Added factorial C library example

README.md

@@ -5,7 +5,9 @@ http://github.com/rbranson/node-ffi
 
 # DESCRIPTION
 
-node-ffi is a Node.js addon for loading and calling dynamic libraries using pure JavaScript. It can be used to create bindings to native libraries without writing any C++ code.
+node-ffi is a Node.js addon for loading and calling dynamic libraries using pure JavaScript. It can be used to create bindings to native libraries without writing any C++ code. 
+
+It also simplifies the augmentation of node.js with C code as it takes care of handling the translation of types across JavaScript and C, which can add reams of boilerplate code to your otherwise simple C. See the `examples/factorial` for an example of this use case.
 
 WARNING: node-ffi assumes you know what you're doing. You can pretty easily create situations where you will segfault the interpreter and unless you've got C debugger skills, you probably won't know what's going on.
 

example/factorial/README

@@ -0,0 +1,6 @@
+If you've already got node installed, this can be used:
+
+    $ node-waf build
+    ...
+    $ node factorial.js 35
+    Your output: 6399018521010896896

example/factorial/factorial.c

@@ -0,0 +1,11 @@
+#include <stdint.h>
+
+uint64_t factorial(int max) {
+    int i           = max;
+    uint64_t result = 1;
+
+    while (i >= 2)
+        result *= i--;
+
+    return result;
+}

example/factorial/factorial.js

@@ -0,0 +1,14 @@
+var FFI = require("../../lib/ffi");
+
+var libfactorial = new FFI.Library("libfactorial", {
+    "factorial": [ "long", [ "uint64" ] ]
+});
+
+if (process.argv.length < 3) {
+    console.log("Arguments: " + process.argv[0] + " " + process.argv[1] + " <max>");
+    process.exit();
+}
+
+var output = libfactorial.factorial(parseInt(process.argv[2]))
+
+console.log("Your output: " + output);

example/factorial/wscript

@@ -0,0 +1,24 @@
+import Options
+from os import unlink, symlink, popen
+from os.path import exists 
+from logging import fatal
+
+srcdir = '.'
+blddir = 'build'
+
+def set_options(opt):
+  opt.tool_options('compiler_cc')
+
+def configure(conf):
+  conf.check_tool('compiler_cc')
+
+def build(bld):
+  obj = bld.new_task_gen('cc', 'shlib')
+  obj.target = 'factorial'
+  obj.source = 'factorial.c'
+
+def shutdown():
+  if exists("build/default/libfactorial.dylib") and not exists("libfactorial.dylib"):
+    symlink("build/default/libfactorial.dylib", "libfactorial.dylib")
+  if exists("build/default/libfactorial.so") and not exists("libfactorial.so"):
+    symlink("build/default/libfactorial.so", "libfactorial.so")