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cindex.rs
183 lines | 5.9 KiB | application/rls-services+xml | RustLexer
// cindex.rs
//
// Copyright 2018 Georges Racinet <gracinet@anybox.fr>
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.
//! Bindings to use the Index defined by the parsers C extension
//!
//! Ideally, we should use an Index entirely implemented in Rust,
//! but this will take some time to get there.
use cpython::{
exc::ImportError, exc::TypeError, ObjectProtocol, PyClone, PyErr,
PyObject, PyResult, PyTuple, Python, PythonObject,
};
use hg::revlog::{Node, RevlogIndex};
use hg::{Graph, GraphError, Revision, WORKING_DIRECTORY_REVISION};
use libc::{c_int, ssize_t};
const REVLOG_CABI_VERSION: c_int = 2;
#[repr(C)]
pub struct Revlog_CAPI {
abi_version: c_int,
index_length:
unsafe extern "C" fn(index: *mut revlog_capi::RawPyObject) -> ssize_t,
index_node: unsafe extern "C" fn(
index: *mut revlog_capi::RawPyObject,
rev: ssize_t,
) -> *const Node,
index_parents: unsafe extern "C" fn(
index: *mut revlog_capi::RawPyObject,
rev: c_int,
ps: *mut [c_int; 2],
) -> c_int,
}
py_capsule!(
from mercurial.cext.parsers import revlog_CAPI
as revlog_capi for Revlog_CAPI);
/// A `Graph` backed up by objects and functions from revlog.c
///
/// This implementation of the `Graph` trait, relies on (pointers to)
/// - the C index object (`index` member)
/// - the `index_get_parents()` function (`parents` member)
///
/// # Safety
///
/// The C index itself is mutable, and this Rust exposition is **not
/// protected by the GIL**, meaning that this construct isn't safe with respect
/// to Python threads.
///
/// All callers of this `Index` must acquire the GIL and must not release it
/// while working.
///
/// # TODO find a solution to make it GIL safe again.
///
/// This is non trivial, and can wait until we have a clearer picture with
/// more Rust Mercurial constructs.
///
/// One possibility would be to a `GILProtectedIndex` wrapper enclosing
/// a `Python<'p>` marker and have it be the one implementing the
/// `Graph` trait, but this would mean the `Graph` implementor would become
/// likely to change between subsequent method invocations of the `hg-core`
/// objects (a serious change of the `hg-core` API):
/// either exposing ways to mutate the `Graph`, or making it a non persistent
/// parameter in the relevant methods that need one.
///
/// Another possibility would be to introduce an abstract lock handle into
/// the core API, that would be tied to `GILGuard` / `Python<'p>`
/// in the case of the `cpython` crate bindings yet could leave room for other
/// mechanisms in other contexts.
pub struct Index {
index: PyObject,
capi: &'static Revlog_CAPI,
}
impl Index {
pub fn new(py: Python, index: PyObject) -> PyResult<Self> {
let capi = unsafe { revlog_capi::retrieve(py)? };
if capi.abi_version != REVLOG_CABI_VERSION {
return Err(PyErr::new::<ImportError, _>(
py,
format!(
"ABI version mismatch: the C ABI revlog version {} \
does not match the {} expected by Rust hg-cpython",
capi.abi_version, REVLOG_CABI_VERSION
),
));
}
let compat: u64 = index.getattr(py, "rust_ext_compat")?.extract(py)?;
if compat == 0 {
return Err(PyErr::new::<TypeError, _>(
py,
"index object not compatible with Rust",
));
}
Ok(Index { index, capi })
}
/// return a reference to the CPython Index object in this Struct
pub fn inner(&self) -> &PyObject {
&self.index
}
pub fn append(&mut self, py: Python, tup: PyTuple) -> PyResult<PyObject> {
self.index.call_method(
py,
"append",
PyTuple::new(py, &[tup.into_object()]),
None,
)
}
}
impl Clone for Index {
fn clone(&self) -> Self {
let guard = Python::acquire_gil();
Index {
index: self.index.clone_ref(guard.python()),
capi: self.capi,
}
}
}
impl PyClone for Index {
fn clone_ref(&self, py: Python) -> Self {
Index {
index: self.index.clone_ref(py),
capi: self.capi,
}
}
}
impl Graph for Index {
/// wrap a call to the C extern parents function
fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {
if rev == WORKING_DIRECTORY_REVISION {
return Err(GraphError::WorkingDirectoryUnsupported);
}
let mut res: [c_int; 2] = [0; 2];
let code = unsafe {
(self.capi.index_parents)(
self.index.as_ptr(),
rev as c_int,
&mut res as *mut [c_int; 2],
)
};
match code {
0 => Ok(res),
_ => Err(GraphError::ParentOutOfRange(rev)),
}
}
}
impl RevlogIndex for Index {
/// Note C return type is Py_ssize_t (hence signed), but we shall
/// force it to unsigned, because it's a length
fn len(&self) -> usize {
unsafe { (self.capi.index_length)(self.index.as_ptr()) as usize }
}
fn node(&self, rev: Revision) -> Option<&Node> {
let raw = unsafe {
(self.capi.index_node)(self.index.as_ptr(), rev as ssize_t)
};
if raw.is_null() {
None
} else {
// TODO it would be much better for the C layer to give us
// a length, since the hash length will change in the near
// future, but that's probably out of scope for the nodemap
// patch series.
//
// The root of that unsafety relies in the signature of
// `capi.index_node()` itself: returning a `Node` pointer
// whereas it's a `char *` in the C counterpart.
Some(unsafe { &*raw })
}
}
}