Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 160 insertions, 0 deletions

diff --git a/mfbt/PodOperations.h b/mfbt/PodOperations.h
new file mode 100644
index 0000000000..f4e5da4c79
--- /dev/null
+++ b/mfbt/PodOperations.h
@@ -0,0 +1,160 @@
+/* -*- 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/Assertions.h"
+#include "mozilla/Attributes.h"
+
+#include <stdint.h>
+#include <string.h>
+
+namespace mozilla {
+
+template <typename T, size_t Length>
+class Array;
+
+template <typename T>
+class NotNull;
+
+/** 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));
+  }
+}
+
+/** Set the contents of |aNElem| elements starting at |aT| to 0. */
+template <typename T>
+static MOZ_ALWAYS_INLINE void PodZero(NotNull<T*> aT, size_t aNElem) {
+  PodZero(aT.get(), aNElem);
+}
+
+/*
+ * 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));
+}
+
+/**
+ * Looking for a PodEqual? Use ArrayEqual from ArrayUtils.h.
+ * Note that we *cannot* use memcmp for this, due to padding bytes, etc..
+ */
+
+}  // namespace mozilla
+
+#endif /* mozilla_PodOperations_h */