codes. Thes variables are all defined in the CodeBase
package and so need to be referred with the package prefix (e.g. $CodeBase::e4close
).
General disk access errors
$e4close = -10; # Closing file
$e4create = -20; # Creating file
$e4len = -30; # Determining file length
$e4len_set = -40; # Setting file length
$e4lock = -50; # Locking file
$e4open = -60; # Opening file
$e4read = -70; # Reading file
$e4remove = -80; # Removing file
$e4rename = -90; # Renaming file
$e4seek = -100; # Seeking to a file position
$e4unlock = -110; # Unlocking file
$e4write = -120; # Writing to file
Data file specific errors
$e4data = -200; # File is not a data file
$e4field_name = -210; # Unrecognized field name
$e4field_type = -220; # Unrecognized field type
$e4record_len = -230; # Record length too large
Index file specific errors
$e4entry = -300; # Tag entry missing
$e4index = -310; # Not a correct index file
$e4tag_name = -330; # Tag name not found
$e4unique = -340; # Unique key error
Expression evaluation errors
$e4comma_expected = -400; # Comma or bracket expected
$e4complete = -410; # Expression not complete
$e4data_name = -420; # Data file name not located
$e4length_err = -422; # IIF() needs parameters of same length
$e4not_constant = -425; # SUBSTR() and STR() need constant parameters
$e4num_params = -430; # Number of parameters is wrong
$e4overflow = -440; # Overflow while evaluating expression
$e4right_missing = -450; # Right bracket missing
$e4type_sub = -460; # Sub-expression type is wrong
$e4unrec_function = -470; # Unrecognized function
$e4unrec_operator = -480; # Unrecognized operator
$e4unrec_value = -490; # Unrecognized value
$e4unterminated = -500; # Unterminated string
Optimization errors
$e4opt = -610; # Optimization error
$e4opt_suspend = -620; # Optimization removal error
$e4opt_flush = -630; # Optimization file flushing failure
Relation errors (not used)
$e4relate = -710; # Relation error
$e4lookup_err = -720; # Matching slave record not located
Severe errors
$e4info = -910; # Unexpected information
$e4memory = -920; # Out of memory
$e4parm = -930; # Unexpected parameter
$e4result = -950; # Unexpected result
For detailed explanations of these codes refer to the CodeBase Reference Guide by Sequiter Software Inc.
RESTRICTIONS
Tags cannot be added to existing index files -- the entire index file must be recreated. This is a restriction imposed by CodeBase 5.1.
FUTURE DIRECTIONS
Record fields may be made into an associative array allowing their values to be accessed and set with the following syntax:
$val = $file->{"F1"};
# rather than: $val = $file->value("F1");
$file->{"F1"} = $newval;
# rather than: $file->set_value("F1", $newval);
The query functionality will be expanded.
COMPATIBILTY
CodeBase Functions
CodeBase 6.4 CodeBase 5.1 CodeBase.pm
============ ============ ===========
code4calcCreate expr4calc_create
code4calcReset expr4calc_reset
code4close d4close_all implicit on exit
code4connect
code4data d4data
code4dateFormat
code4dateFormatSet
code4exit e4exit
code4flush d4flush_files
code4indexExtension
code4init d4init
code4initUndo d4init_undo
code4lock
code4lockClear
code4lockFileName
code4lockItem
code4lockNetworkId
code4lockUserId
code4logCreate
code4logFileName
code4logOpen
code4logOpenOff
code4optAll
code4optStart d4opt_start
code4optSuspend d4opt_suspend
code4timeout
code4timeoutSet
code4tranCommit
code4tranRollback
code4tranStart
code4tranStatus
code4unlock d4unlock_files
code4unlockAuto
code4unlockAutoSet
Data File Functions
CodeBase 6.4 CodeBase 5.1 CodeBase.pm
============ ============ ===========
d4alias d4alias
d4aliasSet d4alias_set
d4append
d4appendBlank d4append_blank
d4appendStart d4append_start
d4blank
d4bottom
d4changed
d4check
d4close d4close undef $fh
d4create
d4delete
d4deleted
d4eof
d4field
d4fieldInfo d4field_info
d4fieldJ d4field_j
d4fieldNumber d4field_number
d4fileName
d4flush d4flush $fh->flush
d4flushData d4flush_data
d4freeBlocks d4free_blocks
d4go d4go $fh->go
d4goBof d4go_bof
d4goData d4go_data
d4goEof d4go_eof
d4index
d4lock
d4lockAdd
d4lockAddAll
d4lockAddAppend
d4lockAddFile
d4lockAll d4lock_all
d4lockAppend d4lock_append
d4lockFile d4lock_file $fh->lock('FILE')
d4lockIndex d4lock_index
d4lockTest d4lock_test
d4lockTestAppend d4lock_test_append
d4lockTestFile d4lock_test_file
d4log
d4logStatus
d4memoCompress d4memo_compress
d4numFields d4num_fields $fh->fldcount
d4open d4open $fh = CodeBase::open($file ...)
