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 From: kuehl@ramsen.informatik.uni-konstanz.de (Dietmar Kuehl)
 Newsgroups: comp.std.c++
 Subject: Re: binary iostreams ?
 Date: Sat,  3 Feb 2001 17:17:49 GMT
 Message-ID: <95hctq$suu$2@news.BelWue.DE>

 Hi,
 Plinio Conti (plinio.contiNO@SPAMMINGmclink.it) wrote:
 : Why std c++ library stream classes are only text-oriented?

 There is only a text oriented front end to stream buffers because text
 input and output does not vary between platforms. This is very
 different for binary output. For example, binary output has to consider

 - word sizes: Is an 'int' two, four, or eight bytes long? The same
   questions arise for all other built-in types.

 - what is the bit pattern of a value? I think that at least implicitly
   in the standard a binary representation for integer types is required.
   I don't think that it is required to use two's complement. In any
   case, the floating point representations do differ, eg. in their
   number of bytes used.

 - what "endianess" is to be used?

 Basically it is possible to decide a format for each of those. This,
 however, implies inefficient implementations on platforms where the
 format does not match the internal representation.

 What many people asking for binary I/O forget is that binary I/O also
 requires some form of formatting! Assuming that just writing data and
 then reading it in will work is asking for problems, eg. when the
 compiler version changes and they decided to use a 32 bit integer
 rather than a 16 bit integer: It is not even necessary to switch
 platforms to run into problems!

 : I mean, if I want to write an int, a float, etc. AS IT IS I can't use
 : streams, because they write and read a human readable text format of
 : numbers.

 Which is for most I/O a reasonable approach. If it is not for you, you
 might want to consider a data base: File I/O is not really useful as a
 persistance mechanism. It is fine eg. for user interaction (text I/O),
 logging (text I/O), cross platfrom program interaction (formatted I/O),
 and data exchange (formatted I/O). In all these cases, the I/O is
 formatted, although possible using a binary format. For persistance,
 data bases are used. Depending on your needs, a relational or an object
 oriented one may be better suited.

 That said, it is worth to mention that it is easy to create a hierarchy
 similar to IOStreams built on top of stream buffers but doing binary
 formatting. A somewhat aged example is found at
 <ftp://ftp.fmi.uni-konstanz.de/pub/algo/personal/kuehl/binio.tar.gz>.
 This uses XDR formatting of the binary data (well, if I remmeber
 correctly, it is easy to plug in a different binary formatting).

 : Does anyone know how to solve the problem?

 Use a data base, text formatting, or binary formatting. With the
 details you have given it is impossible to tell which of those is the
 right approach because you haven't told *why* you want a binary format
 and *what* you want to do. That basically means that you came up with
 solution and you want us to confirm that it is the right one without
 telling us what problem is solved! Until I have seen the problem I
 doubt that binary I/O is the right approach...

 ... and, BTW, using 'std::istream::read()' and 'std::ostream::write()'
 is almost certainly the *wrong* approach! These functions are an
 historical mistake which should have been corrected in the standard:
 It is my understanding that these methods were present in the IOStream
 version predating the rework from Jerry Schwartz and were left in to
 be compatible with the earlier stuff although they were not necessary:
 You could get binary I/O from the stream buffer level. The original
 IOStream library (maybe you remember using <stream.h>) did not have
 stream buffers and thus basic support for binary I/O was also present
 on the streams level.

 : What do you think about this choice?

