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1996-07-10
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{HISTORY of BTP - the Btrieve Unit for Turbo Pascal 6.0 V1.5, 11/9/91 }
(* ----------------------------------------------------------------------- *)
Version 1.0 4/9/91: Initial functioning unit, released 9/5/91.
Version 1.1 9/8/91: Corrected a problem occuring in Btrieve files that had
segmented keys with more than one segment. The stats
stored by the BFile.Init constructor were not calculating the number of
segments properly. The CreateFile function was also modified to deal with
the same key problem. This change forces one more statement to be placed
in any 'create file' routine. Any of the 24 key arrays not used in a file
must have their key flags set to zero. See Create.PAS for an example.
Version 1.2 9/16/91: NOT RELEASED PUBLICLY.
Derived a new base object, BRecMgr, from what HAD been
my base object, BFile. It made sense to me to provide access directly
thru an object to the basic, non-file, non-record oriented Btrieve
operations: Begin/End/Abort Transaction, Version, Stop and Reset. This
BLOWS compatibility with any code you wrote under prior versions of this
unit as the BT function is now virtual. You should NOT call the ancestor
BT function in your override...replace it completely as shown in the
example programs and in BTP.DOC.
BRecMgr has a variant record field to hold info on the version of Btrieve
the user is running. That data is set by BRecMgr.Init.
Version 1.3 10/11/91: Unit name changed to BTP. Bug fixed that would give
incorrect result in BFile.NumRecs if number of records
exceeded 32,767. Made a number of "touch-up" changes to make it easier to
use dynamic variables of the various data types in BTP. Note particularly
that the CreateFile function now requires a second parameter, a pointer to
a Btrieve file spec as defined in BTP.
The constructors for BRecMgr and BFile now set up a string data field,
VersionString, equal to the version number of Btrieve running in the user's
computer. This is in addition to establishing the record field Version,
which contains the exact bytes returned by the Btrieve version call.
All example programs were modified to reflect the changes in 1.2 and 1.3.
Version 1.4 10/27/91: Nomenclature of data types improved and made more
consistent, both within BTP and with TP6's own internal
Turbo Vision style. TRecMgr and BFile are now separate "base" objects.
Added BFixed and BFileExt objects, both descendants of BFile. Together
these permit handling any standard fixed-length file, and provide complete
support for the get/step extended calls, including handling of all the
drudgery of constructing data buffers. This was no small task! For
extended calls, you need simply insert your filter and extractor specs into
the provided collections in BFileExt. The rest of the setup is transparent
to you, being handled by the object's internal methods and your standard
override of the BTExt function.
An object of type BFileExt can freely entertain both standard BT and
extended BTExt calls thanks to encapsulation of the position block in the
object (see EXAMPLE2.PAS). However, I recommend use of BFileExt only if
you are truly going to use extended calls for a particular file. This is
because there is about 32K more overhead per BFileExt object than BFile.
The size of a BFile object is 698 bytes. The size of a BFileExt object is
722 bytes, plus the size of the extended data buffer, which I default to
32767 bytes, plus the size of any items inserted into the two collections.
Note that the size of a BFixed object is 5043 bytes, to hold room for a
buffer equal to the maximum size of a fixed length record, and the maximum
length of a key.
BFile and its descendants now take an Open mode parameter.
The BFile.BT virtual function is now Abstract, to assure you don't call
it without overriding it.
The BFileExt.BTExt method must be overridden, with the override calling
the ancestor; i.e. your override must be of a standard form, and must call
BFileExt.BTExt. This is because BFileExt.BTExt is what sets the buffer
length and constructs the buffer for extended read calls. This is in
contrast to BFile.BT or BFileExt.BT, which must be overridden by REPLACING
them, as shown in the example programs and in BTP.DOC.
BFileExt's data fields include two collections. The FilterSpec collection
need not hold any objects, but the ExtractorSpec must always hold at least
one. Now, for extended calls, you handle these data fields as follows
(see EXAMPLE2.PAS):
1: HEADER is handled internally. Don't mess with it.
2: FILTER's fields are assigned by your program.
3: FILTERSPEC collection may or may not hold any objects, depending on
your program's needs.
4: EXTRACTOR must be initialized.
5: EXTRACTORSPEC collection must hold at least one object.
6: EXTDBUFFER is handled internally. Don't mess with it, except to
use it as shown in EXAMPLE2.PAS when you override BFileExt.BTExt.
BTP 1.4 IS THE FIRST *SHAREWARE* RELEASE. The BTP product is no longer
FreeWare.
Version 1.5 11/9/91: New in this release...complete support for alternate
collating sequences. This required modifying the BFile
object and its constructor, and the CreateFile function, and the addition of
data structures for an alternate collating sequence file. A boolean field in
BFile, HasAltCol, has been established. The CreateFile function now takes a
third parameter, being the name of an alternate collating sequence file, if
any.
Also changed in this version:
BFile has an additional field for a file's actual filespec length. This
can be useful when cloning a file. A new function, CloneFile, has been
added, which reduces the cloning process to a single function call, with only
the names of the existing and new files passed as parameters. Miscellaneous
changes in V1.5 include elimination of a redundant parameter previously
required by the FilterSpec object's constructors. Added a variant to both
the FileSpec and KeySpec objects to allow easier reporting of certain stats
after a stat call.
Some minor optimizations done here and there thruout the unit and example
programs.
BEST NEWS! The STATS program has been greatly enhanced. It now produces
substantially the same output as 'BUTIL -STAT', but is a standalone program
and can be freely distributed with your applications (unlike BUTIL) IF YOU ARE
A REGISTERED USER of BTP.