cache SkImage::Info calculation in lazypixelref

BUG=
R=scroggo@google.com

Review URL: https://codereview.chromium.org/28493003

git-svn-id: http://skia.googlecode.com/svn/trunk@11893 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 25 insertions, 10 deletions

diff --git a/src/lazy/SkLazyPixelRef.cpp b/src/lazy/SkLazyPixelRef.cpp
index 22d4b112f1..ad60892ad1 100644
--- a/src/lazy/SkLazyPixelRef.cpp
+++ b/src/lazy/SkLazyPixelRef.cpp
@@ -37,6 +37,10 @@ SkLazyPixelRef::SkLazyPixelRef(SkData* data, SkBitmapFactory::DecodeProc proc, S
     }
     SkASSERT(cache != NULL);
     cache->ref();
+
+    // mark as uninitialized -- all fields are -1
+    memset(&fLazilyCachedInfo, 0xFF, sizeof(fLazilyCachedInfo));
+        
     // Since this pixel ref bases its data on encoded data, it should never change.
     this->setImmutable();
 }
@@ -63,6 +67,18 @@ static size_t ComputeMinRowBytesAndSize(const SkImage::Info& info, size_t* rowBy
     return safeSize.is32() ? safeSize.get32() : 0;
 }
 
+const SkImage::Info* SkLazyPixelRef::getCachedInfo() {
+    if (fLazilyCachedInfo.fWidth < 0) {
+        SkImage::Info info;
+        fErrorInDecoding = !fDecodeProc(fData->data(), fData->size(), &info, NULL);
+        if (fErrorInDecoding) {
+            return NULL;
+        }
+        fLazilyCachedInfo = info;
+    }
+    return &fLazilyCachedInfo;
+}
+
 void* SkLazyPixelRef::onLockPixels(SkColorTable**) {
     if (fErrorInDecoding) {
         return NULL;
@@ -91,20 +107,15 @@ void* SkLazyPixelRef::onLockPixels(SkColorTable**) {
         sk_atomic_inc(&gCacheMisses);
 #endif
     }
-    SkImage::Info info;
+
     SkASSERT(fData != NULL && fData->size() > 0);
     if (NULL == target.fAddr) {
-        // Determine the size of the image in order to determine how much memory to allocate.
-        // FIXME: As an optimization, only do this part once.
-        fErrorInDecoding = !fDecodeProc(fData->data(), fData->size(), &info, NULL);
-        if (fErrorInDecoding) {
-            // We can only reach here if fCacheId was already set to UNINITIALIZED_ID, or if
-            // pinCache returned NULL, in which case it was reset to UNINITIALIZED_ID.
+        const SkImage::Info* info = this->getCachedInfo();
+        if (NULL == info) {
             SkASSERT(SkImageCache::UNINITIALIZED_ID == fCacheId);
             return NULL;
         }
-
-        size_t bytes = ComputeMinRowBytesAndSize(info, &target.fRowBytes);
+        size_t bytes = ComputeMinRowBytesAndSize(*info, &target.fRowBytes);
         target.fAddr = fImageCache->allocAndPinCache(bytes, &fCacheId);
         if (NULL == target.fAddr) {
             // Space could not be allocated.
@@ -121,7 +132,7 @@ void* SkLazyPixelRef::onLockPixels(SkColorTable**) {
     }
     SkASSERT(target.fAddr != NULL);
     SkASSERT(SkImageCache::UNINITIALIZED_ID != fCacheId);
-    fErrorInDecoding = !fDecodeProc(fData->data(), fData->size(), &info, &target);
+    fErrorInDecoding = !fDecodeProc(fData->data(), fData->size(), NULL, &target);
     if (fErrorInDecoding) {
         fImageCache->throwAwayCache(fCacheId);
         fCacheId = SkImageCache::UNINITIALIZED_ID;
diff --git a/src/lazy/SkLazyPixelRef.h b/src/lazy/SkLazyPixelRef.h
index c51675dd5f..8f7a751e95 100644
--- a/src/lazy/SkLazyPixelRef.h
+++ b/src/lazy/SkLazyPixelRef.h
@@ -71,12 +71,16 @@ private:
     SkImageCache*               fImageCache;
     intptr_t                    fCacheId;
     size_t                      fRowBytes;
+    SkImage::Info               fLazilyCachedInfo;
 
 #if LAZY_CACHE_STATS
     static int32_t              gCacheHits;
     static int32_t              gCacheMisses;
 #endif
 
+    // lazily initialized our cached info. Returns NULL on failure.
+    const SkImage::Info* getCachedInfo();
+
     typedef SkPixelRef INHERITED;
 };