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#pragma once
#include <atomic>
#include <library/cpp/deprecated/atomic/atomic.h>
#include <util/system/types.h>
#include <util/system/compiler.h>
#include <util/generic/array_ref.h>
#include <util/system/sys_alloc.h>
namespace NDetail {
struct TRcBufInternalBackend {
public:
struct TCookies {
using TSelf = TCookies;
std::atomic<const char*> Begin;
std::atomic<const char*> End;
static size_t BytesToAligned(size_t size) {
bool misaligned = size % alignof(TSelf);
return misaligned ? alignof(TSelf) - size % alignof(TSelf) : 0;
}
static size_t BytesToAlloc(size_t size) {
return size + BytesToAligned(size) + sizeof(TSelf);
}
};
private:
// to be binary compatible with TSharedData
struct THeader : public TCookies {
TAtomic RefCount;
ui64 Zero = 0;
};
enum : size_t {
HeaderSize = sizeof(THeader),
OverheadSize = HeaderSize,
MaxDataSize = (std::numeric_limits<size_t>::max() - OverheadSize)
};
public:
TRcBufInternalBackend() noexcept
: Data_(nullptr)
, Size_(0)
{ }
~TRcBufInternalBackend() noexcept {
Release();
}
TRcBufInternalBackend(const TRcBufInternalBackend& other) noexcept
: Data_(other.Data_)
, Size_(other.Size_)
{
AddRef();
}
TRcBufInternalBackend(TRcBufInternalBackend&& other) noexcept
: Data_(other.Data_)
, Size_(other.Size_)
{
other.Data_ = nullptr;
other.Size_ = 0;
}
TRcBufInternalBackend& operator=(const TRcBufInternalBackend& other) noexcept {
if (this != &other) {
Release();
Data_ = other.Data_;
Size_ = other.Size_;
AddRef();
}
return *this;
}
TRcBufInternalBackend& operator=(TRcBufInternalBackend&& other) noexcept {
if (this != &other) {
Release();
Data_ = other.Data_;
Size_ = other.Size_;
other.Data_ = nullptr;
other.Size_ = 0;
}
return *this;
}
Y_FORCE_INLINE explicit operator bool() const { return Size_ > 0; }
Y_FORCE_INLINE char* mutable_data() { return Data(); }
Y_FORCE_INLINE char* mutable_begin() { return Data(); }
Y_FORCE_INLINE char* mutable_end() { return Data() + Size_; }
Y_FORCE_INLINE const char* data() const { return Data(); }
Y_FORCE_INLINE const char* begin() const { return Data(); }
Y_FORCE_INLINE const char* end() const { return Data() + Size_; }
Y_FORCE_INLINE size_t size() const { return Size_; }
/**
* Copies data to new allocated buffer if data is shared
* New container loses original owner
* Returns pointer to mutable buffer
*/
char* Detach() {
if (IsShared()) {
*this = TRcBufInternalBackend::Copy(data(), size());
}
return Data_;
}
bool IsPrivate() const {
return Data_ ? IsPrivate(Header()) : true;
}
bool IsShared() const {
return !IsPrivate();
}
TString ToString() const {
return TString(data(), size());
}
TCookies* GetCookies() {
return Header();
}
/**
* Attach to pre-allocated data with a preceding THeader
*/
static TRcBufInternalBackend AttachUnsafe(char* data, size_t size) noexcept {
TRcBufInternalBackend result;
result.Data_ = data;
result.Size_ = size;
return result;
}
/**
* Make uninitialized buffer of the specified size
*/
static TRcBufInternalBackend Uninitialized(size_t size, size_t headroom = 0, size_t tailroom = 0) {
size_t fullSize = checkedSum(size, checkedSum(headroom, tailroom));
return AttachUnsafe(Allocate(size, headroom, tailroom), fullSize);
}
/**
* Make a copy of the specified data
*/
static TRcBufInternalBackend Copy(const void* data, size_t size) {
TRcBufInternalBackend result = Uninitialized(size);
if (size) {
::memcpy(result.Data(), data, size);
}
return result;
}
private:
Y_FORCE_INLINE THeader* Header() const noexcept {
Y_VERIFY_DEBUG(Data_);
return reinterpret_cast<THeader*>(Data_);
}
Y_FORCE_INLINE char* Data() const noexcept {
Y_VERIFY_DEBUG(Data_);
return Data_ + OverheadSize;
}
static bool IsPrivate(THeader* header) noexcept {
return 1 == AtomicGet(header->RefCount);
}
void AddRef() noexcept {
if (Data_) {
AtomicIncrement(Header()->RefCount);
}
}
void Release() noexcept {
if (Data_) {
auto* header = Header();
if (IsPrivate(header) || 0 == AtomicDecrement(header->RefCount)) {
Deallocate(Data_);
}
}
}
private:
static size_t checkedSum(size_t a, size_t b) {
if (a > std::numeric_limits<size_t>::max() - b) {
throw std::length_error("Allocate size overflow");
}
return a + b;
}
static char* Allocate(size_t size, size_t headroom = 0, size_t tailroom = 0) {
char* data = nullptr;
size_t fullSize = checkedSum(size, checkedSum(headroom, tailroom));
if (fullSize > 0) {
if (fullSize >= MaxDataSize) {
throw std::length_error("Allocate size overflow");
}
auto allocSize = OverheadSize + fullSize;
char* raw = reinterpret_cast<char*>(y_allocate(allocSize));
auto* header = reinterpret_cast<THeader*>(raw);
header->Begin = raw + OverheadSize + headroom;
header->End = raw + allocSize - tailroom;
header->RefCount = 1;
data = raw;
}
return data;
}
static void Deallocate(char* data) noexcept {
if (data) {
char* raw = data;
y_deallocate(raw);
}
}
private:
char* Data_;
size_t Size_;
};
} // namespace NDetail
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