Text_IO from a stream
in [ADA]
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From: Gautier on 31 Mar 2008 15:17 Dmitry A. Kazakov: > But a stream has no defined formatting and is unrelated to ASCII. Still, you can read the stream through Character'Read(s,c). > Then the idea of parsing stream looks problematic. If you have in the stream a > sequence " + -", what Get should do after discovering '-'? Exactly the same behaviour as when parsing an ill-formatted text. Reading a text file (or supposedly so) indirectly via a stream and Stream_IO would have the same result that via Ada.Text_IO. > Anyway, it is quite simple to do. You can do > > type Formatted_Stream (Source : access Root_Stream_Type'Class) is > tagged limited private; > function Get (Stream : access Formatted_Stream) return Integer; > ... > > The implementation of Formatted_Stream will use Source for all its I/O. So > you could hang it on any existing stream. Fine, seems I need to rewrite a Text_IO for streams. I hoped for a ready-made solution... Well, I think I'll switch to a binary format... ______________________________________________________________ Gautier -- http://www.mysunrise.ch/users/gdm/index.htm Ada programming -- http://www.mysunrise.ch/users/gdm/gsoft.htm NB: For a direct answer, e-mail address on the Web site!
From: Dmitry A. Kazakov on 31 Mar 2008 15:47 On Mon, 31 Mar 2008 21:17:10 +0200, Gautier wrote: > Dmitry A. Kazakov: >> But a stream has no defined formatting and is unrelated to ASCII. > > Still, you can read the stream through Character'Read(s,c). Yes, but will that be ASCII-encoded? And it has somehow invent lines and pages. >> Then the idea of parsing stream looks problematic. If you have in the stream a >> sequence " + -", what Get should do after discovering '-'? > > Exactly the same behaviour as when parsing an ill-formatted text. Ah, yes. I cannot find the place in ARM, but it seems that Text_IO would swallow syntactically incorrect input before propagating Data_Error. > Reading a text file (or supposedly so) indirectly via a stream and Stream_IO > would have the same result that via Ada.Text_IO. > >> Anyway, it is quite simple to do. You can do >> >> type Formatted_Stream (Source : access Root_Stream_Type'Class) is >> tagged limited private; >> function Get (Stream : access Formatted_Stream) return Integer; >> ... >> >> The implementation of Formatted_Stream will use Source for all its I/O. So >> you could hang it on any existing stream. > > Fine, seems I need to rewrite a Text_IO for streams. I hoped for a ready-made > solution... But Text_IO also defines all Get procedures on String. So if you knew where line ends are in your stream you could cache the current line in Formatted_Stream and then simply route all its Gets to Ada.Text_IO Gets. > Well, I think I'll switch to a binary format... I would do that too. Also I would override 'Read and 'Write in order to make it platform-independent. (Stream_Element should be replaced by octets.) -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de
From: Gautier on 31 Mar 2008 16:54
Dmitry A. Kazakov: > Yes, but will that be ASCII-encoded? And it has somehow invent lines and > pages. Sure, it is indeed a zip-archived text file that I intend to read through UnZip.Streams. Meanwhile (#ada irc...) there seems to be a nice solution: http://jesselang.com/software/streams_text_io/ .... >> Well, I think I'll switch to a binary format... > > I would do that too. Also I would override 'Read and 'Write in order to > make it platform-independent. (Stream_Element should be replaced by > octets.) No problem with that - there is already a framework in that package (for other files) that sends things byte-per-byte in a deterministic endianess; floats are split/merged with certain a Float_portable_binary_transfer package. Thanks for the help! ______________________________________________________________ Gautier -- http://www.mysunrise.ch/users/gdm/index.htm Ada programming -- http://www.mysunrise.ch/users/gdm/gsoft.htm NB: For a direct answer, e-mail address on the Web site! |