Patchwork [2,of,5,V3] rust: iterator bindings to C code

login
register
mail settings
Submitter Georges Racinet
Date Oct. 13, 2018, 1:59 p.m.
Message ID <4b490e500a3551b03c41.1539439180@ishtar>
Download mbox | patch
Permalink /patch/35928/
State Accepted
Headers show

Comments

Georges Racinet - Oct. 13, 2018, 1:59 p.m.
# HG changeset patch
# User Georges Racinet <gracinet@anybox.fr>
# Date 1538059896 -7200
#      Thu Sep 27 16:51:36 2018 +0200
# Node ID 4b490e500a3551b03c41dc06f16aa506523719c6
# Parent  41b32e06629466bbe671c6ebfc1c5a4133c8af99
# EXP-Topic rustancestors-contains
rust: iterator bindings to C code

In this changeset, still made of Rust code only,
we expose the Rust iterator for instantiation and
consumption from C code.

The idea is that both the index and index_get_parents()
will be passed from the C extension, hence avoiding a hard
link dependency to parsers.so, so that the crate can
still be built and tested independently.

On the other hand, parsers.so will use the symbols
defined in this changeset.

Patch

diff -r 41b32e066294 -r 4b490e500a35 rust/Cargo.lock
--- a/rust/Cargo.lock	Thu Sep 27 17:03:16 2018 +0200
+++ b/rust/Cargo.lock	Thu Sep 27 16:51:36 2018 +0200
@@ -30,6 +30,14 @@ 
 ]
 
