SkCachingPixelRef.cpp revision ba82bd11e2c055f885b2327aa230d2dac8b53f03 
1/*
2 * Copyright 2013 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#include "SkCachingPixelRef.h"
9#include "SkScaledImageCache.h"
10
11
12bool SkCachingPixelRef::Install(SkImageGenerator* generator,
13                                SkBitmap* dst) {
14    SkImageInfo info;
15    SkASSERT(dst != NULL);
16    if ((NULL == generator)
17        || !(generator->getInfo(&info))
18        || !dst->setConfig(info, 0)) {
19        SkDELETE(generator);
20        return false;
21    }
22    SkAutoTUnref<SkCachingPixelRef> ref(SkNEW_ARGS(SkCachingPixelRef,
23                                           (info, generator, dst->rowBytes())));
24    dst->setPixelRef(ref);
25    return true;
26}
27
28SkCachingPixelRef::SkCachingPixelRef(const SkImageInfo& info,
29                                     SkImageGenerator* generator,
30                                     size_t rowBytes)
31    : INHERITED(info)
32    , fImageGenerator(generator)
33    , fErrorInDecoding(false)
34    , fScaledCacheId(NULL)
35    , fRowBytes(rowBytes) {
36    SkASSERT(fImageGenerator != NULL);
37}
38SkCachingPixelRef::~SkCachingPixelRef() {
39    SkDELETE(fImageGenerator);
40    SkASSERT(NULL == fScaledCacheId);
41    // Assert always unlock before unref.
42}
43
44void* SkCachingPixelRef::onLockPixels(SkColorTable**) {
45    if (fErrorInDecoding) {
46        return NULL;  // don't try again.
47    }
48
49    const SkImageInfo& info = this->info();
50
51    SkBitmap bitmap;
52    SkASSERT(NULL == fScaledCacheId);
53    fScaledCacheId = SkScaledImageCache::FindAndLock(this->getGenerationID(),
54                                                     info.fWidth,
55                                                     info.fHeight,
56                                                     &bitmap);
57    if (NULL == fScaledCacheId) {
58        // Cache has been purged, must re-decode.
59        if ((!bitmap.setConfig(info, fRowBytes)) || !bitmap.allocPixels()) {
60            fErrorInDecoding = true;
61            return NULL;
62        }
63        SkAutoLockPixels autoLockPixels(bitmap);
64        if (!fImageGenerator->getPixels(info, bitmap.getPixels(), fRowBytes)) {
65            fErrorInDecoding = true;
66            return NULL;
67        }
68        fScaledCacheId = SkScaledImageCache::AddAndLock(this->getGenerationID(),
69                                                        info.fWidth,
70                                                        info.fHeight,
71                                                        bitmap);
72        SkASSERT(fScaledCacheId != NULL);
73    }
74
75    // Now bitmap should contain a concrete PixelRef of the decoded
76    // image.
77    SkAutoLockPixels autoLockPixels(bitmap);
78    void* pixels = bitmap.getPixels();
79    SkASSERT(pixels != NULL);
80
81    // At this point, the autoLockPixels will unlockPixels()
82    // to remove bitmap's lock on the pixels.  We will then
83    // destroy bitmap.  The *only* guarantee that this pointer
84    // remains valid is the guarantee made by
85    // SkScaledImageCache that it will not destroy the *other*
86    // bitmap (SkScaledImageCache::Rec.fBitmap) that holds a
87    // reference to the concrete PixelRef while this record is
88    // locked.
89    return pixels;
90}
91
92void SkCachingPixelRef::onUnlockPixels() {
93    SkASSERT(fScaledCacheId != NULL);
94    SkScaledImageCache::Unlock( static_cast<SkScaledImageCache::ID*>(fScaledCacheId));
95    fScaledCacheId = NULL;
96}
97