HELP: Mode in which the original file is compressed and, when desired, encrypted TYPE: NUMBER SYNTAX: MODE/MO/CMPMODE=CX7/CX8/VR8/ADC/NDC/AES/FLAMENC
Input file(s) are compressed with the specified FLAM mode.
FLAM supports four compression modes: adc, cx7, cx8, and vr8. In the adc, cx8, and vr8 modes, it creates the FLAMFILE as a binary file. Mode adc is the most efficient one. It compresses the datastream by removing the redundancy of repetitive sequences and can be used universally. The other modes mainly eliminate "vertical redundancy", i.e. their efficiency relies on the recognition of re-occurring column contents in table-structured data.
Compression mode adc can be combined with one of two encryption methods supported by FLAM. The first is AES, that has been declared standard for US government agencies by NIST (National Institute of Standards and Technology), the second flamenc is a proprietary algoriths of limes datentechnik gmbh. None of the other compression methods allows encryption.
In all binary modes the compressed information is largely independent of the characteristics of the system on which the compression took place, i.e. the FLAMFILEs must not be modified, for example, if they are transmitted on a line which translates codes automatically. FLAMFILEs which are compressed in the cx7 mode, on the other hand, are insensitive to code translations, since they represent all control information by means of alphanumeric characters, the codes for which are standardized internationally in the ASCII and EBCDIC systems. Providing the original data is character-coded and suitable for exchange between systems with different character sets, the information content of the FLAMFILE remains fully intact after it has been converted to the character set of the destination system, despite the altered binary contents, thanks to the character-oriented interpretation.
The compression mode is identified automatically when the file is decompressed. The user thus does not need to know the compression mode in order to decompress a file.
Compression mode CX8 and VR8 does not support CRYPTOMODE=FLAM
.
Compression mode CX7 does not support either CRYPTOMODE=ADC
nor CRYPTOMODE=FLAM
.
Syntax restrictions for FLAMv4 or older:
MODE=ADC/CX7/CX8/VR8/NDC
MO=ADC/CX7/CX8/VR8/NDC
-mode=adc/aes/cx7/cx8/vr8/flamenc
mode=adc/aes/cx7/cx8/vr8/ndc
ADC
- 8 bit compression of highest efficiencyCX7
- transformable 7 bit compressionCX8
- 8 bit compression (CPU time optimised)VR8
- 8 bit compression (space optimised)NDC
- no compressionadc
- 8 bit compression of highest efficiency.-mode=adc
the input file is compressed in adc mode and a
binary FLAMFILE is created. This is the most efficient
mode and can be used universally irrespective of the
data structure. With this mode, a password can be
specified to encrypt the FLAMFILE, see also parameters
CRYPTOKEY and PASSWORDaes
- mode=aes
causes the input file to be compressed in the adc
mode with AES encryption. A password must be specified with
the -password
parameter, see also parameters
CRYPTOKEY and PASSWORD.cx7
- transformable 7 bit compression.-mode=cx7
, the input file is compressed in the cx7 mode
and a character-coded FLAMFILE is created. However,
files should only be compressed in this mode if they do not
contain any non-printing characters. It is a slightly less
efficient mode, though on the other hand the FLAMFILE which
is created can be converted to other character sets, e.g.
from ASCII to EBCDIC, without losing information.cx8
- 8 bit compression (CPU time optimised).-mode=cx8
the input file is compressed in the cx8 mode,
respectively, and a binary FLAMFILE is created. The purpose
of this mode is to ensure compatibility with previous versions.vr8
- 8 bit compression (space optimised).-mode=vr8
, the input file is compressed in
vr8 mode, respectively, and a binary FLAMFILE is
created. The purpose of this mode is to ensure compatibility
with previous versions.flamenc
- mode=flamenc
causes the input file to be compressed in the
adc mode with FLAM encryption (the proprietary
encryption method used with FLAM 3).
A password must be specified with the -password
parameter.
See also parameters CRYPTOKEY and
PASSWORD.adc
- 8 bit compression of highest efficiency.aes
- FLAM Version 4: The input file is compressed
with the AES method. A password must be specified, see also
parameters CRYPTOKEY and
PASSWORD.cx7
- Transformable 7 bit compression.cx8
- 8 bit compression (CPU time optimised).vr8
- 8 bit compression (space optimised).ndc
- No data compression. CX7 - Compression encoding as printable characters
CX8 - Compression encoding as binary data
VR8 - Enhanced compression encoding as binary data
ADC - Advanced Data Compression
NDC - No data compression
AES - AES encryption
FLAMENC - FLAM encryption