修改pods

This commit is contained in:
2025-09-20 17:13:38 +08:00
parent 7787b3ee30
commit 28ff2b0264
5251 changed files with 345029 additions and 285168 deletions

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@@ -81,9 +81,30 @@
// }
//
// The layout we used above combines fixed-size with dynamically-sized fields.
// This is quite common. Layout is optimized for this use case and generates
// optimal code. All computations that can be performed at compile time are
// indeed performed at compile time.
// This is quite common. Layout is optimized for this use case and attempts to
// generate optimal code. To help the compiler do that in more cases, you can
// specify the fixed sizes using `WithStaticSizes`. This ensures that all
// computations that can be performed at compile time are indeed performed at
// compile time. Note that sometimes the `template` keyword is needed. E.g.:
//
// using SL = L::template WithStaticSizes<1, 1>;
//
// void Use(unsigned char* p) {
// // First, extract N and M.
// // Using `prefix` we can access the first three arrays but not more.
// //
// // More details: The first element always has offset 0. `SL`
// // has offsets for the second and third array based on sizes of
// // the first and second array, specified via `WithStaticSizes`.
// constexpr auto prefix = SL::Partial();
// size_t n = *prefix.Pointer<0>(p);
// size_t m = *prefix.Pointer<1>(p);
//
// // Now we can get a pointer to the final payload.
// const SL layout(n, m);
// double* a = layout.Pointer<double>(p);
// int* b = layout.Pointer<int>(p);
// }
//
// Efficiency tip: The order of fields matters. In `Layout<T1, ..., TN>` try to
// ensure that `alignof(T1) >= ... >= alignof(TN)`. This way you'll have no
@@ -107,7 +128,7 @@
// CompactString(const char* s = "") {
// const size_t size = strlen(s);
// // size_t[1] followed by char[size + 1].
// const L layout(1, size + 1);
// const L layout(size + 1);
// p_.reset(new unsigned char[layout.AllocSize()]);
// // If running under ASAN, mark the padding bytes, if any, to catch
// // memory errors.
@@ -125,14 +146,13 @@
//
// const char* c_str() const {
// // Equivalent to reinterpret_cast<char*>(p.get() + sizeof(size_t)).
// // The argument in Partial(1) specifies that we have size_t[1] in front
// // of the characters.
// return L::Partial(1).Pointer<char>(p_.get());
// return L::Partial().Pointer<char>(p_.get());
// }
//
// private:
// // Our heap allocation contains a size_t followed by an array of chars.
// using L = Layout<size_t, char>;
// // Our heap allocation contains a single size_t followed by an array of
// // chars.
// using L = Layout<size_t, char>::WithStaticSizes<1>;
// std::unique_ptr<unsigned char[]> p_;
// };
//
@@ -146,11 +166,12 @@
//
// The interface exported by this file consists of:
// - class `Layout<>` and its public members.
// - The public members of class `internal_layout::LayoutImpl<>`. That class
// isn't intended to be used directly, and its name and template parameter
// list are internal implementation details, but the class itself provides
// most of the functionality in this file. See comments on its members for
// detailed documentation.
// - The public members of classes `internal_layout::LayoutWithStaticSizes<>`
// and `internal_layout::LayoutImpl<>`. Those classes aren't intended to be
// used directly, and their name and template parameter list are internal
// implementation details, but the classes themselves provide most of the
// functionality in this file. See comments on their members for detailed
// documentation.
//
// `Layout<T1,... Tn>::Partial(count1,..., countm)` (where `m` <= `n`) returns a
// `LayoutImpl<>` object. `Layout<T1,..., Tn> layout(count1,..., countn)`
@@ -164,13 +185,14 @@
#include <stddef.h>
#include <stdint.h>
#include <ostream>
#include <array>
#include <string>
#include <tuple>
#include <type_traits>
#include <typeinfo>
#include <utility>
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/debugging/internal/demangle.h"
#include "absl/meta/type_traits.h"
@@ -209,9 +231,6 @@ struct NotAligned<const Aligned<T, N>> {
template <size_t>
using IntToSize = size_t;
template <class>
using TypeToSize = size_t;
template <class T>
struct Type : NotAligned<T> {
using type = T;
@@ -308,7 +327,8 @@ using IsLegalElementType = std::integral_constant<
!std::is_volatile<typename Type<T>::type>::value &&
adl_barrier::IsPow2(AlignOf<T>::value)>;
template <class Elements, class SizeSeq, class OffsetSeq>
template <class Elements, class StaticSizeSeq, class RuntimeSizeSeq,
class SizeSeq, class OffsetSeq>
class LayoutImpl;
// Public base class of `Layout` and the result type of `Layout::Partial()`.
