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diff --git a/third_party/jpeg-xl/lib/jxl/base/span.h b/third_party/jpeg-xl/lib/jxl/base/span.h
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+++ b/third_party/jpeg-xl/lib/jxl/base/span.h
@@ -0,0 +1,60 @@
+// 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.
+
+#ifndef LIB_JXL_BASE_SPAN_H_
+#define LIB_JXL_BASE_SPAN_H_
+
+// Span (array view) is a non-owning container that provides cheap "cut"
+// operations and could be used as "ArrayLike" data source for PaddedBytes.
+
+#include <stddef.h>
+
+#include "lib/jxl/base/status.h"
+
+namespace jxl {
+
+template <typename T>
+class Span {
+ public:
+  constexpr Span() noexcept : Span(nullptr, 0) {}
+
+  constexpr Span(T* array, size_t length) noexcept
+      : ptr_(array), len_(length) {}
+
+  template <size_t N>
+  explicit constexpr Span(T (&a)[N]) noexcept : Span(a, N) {}
+
+  template <typename ArrayLike>
+  explicit constexpr Span(const ArrayLike& other) noexcept
+      : Span(reinterpret_cast<T*>(other.data()), other.size()) {
+    static_assert(sizeof(*other.data()) == sizeof(T),
+                  "Incompatible type of source.");
+  }
+
+  constexpr T* data() const noexcept { return ptr_; }
+
+  constexpr size_t size() const noexcept { return len_; }
+
+  constexpr bool empty() const noexcept { return len_ == 0; }
+
+  constexpr T& operator[](size_t i) const noexcept {
+    // MSVC 2015 accepts this as constexpr, but not ptr_[i]
+    return *(data() + i);
+  }
+
+  void remove_prefix(size_t n) noexcept {
+    JXL_ASSERT(size() >= n);
+    ptr_ += n;
+    len_ -= n;
+  }
+
+ private:
+  T* ptr_;
+  size_t len_;
+};
+
+}  // namespace jxl
+
+#endif  // LIB_JXL_BASE_SPAN_H_