Adds a modified copy of talk/base to webrtc/base. It is the first step in
migrating talk/base to webrtc/base.
BUG=N/A
R=niklas.enbom@webrtc.org
Review URL: https://webrtc-codereview.appspot.com/17479005
git-svn-id: http://webrtc.googlecode.com/svn/trunk@6129 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/callback.h.pump b/webrtc/base/callback.h.pump
new file mode 100644
index 0000000..86957df
--- /dev/null
+++ b/webrtc/base/callback.h.pump
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ * Use of this source code is governed by a BSD-style license
+ * that can be found in the LICENSE file in the root of the source
+ * tree. An additional intellectual property rights grant can be found
+ * in the file PATENTS. All contributing project authors may
+ * be found in the AUTHORS file in the root of the source tree.
+ */
+
+// To generate callback.h from callback.h.pump, execute:
+// /home/build/google3/third_party/gtest/scripts/pump.py callback.h.pump
+
+// Callbacks are callable object containers. They can hold a function pointer
+// or a function object and behave like a value type. Internally, data is
+// reference-counted, making copies and pass-by-value inexpensive.
+//
+// Callbacks are typed using template arguments. The format is:
+// CallbackN<ReturnType, ParamType1, ..., ParamTypeN>
+// where N is the number of arguments supplied to the callable object.
+// Callbacks are invoked using operator(), just like a function or a function
+// object. Default-constructed callbacks are "empty," and executing an empty
+// callback does nothing. A callback can be made empty by assigning it from
+// a default-constructed callback.
+//
+// Callbacks are similar in purpose to std::function (which isn't available on
+// all platforms we support) and a lightweight alternative to sigslots. Since
+// they effectively hide the type of the object they call, they're useful in
+// breaking dependencies between objects that need to interact with one another.
+// Notably, they can hold the results of Bind(), std::bind*, etc, without needing
+// to know the resulting object type of those calls.
+//
+// Sigslots, on the other hand, provide a fuller feature set, such as multiple
+// subscriptions to a signal, optional thread-safety, and lifetime tracking of
+// slots. When these features are needed, choose sigslots.
+//
+// Example:
+// int sqr(int x) { return x * x; }
+// struct AddK {
+// int k;
+// int operator()(int x) const { return x + k; }
+// } add_k = {5};
+//
+// Callback1<int, int> my_callback;
+// cout << my_callback.empty() << endl; // true
+//
+// my_callback = Callback1<int, int>(&sqr);
+// cout << my_callback.empty() << endl; // false
+// cout << my_callback(3) << endl; // 9
+//
+// my_callback = Callback1<int, int>(add_k);
+// cout << my_callback(10) << endl; // 15
+//
+// my_callback = Callback1<int, int>();
+// cout << my_callback.empty() << endl; // true
+
+#ifndef WEBRTC_BASE_CALLBACK_H_
+#define WEBRTC_BASE_CALLBACK_H_
+
+#include "webrtc/base/refcount.h"
+#include "webrtc/base/scoped_ref_ptr.h"
+
+namespace rtc {
+
+$var n = 5
+$range i 0..n
+$for i [[
+$range j 1..i
+
+template <class R$for j [[,
+ class P$j]]>
+class Callback$i {
+ public:
+ // Default copy operations are appropriate for this class.
+ Callback$i() {}
+ template <class T> Callback$i(const T& functor)
+ : helper_(new RefCountedObject< HelperImpl<T> >(functor)) {}
+ R operator()($for j , [[P$j p$j]]) {
+ if (empty())
+ return R();
+ return helper_->Run($for j , [[p$j]]);
+ }
+ bool empty() const { return !helper_; }
+
+ private:
+ struct Helper : RefCountInterface {
+ virtual ~Helper() {}
+ virtual R Run($for j , [[P$j p$j]]) = 0;
+ };
+ template <class T> struct HelperImpl : Helper {
+ explicit HelperImpl(const T& functor) : functor_(functor) {}
+ virtual R Run($for j , [[P$j p$j]]) {
+ return functor_($for j , [[p$j]]);
+ }
+ T functor_;
+ };
+ scoped_refptr<Helper> helper_;
+};
+
+]]
+} // namespace rtc
+
+#endif // WEBRTC_BASE_CALLBACK_H_