 When I wrote the above paragraph about confirming your choice, I haven't
 read this question! As I said above: You told us what solution you have
 choosen without stating what problem is solved. We cannot determine
 whether your choice is the right one. Actually, I'm pretty sure it is
 the wrong one but without seen the details I can't be certain.
 --
 <mailto:dietmar_kuehl@yahoo.com> <http://www.dietmar-kuehl.de/>
 Phaidros eaSE - Easy Software Engineering: <http://www.phaidros.com/>

	From: kuehl@ramsen.informatik.uni-konstanz.de (Dietmar Kuehl)
	Newsgroups: comp.std.c++
	Subject: Re: binary iostreams ?
	Date: Sat, 3 Feb 2001 17:17:49 GMT
	Message-ID: <95hctq$suu$2@news.BelWue.DE>

	Hi,
	Plinio Conti (plinio.contiNO@SPAMMINGmclink.it) wrote:
	: Why std c++ library stream classes are only text-oriented?

	There is only a text oriented front end to stream buffers because text
	input and output does not vary between platforms. This is very
	different for binary output. For example, binary output has to consider

	- word sizes: Is an 'int' two, four, or eight bytes long? The same
	questions arise for all other built-in types.

	- what is the bit pattern of a value? I think that at least implicitly
	in the standard a binary representation for integer types is required.
	I don't think that it is required to use two's complement. In any
	case, the floating point representations do differ, eg. in their
	number of bytes used.

	- what "endianess" is to be used?

	Basically it is possible to decide a format for each of those. This,
	however, implies inefficient implementations on platforms where the
	format does not match the internal representation.

	What many people asking for binary I/O forget is that binary I/O also
	requires some form of formatting! Assuming that just writing data and
	then reading it in will work is asking for problems, eg. when the
	compiler version changes and they decided to use a 32 bit integer
	rather than a 16 bit integer: It is not even necessary to switch
	platforms to run into problems!

	: I mean, if I want to write an int, a float, etc. AS IT IS I can't use
	: streams, because they write and read a human readable text format of
	: numbers.

	Which is for most I/O a reasonable approach. If it is not for you, you
	might want to consider a data base: File I/O is not really useful as a
	persistance mechanism. It is fine eg. for user interaction (text I/O),
	logging (text I/O), cross platfrom program interaction (formatted I/O),
	and data exchange (formatted I/O). In all these cases, the I/O is
	formatted, although possible using a binary format. For persistance,
	data bases are used. Depending on your needs, a relational or an object
	oriented one may be better suited.

	That said, it is worth to mention that it is easy to create a hierarchy
	similar to IOStreams built on top of stream buffers but doing binary
	formatting. A somewhat aged example is found at
	<ftp://ftp.fmi.uni-konstanz.de/pub/algo/personal/kuehl/binio.tar.gz>.
	This uses XDR formatting of the binary data (well, if I remmeber
	correctly, it is easy to plug in a different binary formatting).

	: Does anyone know how to solve the problem?

	Use a data base, text formatting, or binary formatting. With the
	details you have given it is impossible to tell which of those is the
	right approach because you haven't told why you want a binary format
	and what you want to do. That basically means that you came up with
	solution and you want us to confirm that it is the right one without
	telling us what problem is solved! Until I have seen the problem I
	doubt that binary I/O is the right approach...

	... and, BTW, using 'std::istream::read()' and 'std::ostream::write()'
	is almost certainly the wrong approach! These functions are an
	historical mistake which should have been corrected in the standard:
	It is my understanding that these methods were present in the IOStream
	version predating the rework from Jerry Schwartz and were left in to
	be compatible with the earlier stuff although they were not necessary:
	You could get binary I/O from the stream buffer level. The original
	IOStream library (maybe you remember using <stream.h>) did not have
	stream buffers and thus basic support for binary I/O was also present
	on the streams level.

	: What do you think about this choice?

	When I wrote the above paragraph about confirming your choice, I haven't
	read this question! As I said above: You told us what solution you have
	choosen without stating what problem is solved. We cannot determine
	whether your choice is the right one. Actually, I'm pretty sure it is
	the wrong one but without seen the details I can't be certain.
	--
	<mailto:dietmar_kuehl@yahoo.com> <http://www.dietmar-kuehl.de/>
	Phaidros eaSE - Easy Software Engineering: <http://www.phaidros.com/>