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diff --git a/media/libjxl/src/lib/jxl/dct_block-inl.h b/media/libjxl/src/lib/jxl/dct_block-inl.h
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+++ b/media/libjxl/src/lib/jxl/dct_block-inl.h
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+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Adapters for DCT input/output: from/to contiguous blocks or image rows.
+
+#if defined(LIB_JXL_DCT_BLOCK_INL_H_) == defined(HWY_TARGET_TOGGLE)
+#ifdef LIB_JXL_DCT_BLOCK_INL_H_
+#undef LIB_JXL_DCT_BLOCK_INL_H_
+#else
+#define LIB_JXL_DCT_BLOCK_INL_H_
+#endif
+
+#include <stddef.h>
+
+#include <hwy/highway.h>
+
+#include "lib/jxl/base/status.h"
+HWY_BEFORE_NAMESPACE();
+namespace jxl {
+namespace HWY_NAMESPACE {
+namespace {
+
+// These templates are not found via ADL.
+using hwy::HWY_NAMESPACE::Vec;
+
+// Block: (x, y) <-> (N * y + x)
+// Lines: (x, y) <-> (stride * y + x)
+//
+// I.e. Block is a specialization of Lines with fixed stride.
+//
+// FromXXX should implement Read and Load (Read vector).
+// ToXXX should implement Write and Store (Write vector).
+
+template <size_t N>
+using BlockDesc = HWY_CAPPED(float, N);
+
+// Here and in the following, the SZ template parameter specifies the number of
+// values to load/store. Needed because we want to handle 4x4 sub-blocks of
+// 16x16 blocks.
+class DCTFrom {
+ public:
+  DCTFrom(const float* data, size_t stride) : stride_(stride), data_(data) {}
+
+  template <typename D>
+  HWY_INLINE Vec<D> LoadPart(D, const size_t row, size_t i) const {
+    JXL_DASSERT(Lanes(D()) <= stride_);
+    // Since these functions are used also for DC, no alignment at all is
+    // guaranteed in the case of floating blocks.
+    // TODO(veluca): consider using a different class for DC-to-LF and
+    // DC-from-LF, or copying DC values to/from a temporary aligned location.
+    return LoadU(D(), Address(row, i));
+  }
+
+  HWY_INLINE float Read(const size_t row, const size_t i) const {
+    return *Address(row, i);
+  }
+
+  constexpr HWY_INLINE const float* Address(const size_t row,
+                                            const size_t i) const {
+    return data_ + row * stride_ + i;
+  }
+
+  size_t Stride() const { return stride_; }
+
+ private:
+  size_t stride_;
+  const float* JXL_RESTRICT data_;
+};
+
+class DCTTo {
+ public:
+  DCTTo(float* data, size_t stride) : stride_(stride), data_(data) {}
+
+  template <typename D>
+  HWY_INLINE void StorePart(D, const Vec<D>& v, const size_t row,
+                            size_t i) const {
+    JXL_DASSERT(Lanes(D()) <= stride_);
+    // Since these functions are used also for DC, no alignment at all is
+    // guaranteed in the case of floating blocks.
+    // TODO(veluca): consider using a different class for DC-to-LF and
+    // DC-from-LF, or copying DC values to/from a temporary aligned location.
+    StoreU(v, D(), Address(row, i));
+  }
+
+  HWY_INLINE void Write(float v, const size_t row, const size_t i) const {
+    *Address(row, i) = v;
+  }
+
+  constexpr HWY_INLINE float* Address(const size_t row, const size_t i) const {
+    return data_ + row * stride_ + i;
+  }
+
+  size_t Stride() const { return stride_; }
+
+ private:
+  size_t stride_;
+  float* JXL_RESTRICT data_;
+};
+
+}  // namespace
+// NOLINTNEXTLINE(google-readability-namespace-comments)
+}  // namespace HWY_NAMESPACE
+}  // namespace jxl
+HWY_AFTER_NAMESPACE();
+
+#endif  // LIB_JXL_DCT_BLOCK_INL_H_