1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
|
#pragma once
#include <util/generic/vector.h>
#include <util/ysaveload.h>
#include <type_traits>
// A vector preallocated on the stack.
// After exceeding the preconfigured stack space falls back to the heap.
// Publicly inherits TVector, but disallows swap (and hence shrink_to_fit, also operator= is reimplemented via copying).
//
// Inspired by: http://qt-project.org/doc/qt-4.8/qvarlengtharray.html#details
template <typename T, size_t CountOnStack = 256, bool UseFallbackAlloc = true, class Alloc = std::allocator<T>>
class TStackVec;
template <typename T, class Alloc = std::allocator<T>>
using TSmallVec = TStackVec<T, 16, true, Alloc>;
template <typename T, size_t CountOnStack = 256>
using TStackOnlyVec = TStackVec<T, CountOnStack, false>;
namespace NPrivate {
template <class Alloc, class StackAlloc, typename T, typename U>
struct TRebind {
typedef TReboundAllocator<Alloc, U> other;
};
template <class Alloc, class StackAlloc, typename T>
struct TRebind<Alloc, StackAlloc, T, T> {
typedef StackAlloc other;
};
template <typename T, size_t CountOnStack, bool UseFallbackAlloc, class Alloc = std::allocator<T>>
class TStackBasedAllocator: public Alloc {
public:
typedef TStackBasedAllocator<T, CountOnStack, UseFallbackAlloc, Alloc> TSelf;
using typename Alloc::difference_type;
using typename Alloc::size_type;
using typename Alloc::value_type;
template <class U>
struct rebind: public ::NPrivate::TRebind<Alloc, TSelf, T, U> {
};
public:
//NOTE: it is important to make this syntax; using =default will lead to memset https://godbolt.org/z/vTqzK9aWr
TStackBasedAllocator() noexcept {}
template <
typename... TArgs,
typename = std::enable_if_t<
std::is_constructible_v<Alloc, TArgs...>
>
>
TStackBasedAllocator(TArgs&&... args)
: Alloc(std::forward<TArgs>(args)...)
{}
T* allocate(size_type n) {
if (!IsStorageUsed && CountOnStack >= n) {
IsStorageUsed = true;
return reinterpret_cast<T*>(&StackBasedStorage[0]);
} else {
if constexpr (!UseFallbackAlloc) {
Y_FAIL(
"Stack storage overflow. Capacity: %d, requested: %d", (int)CountOnStack, int(n));
}
return FallbackAllocator().allocate(n);
}
}
void deallocate(T* p, size_type n) {
if (p >= reinterpret_cast<T*>(&StackBasedStorage[0]) &&
p < reinterpret_cast<T*>(&StackBasedStorage[CountOnStack])) {
Y_ABORT_UNLESS(IsStorageUsed);
IsStorageUsed = false;
} else {
FallbackAllocator().deallocate(p, n);
}
}
private:
std::aligned_storage_t<sizeof(T), alignof(T)> StackBasedStorage[CountOnStack];
bool IsStorageUsed = false;
private:
Alloc& FallbackAllocator() noexcept {
return static_cast<Alloc&>(*this);
}
};
}
template <typename T, size_t CountOnStack, bool UseFallbackAlloc, class Alloc>
class TStackVec: public TVector<T, ::NPrivate::TStackBasedAllocator<T, CountOnStack, UseFallbackAlloc, TReboundAllocator<Alloc, T>>> {
private:
using TBase = TVector<T, ::NPrivate::TStackBasedAllocator<T, CountOnStack, UseFallbackAlloc, TReboundAllocator<Alloc, T>>>;
using TAllocator = typename TBase::allocator_type;
public:
using typename TBase::const_iterator;
using typename TBase::const_reverse_iterator;
using typename TBase::iterator;
using typename TBase::reverse_iterator;
using typename TBase::size_type;
using typename TBase::value_type;
public:
TStackVec(const TAllocator& alloc = TAllocator())
: TBase(alloc)
{
TBase::reserve(CountOnStack);
}
explicit TStackVec(size_type count, const TAllocator& alloc = TAllocator())
: TBase(alloc)
{
if (count <= CountOnStack) {
TBase::reserve(CountOnStack);
}
TBase::resize(count);
}
TStackVec(size_type count, const T& val, const TAllocator& alloc = TAllocator())
: TBase(alloc)
{
if (count <= CountOnStack) {
TBase::reserve(CountOnStack);
}
TBase::assign(count, val);
}
TStackVec(const TStackVec& src)
: TStackVec(src.begin(), src.end())
{
}
template <class A>
TStackVec(const TVector<T, A>& src)
: TStackVec(src.begin(), src.end())
{
}
TStackVec(std::initializer_list<T> il, const TAllocator& alloc = TAllocator())
: TStackVec(il.begin(), il.end(), alloc)
{
}
template <class TIter>
TStackVec(TIter first, TIter last, const TAllocator& alloc = TAllocator())
: TBase(alloc)
{
// NB(eeight) Since we want to call 'reserve' here, we cannot just delegate to TVector ctor.
// The best way to insert values afterwards is to call TVector::insert. However there is a caveat.
// In order to call this ctor of TVector, T needs to be just move-constructible. Insert however
// requires T to be move-assignable.
TBase::reserve(CountOnStack);
if constexpr (std::is_move_assignable_v<T>) {
// Fast path
TBase::insert(TBase::end(), first, last);
} else {
// Slow path.
for (; first != last; ++first) {
TBase::push_back(*first);
}
}
}
public:
void swap(TStackVec&) = delete;
void shrink_to_fit() = delete;
TStackVec& operator=(const TStackVec& src) {
TBase::assign(src.begin(), src.end());
return *this;
}
template <class A>
TStackVec& operator=(const TVector<T, A>& src) {
TBase::assign(src.begin(), src.end());
return *this;
}
TStackVec& operator=(std::initializer_list<T> il) {
TBase::assign(il.begin(), il.end());
return *this;
}
};
template <typename T, size_t CountOnStack, class Alloc>
class TSerializer<TStackVec<T, CountOnStack, true, Alloc>>: public TVectorSerializer<TStackVec<T, CountOnStack, true, Alloc>> {
};
template <typename T, size_t CountOnStack, class Alloc>
class TSerializer<TStackVec<T, CountOnStack, false, Alloc>> {
public:
static void Save(IOutputStream* rh, const TStackVec<T, CountOnStack, false, Alloc>& v) {
if constexpr (CountOnStack < 256) {
::Save(rh, (ui8)v.size());
} else {
::Save(rh, v.size());
}
::SaveArray(rh, v.data(), v.size());
}
static void Load(IInputStream* rh, TStackVec<T, CountOnStack, false, Alloc>& v) {
std::conditional_t<CountOnStack < 256, ui8, size_t> size;
::Load(rh, size);
v.resize(size);
::LoadPodArray(rh, v.data(), v.size());
}
};
|
