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<title>skalibs: the genwrite library interface</title>
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<h1> The <tt>genwrite</tt> library interface </h1>
<p>
The following functions are declared in the <tt>skalibs/genwrite.h</tt> header,
and implemented in the <tt>libskarnet.a</tt> or <tt>libskarnet.so</tt> library.
</p>
<h2> General information </h2>
<p>
<tt>genwrite</tt> is syntactic sugar to help write functions that might
want to write either to memory or to a file descriptor.
</p>
<p>
Writing to memory is achieved via appending to a
<a href="stralloc.html">stralloc</a>; writing to a file descriptor is achieved
via appending to a <a href="buffer.html">buffer</a> or a
<a href="bufalloc.html">bufalloc</a>.
</p>
<h2> Usage </h2>
<p>
A <tt>genwrite_t</tt> structure contains a pointer to a function that writes
stuff to the target without flushing it
(which can be <tt>genwrite_put_stralloc</tt>, <tt>genwrite_put_buffer</tt>,
<tt>genwrite_put_bufalloc</tt> or any
compatible user-defined function) in <tt>.put</tt>, a pointer to a function
that flushes the target (which can be <tt>genwrite_flush_stralloc</tt>,
<tt>genwrite_flush_buffer</tt>, <tt>genwrite_flush_bufalloc</tt> or any
compatible user-defined function) in <tt>.flush</tt>, and a pointer to
the target writing structure in <tt>.target</tt>.
</p>
<p>
Users should define a <tt>genwrite_t</tt> first, using the provided functions,
and give applications a pointer <tt>gp</tt> to this structure. To write <em>len</em>
characters at position <em>s</em> to the target, the application should then call
<code>(*gp->put)(gp->target, s, len)</code>. When it is done writing, the
application should call <code>(*gp->flush)(gp->target)</code> to flush the
output.
</p>
<p>
<tt>genwrite_stdout</tt> and <tt>genwrite_stderr</tt> are predefined; they
write to <tt>buffer_1</tt> and <tt>buffer_2</tt> respectively.
</p>
<h2> Macros </h2>
<p>
<code> GENWRITE_STRALLOC_INIT(sa) </code> <br />
Declares a <tt>genwrite_t</tt> writing to the stralloc *<em>sa</em>.
</p>
<p>
<code> GENWRITE_BUFFER_INIT(b) </code> <br />
Declares a <tt>genwrite_t</tt> writing to the buffer *<em>b</em>. Use
of such a buffer might interact badly with nonblocking I/O.
</p>
<p>
<code> GENWRITE_BUFALLOC_INIT(ba) </code> <br />
Declares a <tt>genwrite_t</tt> writing to the bufalloc *<em>ba</em>.
</p>
<h2> Note </h2>
<p>
Object-oriented programming in C is inefficient and cumbersome. It is
usually possible to avoid it in Unix system programming, because Unix
primitives are often generic enough. Unfortunately, it is not the case
here: Unix does not provide an abstraction representing either a file
or a memory buffer. So an object-oriented approach is unavoidable.
</p>
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