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decompressordtypev39.0.lha
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DecompressorDT
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decompressor_dtc.doc
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1996-09-24
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TABLE OF CONTENTS
decompressor/decompressor.datatype
decompressor/decompressor.datatype decompressor/decompressor.datatype
NAME
decompressor.datatype -- Special root data type for compressed files.
FUNCTION
The decompressor.datatype is special DataTypes class for multiformat
compressed files.
METHODS
OM_NEW -- Decompress source file, place it in temporary directory and
call OM_NEW method on that file.
NOTES
*VERY IMPORTANT NOTE*
However this is a programmer document, the decompressor.datatype should
not be used by programmers in general and this information is enclosed
here just for completness and to satisfy the standards. This datatype
is considered as a temporary solution and is very likely to become
obsolete in next revisions of DatyTypes system.
Decompressor.datatype has been written to be as transparent to DataTypes
system as possible. However, accomplishing this task needed some not so
system-friendly programming on my part - I was forced to do a patch of
DisposeDTObject() function of datatypes.library (that is why OM_DISPOSE
method is not provided). While this is still legal, such a practice is
generally not recommended. Maybe I will try to remedy the situation by
possible use of model class in the future.
Actual decompression is performed with help of temporary files, which
are placed in unique directories on T: logical device and then fed to
NewDTObject() function.
Due to strange programming of amigaguide.datatype this is not possible
to properly load and display packed amigaguide databases from within an
amigaguide database. At this time I can see no workaround for this.
Because filetype recognition is performed via use of xfdmaster.library
(© Georg Hörmann), number of supported compression formats is not
predefined - and will automatically enlarge when new, future versions of
this library are installed to the system.
BUGS
16 (XFDPF_KEY16) and 32 (XFDPF_KEY32) bit keys as password inputs are
not supported.
Maximal length of password is 65534, without terminating zero. Unlimited
length passwords of xfdmaster.library are not supported and will be
treated as 65535 bytes long (unsigned word) passwords - thus they most
propably won't work. ;-)
Unfortunately, at a time, decompressor.datatype completely lacks support
for descriptive error messages. Hopefully I will fix it in final release.
Not my bugs:
- unable to load packed amigaguide databases from within an amigaguide
document (this is due to weird programming of amigaguide.datatype)
- amigaguide path environment variable is not handled properly when
version 0.7 of HappyENV-Handler (© Martin Gierich) is installed (this
is due to the fact, that curently this handler lacks support for some
important dos functions like Seek(), OpenFromLock(), etc.)
SEE ALSO
xpk.datatype, xfdmaster.library, dos.library