@@ -316,31 +336,49 @@ class LayoutImpl;
// `Elements...` contains all template arguments of `Layout` that created this
// instance.
//
// `SizeSeq...` is `[0, NumSizes)` where `NumSizes` is the number of arguments
// passed to `Layout::Partial()` or `Layout::Layout()`.
// `StaticSizeSeq...` is an index_sequence containing the sizes specified at
// compile-time.
//
// `RuntimeSizeSeq...` is `[0, NumRuntimeSizes)`, where `NumRuntimeSizes` is the
// number of arguments passed to `Layout::Partial()` or `Layout::Layout()`.
//
// `SizeSeq...` is `[0, NumSizes)` where `NumSizes` is `NumRuntimeSizes` plus
// the number of sizes in `StaticSizeSeq`.
//
// `OffsetSeq...` is `[0, NumOffsets)` where `NumOffsets` is
// `Min(sizeof...(Elements), NumSizes + 1)` (the number of arrays for which we
// can compute offsets).
template <class... Elements, size_t... SizeSeq, size_t... OffsetSeq>
class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
absl::index_sequence<OffsetSeq...>> {
template <class... Elements, size_t... StaticSizeSeq, size_t... RuntimeSizeSeq,
size_t... SizeSeq, size_t... OffsetSeq>
class LayoutImpl<
std::tuple<Elements...>, absl::index_sequence<StaticSizeSeq...>,
absl::index_sequence<RuntimeSizeSeq...>, absl::index_sequence<SizeSeq...>,
absl::index_sequence<OffsetSeq...>> {
private:
static_assert(sizeof...(Elements) > 0, "At least one field is required");
static_assert(absl::conjunction<IsLegalElementType<Elements>...>::value,
"Invalid element type (see IsLegalElementType)");
static_assert(sizeof...(StaticSizeSeq) <= sizeof...(Elements),
"Too many static sizes specified");
enum {
NumTypes = sizeof...(Elements),
NumStaticSizes = sizeof...(StaticSizeSeq),
NumRuntimeSizes = sizeof...(RuntimeSizeSeq),
NumSizes = sizeof...(SizeSeq),
NumOffsets = sizeof...(OffsetSeq),
};
// These are guaranteed by `Layout`.
static_assert(NumStaticSizes + NumRuntimeSizes == NumSizes, "Internal error");
static_assert(NumSizes <= NumTypes, "Internal error");
static_assert(NumOffsets == adl_barrier::Min(NumTypes, NumSizes + 1),
"Internal error");
static_assert(NumTypes > 0, "Internal error");
static constexpr std::array<size_t, sizeof...(StaticSizeSeq)> kStaticSizes = {
StaticSizeSeq...};
// Returns the index of `T` in `Elements...`. Results in a compilation error
// if `Elements...` doesn't contain exactly one instance of `T`.
template <class T>
@@ -363,7 +401,7 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
template <size_t N>
using ElementType = typename std::tuple_element<N, ElementTypes>::type;
constexpr explicit LayoutImpl(IntToSize<SizeSeq>... sizes)
constexpr explicit LayoutImpl(IntToSize<RuntimeSizeSeq>... sizes)
: size_{sizes...} {}
// Alignment of the layout, equal to the strictest alignment of all elements.
