xdiff: implement xdl_trim_ends() in Rust

Replace the C implementation of xdl_trim_ends() with a Rust
implementation.

Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>

Author: ezekielnewren

rust/xdiff/src/lib.rs

@@ -0,0 +1,15 @@
+pub mod xprepare;
+pub mod xtypes;
+
+use crate::xprepare::trim_ends;
+use crate::xtypes::xdfile;
+
+#[no_mangle]
+unsafe extern "C" fn xdl_trim_ends(xdf1: *mut xdfile, xdf2: *mut xdfile) -> i32 {
+    let xdf1 = xdf1.as_mut().expect("null pointer");
+    let xdf2 = xdf2.as_mut().expect("null pointer");
+
+    trim_ends(xdf1, xdf2);
+
+    0
+}

rust/xdiff/src/xprepare.rs

@@ -0,0 +1,27 @@
+use crate::xtypes::xdfile;
+
+///
+/// Early trim initial and terminal matching records.
+///
+pub(crate) fn trim_ends(xdf1: &mut xdfile, xdf2: &mut xdfile) {
+    let mut lim = std::cmp::min(xdf1.record.len(), xdf2.record.len());
+
+    for i in 0..lim {
+        if xdf1.record[i].ha != xdf2.record[i].ha {
+            xdf1.dstart = i as isize;
+            xdf2.dstart = i as isize;
+            lim -= i;
+            break;
+        }
+    }
+
+    for i in 0..lim {
+        let f1i = xdf1.record.len() - 1 - i;
+        let f2i = xdf2.record.len() - 1 - i;
+        if xdf1.record[f1i].ha != xdf2.record[f2i].ha {
+            xdf1.dend = f1i as isize;
+            xdf2.dend = f2i as isize;
+            break;
+        }
+    }
+}

rust/xdiff/src/xtypes.rs

@@ -0,0 +1,19 @@
+use interop::ivec::IVec;
+
+#[repr(C)]
+pub(crate) struct xrecord {
+    pub(crate) ptr: *const u8,
+    pub(crate) size: usize,
+    pub(crate) ha: u64,
+}
+
+#[repr(C)]
+pub(crate) struct xdfile {
+    pub(crate) record: IVec<xrecord>,
+    pub(crate) dstart: isize,
+    pub(crate) dend: isize,
+    pub(crate) rchg: *mut u8,
+    pub(crate) rindex: *mut usize,
+    pub(crate) nreff: usize,
+    pub(crate) ha: *mut u64,
+}

xdiff/xprepare.c

@@ -318,33 +318,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 }
 
 
-/*
- * Early trim initial and terminal matching records.
- */
-static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {
-	long i, lim;
-	xrecord_t *recs1, *recs2;
-
-	recs1 = xdf1->record.ptr;
-	recs2 = xdf2->record.ptr;
-	for (i = 0, lim = XDL_MIN(xdf1->record.length, xdf2->record.length); i < lim;
-	     i++, recs1++, recs2++)
-		if (recs1->ha != recs2->ha)
-			break;
-
-	xdf1->dstart = xdf2->dstart = i;
-
-	recs1 = xdf1->record.ptr + xdf1->record.length - 1;
-	recs2 = xdf2->record.ptr + xdf2->record.length - 1;
-	for (lim -= i, i = 0; i < lim; i++, recs1--, recs2--)
-		if (recs1->ha != recs2->ha)
-			break;
-
-	xdf1->dend = xdf1->record.length - i - 1;
-	xdf2->dend = xdf2->record.length - i - 1;
-
-	return 0;
-}
+extern i32 xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2);
 
 
 static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {