Creating a new wrapper for gif decoder

src/codec/SkGifInterlaceIter.h

+/*
+ * Copyright 2015 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 "SkTypes.h"
+
+/*
+ * Helper class to determine the destination y-values for interlaced gifs
+ */
+class SkGifInterlaceIter {

[scroggo, 2015/03/25 19:44:49]

Unless you want this to be copyable, make it inherit from SkNoncopyable (in
SkTypes.h)

[msarett, 2015/03/26 19:15:57]

Done.

+public:
+
+    /*
+     * Constructor

[scroggo, 2015/03/25 19:44:49]

This comment does not provide any useful information, so we don't need it.

[msarett, 2015/03/26 19:15:57]

Done.

+     */
+    SkGifInterlaceIter(int height);

[scroggo, 2015/03/25 19:44:49]

We typically declare constructors that take one parameter explicit, unless they
are intended to be called implicitly.

[msarett, 2015/03/26 19:15:57]

Done.

+
+    /*
+     * Get the next destination y-value
+     */
+    uint32_t nextY();

[scroggo, 2015/03/25 19:44:49]

It's weird that this returns a uint32_t while we create one with an int. (Is
this because the caller expects something unsigned?)

[msarett, 2015/03/26 19:15:57]

This code now deals with int32_t uniformly.

+
+private:
+
+    /*
+     * Updates the iterator to prepare the next y-value
+     */
+    void prepareY();
+
+    // Fields

[scroggo, 2015/03/25 19:44:49]

Again, this comment is unnecessary.

[msarett, 2015/03/26 19:15:57]

Done.

+    const uint32_t fHeight;
+    int32_t        fCurrY;
+    int32_t        fDeltaY;
+    const uint8_t* fStartYPtr;
+    const uint8_t* fDeltaYPtr;
+};