Add xdiff patch application code and share it with GitChangesetPatch

helper/store.rs

@@ -19,6 +19,7 @@ use crate::libgit::{BlobId, CommitId, RawBlob, RawCommit};
 use crate::oid::{HgObjectId, ObjectId};
 use crate::oid_type;
 use crate::util::{FromBytes, SliceExt};
+use crate::xdiff::{apply, PatchInfo};
 
 macro_rules! hg2git {
     ($h:ident => $g:ident($i:ident)) => {
@@ -194,19 +195,22 @@ impl<'a> Iterator for ChangesetFilesIter<'a> {
 pub struct GitChangesetPatch<'a>(&'a [u8]);
 
 impl<'a> GitChangesetPatch<'a> {
+    pub fn iter(&self) -> Option<impl Iterator<Item = PatchInfo<Cow<'a, [u8]>>>> {
+        self.0
+            .split(|c| *c == b'\0')
+            .map(|part| {
+                let (start, end, data) = part.split3(b',')?;
+                let start = usize::from_bytes(start).ok()?;
+                let end = usize::from_bytes(end).ok()?;
+                let data = Cow::from(percent_decode(data));
+                Some(PatchInfo { start, end, data })
+            })
+            .collect::<Option<Vec<_>>>()
+            .map(|v| v.into_iter())
+    }
+
     pub fn apply(&self, input: &[u8]) -> Option<Vec<u8>> {
-        let mut patched = Vec::new();
-        let mut last_end = 0;
-        for part in self.0.split(|c| *c == b'\0') {
-            let (start, end, data) = part.split3(b',')?;
-            let start = usize::from_bytes(start).ok()?;
-            let data = Cow::from(percent_decode(data));
-            patched.extend_from_slice(&input[last_end..start]);
-            patched.extend_from_slice(&data);
-            last_end = usize::from_bytes(end).ok()?;
-        }
-        patched.extend_from_slice(&input[last_end..]);
-        Some(patched)
+        Some(apply(self.iter()?, input))
     }
 }
 

helper/xdiff.rs

@@ -67,17 +67,29 @@ extern "C" {
     ) -> c_int;
 }
 
-#[derive(Derivative, PartialEq)]
+#[derive(Clone, Copy, Derivative, PartialEq)]
 #[derivative(Debug)]
-pub struct PatchInfo<'a> {
+pub struct PatchInfo<S: AsRef<[u8]>> {
     pub start: usize,
     pub end: usize,
     #[derivative(Debug(format_with = "crate::util::bstr_fmt"))]
-    pub data: &'a [u8],
+    pub data: S,
+}
+
+pub fn apply<S: AsRef<[u8]>>(patch: impl Iterator<Item = PatchInfo<S>>, input: &[u8]) -> Vec<u8> {
+    let mut patched = Vec::new();
+    let mut last_end = 0;
+    for PatchInfo { start, end, data } in patch {
+        patched.extend_from_slice(&input[last_end..start]);
+        patched.extend_from_slice(data.as_ref());
+        last_end = end;
+    }
+    patched.extend_from_slice(&input[last_end..]);
+    patched
 }
 
 struct HunkContext<'a> {
-    patch_info: Vec<PatchInfo<'a>>,
+    patch_info: Vec<PatchInfo<&'a [u8]>>,
     a_line_offsets: Vec<usize>,
     b_line_offsets: Vec<usize>,
     b: &'a [u8],
@@ -121,7 +133,7 @@ fn line_offsets(buf: &[u8]) -> Vec<usize> {
         .collect()
 }
 
-pub fn textdiff<'a>(a: &[u8], b: &'a [u8]) -> Vec<PatchInfo<'a>> {
+pub fn textdiff<'a>(a: &[u8], b: &'a [u8]) -> Vec<PatchInfo<&'a [u8]>> {
     let mut ctx = HunkContext {
         patch_info: Vec::new(),
         a_line_offsets: line_offsets(a),