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/* SPDX-License-Identifier: GPL-2.0-or-later */
#pragma once
/** \file
* \ingroup bli
* Some of the functions below have very similar alternatives in the standard library. However, it
* is rather annoying to use those when debugging. Therefore, some more specialized and easier to
* debug functions are provided here.
*/
#include <memory>
#include <new>
#include <type_traits>
#include "BLI_utildefines.h"
#include "MEM_guardedalloc.h"
namespace blender {
/**
* Under some circumstances #std::is_trivial_v<T> is false even though we know that the type is
* actually trivial. Using that extra knowledge allows for some optimizations.
*/
template<typename T> inline constexpr bool is_trivial_extended_v = std::is_trivial_v<T>;
template<typename T>
inline constexpr bool is_trivially_destructible_extended_v = is_trivial_extended_v<T> ||
std::is_trivially_destructible_v<T>;
template<typename T>
inline constexpr bool is_trivially_copy_constructible_extended_v =
is_trivial_extended_v<T> || std::is_trivially_copy_constructible_v<T>;
template<typename T>
inline constexpr bool is_trivially_move_constructible_extended_v =
is_trivial_extended_v<T> || std::is_trivially_move_constructible_v<T>;
/**
* Call the destructor on n consecutive values. For trivially destructible types, this does
* nothing.
*
* Exception Safety: Destructors shouldn't throw exceptions.
*
* Before:
* ptr: initialized
* After:
* ptr: uninitialized
*/
template<typename T> void destruct_n(T *ptr, int64_t n)
{
BLI_assert(n >= 0);
static_assert(std::is_nothrow_destructible_v<T>,
"This should be true for all types. Destructors are noexcept by default.");
/* This is not strictly necessary, because the loop below will be optimized away anyway. It is
* nice to make behavior this explicitly, though. */
if (is_trivially_destructible_extended_v<T>) {
return;
}
for (int64_t i = 0; i < n; i++) {
ptr[i].~T();
}
}
/**
* Call the default constructor on n consecutive elements. For trivially constructible types, this
* does nothing.
*
* Exception Safety: Strong.
*
* Before:
* ptr: uninitialized
* After:
* ptr: initialized
*/
template<typename T> void default_construct_n(T *ptr, int64_t n)
{
BLI_assert(n >= 0);
/* This is not strictly necessary, because the loop below will be optimized away anyway. It is
* nice to make behavior this explicitly, though. */
if (std::is_trivially_constructible_v<T>) {
return;
}
int64_t current = 0;
try {
for (; current < n; current++) {
new (static_cast<void *>(ptr + current)) T;
}
}
catch (...) {
destruct_n(ptr, current);
throw;
}
}
/**
* Copy n values from src to dst.
*
* Exception Safety: Basic.
*
* Before:
* src: initialized
* dst: initialized
* After:
* src: initialized
* dst: initialized
*/
template<typename T> void initialized_copy_n(const T *src, int64_t n, T *dst)
{
BLI_assert(n >= 0);
for (int64_t i = 0; i < n; i++) {
dst[i] = src[i];
}
}
/**
* Copy n values from src to dst.
*
* Exception Safety: Strong.
*
* Before:
* src: initialized
* dst: uninitialized
* After:
* src: initialized
* dst: initialized
*/
template<typename T> void uninitialized_copy_n(const T *src, int64_t n, T *dst)
{
BLI_assert(n >= 0);
int64_t current = 0;
try {
for (; current < n; current++) {
new (static_cast<void *>(dst + current)) T(src[current]);
}
}
catch (...) {
destruct_n(dst, current);
throw;
}
}
/**
* Convert n values from type `From` to type `To`.
*
* Exception Safety: Strong.
*
* Before:
* src: initialized
* dst: uninitialized
* After:
* src: initialized
* dst: initialized
*/
template<typename From, typename To>
void uninitialized_convert_n(const From *src, int64_t n, To *dst)
{
BLI_assert(n >= 0);
int64_t current = 0;
try {
for (; current < n; current++) {
new (static_cast<void *>(dst + current)) To(static_cast<To>(src[current]));
}
}
catch (...) {
destruct_n(dst, current);
throw;
}
}
/**
* Move n values from src to dst.