@@ -389,7 +427,7 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
constexpr size_t Offset() const {
static_assert(N < NumOffsets, "Index out of bounds");
return adl_barrier::Align(
Offset<N - 1>() + SizeOf<ElementType<N - 1>>::value * size_[N - 1],
Offset<N - 1>() + SizeOf<ElementType<N - 1>>::value * Size<N - 1>(),
ElementAlignment<N>::value);
}
@@ -411,8 +449,7 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
return {{Offset<OffsetSeq>()...}};
}
// The number of elements in the Nth array. This is the Nth argument of
// `Layout::Partial()` or `Layout::Layout()` (zero-based).
// The number of elements in the Nth array (zero-based).
//
// // int[3], 4 bytes of padding, double[4].
// Layout<int, double> x(3, 4);
@@ -420,10 +457,15 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
// assert(x.Size<1>() == 4);
//
// Requires: `N < NumSizes`.
template <size_t N>
template <size_t N, EnableIf<(N < NumStaticSizes)> = 0>
constexpr size_t Size() const {
return kStaticSizes[N];
}
template <size_t N, EnableIf<(N >= NumStaticSizes)> = 0>
constexpr size_t Size() const {
static_assert(N < NumSizes, "Index out of bounds");
return size_[N];
return size_[N - NumStaticSizes];
}
// The number of elements in the array with the specified element type.
@@ -500,13 +542,8 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
// std::tie(ints, doubles) = x.Pointers(p);
//
// Requires: `p` is aligned to `Alignment()`.
//
// Note: We're not using ElementType alias here because it does not compile
// under MSVC.
template <class Char>
std::tuple<CopyConst<
Char, typename std::tuple_element<OffsetSeq, ElementTypes>::type>*...>
Pointers(Char* p) const {
auto Pointers(Char* p) const {
return std::tuple<CopyConst<Char, ElementType<OffsetSeq>>*...>(
Pointer<OffsetSeq>(p)...);
}
@@ -559,15 +596,10 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
//
// Requires: `p` is aligned to `Alignment()`.
//
// Note: We're not using ElementType alias here because it does not compile
// under MSVC.
// Note: We mark the parameter as unused because GCC detects it is not used
// when `SizeSeq` is empty [-Werror=unused-but-set-parameter].
template <class Char>
std::tuple<SliceType<CopyConst<
Char, typename std::tuple_element<SizeSeq, ElementTypes>::type>>...>
Slices(Char* p) const {
// Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63875 (fixed
// in 6.1).
(void)p;
auto Slices(ABSL_ATTRIBUTE_UNUSED Char* p) const {
return std::tuple<SliceType<CopyConst<Char, ElementType<SizeSeq>>>...>(
Slice<SizeSeq>(p)...);
}
@@ -582,7 +614,7 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
constexpr size_t AllocSize() const {
static_assert(NumTypes == NumSizes, "You must specify sizes of all fields");
return Offset<NumTypes - 1>() +
SizeOf<ElementType<NumTypes - 1>>::value * size_[NumTypes - 1];
SizeOf<ElementType<NumTypes - 1>>::value * Size<NumTypes - 1>();
}
// If built with --config=asan, poisons padding bytes (if any) in the
@@ -606,7 +638,7 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
// The `if` is an optimization. It doesn't affect the observable behaviour.
if (ElementAlignment<N - 1>::value % ElementAlignment<N>::value) {
size_t start =
Offset<N - 1>() + SizeOf<ElementType<N - 1>>::value * size_[N - 1];
Offset<N - 1>() + SizeOf<ElementType<N - 1>>::value * Size<N - 1>();
ASAN_POISON_MEMORY_REGION(p + start, Offset<N>() - start);
}
#endif
@@ -635,47 +667,66 @@ class LayoutImpl<std::tuple<Elements...>, absl::index_sequence<SizeSeq...>,
adl_barrier::TypeName<ElementType<OffsetSeq>>()...};
std::string res = absl::StrCat("@0", types[0], "(", sizes[0], ")");
for (size_t i = 0; i != NumOffsets - 1; ++i) {
absl::StrAppend(&res, "[", size_[i], "]; @", offsets[i + 1], types[i + 1],
"(", sizes[i + 1], ")");
absl::StrAppend(&res, "[", DebugSize(i), "]; @", offsets[i + 1],
types[i + 1], "(", sizes[i + 1], ")");
}
// NumSizes is a constant that may be zero. Some compilers cannot see that
// inside the if statement "size_[NumSizes - 1]" must be valid.
