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(generator != NULL);
16    SkASSERT(dst != NULL);
17    if ((NULL == generator)
18        || !(generator->getInfo(&info))
19        || !dst->setConfig(info, 0)) {
20        SkDELETE(generator);
21        return false;
22    }
23    SkAutoTUnref<SkCachingPixelRef> ref(SkNEW_ARGS(SkCachingPixelRef,
24                                           (info, generator, dst->rowBytes())));
25    dst->setPixelRef(ref);
26    return true;
27}
28
29SkCachingPixelRef::SkCachingPixelRef(const SkImageInfo& info,
30                                     SkImageGenerator* generator,
31                                     size_t rowBytes)
32    : INHERITED(info)
33    , fImageGenerator(generator)
34    , fErrorInDecoding(false)
35    , fScaledCacheId(NULL)
36    , fRowBytes(rowBytes) {
37    SkASSERT(fImageGenerator != NULL);
38}
39SkCachingPixelRef::~SkCachingPixelRef() {
40    SkDELETE(fImageGenerator);
41    SkASSERT(NULL == fScaledCacheId);
42    // Assert always unlock before unref.
43}
44
45void* SkCachingPixelRef::onLockPixels(SkColorTable**) {
46    const SkImageInfo& info = this->info();
47
48    if (fErrorInDecoding) {
49        return NULL;  // don't try again.
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    // At this point, the autoLockPixels will unlockPixels()
81    // to remove bitmap's lock on the pixels.  We will then
82    // destroy bitmap.  The *only* guarantee that this pointer
83    // remains valid is the guarantee made by
84    // SkScaledImageCache that it will not destroy the *other*
85    // bitmap (SkScaledImageCache::Rec.fBitmap) that holds a
86    // reference to the concrete PixelRef while this record is
87    // locked.
88    return pixels;
89}
90
91void SkCachingPixelRef::onUnlockPixels() {
92    SkASSERT(fScaledCacheId != NULL);
93    SkScaledImageCache::Unlock( static_cast<SkScaledImageCache::ID*>(fScaledCacheId));
94    fScaledCacheId = NULL;
95}
96