impotent/stc/arc.h

/* MIT License
 *
 * Copyright (c) 2025 Tyge Løvset
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
/* arc: atomic reference counted shared_ptr (new implementation)
 *
 * The difference between arc and arc2 is that arc only takes up one pointer,
 * whereas arc2 uses two. arc cannot be constructed from an already allocated pointer,
 * which arc2 may. To use arc2, specify the `(c_arc2)` option after the key type, e.g.:
 * #define T MyArc, MyType, (c_arc2 | c_no_atomic)
 */
/*
#include <stc/cstr.h>

typedef struct { cstr name, last; } Person;

Person Person_make(const char* name, const char* last) {
    return (Person){.name = cstr_from(name), .last = cstr_from(last)};
}
Person Person_clone(Person p) {
    p.name = cstr_clone(p.name);
    p.last = cstr_clone(p.last);
    return p;
}
void Person_drop(Person* p) {
    printf("drop: %s %s\n", cstr_str(&p->name), cstr_str(&p->last));
    cstr_drop(&p->name);
    cstr_drop(&p->last);
}

#define T ArcPers, Person, (c_keyclass)  // clone, drop, cmp, hash
#include <stc/arc.h>

int main(void) {
    ArcPers p = ArcPers_from(Person_make("John", "Smiths"));
    ArcPers q = ArcPers_clone(p); // share the pointer

    printf("%s %s. uses: %ld\n", cstr_str(&q.get->name), cstr_str(&q.get->last), ArcPers_use_count(q));
    c_drop(ArcPers, &p, &q);
}
*/
#include "priv/linkage.h"
#include "types.h"

#ifndef STC_ARC_H_INCLUDED
#define STC_ARC_H_INCLUDED
#include "common.h"
#include <stdlib.h>

#if defined __GNUC__ || defined __clang__ || defined _MSC_VER || defined i_no_atomic
    typedef long catomic_long;
#else // try with C11
    typedef _Atomic(long) catomic_long;
#endif
#if defined _MSC_VER
    #include <intrin.h>
    #define c_atomic_inc(v) (void)_InterlockedIncrement(v)
    #define c_atomic_dec_and_test(v) !_InterlockedDecrement(v)
#elif defined __GNUC__ || defined __clang__
    #define c_atomic_inc(v) (void)__atomic_add_fetch(v, 1, __ATOMIC_SEQ_CST)
    #define c_atomic_dec_and_test(v) !__atomic_sub_fetch(v, 1, __ATOMIC_SEQ_CST)
#else // try with C11
    #include <stdatomic.h>
    #define c_atomic_inc(v) (void)atomic_fetch_add(v, 1)
    #define c_atomic_dec_and_test(v) (atomic_fetch_sub(v, 1) == 1)
#endif
#endif // STC_ARC_H_INCLUDED

#ifndef _i_prefix
  #define _i_prefix arc_
#endif
#define _i_is_arc
#include "priv/template.h"
typedef i_keyraw _m_raw;

#if c_OPTION(c_no_atomic)
  #define i_no_atomic
#endif
#if !defined i_no_atomic
  #define _i_atomic_inc(v)          c_atomic_inc(v)
  #define _i_atomic_dec_and_test(v) c_atomic_dec_and_test(v)
#else
  #define _i_atomic_inc(v)          (void)(++*(v))
  #define _i_atomic_dec_and_test(v) !(--*(v))
#endif

#if c_OPTION(c_arc2)
  #define i_arc2
#endif
#if !(defined i_arc2 || defined STC_USE_ARC2)
// ------------ Arc1 size of one pointer (union) -------------

#ifndef i_declared
_c_DEFTYPES(declare_arc, Self, i_key);
#endif
struct _c_MEMB(_ctrl) {
    _m_value value;
    catomic_long counter;
};

// c++: std::make_shared<_m_value>(val)
STC_INLINE Self _c_MEMB(_make)(_m_value val) {
    Self arc = {.ctrl=_i_new_n(_c_MEMB(_ctrl), 1)};
    arc.ctrl->value = val;
    arc.ctrl->counter = 1;
    return arc;
}

STC_INLINE Self _c_MEMB(_toarc)(_m_value* arc_raw)
    { Self arc = {.ctrl=(_c_MEMB(_ctrl) *)arc_raw}; return arc; }

// destructor
STC_INLINE void _c_MEMB(_drop)(const Self* self) {
    if (self->ctrl && _i_atomic_dec_and_test(&self->ctrl->counter)) {
        i_keydrop(self->get);
        i_free(self->ctrl, c_sizeof *self->ctrl);
    }
}

