1 /*
2  * Copyright 2014 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 GrGpuResourceRef_DEFINED
9 #define GrGpuResourceRef_DEFINED
10 
11 #include "GrGpuResource.h"
12 #include "SkRefCnt.h"
13 
14 /**
15  * This class is intended only for internal use in core Gr code.
16  *
17  * Class that wraps a resource referenced by a GrProgramElement or GrDrawState. It manages
18  * converting refs to pending IO operations. It allows a resource ownership to be in three
19  * states:
20  *          1. Owns a single ref
21  *          2. Owns a single ref and a pending IO operation (read, write, or read-write)
22  *          3. Owns a single pending IO operation.
23  *
24  * It is legal to destroy the GrGpuResourceRef in any of these states. It starts in state
25  * 1. Calling markPendingIO() converts it from state 1 to state 2. Calling removeRef() goes from
26  * state 2 to state 3. Calling pendingIOComplete() moves from state 2 to state 1. There is no
27  * valid way of going from state 3 back to 2 or 1.
28  *
29  * Like sk_sp, its constructor and setter adopt a ref from their caller.
30  *
31  * TODO: Once GrDODrawState no longer exists and therefore GrDrawState and GrOptDrawState no
32  * longer share an instance of this class, attempt to make the resource owned by GrGpuResourceRef
33  * only settable via the constructor.
34  */
35 class GrGpuResourceRef : SkNoncopyable {
36 public:
37     ~GrGpuResourceRef();
38 
39     GrGpuResource* getResource() const { return fResource; }
40 
41     /** Does this object own a pending read or write on the resource it is wrapping. */
42     bool ownsPendingIO() const { return fPendingIO; }
43 
44     /** What type of IO does this represent? This is independent of whether a normal ref or a
45         pending IO is currently held. */
46     GrIOType ioType() const { return fIOType; }
47 
48     /** Shortcut for calling setResource() with NULL. It cannot be called after markingPendingIO
49         is called. */
50     void reset();
51 
52 protected:
53     GrGpuResourceRef();
54 
55     /** Adopts a ref from the caller. ioType expresses what type of IO operations will be marked as
56         pending on the resource when markPendingIO is called. */
57     GrGpuResourceRef(GrGpuResource*, GrIOType);
58 
59     /** Adopts a ref from the caller. ioType expresses what type of IO operations will be marked as
60         pending on the resource when markPendingIO is called. */
61     void setResource(GrGpuResource*, GrIOType);
62 
63 private:
64     /** Called by owning GrProgramElement when the program element is first scheduled for
65         execution. It can only be called once. */
66     void markPendingIO() const;
67 
68     /** Called when the program element/draw state is no longer owned by GrOpList-client code.
69         This lets the cache know that the drawing code will no longer schedule additional reads or
70         writes to the resource using the program element or draw state. It can only be called once.
71       */
72     void removeRef() const;
73 
74     /** Called to indicate that the previous pending IO is complete. Useful when the owning object
75         still has refs, so it is not about to destroy this GrGpuResourceRef, but its previously
76         pending executions have been complete. Can only be called if removeRef() was not previously
77         called. */
78     void pendingIOComplete() const;
79 
80     friend class GrResourceIOProcessor;
81 
82     GrGpuResource*  fResource;
83     mutable bool    fOwnRef;
84     mutable bool    fPendingIO;
85     GrIOType        fIOType;
86 
87     typedef SkNoncopyable INHERITED;
88 };
89 
90 /**
91  * Templated version of GrGpuResourceRef to enforce type safety.
92  */
93 template <typename T> class GrTGpuResourceRef : public GrGpuResourceRef {
94 public:
95     GrTGpuResourceRef() {}
96 
97     /** Adopts a ref from the caller. ioType expresses what type of IO operations will be marked as
98         pending on the resource when markPendingIO is called. */
99     GrTGpuResourceRef(T* resource, GrIOType ioType) : INHERITED(resource, ioType) {}
100     GrTGpuResourceRef(sk_sp<T> resource, GrIOType ioType) : INHERITED(resource, ioType) {}
101 
102     T* get() const { return static_cast<T*>(this->getResource()); }
103 
104     /** Adopts a ref from the caller. ioType expresses what type of IO operations will be marked as
105         pending on the resource when markPendingIO is called. */
106     void set(T* resource, GrIOType ioType) { this->setResource(resource, ioType); }
107 
108 private:
109     typedef GrGpuResourceRef INHERITED;
110 };
111 
112 /**
113  * This is similar to GrTGpuResourceRef but can only be in the pending IO state. It never owns a
114  * ref.
115  */
116 template <typename T, GrIOType IO_TYPE> class GrPendingIOResource : SkNoncopyable {
117 public:
118     GrPendingIOResource(T* resource = nullptr) : fResource(nullptr) {
119         this->reset(resource);
120     }
121 
122     GrPendingIOResource(const GrPendingIOResource& that)
123         : GrPendingIOResource(that.get()) {
124     }
125 
126     void reset(T* resource = nullptr) {
127         if (resource) {
128             switch (IO_TYPE) {
129                 case kRead_GrIOType:
130                     resource->addPendingRead();
131                     break;
132                 case kWrite_GrIOType:
133                     resource->addPendingWrite();
134                     break;
135                 case kRW_GrIOType:
136                     resource->addPendingRead();
137                     resource->addPendingWrite();
138                     break;
139             }
140         }
141         this->release();
142         fResource = resource;
143     }
144 
145     ~GrPendingIOResource() {
146         this->release();
147     }
148 
149     explicit operator bool() const { return SkToBool(fResource); }
150 
151     bool operator==(const GrPendingIOResource& other) const {
152         return fResource == other.fResource;
153     }
154 
155     T* get() const { return fResource; }
156 
157 private:
158     void release() {
159         if (fResource) {
160             switch (IO_TYPE) {
161                 case kRead_GrIOType:
162                     fResource->completedRead();
163                     break;
164                 case kWrite_GrIOType:
165                     fResource->completedWrite();
166                     break;
167                 case kRW_GrIOType:
168                     fResource->completedRead();
169                     fResource->completedWrite();
170                     break;
171             }
172         }
173     }
174 
175     T* fResource;
176 };
177 
178 #endif
179