Break up SkLazyPixelRef functionally into class hierarchy.

src/lazy/SkCachingPixelRef.cpp

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCachingPixelRef.h"
+#include "SkScaledImageCache.h"
+
+SkCachingPixelRef::SkCachingPixelRef()
+    : fErrorInDecoding(false)
+    , fScaledCacheId(NULL) {
+    memset(&fInfo, 0xFF, sizeof(fInfo));
+}
+SkCachingPixelRef::~SkCachingPixelRef() {
+    SkASSERT(NULL == fScaledCacheId);
+    // Assert always unlock before unref.
+}
+
+bool SkCachingPixelRef::getInfo(SkImageInfo* info) {
+    SkASSERT(info != NULL);
+    if (fErrorInDecoding) {
+        SkASSERT(fInfo.fWidth < 0);
+        return false;  // Don't try again.
+    }
+    if (fInfo.fWidth >= 0) {
+        *info = fInfo;
+        return true;  // already successful
+    }
+    SkImageInfo tmp;
+    if (!this->onDecodeInfo(&tmp)) {
+        fErrorInDecoding = true;
+        return false;
+    }
+    SkASSERT(tmp.fWidth >= 0);
+    *info = fInfo = tmp;
+    return true;
+}
+
+bool SkCachingPixelRef::configure(SkBitmap* bitmap) {
+    SkASSERT(bitmap != NULL);
+    SkImageInfo info;
+    if (!this->getInfo(&info)) {
+        return false;
+    }
+    return bitmap->setConfig(info, 0);
+}
+
+void* SkCachingPixelRef::onLockPixels(SkColorTable** colorTable) {
+    (void)colorTable;
+    SkImageInfo info;
+    if (!this->getInfo(&info)) {
+        return NULL;
+    }
+    SkBitmap bitmap;
+
+    fScaledCacheId = SkScaledImageCache::FindAndLock(this->getGenerationID(),
+                                                     info.fWidth,
+                                                     info.fHeight,
+                                                     &bitmap);
+    if (NULL == fScaledCacheId) {
+        // Cache has been purged, must re-decode.
+        if (!this->onDecodeInto(0, &bitmap)) {
+            return NULL;
+        }
+        fScaledCacheId = SkScaledImageCache::AddAndLock(this->getGenerationID(),
+                                                        info.fWidth,
+                                                        info.fHeight,
+                                                        bitmap);
+        SkASSERT(fScaledCacheId != NULL);
+    }
+    // Now bitmap should contain a concrete PixelRef of the decoded
+    // image.
+    SkAutoLockPixels autoLockPixels(bitmap);
+    void* pixels = bitmap.getPixels();
+    SkASSERT(pixels != NULL);
+    // At this point, the autoLockPixels will unlockPixels()
+    // to remove bitmap's lock on the pixels.  We will then
+    // destroy bitmap.  The *only* guarantee that this pointer
+    // remains valid is the guarantee made by
+    // SkScaledImageCache that it will not destroy the *other*
+    // bitmap (SkScaledImageCache::Rec.fBitmap) that holds a
+    // reference to the concrete PixelRef while this record is
+    // locked.
+    return pixels;
+}
+
+void SkCachingPixelRef::onUnlockPixels() {
+    if (fScaledCacheId != NULL) {
+        SkScaledImageCache::Unlock(
+            static_cast<SkScaledImageCache::ID*>(fScaledCacheId));
+        fScaledCacheId = NULL;
+    }
+}
+
+bool SkCachingPixelRef::onDecodeInto(int pow2, SkBitmap* bitmap) {
+    SkASSERT(bitmap != NULL);
+    SkBitmap tmp;
+    SkImageInfo info;
+    // TODO(halcanary) - Enable SkCachingPixelRef to use a custom
+    // allocator. `tmp.allocPixels(fAllocator, NULL)`
+    if (!(this->getInfo(&info)
+          && this->configure(&tmp)
+          && tmp.allocPixels(NULL, NULL))) {
+        fErrorInDecoding = true;

[reed1, 2013/11/04 18:34:47]

This could just be

if (!(this->configure(&tmp) && tmp.allocPixels())) {
    return false;
}

No need to touch fErrorInDecoding, since we are just calling other apis, and it
is their job to worry about internal error codes.

[hal.canary, 2013/11/04 19:41:07]

Done.

+        return false;
+    }
+    if (!this->onDecodePixels(info, tmp.getPixels(), tmp.rowBytes())) {
+        fErrorInDecoding = true;

[reed1, 2013/11/04 18:34:47]

should you set fInfo.fWidth = -1 here? If not, perhaps we shouldn't assert on
that up in getInfo().

[hal.canary, 2013/11/04 19:41:07]

Good catch.

+        return false;
+    }
+    *bitmap = tmp;
+    return true;
+}
+