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From: "David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>
Subject: Re: Extracting Fields in Files
Date: 2000/01/13
Message-ID: <85l7t4$18c$1@hobbes2.crc.com>#1/1
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 <85l0iu$6uj$1@nnrp1.deja.com>
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Date: 2000-01-13T19:09:24+00:00
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<jmoor@my-deja.com> wrote in message news:85l0iu$6uj$1@nnrp1.deja.com...
> Would you believe that I am reading a variable length record created on
> a Unisys machine whose records are in the following sequence:
>
> record    size
>   #       (bytes)
>
> 1          16
> 2         212
> 3          16
> 4         212
> 5          16
> 6         212
> 7          16
> 8         212
> 9          16
>
> I open the file with the following statement;
>   text_io_open ( file => tip0125,
>        mode => text_i.in_file,
>        name => "tip0125");
>
> Every time I read the file with the following statement;
>   get_line (file => tip0125,
>       item => rec01,
>       last => rec01_length,)
>
> After each 212 byte record is read, the get_line goes through a cycle
> where it believes a zero byte record has been read.  I can easily get
> around the problem by testing "rec01_length" for zero bytes, but this
> is evidence that I might not understand the nature of the "get_line"
> command when reading a variable length file.
Well.... Ada doesn't really speak of file "records," as such.

Ada.Text_IO.Get_Line reads based on whatever the line terminator is
for the OS in question.  Reading a file on an OS with a different line
termination convention may produce unexpected results.

You may find it more useful to use Ada.Streams.Stream_IO, because it
allows you to read the file as a stream of bytes -- in which case you can
do your own thing to recognize line terminators.

>From your earlier post it appeared that your code also depended on
the fields beginning and ending in specific columns.  You may find
the procedures like Ada.Strings.Fixed.Find_Token helpful in breaking
a line up into tokens if the fields are always delimited by characters
that never appear within any field.