 [[package]]
+name = "hgdirectffi"
+version = "0.1.0"
+dependencies = [
+ "hg-core 0.1.0",
+ "libc 0.2.35 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "kernel32-sys"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff -r 41b32e066294 -r 4b490e500a35 rust/Cargo.toml
--- a/rust/Cargo.toml	Thu Sep 27 17:03:16 2018 +0200
+++ b/rust/Cargo.toml	Thu Sep 27 16:51:36 2018 +0200
@@ -1,3 +1,3 @@ 
 [workspace]
-members = ["hgcli", "hg-core"]
+members = ["hgcli", "hg-core", "hg-direct-ffi"]
 exclude = ["chg"]
diff -r 41b32e066294 -r 4b490e500a35 rust/hg-direct-ffi/Cargo.toml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/hg-direct-ffi/Cargo.toml	Thu Sep 27 16:51:36 2018 +0200
@@ -0,0 +1,12 @@ 
+[package]
+name = "hgdirectffi"
+version = "0.1.0"
+authors = ["Georges Racinet <gracinet@anybox.fr>"]
+description = "Low level Python bindings for hg-core, going through existing C extensions"
+
+[dependencies]
+libc = "*"
+hg-core = { path = "../hg-core" }
+
+[lib]
+crate-type = ["staticlib"]
diff -r 41b32e066294 -r 4b490e500a35 rust/hg-direct-ffi/src/ancestors.rs
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/hg-direct-ffi/src/ancestors.rs	Thu Sep 27 16:51:36 2018 +0200
@@ -0,0 +1,229 @@ 
+// 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 for CPython extension code
+//!
+//! This exposes methods to build and use a `rustlazyancestors` iterator
+//! from C code, using an index and its parents function that are passed
+//! from the caller at instantiation.
+
+use hg::AncestorsIterator;
+use hg::{Graph, GraphError, Revision, NULL_REVISION};
+use libc::{c_int, c_long, c_void, ssize_t};
+use std::ptr::null_mut;
+use std::slice;
+
+type IndexPtr = *mut c_void;
+type IndexParentsFn =
+    unsafe extern "C" fn(index: IndexPtr, rev: ssize_t, ps: *mut [c_int; 2], max_rev: c_int)
+        -> c_int;
+
+/// 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)
+pub struct Index {
+    index: IndexPtr,
+    parents: IndexParentsFn,
+}
+
+impl Index {
+    pub fn new(index: IndexPtr, parents: IndexParentsFn) -> Self {
+        Index {
+            index: index,
+            parents: parents,
+        }
+    }
+}
+
+impl Graph for Index {
+    /// wrap a call to the C extern parents function
+    fn parents(&self, rev: Revision) -> Result<(Revision, Revision), GraphError> {
+        let mut res: [c_int; 2] = [0; 2];
+        let code =
+            unsafe { (self.parents)(self.index, rev as ssize_t, &mut res as *mut [c_int; 2], rev) };
+        match code {
+            0 => Ok((res[0], res[1])),
+            _ => Err(GraphError::ParentOutOfRange(rev)),
+        }
+    }
+}
+
+/// Wrapping of AncestorsIterator<Index> constructor, for C callers.
+///
+/// Besides `initrevs`, `stoprev` and `inclusive`, that are converted
+/// we receive the index and the parents function as pointers
+#[no_mangle]
+pub extern "C" fn rustlazyancestors_init(
+    index: IndexPtr,
+    parents: IndexParentsFn,
+    initrevslen: usize,
+    initrevs: *mut c_long,
+    stoprev: c_long,
+    inclusive: c_int,
+) -> *mut AncestorsIterator<Index> {
+    unsafe {
+        raw_init(
+            Index::new(index, parents),
+            initrevslen,
+            initrevs,
+            stoprev,
+            inclusive,
+        )
+    }
+}
+
+/// Testable (for any Graph) version of rustlazyancestors_init
+#[inline]
+unsafe fn raw_init<G: Graph>(
+    graph: G,
+    initrevslen: usize,
+    initrevs: *mut c_long,
+    stoprev: c_long,
+    inclusive: c_int,
+) -> *mut AncestorsIterator<G> {
+    let inclb = match inclusive {
+        0 => false,
+        1 => true,
+        _ => {
+            return null_mut();
+        }
+    };
+
+    let slice = slice::from_raw_parts(initrevs, initrevslen);
+
+    Box::into_raw(Box::new(match AncestorsIterator::new(
+        graph,
+        slice.into_iter().map(|&r| r as Revision),
+        stoprev as Revision,
+        inclb,
+    ) {
+        Ok(it) => it,
+        Err(_) => {
+            return null_mut();
+        }
+    }))
+}
+
+/// Deallocator to be called from C code
+#[no_mangle]
+pub extern "C" fn rustlazyancestors_drop(raw_iter: *mut AncestorsIterator<Index>) {
+    raw_drop(raw_iter);
+}
+
+/// Testable (for any Graph) version of rustlazayancestors_drop
+#[inline]
+fn raw_drop<G: Graph>(raw_iter: *mut AncestorsIterator<G>) {
+    unsafe {
+        Box::from_raw(raw_iter);
+    }
+}
+
+/// Iteration main method to be called from C code
+///
+/// We convert the end of iteration into NULL_REVISION,
+/// it will be up to the C wrapper to convert that back into a Python end of
+/// iteration
+#[no_mangle]
+pub extern "C" fn rustlazyancestors_next(raw: *mut AncestorsIterator<Index>) -> c_long {
+    raw_next(raw)
+}
+
+/// Testable (for any Graph) version of rustlazayancestors_next
+#[inline]
+fn raw_next<G: Graph>(raw: *mut AncestorsIterator<G>) -> c_long {
+    let as_ref = unsafe { &mut *raw };
+    as_ref.next().unwrap_or(NULL_REVISION) as c_long
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::thread;
+
+    #[derive(Clone, Debug)]
+    struct Stub;
+
+    impl Graph for Stub {
+        fn parents(&self, r: Revision) -> Result<(Revision, Revision), GraphError> {
+            match r {
+                25 => Err(GraphError::ParentOutOfRange(25)),
+                _ => Ok((1, 2)),
+            }
+        }
+    }
+
+    /// Helper for test_init_next()
+    fn stub_raw_init(
+        initrevslen: usize,
+        initrevs: usize,
+        stoprev: c_long,
+        inclusive: c_int,
+    ) -> usize {
+        unsafe {
+            raw_init(
+                Stub,
+                initrevslen,
+                initrevs as *mut c_long,
+                stoprev,
+                inclusive,
+            ) as usize
+        }
+    }
+
+    fn stub_raw_init_from_vec(
+        mut initrevs: Vec<c_long>,
+        stoprev: c_long,
+        inclusive: c_int,
+    ) -> *mut AncestorsIterator<Stub> {
+        unsafe {
+            raw_init(
+                Stub,
+                initrevs.len(),
+                initrevs.as_mut_ptr(),
+                stoprev,
+                inclusive,
+            )
+        }
+    }
+
+    #[test]
+    // Test what happens when we init an Iterator as with the exposed C ABI
+    // and try to use it afterwards
+    // We spawn new threads, in order to make memory consistency harder
+    // but this forces us to convert the pointers into shareable usizes.
+    fn test_init_next() {
+        let mut initrevs: Vec<c_long> = vec![11, 13];
+        let initrevs_len = initrevs.len();
+        let initrevs_ptr = initrevs.as_mut_ptr() as usize;
+        let handler = thread::spawn(move || stub_raw_init(initrevs_len, initrevs_ptr, 0, 1));
+        let raw = handler.join().unwrap() as *mut AncestorsIterator<Stub>;
+
+        assert_eq!(raw_next(raw), 13);
+        assert_eq!(raw_next(raw), 11);
+        assert_eq!(raw_next(raw), 2);
+        assert_eq!(raw_next(raw), 1);
+        assert_eq!(raw_next(raw), NULL_REVISION as c_long);
+        raw_drop(raw);
+    }
+
+    #[test]
+    fn test_init_wrong_bool() {
+        assert_eq!(stub_raw_init_from_vec(vec![11, 13], 0, 2), null_mut());
+    }
+
+    #[test]
+    fn test_empty() {
+        let raw = stub_raw_init_from_vec(vec![], 0, 1);
+        assert_eq!(raw_next(raw), NULL_REVISION as c_long);
+        raw_drop(raw);
+    }
+
+    #[test]
+    fn test_init_err_out_of_range() {
+        assert!(stub_raw_init_from_vec(vec![25], 0, 0).is_null());
+    }
+}
diff -r 41b32e066294 -r 4b490e500a35 rust/hg-direct-ffi/src/lib.rs
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/hg-direct-ffi/src/lib.rs	Thu Sep 27 16:51:36 2018 +0200
@@ -0,0 +1,16 @@ 
+// 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 for CPython extension code
+//!
+//! This exposes methods to build and use a `rustlazyancestors` iterator
+//! from C code, using an index and its parents function that are passed
+//! from the caller at instantiation.
+
+extern crate hg;
+extern crate libc;
+
+mod ancestors;
+pub use ancestors::{rustlazyancestors_drop, rustlazyancestors_init, rustlazyancestors_next};