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libcow/include/cow.hpp

93 lines
2.2 KiB

#pragma once
#include "cow.h"
#include <memory>
#include <exception>
#include "cow/slice.hpp"
struct CowException : public std::exception
{
inline CowException(cow_err_kind k) : kind(k){}
const char* what() const noexcept override;
inline ~CowException(){}
const cow_err_kind kind;
};
struct Cow : public _cow_util::Span<unsigned char> {
struct Fake;
Cow() = delete;
Cow(int fd, size_t size);
explicit Cow(size_t size);
Cow(Cow&& m);
virtual ~Cow();
virtual Fake clone() const;
protected:
inline void* area() override {
auto raw = get_raw();
return raw ? cow_ptr(raw) : nullptr;
}
inline const void* area() const override {
auto raw = get_raw();
return raw ? cow_ptr_of(const void, raw) : nullptr;
}
public:
/// Get the size of the mapped area.
///
/// Note: This calls into `_inner`'s internals. To skip the call on non-LTO builds, use `size_unsafe()`.
size_t size() const override;
/// Get the size by assuming the ABI layout of cow_t to be correct. Potentially faster but ABI sensitive.
/// This shouldn't be a problem if all build static assertions passed.
///
/// Note: This behaviour can be diabled by building with `-DCOW_NO_ASSUME_ABI`. In this case, this function calls out to the C API to determine the size.
/// There is also likely no benefit using this over `size()` in LTO enabled builds.
///
/// XXX: Deprecated function for now. It seems `size()` offers better codegen on LTO and non-LTO enabled builds.
[[deprecated("size() is safer and offers better codegen.")]] inline size_t size_unsafe() const { return _cow_size_unsafe(get_raw()); }
static Cow from_raw(cow_t* owned);
virtual cow_t* raw() const;
private:
struct _inner;
Cow(cow_t* raw);
protected:
Cow(const Cow& c);
explicit inline Cow(std::shared_ptr<_inner>&& super) : super(std::move(super)){}
const std::shared_ptr<_inner> super;
virtual cow_t* get_raw() const;
};
struct Cow::Fake : public Cow {
Fake() = delete;
Fake(const Cow& real);
Fake(const Fake& copy);
Fake(Fake&& move);
~Fake();
Fake clone() const override;
static Fake from_real(const Cow& real);
inline cow_t* raw() const override { return fake; }
protected:
cow_t* get_raw() const override;
private:
cow_t* const fake;
};