*
* Exception Safety: Basic.
*
* Before:
* src: initialized
* dst: initialized
* After:
* src: initialized, moved-from
* dst: initialized
*/
template<typename T> void initialized_move_n(T *src, int64_t n, T *dst)
{
BLI_assert(n >= 0);
for (int64_t i = 0; i < n; i++) {
dst[i] = std::move(src[i]);
}
}
/**
* Move n values from src to dst.
*
* Exception Safety: Basic.
*
* Before:
* src: initialized
* dst: uninitialized
* After:
* src: initialized, moved-from
* dst: initialized
*/
template<typename T> void uninitialized_move_n(T *src, int64_t n, T *dst)
{
BLI_assert(n >= 0);
int64_t current = 0;
try {
for (; current < n; current++) {
new (static_cast<void *>(dst + current)) T(std::move(src[current]));
}
}
catch (...) {
destruct_n(dst, current);
throw;
}
}
/**
* Move n values from src to dst starting with the last value.
*
* Exception Safety: Basic.
*
* Before:
* src: initialized
* dst: initialized
* After:
* src: initialized, moved-from
* dst: initialized
*/
template<typename T> void initialized_reversed_move_n(T *src, int64_t n, T *dst)
{
BLI_assert(n >= 0);
for (int64_t i = n - 1; i >= 0; i--) {
dst[i] = std::move(src[i]);
}
}
/**
* Relocate n values from src to dst. Relocation is a move followed by destruction of the src
* value.
*
* Exception Safety: Basic.
*
* Before:
* src: initialized
* dst: initialized
* After:
* src: uninitialized
* dst: initialized
*/
template<typename T> void initialized_relocate_n(T *src, int64_t n, T *dst)
{
BLI_assert(n >= 0);
initialized_move_n(src, n, dst);
destruct_n(src, n);
}
/**
* Relocate n values from src to dst. Relocation is a move followed by destruction of the src
* value.
*
* Exception Safety: Basic.
*
* Before:
* src: initialized
* dst: uninitialized
* After:
* src: uninitialized
* dst: initialized
*/
template<typename T> void uninitialized_relocate_n(T *src, int64_t n, T *dst)
{
BLI_assert(n >= 0);
uninitialized_move_n(src, n, dst);
destruct_n(src, n);
}
/**
* Copy the value to n consecutive elements.
*
* Exception Safety: Basic.
*
* Before:
* dst: initialized
* After:
* dst: initialized
*/
template<typename T> void initialized_fill_n(T *dst, int64_t n, const T &value)
{
BLI_assert(n >= 0);
for (int64_t i = 0; i < n; i++) {
dst[i] = value;
}
}
/**
* Copy the value to n consecutive elements.
*
* Exception Safety: Strong.
*
* Before:
* dst: uninitialized
* After:
* dst: initialized
*/
template<typename T> void uninitialized_fill_n(T *dst, int64_t n, const T &value)
{
BLI_assert(n >= 0);
int64_t current = 0;
try {
for (; current < n; current++) {
new (static_cast<void *>(dst + current)) T(value);
}
}
catch (...) {
destruct_n(dst, current);
throw;
}
}
template<typename T> struct DestructValueAtAddress {
DestructValueAtAddress() = default;
template<typename U> DestructValueAtAddress(const U &)
{
}
void operator()(T *ptr)
{
ptr->~T();
}
};
/**
* A destruct_ptr is like unique_ptr, but it will only call the destructor and will not free the
* memory. This is useful when using custom allocators.
*/
template<typename T> using destruct_ptr = std::unique_ptr<T, DestructValueAtAddress<T>>;
/**
* An `AlignedBuffer` is a byte array with at least the given size and alignment. The buffer will
* not be initialized by the default constructor.