d4openClone
d4optimize
d4optimizeWrite d4optimize_write
d4pack d4pack
d4packData d4pack_data
d4position d4position
d4positionSet d4position_set
d4recall d4recall
d4recCount d4reccount
d4recNo d4recno $fh->recno
d4record
d4recPosition d4record_position
d4recWidth d4record_width $fh->recsize
d4refresh d4refresh $fh->refresh
d4refreshRecord d4refresh_record
d4reindex d4reindex
d4remove
d4seek d4seek $fh->seek
d4seekDouble d4seek_double
d4seekN d4seek_n
d4seekNext
d4seekNextDouble
d4seekNextN
d4skip d4skip $fh->skip
d4tag d4tag
d4tagDefault d4tag_default
d4tagNext d4tag_next
d4tagPrev d4tag_prev
d4tagSelect d4tag_select
d4tagSelected d4tag_selected
d4tagSync
d4top d4top
d4unlock d4unlock
d4write d4write
d4writeData d4write_data
d4writeKeys d4write_keys
d4zapData d4zap_data
Date Functions
date4formatMdx date4format_mdx
date4formatMdx2 date4format_mdx2
date4timeNow date4time_now
dfile4updateHeader d4update_header
e4exitTest e4exit_test
error4code e4code
error4set e4set
expr4calcDelete expr4calc_delete
expr4calcLookup expr4calc_lookup
expr4calcMassage expr4calc_massage
expr4calcModify expr4calc_modify
expr4calcNameChange expr4calc_name_change
expr4keyConvert expr4key_convert
expr4keyLen expr4key_len
Field Functions
f4assignChar f4assign_char $fh->field_set($name, $value)
f4assignDouble f4assign_double
f4assignField f4assign_field
f4assignInt f4assign_int
f4assignLong f4assign_long
f4assignN f4assign_n
f4assignPtr f4assign_ptr
f4memoAssign f4memo_assign
f4memoAssignN f4memo_assign_n
f4memoFree f4memo_free
f4memoLen f4memo_len
f4memoNcpy f4memo_ncpy
f4memoPtr f4memo_ptr
f4memoSetLen f4memo_set_len
f4memoStr f4memo_str
file4lenSet file4len_set
file4lockHook file4lock_hook
file4optimizeWrite file4optimize_write
file4readAll file4read_all
file4readError file4read_error
file4seqRead file4seq_read
file4seqReadAll file4seq_read_all
file4seqReadInit file4seq_read_init
file4seqWrite file4seq_write
file4seqWriteFlush file4seq_write_flush
file4seqWriteInit file4seq_write_init
file4seqWriteRepeat file4seq_write_repeat
i4tagAdd i4add_tag
i4tagInfo i4tag_info
relate4createSlave relate4create_slave
relate4doAll relate4do
relate4doOne relate4do_one
relate4errorAction relate4error_action
relate4freeRelate relate4free_relate
relate4matchLen relate4match_len
relate4querySet relate4query_set
relate4skipEnable relate4skip_enable
relate4sortSet relate4sort_set
t4addCalc t4add_calc
t4uniqueSet t4unique_set
tfile4add t4add(a)->tagFile, b, c
tfile4block t4block(a)->tagFile
tfile4bottom t4bottom( (a)->tagFile
tfile4down t4down( (a)->tagFile
tfile4dskip t4dskip(a)->tagFile, b
tfile4dump t4dump(a)->tagFile, b, c
tfile4eof t4eof(a)->tagFile
tfile4flush t4flush(a)->tagFile
tfile4freeAll t4free_all(a)->tagFile
tfile4go t4go(a)->tagFile, b, c, 0
tfile4isDescending t4is_descending(a)->tagFile
tfile4key t4key(a)->tagFile
tfile4position t4position(a)->tagFile
tfile4positionSet t4position_set(a)->tagFile, b
tfile4recNo t4recno(a)->tagFile
tfile4remove t4remove(a)->tagFile, b, c
tfile4removeCalc t4remove_calc(a)->tagFile, b
tfile4seek t4seek(a)->tagFile, b, c
tfile4skip t4skip(a)->tagFile, b
tfile4top t4top(a)->tagFile
tfile4up t4up(a)->tagFile
tfile4upToRoot t4up_to_root(a)->tagFile
Unsupported functions
Many lower level functions are not directly accessible from CodeBase.pm. These include:
conversion functions (c4xxx)
linked list functions (l4xxx)
memory functions (m4xxx)
sort functions (sort4xxx)
utility functions (u4xxx)
COPYRIGHT AND TRADEMARKS
The CodeBase module is Copyright (C) 1996-1999, Andrew Ford and Ford & Mason Ltd. All rights reserved. The CodeBase library is copyright Sequiter Software, Inc.
CodeBase is a trademark of Sequiter Software, Inc.
AUTHOR
Andrew Ford (andrew@icarus.demon.co.uk)
SEE ALSO
The Perl reference manual, especially the following sections: perlmod (modules), perldata (data types), perlobj (objects), perlref (references and nested data structures), perldsc (data structures cookbook), perllol (manipulating lists of lists).
The second edition of Programming Perl by Larry Wall and Randal L. Schwarz (O'Reilly and Associates) covers Perl 5.
The CodeBase Reference Guide and the CodeBase User Guide, both from Sequiter Software Inc. cover the underlying C library.