1/*
2 * Copyright 2015 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkFunction_DEFINED
9#define SkFunction_DEFINED
10
11// TODO: document, more pervasive move support in constructors, small-Fn optimization
12
13#include "SkTemplates.h"
14#include "SkTypes.h"
15
16template <typename> class SkFunction;
17
18template <typename R, typename... Args>
19class SkFunction<R(Args...)> {
20public:
21    SkFunction() {}
22
23    template <typename Fn>
24    SkFunction(const Fn& fn) : fFunction(SkNEW_ARGS(LambdaImpl<Fn>, (fn))) {}
25
26    SkFunction(R (*fn)(Args...)) : fFunction(SkNEW_ARGS(FnPtrImpl, (fn))) {}
27
28    SkFunction(const SkFunction& other) { *this = other; }
29    SkFunction& operator=(const SkFunction& other) {
30        if (this != &other) {
31            fFunction.reset(other.fFunction ? other.fFunction->clone() : nullptr);
32        }
33        return *this;
34    }
35
36    R operator()(Args... args) const {
37        SkASSERT(fFunction.get());
38        return fFunction->call(Forward(args)...);
39    }
40
41private:
42    // ~= std::forward.  This moves its argument if possible, falling back to a copy if not.
43    template <typename T> static T&& Forward(T& v) { return (T&&)v; }
44
45    struct Interface {
46        virtual ~Interface() {}
47        virtual R call(Args...) const = 0;
48        virtual Interface* clone() const = 0;
49    };
50
51    template <typename Fn>
52    class LambdaImpl final : public Interface {
53    public:
54        LambdaImpl(const Fn& fn) : fFn(fn) {}
55
56        R call(Args... args) const override { return fFn(Forward(args)...); }
57        Interface* clone() const { return SkNEW_ARGS(LambdaImpl<Fn>, (fFn)); }
58    private:
59        Fn fFn;
60    };
61
62    class FnPtrImpl final : public Interface {
63    public:
64        FnPtrImpl(R (*fn)(Args...)) : fFn(fn) {}
65
66        R call(Args... args) const override { return fFn(Forward(args)...); }
67        Interface* clone() const { return SkNEW_ARGS(FnPtrImpl, (fFn)); }
68    private:
69        R (*fFn)(Args...);
70    };
71
72    SkAutoTDelete<Interface> fFunction;
73};
74
75#endif//SkFunction_DEFINED
76