Handle zero-length encoded images gracefully during deserialization

Image encoding may fail during serialization, resulting in zero-length
encoded data in the SKP.

Instead of invalidating the stream (and preventing deserialization of
the whole picture) we can instantiate placeholder images.

BUG=skia:4285
R=reed@google.com,robertphillips@google.com

Review URL: https://codereview.chromium.org/1308273011

2 files changed, 23 insertions, 2 deletions

diff --git a/src/core/SkPictureData.cpp b/src/core/SkPictureData.cpp
index 5089e5d8d6..9d497f676a 100644
--- a/src/core/SkPictureData.cpp
+++ b/src/core/SkPictureData.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 #include <new>
+#include "SkImageGenerator.h"
 #include "SkPictureData.h"
 #include "SkPictureRecord.h"
 #include "SkReadBuffer.h"
@@ -433,6 +434,20 @@ bool SkPictureData::parseStreamTag(SkStream* stream,
     return true;    // success
 }
 
+namespace {
+
+// This generator intentionally should always fail on all attempts to get its pixels,
+// simulating a bad or empty codec stream.
+class EmptyImageGenerator final : public SkImageGenerator {
+public:
+    EmptyImageGenerator(const SkImageInfo& info) : INHERITED(info) { }
+
+private:
+    typedef SkImageGenerator INHERITED;
+};
+
+} // anonymous namespace
+
 static const SkImage* create_image_from_buffer(SkReadBuffer& buffer) {
     int width = buffer.read32();
     int height = buffer.read32();
@@ -442,9 +457,15 @@ static const SkImage* create_image_from_buffer(SkReadBuffer& buffer) {
     }
 
     SkAutoTUnref<SkData> encoded(buffer.readByteArrayAsData());
+    if (encoded->size() == 0) {
+        // The image could not be encoded at serialization time - return an empty placeholder.
+        return SkImage::NewFromGenerator(
+            new EmptyImageGenerator(SkImageInfo::MakeN32Premul(width, height)));
+    }
+
     int originX = buffer.read32();
     int originY = buffer.read32();
-    if (0 == encoded->size() || originX < 0 || originY < 0) {
+    if (originX < 0 || originY < 0) {
         buffer.validate(false);
         return nullptr;
     }
diff --git a/src/core/SkWriteBuffer.cpp b/src/core/SkWriteBuffer.cpp
index ac3d678dbc..1dfe0b3972 100644
--- a/src/core/SkWriteBuffer.cpp
+++ b/src/core/SkWriteBuffer.cpp
@@ -223,7 +223,7 @@ void SkWriteBuffer::writeImage(const SkImage* image) {
     this->writeInt(image->height());
 
     SkAutoTUnref<SkData> encoded(image->encode(this->getPixelSerializer()));
-    if (encoded) {
+    if (encoded && encoded->size() > 0) {
         write_encoded_bitmap(this, encoded, SkIPoint::Make(0, 0));
         return;
     }