chromium/components/zucchini/encoded_view.h

// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_ZUCCHINI_ENCODED_VIEW_H_
#define COMPONENTS_ZUCCHINI_ENCODED_VIEW_H_

#include <stddef.h>
#include <stdint.h>

#include <iterator>
#include <vector>

#include "base/memory/raw_ptr.h"
#include "base/memory/raw_ref.h"
#include "components/zucchini/image_index.h"
#include "components/zucchini/image_utils.h"

namespace zucchini {

// Zucchini-gen performs semantics-aware matching:
// - Same-typed reference target in "old" and "new" can be associated.
//   Associated targets are assigned an identifier called "label" (and for
//   unassociated targets, label = 0).
// - EncodedView maps each offset in "old" and "new" images to a "projected
//   value", which can be:
//   - Raw byte value (0-255) for non-references.
//   - Reference "projected value" (> 256) that depends on target {type, label}
//     at each reference's location (byte 0).
//   - Reference padding value (256) at the body of each reference (bytes 1+).
// - The projected values for "old" and "new" are used to build the equivalence
//   map.

constexpr size_t kReferencePaddingProjection = …;
constexpr size_t kBaseReferenceProjection = …;

// A Range (providing begin and end iterators) that adapts ImageIndex to make
// image data appear as an Encoded Image, that is encoded data under a higher
// level of abstraction than raw bytes. In particular:
// - First byte of each reference become a projection of its type and label.
// - Subsequent bytes of each reference becomes |kReferencePaddingProjection|.
// - Non-reference raw bytes remain as raw bytes.
class EncodedView { … };

}  // namespace zucchini

#endif  // COMPONENTS_ZUCCHINI_ENCODED_VIEW_H_