int last = static_cast<int>(NumSizes) - 1;
if (NumTypes == NumSizes && last >= 0) {
absl::StrAppend(&res, "[", size_[last], "]");
absl::StrAppend(&res, "[", DebugSize(static_cast<size_t>(last)), "]");
}
return res;
}
private:
size_t DebugSize(size_t n) const {
if (n < NumStaticSizes) {
return kStaticSizes[n];
} else {
return size_[n - NumStaticSizes];
}
}
// Arguments of `Layout::Partial()` or `Layout::Layout()`.
size_t size_[NumSizes > 0 ? NumSizes : 1];
size_t size_[NumRuntimeSizes > 0 ? NumRuntimeSizes : 1];
};
template <size_t NumSizes, class... Ts>
// Defining a constexpr static class member variable is redundant and deprecated
// in C++17, but required in C++14.
template <class... Elements, size_t... StaticSizeSeq, size_t... RuntimeSizeSeq,
size_t... SizeSeq, size_t... OffsetSeq>
constexpr std::array<size_t, sizeof...(StaticSizeSeq)> LayoutImpl<
std::tuple<Elements...>, absl::index_sequence<StaticSizeSeq...>,
absl::index_sequence<RuntimeSizeSeq...>, absl::index_sequence<SizeSeq...>,
absl::index_sequence<OffsetSeq...>>::kStaticSizes;
template <class StaticSizeSeq, size_t NumRuntimeSizes, class... Ts>
using LayoutType = LayoutImpl<
std::tuple<Ts...>, absl::make_index_sequence<NumSizes>,
absl::make_index_sequence<adl_barrier::Min(sizeof...(Ts), NumSizes + 1)>>;
std::tuple<Ts...>, StaticSizeSeq,
absl::make_index_sequence<NumRuntimeSizes>,
absl::make_index_sequence<NumRuntimeSizes + StaticSizeSeq::size()>,
absl::make_index_sequence<adl_barrier::Min(
sizeof...(Ts), NumRuntimeSizes + StaticSizeSeq::size() + 1)>>;
} // namespace internal_layout
template <class StaticSizeSeq, class... Ts>
class LayoutWithStaticSizes
: public LayoutType<StaticSizeSeq,
sizeof...(Ts) - adl_barrier::Min(sizeof...(Ts),
StaticSizeSeq::size()),
Ts...> {
private:
using Super =
LayoutType<StaticSizeSeq,
sizeof...(Ts) -
adl_barrier::Min(sizeof...(Ts), StaticSizeSeq::size()),
Ts...>;
// Descriptor of arrays of various types and sizes laid out in memory one after
// another. See the top of the file for documentation.
//
// Check out the public API of internal_layout::LayoutImpl above. The type is
// internal to the library but its methods are public, and they are inherited
// by `Layout`.
template <class... Ts>
class Layout : public internal_layout::LayoutType<sizeof...(Ts), Ts...> {
public:
static_assert(sizeof...(Ts) > 0, "At least one field is required");
static_assert(
absl::conjunction<internal_layout::IsLegalElementType<Ts>...>::value,
"Invalid element type (see IsLegalElementType)");
// The result type of `Partial()` with `NumSizes` arguments.
template <size_t NumSizes>
using PartialType = internal_layout::LayoutType<NumSizes, Ts...>;
using PartialType =
internal_layout::LayoutType<StaticSizeSeq, NumSizes, Ts...>;
// `Layout` knows the element types of the arrays we want to lay out in
// memory but not the number of elements in each array.
@@ -701,14 +752,18 @@ class Layout : public internal_layout::LayoutType<sizeof...(Ts), Ts...> {
// Note: The sizes of the arrays must be specified in number of elements,
// not in bytes.
//
// Requires: `sizeof...(Sizes) <= sizeof...(Ts)`.
// Requires: `sizeof...(Sizes) + NumStaticSizes <= sizeof...(Ts)`.
// Requires: all arguments are convertible to `size_t`.
template <class... Sizes>
static constexpr PartialType<sizeof...(Sizes)> Partial(Sizes&&... sizes) {
static_assert(sizeof...(Sizes) <= sizeof...(Ts), "");
return PartialType<sizeof...(Sizes)>(absl::forward<Sizes>(sizes)...);
static_assert(sizeof...(Sizes) + StaticSizeSeq::size() <= sizeof...(Ts),
"");
return PartialType<sizeof...(Sizes)>(
static_cast<size_t>(std::forward<Sizes>(sizes))...);
}
// Inherit LayoutType's constructor.
//
// Creates a layout with the sizes of all arrays specified. If you know
// only the sizes of the first N arrays (where N can be zero), you can use
// `Partial()` defined above. The constructor is essentially equivalent to
@@ -717,8 +772,69 @@ class Layout : public internal_layout::LayoutType<sizeof...(Ts), Ts...> {
//
// Note: The sizes of the arrays must be specified in number of elements,
// not in bytes.
constexpr explicit Layout(internal_layout::TypeToSize<Ts>... sizes)
: internal_layout::LayoutType<sizeof...(Ts), Ts...>(sizes...) {}
//
// Implementation note: we do this via a `using` declaration instead of
// defining our own explicit constructor because the signature of LayoutType's
// constructor depends on RuntimeSizeSeq, which we don't have access to here.
// If we defined our own constructor here, it would have to use a parameter
// pack and then cast the arguments to size_t when calling the superclass
// constructor, similar to what Partial() does. But that would suffer from the
// same problem that Partial() has, which is that the parameter types are
// inferred from the arguments, which may be signed types, which must then be
// cast to size_t. This can lead to negative values being silently (i.e. with
// no compiler warnings) cast to an unsigned type. Having a constructor with
// size_t parameters helps the compiler generate better warnings about
// potential bad casts, while avoiding false warnings when positive literal
// arguments are used. If an argument is a positive literal integer (e.g.
// `1`), the compiler will understand that it can be safely converted to
// size_t, and hence not generate a warning. But if a negative literal (e.g.
// `-1`) or a variable with signed type is used, then it can generate a
// warning about a potentially unsafe implicit cast. It would be great if we
// could do this for Partial() too, but unfortunately as of C++23 there seems
// to be no way to define a function with a variable number of parameters of a
// certain type, a.k.a. homogeneous function parameter packs. So we're forced
// to choose between explicitly casting the arguments to size_t, which
// suppresses all warnings, even potentially valid ones, or implicitly casting
// them to size_t, which generates bogus warnings whenever literal arguments
// are used, even if they're positive.
using Super::Super;
};
} // namespace internal_layout
// Descriptor of arrays of various types and sizes laid out in memory one after
// another. See the top of the file for documentation.
//
// Check out the public API of internal_layout::LayoutWithStaticSizes and
// internal_layout::LayoutImpl above. Those types are internal to the library
// but their methods are public, and they are inherited by `Layout`.
template <class... Ts>
class Layout : public internal_layout::LayoutWithStaticSizes<
absl::make_index_sequence<0>, Ts...> {
private:
using Super =
internal_layout::LayoutWithStaticSizes<absl::make_index_sequence<0>,
Ts...>;
public:
// If you know the sizes of some or all of the arrays at compile time, you can
// use `WithStaticSizes` or `WithStaticSizeSequence` to create a `Layout` type
// with those sizes baked in. This can help the compiler generate optimal code
// for calculating array offsets and AllocSize().
//
// Like `Partial()`, the N sizes you specify are for the first N arrays, and
// they specify the number of elements in each array, not the number of bytes.
template <class StaticSizeSeq>
using WithStaticSizeSequence =
internal_layout::LayoutWithStaticSizes<StaticSizeSeq, Ts...>;
template <size_t... StaticSizes>
using WithStaticSizes =
WithStaticSizeSequence<std::index_sequence<StaticSizes...>>;
// Inherit LayoutWithStaticSizes's constructor, which requires you to specify
// all the array sizes.
using Super::Super;
};
} // namespace container_internal