Make Jpeg decoding more fault resistant.

src/images/SkImageDecoder_libjpeg.cpp

Index: src/images/SkImageDecoder_libjpeg.cpp
diff --git a/src/images/SkImageDecoder_libjpeg.cpp b/src/images/SkImageDecoder_libjpeg.cpp
index 3b3ea887e3cde437d7469d2a43126a2cb604a6eb..13b8e3ea8102302a51cd892bf5f692160ca3fbab 100644
--- a/src/images/SkImageDecoder_libjpeg.cpp
+++ b/src/images/SkImageDecoder_libjpeg.cpp
@@ -54,12 +54,15 @@ static void overwrite_mem_buffer_size(jpeg_decompress_struct* cinfo) {
 //////////////////////////////////////////////////////////////////////////
 //////////////////////////////////////////////////////////////////////////
 
+static void do_nothing(jpeg_common_struct*, int) {  /* do nothing */ }

[scroggo, 2013/10/01 22:04:14]

Could you make this name more specific? Though it does, in fact, do nothing,
maybe it should be something like do_nothing_emit_message so it's more clear
what it's for.

+
 static void initialize_info(jpeg_decompress_struct* cinfo, skjpeg_source_mgr* src_mgr) {
     SkASSERT(cinfo != NULL);
     SkASSERT(src_mgr != NULL);
     jpeg_create_decompress(cinfo);
     overwrite_mem_buffer_size(cinfo);
     cinfo->src = src_mgr;
+    cinfo->err->emit_message = &do_nothing;

[scroggo, 2013/10/01 22:04:14]

Why not do this inside an

#if !defined(SK_DEBUG)

block. Then we can still see this error message in debug mode.

 }
 
 #ifdef SK_BUILD_FOR_ANDROID
@@ -556,7 +559,8 @@ bool SkJPEGImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
             // if row_count == 0, then we didn't get a scanline, so abort.
             // if we supported partial images, we might return true in this case
             if (0 == row_count) {
-                return return_false(cinfo, *bm, "read_scanlines");
+                // Ignore error: return_false(cinfo, *bm, "read_scanlines");

[scroggo, 2013/10/01 22:04:14]

This line can be removed. Same for the other cases.

+                return true;

[scroggo, 2013/10/01 22:04:14]

Like I said before, this will leave the remainder of the bitmap uninitialized.
Same for the other cases.

             }
             if (this->shouldCancelDecode()) {
                 return return_false(cinfo, *bm, "shouldCancelDecode");
@@ -606,7 +610,8 @@ bool SkJPEGImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
         JSAMPLE* rowptr = (JSAMPLE*)srcRow;
         int row_count = jpeg_read_scanlines(&cinfo, &rowptr, 1);
         if (0 == row_count) {
-            return return_false(cinfo, *bm, "read_scanlines");
+            // Ignore error: return_false(cinfo, *bm, "read_scanlines");
+            return true;
         }
         if (this->shouldCancelDecode()) {
             return return_false(cinfo, *bm, "shouldCancelDecode");
@@ -788,7 +793,8 @@ bool SkJPEGImageDecoder::onDecodeSubset(SkBitmap* bm, const SkIRect& region) {
             // if row_count == 0, then we didn't get a scanline, so abort.
             // if we supported partial images, we might return true in this case
             if (0 == rowCount) {
-                return return_false(*cinfo, bitmap, "read_scanlines");
+                // Ignore error: return_false(*cinfo, bitmap, "read_scanlines");
+                return true;
             }
             if (this->shouldCancelDecode()) {
                 return return_false(*cinfo, bitmap, "shouldCancelDecode");
@@ -845,7 +851,8 @@ bool SkJPEGImageDecoder::onDecodeSubset(SkBitmap* bm, const SkIRect& region) {
         JSAMPLE* rowptr = (JSAMPLE*)srcRow;
         int row_count = jpeg_read_tile_scanline(cinfo, fImageIndex->huffmanIndex(), &rowptr);
         if (0 == row_count) {
-            return return_false(*cinfo, bitmap, "read_scanlines");
+            // Ignore error: return_false(*cinfo, bitmap, "read_scanlines");
+            return true;
         }
         if (this->shouldCancelDecode()) {
             return return_false(*cinfo, bitmap, "shouldCancelDecode");