*/
template<size_t Size, size_t Alignment> class AlignedBuffer {
struct Empty {};
struct alignas(Alignment) Sized {
/* Don't create an empty array. This causes problems with some compilers. */
std::byte buffer_[Size > 0 ? Size : 1];
};
using BufferType = std::conditional_t<Size == 0, Empty, Sized>;
BLI_NO_UNIQUE_ADDRESS BufferType buffer_;
public:
operator void *()
{
return this;
}
operator const void *() const
{
return this;
}
void *ptr()
{
return this;
}
const void *ptr() const
{
return this;
}
};
/**
* This can be used to reserve memory for C++ objects whose lifetime is different from the
* lifetime of the object they are embedded in. It's used by containers with small buffer
* optimization and hash table implementations.
*/
template<typename T, int64_t Size = 1> class TypedBuffer {
private:
BLI_NO_UNIQUE_ADDRESS AlignedBuffer<sizeof(T) * (size_t)Size, alignof(T)> buffer_;
public:
operator T *()
{
return static_cast<T *>(buffer_.ptr());
}
operator const T *() const
{
return static_cast<const T *>(buffer_.ptr());
}
T &operator*()
{
return *static_cast<T *>(buffer_.ptr());
}
const T &operator*() const
{
return *static_cast<const T *>(buffer_.ptr());
}
T *ptr()
{
return static_cast<T *>(buffer_.ptr());
}
const T *ptr() const
{
return static_cast<const T *>(buffer_.ptr());
}
T &ref()
{
return *static_cast<T *>(buffer_.ptr());
}
const T &ref() const
{
return *static_cast<const T *>(buffer_.ptr());
}
};
/* A dynamic stack buffer can be used instead of #alloca when wants to allocate a dynamic amount of
* memory on the stack. Using this class has some advantages:
* - It falls back to heap allocation, when the size is too large.
* - It can be used in loops safely.
* - If the buffer is heap allocated, it is free automatically in the destructor.
*/
template<size_t ReservedSize = 64, size_t ReservedAlignment = 64>
class alignas(ReservedAlignment) DynamicStackBuffer {
private:
/* Don't create an empty array. This causes problems with some compilers. */
char reserved_buffer_[(ReservedSize > 0) ? ReservedSize : 1];
void *buffer_;
public:
DynamicStackBuffer(const int64_t size, const int64_t alignment)
{
BLI_assert(size >= 0);
BLI_assert(alignment >= 0);
if (size <= ReservedSize && alignment <= ReservedAlignment) {
buffer_ = reserved_buffer_;
}
else {
buffer_ = MEM_mallocN_aligned(size, alignment, __func__);
}
}
~DynamicStackBuffer()
{
if (buffer_ != reserved_buffer_) {
MEM_freeN(buffer_);
}
}
/* Don't allow any copying or moving of this type. */
DynamicStackBuffer(const DynamicStackBuffer &other) = delete;
DynamicStackBuffer(DynamicStackBuffer &&other) = delete;
DynamicStackBuffer &operator=(const DynamicStackBuffer &other) = delete;
DynamicStackBuffer &operator=(DynamicStackBuffer &&other) = delete;
void *buffer() const
{
return buffer_;
}
};
/**
* This can be used by container constructors. A parameter of this type should be used to indicate
* that the constructor does not construct the elements.
*/
class NoInitialization {};
/**
* This can be used to mark a constructor of an object that does not throw exceptions. Other
* constructors can delegate to this constructor to make sure that the object lifetime starts.
* With this, the destructor of the object will be called, even when the remaining constructor
* throws.
*/
class NoExceptConstructor {};
/**
* Helper variable that checks if a pointer type can be converted into another pointer type without
* issues. Possible issues are casting away const and casting a pointer to a child class.
* Adding const or casting to a parent class is fine.
*/
template<typename From, typename To>
inline constexpr bool is_convertible_pointer_v =
std::is_convertible_v<From, To> &&std::is_pointer_v<From> &&std::is_pointer_v<To>;
/**
* Helper variable that checks if a Span<From> can be converted to Span<To> safely, whereby From
* and To are pointers. Adding const and casting to a void pointer is allowed.
