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Tron Thomas 11-07-2004 05:26 PM

Detecting binary verses text file streams
 
What does binary mode for an ofstream object do anyway? Despite which
mode the stream uses, operator << writes numeric value as their ASCII
representation.

I read on the Internet that it is possible to change the behavior of
operator << so it will stream numeric values as their actual values
when an ofstream is in binary mode. I did not, however, find any
information on how this can be accomplished. What is involved in
getting this to work?

Given that it might be complicated to change the behavior of operator
<< for binary streams, I would like to be able to determine how an
object should serialize itself to a stream so that numeric values are
written as their actually value for binary streams and as their ASCII
representation for text streams. How can this be done?

osmium 11-07-2004 05:43 PM

Re: Detecting binary verses text file streams
 
"Tron Thomas" writes:

> What does binary mode for an ofstream object do anyway? Despite which
> mode the stream uses, operator << writes numeric value as their ASCII
> representation.
>
> I read on the Internet that it is possible to change the behavior of
> operator << so it will stream numeric values as their actual values
> when an ofstream is in binary mode. I did not, however, find any
> information on how this can be accomplished. What is involved in
> getting this to work?
>
> Given that it might be complicated to change the behavior of operator
> << for binary streams, I would like to be able to determine how an
> object should serialize itself to a stream so that numeric values are
> written as their actually value for binary streams and as their ASCII
> representation for text streams. How can this be done?


There is a lot of bad information on the Internet and it looks like you came
across some of it. << and >> both implicitly specify conversion to or from
the underlying character code. For binary files you should use read() and
write(). Does their use cause you problems? (Other than a presumed
elegance, that is)



John Harrison 11-07-2004 07:26 PM

Re: Detecting binary verses text file streams
 

"Tron Thomas" <tron.thomas@verizon.net> wrote in message
news:a4171f97.0411070926.d101b19@posting.google.co m...
> What does binary mode for an ofstream object do anyway? Despite which
> mode the stream uses, operator << writes numeric value as their ASCII
> representation.


Yes << for for text output, write is for binary output.

>
> I read on the Internet that it is possible to change the behavior of
> operator << so it will stream numeric values as their actual values
> when an ofstream is in binary mode. I did not, however, find any
> information on how this can be accomplished. What is involved in
> getting this to work?


That is garbage.

>
> Given that it might be complicated to change the behavior of operator
> << for binary streams, I would like to be able to determine how an
> object should serialize itself to a stream so that numeric values are
> written as their actually value for binary streams and as their ASCII
> representation for text streams. How can this be done?


There are no such things as binary streams and text streams. Streams are
just streams. File streams can be opened in binary mode or text mode, but
you can do text output on a stream opened in binary mode, and you can do
binary output on a stream opened in text mode (not advisable though).

Text mode, binary mode is commonly misunderstood. In text mode the
implementation is allowed to make certain transformations of characters read
and written, a common example is converting \n to \r\n on output on PC
systems. This makes perfect sense if you are doing text output but it is
disastrous if you are doing binary output.

Text output use <<, binary output use write, and if you are planning on
binary output then open in binary mode so you don't get any character
transformations.

john



Tron Thomas 11-08-2004 10:07 PM

Re: Detecting binary verses text file streams
 
"osmium" <r124c4u102@comcast.net> wrote in message news:<2v756jF2erdsjU1@uni-berlin.de>...
> There is a lot of bad information on the Internet and it looks like you came
> across some of it. << and >> both implicitly specify conversion to or from
> the underlying character code. For binary files you should use read() and
> write(). Does their use cause you problems? (Other than a presumed
> elegance, that is)


The user of read and write do not cause any problems. I justed wanted
to know whether I wanted to use operator << or the write method
depending on whether the file was meant to be written in binary format
or text format.

I was hoping the mode of the stream would help me make this
determination. It appears that there isn't a lot of difference
between a stream in binary mode and a stream in text mode. This looks
like knowing which method of writing to the stream is something I
would have to track outside of the stream.


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