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.NET Forum / Languages / C# / June 2007File I/O for EBCDIC/packed files - read/write
Hi, I have read the "how to's" on MSDN including this one, http://msdn2.microsoft.com/en-us/library/36b93480.aspx, on reading/writing files in C#, but haven't found something that I can put together that is working. The file I have is in EBCDIC, rec length = 250 and delimited by CRLF's. What I want to do is open an EBCDIC file in Read/Write mode so I can read the record, alter the data in a fixed set of positions (position 2, zero based for 19 positions), and re-write the record (same file). I have: private const string FILE_NAME = "d:\\somefile.txt" // file that is in EBCDIC // Create the reader for data. FileStream fs = new FileStream(FILE_NAME, FileMode.Open,FileAccess.ReadWrite); BinaryReader br = new BinaryReader(fs); // ??? use this or something else? I am aware of the "Encoding" class, but am not certain if it's needed for what I want to do. I am also aware of the "MemoryStream" and "BinaryReader" classes, but not sure which to use. Any links to thorough examples or responses with code snippets would be most useful. Thanks. > I have read the "how to's" on MSDN including this one,http://msdn2.microsoft.com/en-us/library/36b93480.aspx, on reading/writing > files in C#, but haven't found something that I can put together that is > working. <snip> > I am aware of the "Encoding" class, but am not certain if it's needed for > what I want to do. Yes it is. To read, use a StreamReader with the appropriate encoding. To write, use a StreamWriter with the appropriate encoding. I have an EBCDIC encoding class at http://pobox.com/~skeet/csharp/ebcdic which lets you specify various different variants of it. Jon Jon, Thanks for the quick reply - I will look it over and try to work on it this week. One question I have that hopefully you can answer: When I specify Encoding ebcdic = Encoding.GetEncoding("IBM01140"); Is there way to see the actual table for this particular encoding, perhaps in a *.h file? The reason I ask, is we have an internal table that we use for ASCII-EBCDIC conversions, based on a table from one of our vendors. I am sure it is a "flavor" of the IBM conversion, but I would like to compare it to what Microsoft is doing to see if it matches our table. It won't do me any good to use the wrong encoding for the object. Or I would need to know how to create my own file that I pass in to the "GetEncoding" function which is what I'm guessing your doing with "using JonSkeet.Ebcdic;" from your link. Thanks. > > I have read the "how to's" on MSDN including this one,http://msdn2.microsoft.com/en-us/library/36b93480.aspx, on reading/writing > > files in C#, but haven't found something that I can put together that is [quoted text clipped - 14 lines] > > Jon You could use Reflector to look into the encoding class, but if it is making any calls to the underlying OS to handle the encoding (which in this case, I imagine it is since you are requesting a code page) then you aren't going to be able to figure it out. However, you can do a comparison by cycling through the range of byte values that are valid for the encoding, and seeing what the encoding spits out for them. If they match your table, then use it. If not, you can always create your own Encoding type, derived from Encoding, so that it encodes/decodes the bytes the way you need it to.  Signature- Nicholas Paldino [.NET/C# MVP] - mvp@spam.guard.caspershouse.com > Jon, > [quoted text clipped - 45 lines] >> >> Jon > Thanks for the quick reply - I will look it over and try to work on it this > week. [quoted text clipped - 15 lines] > "GetEncoding" function which is what I'm guessing your doing with "using > JonSkeet.Ebcdic;" from your link. The tables I use are taken from http://std.dkuug.dk/i18n/charmaps/ but you can fairly easily use your own table if you rebuild my code. If you look in the CharMapReader directory in the source.zip file you'll find CharMapReader.cs which documents the file format (same as the site linked above). You can put your own file in there, rebuild the resources etc, and away you go. SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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