* Casting up and down a class hierarchy generally is not allowed, because this might change the
* pointer under some circumstances.
*/
template<typename From, typename To>
inline constexpr bool is_span_convertible_pointer_v =
/* Make sure we are working with pointers. */
std::is_pointer_v<From> &&std::is_pointer_v<To> &&
(/* No casting is necessary when both types are the same. */
std::is_same_v<From, To> ||
/* Allow adding const to the underlying type. */
std::is_same_v<const std::remove_pointer_t<From>, std::remove_pointer_t<To>> ||
/* Allow casting non-const pointers to void pointers. */
(!std::is_const_v<std::remove_pointer_t<From>> && std::is_same_v<To, void *>) ||
/* Allow casting any pointer to const void pointers. */
std::is_same_v<To, const void *>);
/**
* Same as #std::is_same_v but allows for checking multiple types at the same time.
*/
template<typename T, typename... Args>
inline constexpr bool is_same_any_v = (std::is_same_v<T, Args> || ...);
/**
* Inline buffers for small-object-optimization should be disable by default. Otherwise we might
* get large unexpected allocations on the stack.
*/
inline constexpr int64_t default_inline_buffer_capacity(size_t element_size)
{
return (static_cast<int64_t>(element_size) < 100) ? 4 : 0;
}
/**
* This can be used by containers to implement an exception-safe copy-assignment-operator.
* It assumes that the container has an exception safe copy constructor and an exception-safe
* move-assignment-operator.
*/
template<typename Container> Container ©_assign_container(Container &dst, const Container &src)
{
if (&src == &dst) {
return dst;
}
Container container_copy{src};
dst = std::move(container_copy);
return dst;
}
/**
* This can be used by containers to implement an exception-safe move-assignment-operator.
* It assumes that the container has an exception-safe move-constructor and a noexcept constructor
* tagged with the NoExceptConstructor tag.
*/
template<typename Container>
Container &move_assign_container(Container &dst, Container &&src) noexcept(
std::is_nothrow_move_constructible_v<Container>)
{
if (&dst == &src) {
return dst;
}
dst.~Container();
if constexpr (std::is_nothrow_move_constructible_v<Container>) {
new (&dst) Container(std::move(src));
}
else {
try {
new (&dst) Container(std::move(src));
}
catch (...) {
new (&dst) Container(NoExceptConstructor());
throw;
}
}
return dst;
}
/**
* Returns true if the value is different and was assigned.
*/
template<typename T> inline bool assign_if_different(T &old_value, T new_value)
{
if (old_value != new_value) {
old_value = std::move(new_value);
return true;
}
return false;
}
} // namespace blender
namespace blender::detail {
template<typename Func> struct ScopedDeferHelper {
Func func;
~ScopedDeferHelper()
{
func();
}
};
} // namespace blender::detail
#define BLI_SCOPED_DEFER_NAME1(a, b) a##b
#define BLI_SCOPED_DEFER_NAME2(a, b) BLI_SCOPED_DEFER_NAME1(a, b)
#define BLI_SCOPED_DEFER_NAME(a) BLI_SCOPED_DEFER_NAME2(_scoped_defer_##a##_, __LINE__)
/**
* Execute the given function when the current scope ends. This can be used to cheaply implement
* some RAII-like behavior for C types that don't support it. Long term, the types we want to use
* this with should either be converted to C++ or get a proper C++ API. Until then, this function
* can help avoid common resource leakages.
*/
#define BLI_SCOPED_DEFER(function_to_defer) \
auto BLI_SCOPED_DEFER_NAME(func) = (function_to_defer); \
blender::detail::ScopedDeferHelper<decltype(BLI_SCOPED_DEFER_NAME(func))> \
BLI_SCOPED_DEFER_NAME(helper){std::move(BLI_SCOPED_DEFER_NAME(func))};
|