Tickets :: Comment on [#25] error :source-ing files with "variable length" record format

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Comment	> ==================================== > = ONCE MORE (more readable indent) = > = ignore Comment #2 = > ==================================== > > Motivation for this ticket. > > The problem with sourcing appears whenever a vim plugin is copied to > VMS via FTP. If it is dropped into [plugin] or [ftplugin] or > [autoload] it then crashes when it is sourced. > > -------------------- > Details > > Here are some notes I have compiled on copying files from Windows to > VMS via FTP. > > Binary FTP > First of all, binary-FTP-copying is of out of question. The file > created on > the VMS is padded to the next higher multiple of 512 bytes, > which is very > ugly. This also shows when the file is opened in vim. (Other > than that, the > file thus copied is nicely readable on the VMS by vim, and sourcing it > works -- if its fileformat on Windows was "unix".) The rest of this > therefore discusses ASCII FTP. > > ASCII FTP > A file on the local (Windows) machine either has the DOS or UNIX > fileformat. In the former case, the lines are separated by 0d0a, in the > latter case only by 0a. Obviously, the former is native, the > other is alien > to Windows. > > When the file is ASCII-FTP copied to VMS, it is converted to an RMS file > with variable-length record format and carriage-return-carriage-control > record attributes. The FTP knows it is copying a file from > Windows to VMS, > and thus presumes that the original (Windows) file uses 0d0a > sequences as > line separators. (Which assumption is wrong if the fileformat is Unix.) > > Whatever the fileformat was on Windows, the resultant file has now been > converted to an RMS file, whose each line (record) has an attribute > specifying its length. The record attributes are "Carriage > return carriage > control". This would suggest there are still some "carriage returns" > between records (xxd reports line feeds, "0a"s), but this may just be a > trick of OpenVMS: > > Wikipedia: "OpenVMS uses a record-based file system, which > stores text > files as one record per line. In most file formats, no line > terminators > are actually stored, but the Record Management Services facility can > transparently add a terminator to each line when it is > retrieved by an > application." > > This is where the original fileformat makes a difference: a > multi-line file > with fileformat=dos has been converted to a multi-record RMS file, with > records starting wherever 0d0a sequences were found. A > multi-line file with > fileformat=unix was also converted, but since there were no 0d0a > sequences, > it only contains a single record on VMS. xxd sees them > identically: for the > multi-record "dos" file it displays "0a"s where records break; for the > single-record "unix" file it displays "0a"s which have not been > recognised > as line terminators and are "still present" in the single record. > > Example: let's suppose a Windows file contains the text "a\nb". > The "dos" > representation would be 61-0d-0a-62, and this would be converted to a > 2-record file: the first record would have length 1 (the byte 61), the > second record would also have length 1 (the byte 62), and xxd would show > 61-0a-62. The "unix" representation would be 61-0a-62, and this would be > converted to a single-record file: the record would have length 3 > (61-0a-62), and xxd would also show 61-0a-62. > > Now we use vim to open the file. The "dos" file is read as a multi-line > file, with "0a"s used as separators. Good. The "unix" file is read as a > one-liner. That's also fine with vim, which notices the "0a"s > and considers > them line separators. Also good. > > In both cases vim detected the fileformat as "unix" (since there were no > 0d0a sequences). If we were to save either of the files using > the VMS vim, > it would become an RMS file with Stream_LF record format (and the same > carriage-return-carriage-control record attributes). > > Paradoxically, there is a problem when sourcing the multi-record, > originally-dos-fileformat files -- while sourcing the single-record, > originally-unix-fileformat file succeeds. Perhaps this is a vim bug. > > When sourcing the file, vim apparently does not recognise the > record limits > and simply concatenates the records without putting the 0a bytes in > between. Thus, the whole text becomes a mess (the lines are not > separated > at all). > > On the contrary, the originally-unix-fileformat file works because after > vim reads it as a one-liner, it detects the "0a"s, separates the > lines, and > sources it correctly. > > Conclusion > The above would suggest it is best to use fileformat=unix when > FTP copying. > However, there is a serious problem with this: if the file is > longer than > 32767 bytes, the file is truncated because at most 32768 bytes > can be put > into a single RMS-file record. (And we are creating a > single-file record, > as described above.) What's worse, no warning/error is issued when this > happens during the ASCII-FTP copy. > > Thus, it is best and safest to use the dos fileformat, ASCII FTP > copy, and > then change the file's record format to Stream_LF using convert/fdl. > >
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