mojo/edk/system/memory.cc

// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "mojo/edk/system/memory.h"

#include <limits>

#include "base/logging.h"
#include "build/build_config.h"

namespace mojo {
namespace system {
namespace internal {

template <size_t alignment>
bool IsAligned(const void* pointer) {
  return reinterpret_cast<uintptr_t>(pointer) % alignment == 0;
}

// MSVS (2010, 2013) sometimes (on the stack) aligns, e.g., |int64_t|s (for
// which |__alignof(int64_t)| is 8) to 4-byte boundaries. http://goo.gl/Y2n56T
#if defined(COMPILER_MSVC) && defined(ARCH_CPU_32_BITS)
template <>
bool IsAligned<8>(const void* pointer) {
  return reinterpret_cast<uintptr_t>(pointer) % 4 == 0;
}
#endif

template <size_t size, size_t alignment>
void MOJO_SYSTEM_IMPL_EXPORT CheckUserPointer(const void* pointer) {
  CHECK(pointer && IsAligned<alignment>(pointer));
}

// Explicitly instantiate the sizes we need. Add instantiations as needed.
template void MOJO_SYSTEM_IMPL_EXPORT CheckUserPointer<1, 1>(const void*);
template void MOJO_SYSTEM_IMPL_EXPORT CheckUserPointer<4, 4>(const void*);
template void MOJO_SYSTEM_IMPL_EXPORT CheckUserPointer<8, 4>(const void*);
template void MOJO_SYSTEM_IMPL_EXPORT CheckUserPointer<8, 8>(const void*);

template <size_t size, size_t alignment>
void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithCount(const void* pointer, size_t count) {
  CHECK_LE(count, std::numeric_limits<size_t>::max() / size);
  CHECK(count == 0 || (pointer && IsAligned<alignment>(pointer)));
}

// Explicitly instantiate the sizes we need. Add instantiations as needed.
template void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithCount<1, 1>(const void*, size_t);
template void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithCount<4, 4>(const void*, size_t);
template void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithCount<8, 4>(const void*, size_t);
template void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithCount<8, 8>(const void*, size_t);

template <size_t alignment>
void CheckUserPointerWithSize(const void* pointer, size_t size) {
  // TODO(vtl): If running in kernel mode, do a full verification. For now, just
  // check that it's non-null and aligned. (A faster user mode implementation is
  // also possible if this check is skipped.)
  CHECK(size == 0 || (!!pointer && internal::IsAligned<alignment>(pointer)));
}

// Explicitly instantiate the sizes we need. Add instantiations as needed.
template void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithSize<1>(const void*, size_t);
template void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithSize<4>(const void*, size_t);
// Whereas the other |Check...()| functions are usually used with integral typs
// or arrays of integral types, this one is used with Options structs for which
// alignment has been explicitly been specified (using |MOJO_ALIGNAS()|), which
// MSVS *does* respect.
#if defined(COMPILER_MSVC) && defined(ARCH_CPU_32_BITS)
template <>
void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithSize<8>(const void* pointer, size_t size) {
  CHECK(size == 0 ||
        (!!pointer && reinterpret_cast<uintptr_t>(pointer) % 8 == 0));
}
#else
template void MOJO_SYSTEM_IMPL_EXPORT
CheckUserPointerWithSize<8>(const void*, size_t);
#endif

}  // namespace internal
}  // namespace system
}  // namespace mojo