grit_lib/
write_tree.rs

1//! Build tree objects from index entries (`git write-tree` core logic).
2
3use std::collections::BTreeMap;
4
5use crate::error::Result;
6use crate::index::{
7    Index, IndexEntry, MODE_EXECUTABLE, MODE_GITLINK, MODE_REGULAR, MODE_SYMLINK, MODE_TREE,
8};
9use crate::objects::{serialize_tree, tree_entry_cmp, ObjectId, ObjectKind, TreeEntry};
10use crate::odb::Odb;
11
12/// Build and write tree object(s) from index entries and return the tree OID.
13///
14/// The `prefix` argument optionally limits the write to a subtree path.
15pub fn write_tree_from_index(odb: &Odb, index: &Index, prefix: &str) -> Result<ObjectId> {
16    let prefix_bytes = prefix.as_bytes();
17    let mut entries: Vec<&IndexEntry> = index
18        .entries
19        .iter()
20        .filter(|entry| entry.stage() == 0 && entry.path.starts_with(prefix_bytes))
21        .collect();
22    entries.sort_by(|a, b| a.path.cmp(&b.path).then_with(|| a.stage().cmp(&b.stage())));
23    build_tree(odb, &entries, prefix_bytes)
24}
25
26fn build_tree(odb: &Odb, entries: &[&IndexEntry], dir_prefix: &[u8]) -> Result<ObjectId> {
27    let mut children: BTreeMap<Vec<u8>, ChildKind> = BTreeMap::new();
28
29    for entry in entries {
30        let path = &entry.path;
31        let rel = if dir_prefix.is_empty() {
32            path.as_slice()
33        } else {
34            path.strip_prefix(dir_prefix)
35                .and_then(|suffix| suffix.strip_prefix(b"/"))
36                .unwrap_or(path.as_slice())
37        };
38
39        if let Some(slash_pos) = rel.iter().position(|&byte| byte == b'/') {
40            let child_name = rel[..slash_pos].to_vec();
41            let sub_prefix = if dir_prefix.is_empty() {
42                child_name.clone()
43            } else {
44                let mut sub_prefix = dir_prefix.to_vec();
45                sub_prefix.push(b'/');
46                sub_prefix.extend_from_slice(&child_name);
47                sub_prefix
48            };
49            children
50                .entry(child_name)
51                .or_insert_with(|| ChildKind::Tree(sub_prefix, Vec::new()))
52                .push_entry(entry);
53        } else {
54            children
55                .entry(rel.to_vec())
56                .or_insert_with(|| ChildKind::Blob {
57                    mode: canonicalize_blob_mode(entry.mode),
58                    oid: entry.oid,
59                });
60        }
61    }
62
63    let mut tree_entries = Vec::with_capacity(children.len());
64    for (name, child) in children {
65        match child {
66            ChildKind::Blob { mode, oid } => tree_entries.push(TreeEntry { mode, name, oid }),
67            ChildKind::Tree(sub_prefix, sub_entries) => {
68                let sub_oid = build_tree(odb, &sub_entries, &sub_prefix)?;
69                tree_entries.push(TreeEntry {
70                    mode: MODE_TREE,
71                    name,
72                    oid: sub_oid,
73                });
74            }
75        }
76    }
77
78    tree_entries.sort_by(|a, b| {
79        let a_tree = a.mode == MODE_TREE;
80        let b_tree = b.mode == MODE_TREE;
81        tree_entry_cmp(&a.name, a_tree, &b.name, b_tree)
82    });
83
84    let data = serialize_tree(&tree_entries);
85    odb.write(ObjectKind::Tree, &data)
86}
87
88fn canonicalize_blob_mode(mode: u32) -> u32 {
89    match mode & 0o170000 {
90        0o120000 => MODE_SYMLINK,
91        0o160000 => MODE_GITLINK,
92        0o100000 => {
93            if mode & 0o111 != 0 {
94                MODE_EXECUTABLE
95            } else {
96                MODE_REGULAR
97            }
98        }
99        _ => MODE_REGULAR,
100    }
101}
102
103enum ChildKind<'a> {
104    Blob { mode: u32, oid: ObjectId },
105    Tree(Vec<u8>, Vec<&'a IndexEntry>),
106}
107
108impl<'a> ChildKind<'a> {
109    fn push_entry(&mut self, entry: &'a IndexEntry) {
110        if let Self::Tree(_, entries) = self {
111            entries.push(entry);
112        }
113    }
114}
115
116#[cfg(test)]
117mod tests {
118    #![allow(clippy::expect_used, clippy::unwrap_used)]
119
120    use super::*;
121    use crate::index::{IndexEntry, MODE_EXECUTABLE, MODE_REGULAR, MODE_SYMLINK, MODE_TREE};
122    use crate::objects::parse_tree;
123    use tempfile::TempDir;
124
125    fn entry(path: &str, mode: u32, oid: ObjectId) -> IndexEntry {
126        IndexEntry {
127            ctime_sec: 0,
128            ctime_nsec: 0,
129            mtime_sec: 0,
130            mtime_nsec: 0,
131            dev: 0,
132            ino: 0,
133            mode,
134            uid: 0,
135            gid: 0,
136            size: 0,
137            oid,
138            flags: path.len().min(0xFFF) as u16,
139            flags_extended: None,
140            path: path.as_bytes().to_vec(),
141        }
142    }
143
144    #[test]
145    fn writes_sorted_tree_with_canonical_modes() {
146        let temp_dir = TempDir::new().unwrap();
147        let odb = Odb::new(temp_dir.path());
148
149        let oid_a = odb.write(ObjectKind::Blob, b"a").unwrap();
150        let oid_exec = odb.write(ObjectKind::Blob, b"exec").unwrap();
151        let oid_link = odb.write(ObjectKind::Blob, b"target").unwrap();
152
153        let mut index = Index::new();
154        index.add_or_replace(entry("bin/run.sh", 0o100777, oid_exec));
155        index.add_or_replace(entry("link", 0o120777, oid_link));
156        index.add_or_replace(entry("a.txt", 0o100664, oid_a));
157
158        let root_oid = write_tree_from_index(&odb, &index, "").unwrap();
159        let root_tree_obj = odb.read(&root_oid).unwrap();
160        let root_entries = parse_tree(&root_tree_obj.data).unwrap();
161
162        assert_eq!(root_entries.len(), 3);
163        assert_eq!(root_entries[0].name, b"a.txt");
164        assert_eq!(root_entries[0].mode, MODE_REGULAR);
165        assert_eq!(root_entries[1].name, b"bin");
166        assert_eq!(root_entries[1].mode, MODE_TREE);
167        assert_eq!(root_entries[2].name, b"link");
168        assert_eq!(root_entries[2].mode, MODE_SYMLINK);
169
170        let bin_tree_obj = odb.read(&root_entries[1].oid).unwrap();
171        let bin_entries = parse_tree(&bin_tree_obj.data).unwrap();
172        assert_eq!(bin_entries.len(), 1);
173        assert_eq!(bin_entries[0].name, b"run.sh");
174        assert_eq!(bin_entries[0].mode, MODE_EXECUTABLE);
175    }
176}
grit_lib/write_tree.rs

grit_lib/
write_tree.rs
