Re: C++ iostreams

[Jose Orlando Pereira <jop@di.uminho.pt>]

Erwin Rol wrote:
> I am new to XTL and am wondering how to use it with
> C++ streams. In the documentation there is something about
> c FILE* input/output but nothing about C++ streams (at least
> no examples). I also didn't got the cfile_buffer example to work
> thats in the docu.

You're correct. Mentions to externalization to FILEs and streams
are currently just wishful thinking. mem_buffers are enough for
me, so I never got around doing the others.

However, it should be fairly easy to implement them. Take a look
at mem_buffer in objio.h. read() and write() have the expected
semantics and should translate into fread()/fwrite or whatever
is needed. 

In addition, require() and flush() are used for atomic types with
size less or equal to sizeof(longlong) and need to be implemented.
For instance, as:
 
 char buffer[sizeof(longlong)];
 int n=0;

 void* require(int size) {flush();n=size;return buffer;}
 void flush() {write(buffer, n);n=0;}

for a write-only stream and:

 char buffer[sizeof(longlong)];

 void* require(int size) {read(buffer, size);return buffer;}
 void flush() {}

for a read-only stream.

For buffered streams (e.g. FILEs or iostreams), this should be ok.
For unbuffered streams, some coalescing should be done by require(),
making it more complex but vastly faster.

BTW, unrequire() is required :-) only for text format, so it might be
safely ignored.

-- 
Jose Orlando Pereira
* mailto:jop@di.uminho.pt * http://gsd.di.uminho.pt/~jop *