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#pragma once
#include "serialise.hh"
#include <string_view>
#include <cstring>
#include <array>
namespace rust {
typedef void (*DropFun)(void *);
/* A Rust value of N bytes. It can be moved but not copied. When it
goes out of scope, the C++ destructor will run the drop
function. */
template<std::size_t N, DropFun drop>
struct Value
{
protected:
std::array<char, N> raw;
~Value()
{
if (!isEvacuated()) {
drop(this);
evacuate();
}
}
// Must not be called directly.
Value()
{
// Precaution, in case this is used improperly
evacuate();
}
Value(Value && other)
: raw(other.raw)
{
other.evacuate();
}
// Not all Rust types are Clone / Copy, but our base Value class needs to
// have a copy constructor so that types which do implement Copy/Clone
// can be copied/cloned.
Value(const Value & other)
: raw(other.raw)
{
}
void operator =(const Value & other)
{
if (!isEvacuated())
drop(this);
}
void operator =(Value && other)
{
if (!isEvacuated())
drop(this);
raw = other.raw;
other.evacuate();
}
private:
/* FIXME: optimize these (ideally in such a way that the compiler
can elide most calls to evacuate() / isEvacuated(). */
inline void evacuate()
{
for (auto & i : raw) i = 0;
}
inline bool isEvacuated()
{
for (auto & i : raw)
if (i != 0) return false;
return true;
}
};
/* A Rust vector. */
template<typename T, DropFun drop>
struct Vec : Value<3 * sizeof(void *), drop>
{
inline size_t size() const
{
return ((const size_t *) &this->raw)[2];
}
const T * data() const
{
return ((const T * *) &this->raw)[0];
}
protected:
// Must not be called directly.
Vec<T, drop>();
Vec<T, drop>(Vec<T, drop> && other) = default;
// Delete until we know how to do this properly.
Vec<T, drop>(const Vec<T, drop> & other) = delete;
};
/* A Rust slice. */
template<typename T>
struct Slice
{
const T * ptr;
size_t size;
Slice(const T * ptr, size_t size) : ptr(ptr), size(size)
{
assert(ptr);
}
};
struct StringSlice : Slice<char>
{
StringSlice(const std::string & s): Slice(s.data(), s.size()) {}
explicit StringSlice(std::string_view s): Slice(s.data(), s.size()) {}
StringSlice(const char * s): Slice(s, strlen(s)) {}
operator std::string_view() const
{
return std::string_view(ptr, size);
}
};
/* A Rust string. */
struct String;
extern "C" {
void ffi_String_new(StringSlice s, String * out);
void ffi_String_drop(void * s);
}
struct String : Vec<char, ffi_String_drop>
{
String() = delete;
String(std::string_view s)
{
ffi_String_new(StringSlice(s), this);
}
String(const char * s)
: String({s, std::strlen(s)})
{
}
operator std::string_view() const
{
return std::string_view(data(), size());
}
};
std::ostream & operator << (std::ostream & str, const String & s);
/* C++ representation of Rust's Result<T, CppException>. */
template<typename T>
struct Result
{
enum { Ok = 0, Err = 1, Uninit = 2 } tag;
union {
T data;
std::exception_ptr * exc;
};
Result() = delete;
Result(const Result &) = delete;
Result(Result && other)
: tag(other.tag)
{
other.tag = Uninit;
if (tag == Ok)
data = std::move(other.data);
else if (tag == Err)
exc = other.exc;
}
~Result()
{
if (tag == Ok)
data.~T();
else if (tag == Err)
free(exc);
else if (tag == Uninit)
;
else
abort();
}
/* Rethrow the wrapped exception or return the wrapped value. */
T unwrap() &&
{
if (tag == Ok) {
tag = Uninit;
return std::move(data);
}
else if (tag == Err)
std::rethrow_exception(*exc);
else
abort();
}
};
}
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