ch21_03.htm

编程珍珠,里面很多好用的代码,大家可以参考学习呵呵,

our $VERSION = '0.01';

bootstrap Mytest $VERSION;

# Preloaded methods go here.

# Autoload methods go after __END__, and are processed by the autosplit program.

1;
__END__
# Below is the stub of documentation for your module. You better edit it!</pre>
</blockquote>
<a name="INDEX-"></a><a name="INDEX-"></a><a name="INDEX-"></a>
</p>

<p>Most extension modules will <tt class="literal">require</tt> the <tt class="literal">Exporter</tt> and <tt class="literal">DynaLoader</tt> extensions.  After setting <tt class="literal">@ISA</tt> (for inheritance)
and <tt class="literal">@EXPORT</tt> (to make functions available to the package using the
module), the initialization code tells Perl to <tt class="literal">bootstrap</tt> the XS code.  Perl then
dynamically links the shared library into the <em class="emphasis">perl</em> process at run time.</p>
</dd>


<dt>
<b><em class="emphasis">Mytest.xs</em></b>
</dt>
<dd>
<p>The <em class="emphasis">Mytest.xs</em> file contains the XSUBs that tell Perl how to pass data
to the compiled C routines.  Initially, <em class="emphasis">Mytest.xs</em> will look something
like this:
<blockquote>
<pre class="programlisting">#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

MODULE = Mytest                PACKAGE = Mytest</pre>
</blockquote>

Let's edit the XS file by adding this to the end of the file:
<blockquote>
<pre class="programlisting">void
hello()
    CODE:
        printf("Hello, world!\n");</pre>
</blockquote>
</p>
</dd>

</dl>

<p>
</p>

<p>When you run <tt class="literal">perl Makefile.PL</tt>, the <em class="emphasis">Makefile</em> that <em class="emphasis">make</em> needs will
be created:
<blockquote>
<pre class="programlisting">% <tt class="userinput"><b>perl Makefile.PL</b></tt>
Checking if your kit is complete...
Looks good
Writing Makefile for Mytest</pre>
</blockquote>

Running <em class="emphasis">make</em> will now produce output that looks something like this
(some long lines have been shortened for clarity and some extraneous
lines have been deleted):
<blockquote>
<pre class="programlisting">% <tt class="userinput"><b>make</b></tt>
umask 0 &amp;&amp; cp Mytest.pm ./blib/Mytest.pm
perl xsubpp -typemap typemap Mytest.xs &gt;Mytest.tc &amp;&amp; mv Mytest.tc Mytest.c
cc -c Mytest.c
Running Mkbootstrap for Mytest ()
chmod 644 Mytest.bs
LD_RUN_PATH="" ld -o ./blib/PA-RISC1.1/auto/Mytest/Mytest.sl -b Mytest.o
chmod 755 ./blib/PA-RISC1.1/auto/Mytest/Mytest.sl
cp Mytest.bs ./blib/PA-RISC1.1/auto/Mytest/Mytest.bs
chmod 644 ./blib/PA-RISC1.1/auto/Mytest/Mytest.bs
Manifying ./blib/man3/Mytest.3</pre>
</blockquote>

We assume that the <em class="emphasis">make</em> program that Perl uses to build programs is
called <em class="emphasis">make</em>.  Instead of running <em class="emphasis">make</em> in these examples, you may
have to substitute whatever <em class="emphasis">make</em> program Perl has been configured
to use.  You can find out what that program is with:
<blockquote>
<pre class="programlisting">% <tt class="userinput"><b>perl -V:make</b></tt>
</pre>
</blockquote>
<a name="INDEX-3723"></a>
</p>

<p>Running <em class="emphasis">make</em> created a directory called <em class="emphasis">blib</em> (for "build
library") in the current working directory.  This directory will
contain the shared library that we will build.  Once we're sure we
know what we're doing, we can install it from that directory into its
final resting place.  Until then, we'll have to explicitly add the
<em class="emphasis">blib</em> directory to Perl's <tt class="literal">@INC</tt> array by using the
<tt class="literal">ExtUtils::testlib</tt> module.  If we now create a file called <em class="emphasis">hello</em>
that looks like this:</p>

<blockquote>
<pre class="programlisting">use ExtUtils::testlib;   # adds blib/* directories to @INC
use Mytest;
Mytest::hello();</pre>
</blockquote>

<p>we can burrow down from Perl into C:</p>

<blockquote>
<pre class="programlisting">% <tt class="userinput"><b>perl hello</b></tt>
Hello, world!</pre>
</blockquote>

<p>Once your extension is complete and passes all its tests, you can
install it with <tt class="literal">make install</tt>.</p>

<p>You will need write 
permission for your Perl library.  (If you don't have permission, you can 
specify another directory as shown in "Installing CPAN modules" in 
<a href="ch22_01.htm">Chapter 22, "CPAN"</a>.)</p>

