Checking structure sizes before reading them from memory to avoid overflowing the buffer's stream.

tests/SerializationTest.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 "SkOrderedWriteBuffer.h"
+#include "SkValidatingReadBuffer.h"
+#include "Test.h"
+
+static void Tests(skiatest::Reporter* reporter) {
+    // Test matrix serialization
+    {
+        SkMatrix matrix = SkMatrix::I();
+        SkOrderedWriteBuffer writer(1024);
+        writer.setFlags(SkOrderedWriteBuffer::kValidation_Flag);
+        writer.writeMatrix(matrix);
+        uint32_t bytesWritten = writer.bytesWritten();
+        // This should write the length (in 4 bytes) and the array
+        REPORTER_ASSERT(reporter, (9 * sizeof(SkScalar)) == bytesWritten);
+
+        unsigned char dataWritten[1024];
+        writer.writeToMemory(dataWritten);
+
+        // Make sure this fails when it should
+        SkValidatingReadBuffer buffer(dataWritten, bytesWritten - 1);
+        const unsigned char* peekBefore = static_cast<const unsigned char*>(buffer.skip(0));
+        buffer.readMatrix(&matrix);
+        const unsigned char* peekAfter = static_cast<const unsigned char*>(buffer.skip(0));
+        // This should have failed, since the buffer is too small to read a matrix from it
+        REPORTER_ASSERT(reporter, peekBefore == peekAfter);
+
+        // Make sure this succeeds when it should
+        SkValidatingReadBuffer buffer2(dataWritten, bytesWritten);
+        peekBefore = static_cast<const unsigned char*>(buffer2.skip(0));
+        buffer2.readMatrix(&matrix);
+        peekAfter = static_cast<const unsigned char*>(buffer2.skip(0));
+        // This should have succeeded, since there are enough bytes to read this
+        REPORTER_ASSERT(reporter, (peekAfter - peekBefore) == bytesWritten);
+     }
+
+    // Test path serialization
+    {
+        SkPath path;
+        SkOrderedWriteBuffer writer(1024);
+        writer.setFlags(SkOrderedWriteBuffer::kValidation_Flag);
+        writer.writePath(path);
+        uint32_t bytesWritten = writer.bytesWritten();
+
+        unsigned char dataWritten[1024];
+        writer.writeToMemory(dataWritten);
+
+        // Make sure this fails when it should
+        SkValidatingReadBuffer buffer(dataWritten, bytesWritten - 1);
+        const unsigned char* peekBefore = static_cast<const unsigned char*>(buffer.skip(0));
+        buffer.readPath(&path);
+        const unsigned char* peekAfter = static_cast<const unsigned char*>(buffer.skip(0));
+        // This should have failed, since the buffer is too small to read a matrix from it
+        REPORTER_ASSERT(reporter, peekBefore == peekAfter);
+
+        // Make sure this succeeds when it should
+        SkValidatingReadBuffer buffer2(dataWritten, bytesWritten);
+        peekBefore = static_cast<const unsigned char*>(buffer2.skip(0));
+        buffer2.readPath(&path);
+        peekAfter = static_cast<const unsigned char*>(buffer2.skip(0));
+        // This should have succeeded, since there are enough bytes to read this
+        REPORTER_ASSERT(reporter, (peekAfter - peekBefore) == bytesWritten);
+     }
+
+    // Test region serialization
+    {
+        SkRegion region;
+        SkOrderedWriteBuffer writer(1024);
+        writer.setFlags(SkOrderedWriteBuffer::kValidation_Flag);
+        writer.writeRegion(region);
+        uint32_t bytesWritten = writer.bytesWritten();
+
+        unsigned char dataWritten[1024];
+        writer.writeToMemory(dataWritten);
+
+        // Make sure this fails when it should
+        SkValidatingReadBuffer buffer(dataWritten, bytesWritten - 1);
+        const unsigned char* peekBefore = static_cast<const unsigned char*>(buffer.skip(0));
+        buffer.readRegion(&region);
+        const unsigned char* peekAfter = static_cast<const unsigned char*>(buffer.skip(0));
+        // This should have failed, since the buffer is too small to read a matrix from it
+        REPORTER_ASSERT(reporter, peekBefore == peekAfter);
+
+        // Make sure this succeeds when it should
+        SkValidatingReadBuffer buffer2(dataWritten, bytesWritten);
+        peekBefore = static_cast<const unsigned char*>(buffer2.skip(0));
+        buffer2.readRegion(&region);
+        peekAfter = static_cast<const unsigned char*>(buffer2.skip(0));
+        // This should have succeeded, since there are enough bytes to read this
+        REPORTER_ASSERT(reporter, (peekAfter - peekBefore) == bytesWritten);
+     }
+}
+
+#include "TestClassDef.h"
+DEFINE_TESTCLASS("Serialization", SerializationClass, Tests)