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diff --git a/mfbt/PodOperations.h b/mfbt/PodOperations.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Operations for zeroing POD types, arrays, and so on.
+ *
+ * These operations are preferable to memset, memcmp, and the like because they
+ * don't require remembering to multiply by sizeof(T), array lengths, and so on
+ * everywhere.
+ */
+
+#ifndef mozilla_PodOperations_h
+#define mozilla_PodOperations_h
+
+#include "mozilla/Array.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Attributes.h"
+
+#include <stdint.h>
+#include <string.h>
+
+namespace mozilla {
+
+/** Set the contents of |aT| to 0. */
+template<typename T>
+static MOZ_ALWAYS_INLINE void
+PodZero(T* aT)
+{
+ memset(aT, 0, sizeof(T));
+}
+
+/** Set the contents of |aNElem| elements starting at |aT| to 0. */
+template<typename T>
+static MOZ_ALWAYS_INLINE void
+PodZero(T* aT, size_t aNElem)
+{
+ /*
+ * This function is often called with 'aNElem' small; we use an inline loop
+ * instead of calling 'memset' with a non-constant length. The compiler
+ * should inline the memset call with constant size, though.
+ */
+ for (T* end = aT + aNElem; aT < end; aT++) {
+ memset(aT, 0, sizeof(T));
+ }
+}
+
+/*
+ * Arrays implicitly convert to pointers to their first element, which is
+ * dangerous when combined with the above PodZero definitions. Adding an
+ * overload for arrays is ambiguous, so we need another identifier. The
+ * ambiguous overload is left to catch mistaken uses of PodZero; if you get a
+ * compile error involving PodZero and array types, use PodArrayZero instead.
+ */
+template<typename T, size_t N>
+static void PodZero(T (&aT)[N]) = delete;
+template<typename T, size_t N>
+static void PodZero(T (&aT)[N], size_t aNElem) = delete;
+
+/** Set the contents of the array |aT| to zero. */
+template <class T, size_t N>
+static MOZ_ALWAYS_INLINE void
+PodArrayZero(T (&aT)[N])
+{
+ memset(aT, 0, N * sizeof(T));
+}
+
+template <typename T, size_t N>
+static MOZ_ALWAYS_INLINE void
+PodArrayZero(Array<T, N>& aArr)
+{
+ memset(&aArr[0], 0, N * sizeof(T));
+}
+
+/**
+ * Assign |*aSrc| to |*aDst|. The locations must not be the same and must not
+ * overlap.
+ */
+template<typename T>
+static MOZ_ALWAYS_INLINE void
+PodAssign(T* aDst, const T* aSrc)
+{
+ MOZ_ASSERT(aDst + 1 <= aSrc || aSrc + 1 <= aDst,
+ "destination and source must not overlap");
+ memcpy(reinterpret_cast<char*>(aDst), reinterpret_cast<const char*>(aSrc),
+ sizeof(T));
+}
+
+/**
+ * Copy |aNElem| T elements from |aSrc| to |aDst|. The two memory ranges must
+ * not overlap!
+ */
+template<typename T>
+static MOZ_ALWAYS_INLINE void
+PodCopy(T* aDst, const T* aSrc, size_t aNElem)
+{
+ MOZ_ASSERT(aDst + aNElem <= aSrc || aSrc + aNElem <= aDst,
+ "destination and source must not overlap");
+ if (aNElem < 128) {
+ /*
+ * Avoid using operator= in this loop, as it may have been
+ * intentionally deleted by the POD type.
+ */
+ for (const T* srcend = aSrc + aNElem; aSrc < srcend; aSrc++, aDst++) {
+ PodAssign(aDst, aSrc);
+ }
+ } else {
+ memcpy(aDst, aSrc, aNElem * sizeof(T));
+ }
+}
+
+template<typename T>
+static MOZ_ALWAYS_INLINE void
+PodCopy(volatile T* aDst, const volatile T* aSrc, size_t aNElem)
+{
+ MOZ_ASSERT(aDst + aNElem <= aSrc || aSrc + aNElem <= aDst,
+ "destination and source must not overlap");
+
+ /*
+ * Volatile |aDst| requires extra work, because it's undefined behavior to
+ * modify volatile objects using the mem* functions. Just write out the
+ * loops manually, using operator= rather than memcpy for the same reason,
+ * and let the compiler optimize to the extent it can.
+ */
+ for (const volatile T* srcend = aSrc + aNElem;
+ aSrc < srcend;
+ aSrc++, aDst++) {
+ *aDst = *aSrc;
+ }
+}
+
+/*
+ * Copy the contents of the array |aSrc| into the array |aDst|, both of size N.
+ * The arrays must not overlap!
+ */
+template <class T, size_t N>
+static MOZ_ALWAYS_INLINE void
+PodArrayCopy(T (&aDst)[N], const T (&aSrc)[N])
+{
+ PodCopy(aDst, aSrc, N);
+}
+
+/**
+ * Copy the memory for |aNElem| T elements from |aSrc| to |aDst|. If the two
+ * memory ranges overlap, then the effect is as if the |aNElem| elements are
+ * first copied from |aSrc| to a temporary array, and then from the temporary
+ * array to |aDst|.
+ */
+template<typename T>
+static MOZ_ALWAYS_INLINE void
+PodMove(T* aDst, const T* aSrc, size_t aNElem)
+{
+ MOZ_ASSERT(aNElem <= SIZE_MAX / sizeof(T),
+ "trying to move an impossible number of elements");
+ memmove(aDst, aSrc, aNElem * sizeof(T));
+}
+
+/**
+ * Determine whether the |len| elements at |one| are memory-identical to the
+ * |len| elements at |two|.
+ */
+template<typename T>
+static MOZ_ALWAYS_INLINE bool
+PodEqual(const T* one, const T* two, size_t len)
+{
+ if (len < 128) {
+ const T* p1end = one + len;
+ const T* p1 = one;
+ const T* p2 = two;
+ for (; p1 < p1end; p1++, p2++) {
+ if (*p1 != *p2) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ return !memcmp(one, two, len * sizeof(T));
+}
+
+/*
+ * Determine whether the |N| elements at |one| are memory-identical to the
+ * |N| elements at |two|.
+ */
+template <class T, size_t N>
+static MOZ_ALWAYS_INLINE bool
+PodEqual(const T (&one)[N], const T (&two)[N])
+{
+ return PodEqual(one, two, N);
+}
+
+} // namespace mozilla
+
+#endif /* mozilla_PodOperations_h */