#else // ------------ Arc2 size of two pointers -------------

#ifndef i_declared
_c_DEFTYPES(declare_arc2, Self, i_key);
#endif
struct _c_MEMB(_ctrl) {
    catomic_long counter; // nb! counter <-> value order is swapped.
    _m_value value;
};
#define ctrl ctrl2

// c++: std::make_shared<_m_value>(val)
STC_INLINE Self _c_MEMB(_make)(_m_value val) {
    Self out = {.ctrl2=_i_new_n(_c_MEMB(_ctrl), 1)};
    out.ctrl2->counter = 1;
    out.get = &out.ctrl2->value;
    *out.get = val;
    return out;
}

STC_INLINE Self _c_MEMB(_from_ptr)(_m_value* ptr) {
    Self out = {.get=ptr};
    if (ptr) {
        enum {OFFSET = offsetof(_c_MEMB(_ctrl), value)};
        // Adds 2 dummy bytes to ensure that the second if-test in _drop() is safe.
        catomic_long* _rc = (catomic_long*)i_malloc(OFFSET + 2);
        out.ctrl2 = (_c_MEMB(_ctrl)*) _rc;
        out.ctrl2->counter = 1;
    }
    return out;
}

// destructor
STC_INLINE void _c_MEMB(_drop)(const Self* self) {
    if (self->ctrl2 && _i_atomic_dec_and_test(&self->ctrl2->counter)) {
        enum {OFFSET = offsetof(_c_MEMB(_ctrl), value)};
        i_keydrop(self->get);

        if ((char*)self->ctrl2 + OFFSET == (char*)self->get) {
            i_free((void*)self->ctrl2, c_sizeof *self->ctrl2); // _make()
        } else {
            i_free((void*)self->ctrl2, OFFSET + 2); // _from_ptr()
            i_free(self->get, c_sizeof *self->get);
        }
    }
}

// take ownership of pointer p
STC_INLINE void _c_MEMB(_reset_to)(Self* self, _m_value* ptr) {
    _c_MEMB(_drop)(self);
    *self = _c_MEMB(_from_ptr)(ptr);
}

#endif // ---------- end Arc2 with two pointers ------------

STC_INLINE long _c_MEMB(_use_count)(Self arc)
    { return arc.ctrl ? arc.ctrl->counter : 0; }

STC_INLINE Self _c_MEMB(_init)(void)
    { return c_literal(Self){0}; }

STC_INLINE Self _c_MEMB(_from)(_m_raw raw)
    { return _c_MEMB(_make)(i_keyfrom(raw)); }

STC_INLINE _m_raw _c_MEMB(_toraw)(const Self* self)
    { return i_keytoraw(self->get); }

// move ownership to receiving arc
STC_INLINE Self _c_MEMB(_move)(Self* self) {
    Self arc = *self;
    *self = (Self){0};
    return arc; // now unowned
}

// take ownership of unowned arc
STC_INLINE void _c_MEMB(_take)(Self* self, Self unowned) {
    _c_MEMB(_drop)(self);
    *self = unowned; // now owned
}

// make shared ownership with owned arc
STC_INLINE void _c_MEMB(_assign)(Self* self, const Self* owned) {
    if (owned->ctrl)
        _i_atomic_inc(&owned->ctrl->counter);
    _c_MEMB(_drop)(self);
    *self = *owned;
}

// clone by sharing. Does not use i_keyclone, so OK to always define.
STC_INLINE Self _c_MEMB(_clone)(Self owned) {
    if (owned.ctrl)
        _i_atomic_inc(&owned.ctrl->counter);
    return owned;
}

#if defined _i_has_cmp
    STC_INLINE int _c_MEMB(_raw_cmp)(const _m_raw* rx, const _m_raw* ry)
        { return i_cmp(rx, ry); }
#endif

#if defined _i_has_eq
    STC_INLINE bool _c_MEMB(_raw_eq)(const _m_raw* rx, const _m_raw* ry)
        { return i_eq(rx, ry); }
#endif

#if !defined i_no_hash && defined _i_has_eq
    STC_INLINE size_t _c_MEMB(_raw_hash)(const _m_raw* rx)
        { return i_hash(rx); }
#endif // i_no_hash

#undef ctrl
#undef i_no_atomic
#undef i_arc2
#undef _i_atomic_inc
#undef _i_atomic_dec_and_test
#undef _i_is_arc
#include "sys/finalize.h"