enforce 16byte alignment in shader contexts

src/core/SkShader.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAtomics.h"
 #include "SkBitmapProcShader.h"
 #include "SkColorShader.h"
@@ skipping 68 matching lines @@
         colorPtr = &storage;
     }
     if (this->onAsLuminanceColor(colorPtr)) {
         *colorPtr = SkColorSetA(*colorPtr, 0xFF);   // we only return opaque
         return true;
     }
     return false;
 }
 
 SkShader::Context* SkShader::createContext(const ContextRec& rec, void* storage) const {
+    // Currently we require each context to be allocated on 16byte boundary as some of our
+    // subclasses need that. Hence we check the ptr here.
+    SkASSERT(SkIsAlign16((intptr_t)storage));
+
     if (!this->computeTotalInverse(rec, nullptr)) {
         return nullptr;
     }
     return this->onCreateContext(rec, storage);
 }
 
 SkShader::Context* SkShader::onCreateContext(const ContextRec& rec, void*) const {
     return nullptr;
 }
 
-size_t SkShader::contextSize(const ContextRec&) const {
+size_t SkShader::contextSize(const ContextRec& rec) const {
+    size_t size = this->onContextSize(rec);
+
+    // Currently we require each context to be allocated on 16byte boundary as some of our
+    // subclasses need that. Hence we check the size here.
+    SkASSERT(SkIsAlign16(size));
+
+    return size;
+}
+
+size_t SkShader::onContextSize(const ContextRec&) const {
     return 0;
 }
 
 SkShader::Context::Context(const SkShader& shader, const ContextRec& rec)
     : fShader(shader), fCTM(*rec.fMatrix)
 {
     // Because the context parameters must be valid at this point, we know that the matrix is
     // invertible.
     SkAssertResult(fShader.computeTotalInverse(rec, &fTotalInverse));
     fTotalInverseClass = (uint8_t)ComputeMatrixClass(fTotalInverse);
@@ skipping 255 matching lines @@
 #include "SkEmptyShader.h"
 
 void SkEmptyShader::toString(SkString* str) const {
     str->append("SkEmptyShader: (");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif