EOF problem

[BH]

I'm doing a decryption prog which read a enc. file and decrypt it. However,
some of the encrypted text is the same as EOF and thus i cant read the text
that after it. What should i do?

I tried the getline and read.. but still cant work.. can anyone help me?

[osmium]

Re: EOF problem

BH writes:
[color=blue]
> I'm doing a decryption prog which read a enc. file and decrypt it.[/color]
However,[color=blue]
> some of the encrypted text is the same as EOF and thus i cant read the[/color]
text[color=blue]
> that after it. What should i do?
>
> I tried the getline and read.. but still cant work.. can anyone help me?[/color]

There is no EOF character. EOF is a *condition*, not a character, at least
in the context of a C++ program. Rethink your problem. The typical modern
computer has 256 character codes, none of which denote EOF.

[Arne Schmitz]

Re: EOF problem

osmium schrieb:
[color=blue]
> There is no EOF character.  EOF is a condition, not a character, at least
> in the context of a C++ program.  Rethink your problem.  The typical
> modern computer has 256 character codes, none of which denote EOF.[/color]

Well, if he uses a Windows compiler and opened the file in textmode (without
"b"-flag) using fopen(3), then he will stumble over EOF characters as they
existed in the legacy ASCII character set.

Posix ignores the "b"-flag and treats text- and binary files the same.

Cheers,

Arne

--
[--- PGP key FD05BED7 --- http://www.root42.de/ ---]

[David Harmon]

Re: EOF problem

On Sun, 18 Apr 2004 19:09:43 +0800 in comp.lang.c++, "BH" <bbg@cc.com>
wrote,[color=blue]
>I'm doing a decryption prog which read a enc. file and decrypt it. However,
>some of the encrypted text is the same as EOF and thus i cant read the text
>that after it. What should i do?
>
>I tried the getline and read.. but still cant work.. can anyone help me?[/color]

You must open the file in binary mode using the ios::binary openflag
value. See e.g.:

http://groups.google.com/groups?selm=4085bce8.92392772@news.west.earthlink.net

[Kevin Goodsell]

Re: EOF problem

Arne Schmitz wrote:
[color=blue]
> osmium schrieb:
>
>[color=green]
>>There is no EOF character. EOF is a condition, not a character, at least
>>in the context of a C++ program. Rethink your problem. The typical
>>modern computer has 256 character codes, none of which denote EOF.[/color]
>
>
> Well, if he uses a Windows compiler and opened the file in textmode (without
> "b"-flag) using fopen(3), then he will stumble over EOF characters as they
> existed in the legacy ASCII character set.[/color]

Maybe, but as the man said, (C++) EOF is a condition, not a character.
You cannot find (C++) EOF unless you are and the actual end of the file.
Finding ASCII EOF does not cause (C++) EOF. Well, it could, but that
would be the implementation' s fault. Obviously if that's the case he
would need to decide on a solution, such as 1) use binary mode, or 2)
make your text files valid for the host system (remove EOF characters
that don't actually indicate EOF).

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[David Harmon]

Re: EOF problem

On Sun, 18 Apr 2004 19:02:07 GMT in comp.lang.c++, Kevin Goodsell
<usenet2.spamfr ee.fusion@never box.com> wrote,[color=blue]
>Finding ASCII EOF does not cause (C++) EOF. Well, it could, but that
>would be the implementation' s fault.[/color]

It is perfectly within the range of allowable behavior for text mode.
And might even have a justifiable reason in some case(*).
If you do not like it, use binary mode like you are supposed to.

(*)The origin of this nonsense was an ancient filesystem that did not
store the exact file size, so text files needed a internal mark at the
end after the final character. This was not C++'s fault or even C's
fault.

[Kevin Goodsell]

Re: EOF problem

David Harmon wrote:
[color=blue]
> On Sun, 18 Apr 2004 19:02:07 GMT in comp.lang.c++, Kevin Goodsell
> <usenet2.spamfr ee.fusion@never box.com> wrote,
>[color=green]
>>Finding ASCII EOF does not cause (C++) EOF. Well, it could, but that
>>would be the implementation' s fault.[/color]
>
>
> It is perfectly within the range of allowable behavior for text mode.[/color]

Yes, I didn't mean that the implementation would be in error. Just that
it would be a somewhat unusual implementation, or at least behaving in a
rather unexpected (though not wrong) way.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[David Harmon]

Re: EOF problem

On Sun, 18 Apr 2004 22:30:07 GMT in comp.lang.c++, Kevin Goodsell
<usenet2.spamfr ee.fusion@never box.com> wrote,[color=blue]
>David Harmon wrote:[color=green]
>> It is perfectly within the range of allowable behavior for text mode.[/color]
>
>Yes, I didn't mean that the implementation would be in error. Just that
>it would be a somewhat unusual implementation, or at least behaving in a
>rather unexpected (though not wrong) way.[/color]

More prevalent than any of us might wish.

[Jack Klein]

Re: EOF problem

On Sun, 18 Apr 2004 14:44:32 +0200, Arne Schmitz
<arne.schmitz@m mweg.rwth-aachen.de> wrote in comp.lang.c++:
[color=blue]
> osmium schrieb:
>[color=green]
> > There is no EOF character.  EOF is a condition, not a character, at least
> > in the context of a C++ program.  Rethink your problem.  The typical
> > modern computer has 256 character codes, none of which denote EOF.[/color]
>
> Well, if he uses a Windows compiler and opened the file in textmode (without
> "b"-flag) using fopen(3)[/color]

[snip]

"fopen(3)" is, of course, a constraint violation in standard C++,
since the prototype for fopen() is:

FILE *fopen(const char *filename, const char *mode);

===

Yes, I know what you mean by "fopen(3)", but it's a reference to a
system-specific utility for viewing "man pages", nothing to do with C
or C++ or the definition of the function. And it's likely to confuse
newbies, most particularly those working on a Windows platform.

--
Jack Klein
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