view mercurial/pythoncapi_compat.h @ 47123:d8ac62374943

dirstate-tree: Make `DirstateMap` borrow from a bytes buffer

… that has the contents of the `.hg/dirstate` file.
This only applies to the tree-based flavor of `DirstateMap`.

For now only the entire `&[u8]` slice is stored, so this is not useful yet.

Adding a lifetime parameter to the `DirstateMap` struct (in hg-core) makes
Python bindings non-trivial because we keep that struct in a Python object
that has a dynamic lifetime tied to Python’s reference-counting and GC.
As long as we keep the `PyBytes` that owns the borrowed bytes buffer next to
the borrowing struct, the buffer will live long enough for the borrows to stay
valid. However this relationship cannot be expressed in safe Rust code in a
way that would statisfy they borrow-checker. We use `unsafe` code to erase
that lifetime parameter, and encapsulate it in a safe abstraction similar to
the owning-ref crate: https://docs.rs/owning_ref/

Differential Revision: https://phab.mercurial-scm.org/D10557

// Header file providing new functions of the Python C API to old Python
// versions.
//
// File distributed under the MIT license.
//
// Homepage:
// https://github.com/pythoncapi/pythoncapi_compat
//
// Latest version:
// https://raw.githubusercontent.com/pythoncapi/pythoncapi_compat/master/pythoncapi_compat.h

#ifndef PYTHONCAPI_COMPAT
#define PYTHONCAPI_COMPAT

#ifdef __cplusplus
extern "C" {
#endif

#include <Python.h>
#include "frameobject.h"          // PyFrameObject, PyFrame_GetBack()


/* VC 2008 doesn't know about the inline keyword. */
#if defined(_MSC_VER) && _MSC_VER < 1900
#define inline __forceinline
#endif

// Cast argument to PyObject* type.
#ifndef _PyObject_CAST
#  define _PyObject_CAST(op) ((PyObject*)(op))
#endif


// bpo-42262 added Py_NewRef() to Python 3.10.0a3
#if PY_VERSION_HEX < 0x030a00A3 && !defined(Py_NewRef)
static inline PyObject* _Py_NewRef(PyObject *obj)
{
    Py_INCREF(obj);
    return obj;
}
#define Py_NewRef(obj) _Py_NewRef(_PyObject_CAST(obj))
#endif


// bpo-42262 added Py_XNewRef() to Python 3.10.0a3
#if PY_VERSION_HEX < 0x030a00A3 && !defined(Py_XNewRef)
static inline PyObject* _Py_XNewRef(PyObject *obj)
{
    Py_XINCREF(obj);
    return obj;
}
#define Py_XNewRef(obj) _Py_XNewRef(_PyObject_CAST(obj))
#endif


// bpo-39573 added Py_SET_REFCNT() to Python 3.9.0a4
#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_REFCNT)
static inline void _Py_SET_REFCNT(PyObject *ob, Py_ssize_t refcnt)
{
    ob->ob_refcnt = refcnt;
}
#define Py_SET_REFCNT(ob, refcnt) _Py_SET_REFCNT((PyObject*)(ob), refcnt)
#endif


// bpo-39573 added Py_SET_TYPE() to Python 3.9.0a4
#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_TYPE)
static inline void
_Py_SET_TYPE(PyObject *ob, PyTypeObject *type)
{
    ob->ob_type = type;
}
#define Py_SET_TYPE(ob, type) _Py_SET_TYPE((PyObject*)(ob), type)
#endif


// bpo-39573 added Py_SET_SIZE() to Python 3.9.0a4
#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_SIZE)
static inline void
_Py_SET_SIZE(PyVarObject *ob, Py_ssize_t size)
{
    ob->ob_size = size;
}
#define Py_SET_SIZE(ob, size) _Py_SET_SIZE((PyVarObject*)(ob), size)
#endif


// bpo-40421 added PyFrame_GetCode() to Python 3.9.0b1
#if PY_VERSION_HEX < 0x030900B1
static inline PyCodeObject*
PyFrame_GetCode(PyFrameObject *frame)
{
    PyCodeObject *code;
    assert(frame != NULL);
    code = frame->f_code;
    assert(code != NULL);
    Py_INCREF(code);
    return code;
}
#endif

static inline PyCodeObject*
_PyFrame_GetCodeBorrow(PyFrameObject *frame)
{
    PyCodeObject *code = PyFrame_GetCode(frame);
    Py_DECREF(code);
    return code;  // borrowed reference
}


// bpo-40421 added PyFrame_GetCode() to Python 3.9.0b1
#if PY_VERSION_HEX < 0x030900B1
static inline PyFrameObject*
PyFrame_GetBack(PyFrameObject *frame)
{
    PyFrameObject *back;
    assert(frame != NULL);
    back = frame->f_back;
    Py_XINCREF(back);
    return back;
}
#endif

static inline PyFrameObject*
_PyFrame_GetBackBorrow(PyFrameObject *frame)
{
    PyFrameObject *back = PyFrame_GetBack(frame);
    Py_XDECREF(back);
    return back;  // borrowed reference
}