<a name="INDEX-3724"></a><a name="INDEX-3725"></a><a name="INDEX-3726"></a>






<h3 class="sect2">21.3.3. XSUB Input and Output</h3>

<p>
<a name="INDEX-3727"></a><a name="INDEX-3728"></a><a name="INDEX-3729"></a><a name="INDEX-3730"></a><a name="INDEX-3731"></a><a name="INDEX-3732"></a>
Continuing with the previous example, we'll add a second XSUB, which
takes a single numeric argument as input and returns 0 if the number
is even, or 1 if the number is odd:
<blockquote>
<pre class="programlisting">int
is_even(x)
        int x
    CODE:
        RETVAL = (x % 2 == 0);
    OUTPUT:
        RETVAL</pre>
</blockquote>

The list of output parameters occurs at the very end of the function,
just after the <tt class="literal">OUTPUT:</tt> directive.  The use of <tt class="literal">RETVAL</tt> tells Perl
that you wish to send this value back as the return value of the XSUB.
Had we wanted the function to modify its input parameter, we would
have used <tt class="literal">x</tt> in place of <tt class="literal">RETVAL</tt>.</p>

<p>We can rebuild our new shared library with the same steps as before,
generating a <em class="emphasis">Makefile</em> from the <em class="emphasis">Makefile.PL</em> file and running
<em class="emphasis">make</em>.</p>

<p>
<a name="INDEX-3733"></a><a name="INDEX-3734"></a>
In order to verify that our extension works, we'll create a test suite in 
<em class="emphasis">test.pl</em>.  This file is set up by <em class="emphasis">h2xs</em> to mimic the
test script that Perl itself has.  Within the script, you may run tests to confirm that the extension behaves properly,
printing <tt class="literal">ok</tt> when it does and <tt class="literal">not ok</tt> when it doesn't.  Change the
print statement in the <tt class="literal">BEGIN</tt> block of <em class="emphasis">test.pl</em> to <tt class="literal">print "1..4\n";</tt>, 
and add the following code to the end of the file:
<blockquote>
<pre class="programlisting">print Mytest::is_even(0) == 1 ? "ok 2" : "not ok 2", "\n";
print Mytest::is_even(1) == 0 ? "ok 3" : "not ok 3", "\n";
print Mytest::is_even(2) == 1 ? "ok 4" : "not ok 4", "\n";</pre>
</blockquote>

The test script will be executed when you type <tt class="literal">make test</tt>.</p>






<h3 class="sect2">21.3.4. Using Functions from an External C Library</h3>

<p>
<a name="INDEX-3735"></a><a name="INDEX-3736"></a><a name="INDEX-3737"></a><a name="INDEX-3738"></a><a name="INDEX-3739"></a>
So far, our two examples haven't relied on any C code outside of the
XS file.  Now we'll use some functions from the C math library:
<blockquote>
<pre class="programlisting">void
round(arg)
        double  arg
    CODE:
        if (arg &gt; 0.0) {
                arg = floor(arg + 0.5);
        } else if (arg &lt; 0.0) {
                arg = ceil(arg - 0.5);
        } else {
                arg = 0.0;
        }
    OUTPUT:
        arg</pre>
</blockquote>

Note that the <tt class="literal">round</tt> we define above does not return a value, but
instead changes the value of its argument in place.</p>

<p>The <em class="emphasis">floor</em>(3) and <em class="emphasis">ceil</em>(3) functions are part of the C math library.  If
you were compiling a C program and needed to link
in the math library, you'd append <tt class="userinput"><b>-lm</b></tt> to the command line, so that's what you put into
the <tt class="literal">LIBS</tt> line in <em class="emphasis">Makefile.PL</em>:
<blockquote>
<pre class="programlisting">'LIBS'  =&gt; ['-lm'],   # Link in the 'm' math library</pre>
</blockquote>

Generate the <em class="emphasis">Makefile</em> and run <em class="emphasis">make</em>.  Change the <tt class="literal">BEGIN</tt> block to
run nine tests and add the following to <em class="emphasis">test.pl</em>:
<blockquote>
<pre class="programlisting">$i = -1.5; Mytest::round($i); print $i == -2.0 ? "ok 5" : "not ok 5", "\n";
$i = -1.1; Mytest::round($i); print $i == -1.0 ? "ok 6" : "not ok 6", "\n";
$i = 0.0; Mytest::round($i); print $i == 0.0 ? "ok 7" : "not ok 7", "\n";
$i = 0.5; Mytest::round($i); print $i == 1.0 ? "ok 8" : "not ok 8", "\n";
$i = 1.2; Mytest::round($i); print $i == 1.0 ? "ok 9" : "not ok 9", "\n";</pre>
</blockquote>

Running <tt class="literal">make test</tt> should now print out that all nine tests are okay.</p>

<p>The <em class="emphasis">perlxstut</em> documentation bundled with Perl has several more
examples of Perl extensions, including an example that uses <em class="emphasis">h2xs</em>
to automatically make an entire C library available to Perl.</p>

<a name="INDEX-3740"></a><a name="INDEX-3741"></a><a name="INDEX-3742"></a>



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