File Handling In Pascal Binary Files Wiki Needs Work
lazarus / 62-General

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flywire · 2015-03-05 11:35

I have been making the file handling examples in the tutorial
executable but the Binary Files need a bit of work:
http://wiki.freepascal.org/File_Handling_In_Pascal#Binary_files

The first one falls over at the seek and I don't understand the
intended functionality.

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eny · 2015-03-05 12:07

The code fragment is useless:
- the seek should not be there
- the buffer is written with random data (garbage)
So the title of this topic is well chosen

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Leledumbo · 2015-03-05 12:10

Quote from: eny on March 05, 2015, 01:07:39 pmThe code fragment is
useless:
- the seek should not be there
- the buffer is written with random data (garbage)
So the title of this topic is well chosen
Mind fixing it?

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eny · 2015-03-05 15:18

Quote from: Leledumbo on March 05, 2015, 01:10:46 pmMind fixing it?
I assumed flywire was already on top of it

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flywire · 2015-03-05 19:05

Quote from: Leledumbo on March 05, 2015, 01:10:46 pmMind fixing it?

I have made extensive changes to this tutorial page but I can't
understand this section so hopefully someone else can step it.

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Bart · 2015-03-05 19:54

Made some changes.

Bart

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flywire · 2015-03-06 09:25

These tutorials are a good resource but I would like to promote a bit
of discussion on who the audience is for them? If it is newbies, and I
can't see why it shouldn't be, then I think that the tutorials still
assume too much. The Run-Time Library (RTL): Reference guide does a
good job with plenty of executable examples.  For example, how does
the user know which units have to be added to the uses clause? (I
normally run them and do a search on the errors.) I would be useful to
list them in the tutorial, and sysutils is not going to do it. Yes, I
accept that changes are my responsibility too.

I tested the first two binary files examples and they work fine - good
work fellas. The third one falls over at the end of 'FileStream :=
TFileStream.Create;'. Beats me - it works OK in the FileCopy example
below. Thinking about it though, this not a very useful example and
should probably be deleted and the FileCopy adjusted so that it works
with large files.

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eny · 2015-03-06 09:37

Quote from: flywire on March 06, 2015, 10:25:06 amThese tutorials are
a good resource but I would like to promote a bit of discussion on who
the audience is for them? If it is newbies, and I can't see why it
shouldn't be, then I think that the tutorials still assume too much.In
this case the reviewed examples are clear enough.
It would be a waste of time to explain basic language elements on
every page.
BTW (rhetorical question): what is the definition of newbies?

As for the units usage: I agree.
A code fragment that makes use of a specific class that requires a
uses line, should make mention of that.

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marcov · 2015-03-06 12:24

Quote from: flywire on March 06, 2015, 10:25:06 am   For example, how
does the user know which units have to be added to the uses clause? (I
normally run them and do a search on the errors.)

Press "F1" on the symbol with help installed?

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eny · 2015-03-06 14:09

Quote from: Leledumbo on March 05, 2015, 01:10:46 pmMind fixing it?
Done.

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flywire · 2015-03-07 23:35

Quote from: eny on March 06, 2015, 03:09:48 pmDone.

Just ran program ReadBinaryDataInMemoryForAppend because I need to.

Code: [Select]    // Write some arbitrary data to the memory stream
    msApp.WriteByte(68);
    msApp.WriteAnsiString('Some extra text');
    msApp.WriteDWord(671202);
When I first looked at the result in Hex I thought it was screwed up
but then I realised that this demo is really informative, especially
in little endian. Well done.