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use bstr::BStr;
use winnow::{error::ParserError, prelude::*};
use crate::{tree, tree::EntryRef, TreeRef, TreeRefIter};
impl<'a> TreeRefIter<'a> {
/// Instantiate an iterator from the given tree data.
pub fn from_bytes(data: &'a [u8]) -> TreeRefIter<'a> {
TreeRefIter { data }
}
/// Follow a sequence of `path` components starting from this instance, and look them up in `odb` one by one using `buffer`
/// until the last component is looked up and its tree entry is returned.
///
/// # Performance Notes
///
/// Searching tree entries is currently done in sequence, which allows the search to be allocation free. It would be possible
/// to reuse a vector and use a binary search instead, which might be able to improve performance over all.
/// However, a benchmark should be created first to have some data and see which trade-off to choose here.
pub fn lookup_entry<I, P>(
&self,
odb: impl crate::Find,
buffer: &'a mut Vec<u8>,
path: I,
) -> Result<Option<tree::Entry>, crate::find::Error>
where
I: IntoIterator<Item = P>,
P: PartialEq<BStr>,
{
buffer.clear();
let mut path = path.into_iter().peekable();
buffer.extend_from_slice(self.data);
while let Some(component) = path.next() {
match TreeRefIter::from_bytes(buffer)
.filter_map(Result::ok)
.find(|entry| component.eq(entry.filename))
{
Some(entry) => {
if path.peek().is_none() {
return Ok(Some(entry.into()));
} else {
let next_id = entry.oid.to_owned();
let obj = odb.try_find(&next_id, buffer)?;
let Some(obj) = obj else { return Ok(None) };
if !obj.kind.is_tree() {
return Ok(None);
}
}
}
None => return Ok(None),
}
}
Ok(None)
}
/// Like [`Self::lookup_entry()`], but takes any [`AsRef<Path>`](`std::path::Path`) directly via `relative_path`,
/// a path relative to this tree.
/// `odb` and `buffer` are used to lookup intermediate trees.
///
/// # Note
///
/// If any path component contains illformed UTF-8 and thus can't be converted to bytes on platforms which can't do so natively,
/// the returned component will be empty which makes the lookup fail.
pub fn lookup_entry_by_path(
&self,
odb: impl crate::Find,
buffer: &'a mut Vec<u8>,
relative_path: impl AsRef<std::path::Path>,
) -> Result<Option<tree::Entry>, crate::find::Error> {
use crate::bstr::ByteSlice;
self.lookup_entry(
odb,
buffer,
relative_path.as_ref().components().map(|c: std::path::Component<'_>| {
gix_path::os_str_into_bstr(c.as_os_str())
.unwrap_or_else(|_| "".into())
.as_bytes()
}),
)
}
}
impl<'a> TreeRef<'a> {
/// Deserialize a Tree from `data`.
pub fn from_bytes(mut data: &'a [u8]) -> Result<TreeRef<'a>, crate::decode::Error> {
let input = &mut data;
match decode::tree.parse_next(input) {
Ok(tag) => Ok(tag),
Err(err) => Err(crate::decode::Error::with_err(err, input)),
}
}
/// Find an entry named `name` knowing if the entry is a directory or not, using a binary search.
///
/// Note that it's impossible to binary search by name alone as the sort order is special.
pub fn bisect_entry(&self, name: &BStr, is_dir: bool) -> Option<EntryRef<'a>> {
static NULL_HASH: gix_hash::ObjectId = gix_hash::Kind::shortest().null();
let search = EntryRef {
mode: if is_dir {
tree::EntryKind::Tree
} else {
tree::EntryKind::Blob
}
.into(),
filename: name,
oid: &NULL_HASH,
};
self.entries
.binary_search_by(|e| e.cmp(&search))
.ok()
.map(|idx| self.entries[idx])
}
/// Create an instance of the empty tree.
///
/// It's particularly useful as static part of a program.
pub const fn empty() -> TreeRef<'static> {
TreeRef { entries: Vec::new() }
}
}
impl<'a> TreeRefIter<'a> {
/// Consume self and return all parsed entries.
pub fn entries(self) -> Result<Vec<EntryRef<'a>>, crate::decode::Error> {
self.collect()
}
/// Return the offset in bytes that our data advanced from `buf`, the original buffer
/// to the beginning of the data of the tree.
///
/// Then the tree-iteration can be resumed at the entry that would otherwise be returned next.
pub fn offset_to_next_entry(&self, buf: &[u8]) -> usize {
let before = (*buf).as_ptr();
let after = (*self.data).as_ptr();
debug_assert!(
before <= after,
"`TreeRefIter::offset_to_next_entry(): {after:?} <= {before:?}) violated"
);
(after as usize - before as usize) / std::mem::size_of::<u8>()
}
}
impl<'a> Iterator for TreeRefIter<'a> {
type Item = Result<EntryRef<'a>, crate::decode::Error>;
fn next(&mut self) -> Option<Self::Item> {
if self.data.is_empty() {
return None;
}
match decode::fast_entry(self.data) {
Some((data_left, entry)) => {
self.data = data_left;
Some(Ok(entry))
}
None => {
let failing = self.data;
self.data = &[];
#[allow(clippy::unit_arg)]
Some(Err(crate::decode::Error::with_err(
winnow::error::ErrMode::from_input(&failing),
failing,
)))
}
}
}
}
impl<'a> TryFrom<&'a [u8]> for tree::EntryMode {
type Error = &'a [u8];
fn try_from(mode: &'a [u8]) -> Result<Self, Self::Error> {
tree::EntryMode::from_bytes(mode).ok_or(mode)
}
}
mod decode {
use bstr::ByteSlice;
use winnow::{error::ParserError, prelude::*};
use crate::{tree, tree::EntryRef, TreeRef};
pub fn fast_entry(i: &[u8]) -> Option<(&[u8], EntryRef<'_>)> {
let (mode, i) = tree::EntryMode::extract_from_bytes(i)?;
let (filename, i) = i.split_at(i.find_byte(0)?);
let i = &i[1..];
const HASH_LEN_FIXME: usize = 20; // TODO(SHA256): know actual/desired length or we may overshoot
let (oid, i) = match i.len() {
len if len < HASH_LEN_FIXME => return None,
_ => i.split_at(20),
};
Some((
i,
EntryRef {
mode,
filename: filename.as_bstr(),
oid: gix_hash::oid::try_from_bytes(oid).expect("we counted exactly 20 bytes"),
},
))
}
pub fn tree<'a, E: ParserError<&'a [u8]>>(i: &mut &'a [u8]) -> ModalResult<TreeRef<'a>, E> {
let mut out = Vec::new();
let mut i = &**i;
while !i.is_empty() {
let Some((rest, entry)) = fast_entry(i) else {
#[allow(clippy::unit_arg)]
return Err(winnow::error::ErrMode::from_input(&i));
};
i = rest;
out.push(entry);
}
Ok(TreeRef { entries: out })
}
}