// bpo-39947 added PyThreadState_GetInterpreter() to Python 3.9.0a5
#if PY_VERSION_HEX < 0x030900A5
static inline PyInterpreterState *
PyThreadState_GetInterpreter(PyThreadState *tstate)
{
    assert(tstate != NULL);
    return tstate->interp;
}
#endif


// bpo-40429 added PyThreadState_GetFrame() to Python 3.9.0b1
#if PY_VERSION_HEX < 0x030900B1
static inline PyFrameObject*
PyThreadState_GetFrame(PyThreadState *tstate)
{
    PyFrameObject *frame;
    assert(tstate != NULL);
    frame = tstate->frame;
    Py_XINCREF(frame);
    return frame;
}
#endif

static inline PyFrameObject*
_PyThreadState_GetFrameBorrow(PyThreadState *tstate)
{
    PyFrameObject *frame = PyThreadState_GetFrame(tstate);
    Py_XDECREF(frame);
    return frame;  // borrowed reference
}


// bpo-39947 added PyInterpreterState_Get() to Python 3.9.0a5
#if PY_VERSION_HEX < 0x030900A5
static inline PyInterpreterState *
PyInterpreterState_Get(void)
{
    PyThreadState *tstate;
    PyInterpreterState *interp;

    tstate = PyThreadState_GET();
    if (tstate == NULL) {
        Py_FatalError("GIL released (tstate is NULL)");
    }
    interp = tstate->interp;
    if (interp == NULL) {
        Py_FatalError("no current interpreter");
    }
    return interp;
}
#endif


// bpo-39947 added PyInterpreterState_Get() to Python 3.9.0a6
#if 0x030700A1 <= PY_VERSION_HEX && PY_VERSION_HEX < 0x030900A6
static inline uint64_t
PyThreadState_GetID(PyThreadState *tstate)
{
    assert(tstate != NULL);
    return tstate->id;
}
#endif


// bpo-37194 added PyObject_CallNoArgs() to Python 3.9.0a1
#if PY_VERSION_HEX < 0x030900A1
static inline PyObject*
PyObject_CallNoArgs(PyObject *func)
{
    return PyObject_CallFunctionObjArgs(func, NULL);
}
#endif


// bpo-39245 made PyObject_CallOneArg() public (previously called
// _PyObject_CallOneArg) in Python 3.9.0a4
#if PY_VERSION_HEX < 0x030900A4
static inline PyObject*
PyObject_CallOneArg(PyObject *func, PyObject *arg)
{
    return PyObject_CallFunctionObjArgs(func, arg, NULL);
}
#endif


// bpo-40024 added PyModule_AddType() to Python 3.9.0a5
#if PY_VERSION_HEX < 0x030900A5
static inline int
PyModule_AddType(PyObject *module, PyTypeObject *type)
{
    const char *name, *dot;

    if (PyType_Ready(type) < 0) {
        return -1;
    }

    // inline _PyType_Name()
    name = type->tp_name;
    assert(name != NULL);
    dot = strrchr(name, '.');
    if (dot != NULL) {
        name = dot + 1;
    }

    Py_INCREF(type);
    if (PyModule_AddObject(module, name, (PyObject *)type) < 0) {
        Py_DECREF(type);
        return -1;
    }

    return 0;
}
#endif


// bpo-40241 added PyObject_GC_IsTracked() to Python 3.9.0a6.
// bpo-4688 added _PyObject_GC_IS_TRACKED() to Python 2.7.0a2.
#if PY_VERSION_HEX < 0x030900A6
static inline int
PyObject_GC_IsTracked(PyObject* obj)
{
    return (PyObject_IS_GC(obj) && _PyObject_GC_IS_TRACKED(obj));
}
#endif

// bpo-40241 added PyObject_GC_IsFinalized() to Python 3.9.0a6.
// bpo-18112 added _PyGCHead_FINALIZED() to Python 3.4.0 final.
#if PY_VERSION_HEX < 0x030900A6 && PY_VERSION_HEX >= 0x030400F0
static inline int
PyObject_GC_IsFinalized(PyObject *obj)
{
    return (PyObject_IS_GC(obj) && _PyGCHead_FINALIZED((PyGC_Head *)(obj)-1));
}
#endif


// bpo-39573 added Py_IS_TYPE() to Python 3.9.0a4
#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_IS_TYPE)
static inline int
_Py_IS_TYPE(const PyObject *ob, const PyTypeObject *type) {
    return ob->ob_type == type;
}
#define Py_IS_TYPE(ob, type) _Py_IS_TYPE((const PyObject*)(ob), type)
#endif


#ifdef __cplusplus
}
#endif
#endif  // PYTHONCAPI_COMPAT