use std::convert::TryFrom; use nom::error::ParseError; 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 }    }} impl<'a> TreeRef<'a> {    /// Deserialize a Tree from `data`.    pub fn from_bytes(data: &'a [u8]) -> Result<TreeRef<'a>, crate::decode::Error> {        decode::tree(data).map(|(_, t)| t).map_err(crate::decode::Error::from)    }     /// 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()    }} impl<'a> Default for TreeRefIter<'a> {    fn default() -> Self {        TreeRefIter { data: &[] }    }} 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 => {                self.data = &[];                #[allow(clippy::unit_arg)]                Some(Err(nom::Err::Error(crate::decode::ParseError::from_error_kind(                    &[] as &[u8],                    nom::error::ErrorKind::MapRes,                ))                .into()))            }        }    }} impl<'a> TryFrom<&'a [u8]> for tree::EntryMode {    type Error = &'a [u8];     fn try_from(mode: &'a [u8]) -> Result<Self, Self::Error> {        Ok(match mode {            b"40000" => tree::EntryMode::Tree,            b"100644" => tree::EntryMode::Blob,            b"100755" => tree::EntryMode::BlobExecutable,            b"120000" => tree::EntryMode::Link,            b"160000" => tree::EntryMode::Commit,            b"100664" => tree::EntryMode::Blob, // rare and found in the linux kernel            b"100640" => tree::EntryMode::Blob, // rare and found in the Rust repo            _ => return Err(mode),        })    }} impl TryFrom<u32> for tree::EntryMode {    type Error = u32;     fn try_from(mode: u32) -> Result<Self, Self::Error> {        Ok(match mode {            0o40000 => tree::EntryMode::Tree,            0o100644 => tree::EntryMode::Blob,            0o100755 => tree::EntryMode::BlobExecutable,            0o120000 => tree::EntryMode::Link,            0o160000 => tree::EntryMode::Commit,            0o100664 => tree::EntryMode::Blob, // rare and found in the linux kernel            0o100640 => tree::EntryMode::Blob, // rare and found in the Rust repo            _ => return Err(mode),        })    }} mod decode {    use std::convert::TryFrom;     use bstr::ByteSlice;    use nom::{        bytes::complete::{tag, take, take_while1, take_while_m_n},        character::is_digit,        combinator::all_consuming,        error::ParseError,        multi::many0,        sequence::terminated,        IResult,    };     use crate::{parse::SPACE, tree, tree::EntryRef, TreeRef};     const NULL: &[u8] = b"\0";     pub fn fast_entry(i: &[u8]) -> Option<(&[u8], EntryRef<'_>)> {        let mut mode = 0u32;        let mut spacer_pos = 1;        for b in i.iter().take_while(|b| **b != b' ') {            if *b < b'0' || *b > b'7' {                return None;            }            mode = (mode << 3) + (b - b'0') as u32;            spacer_pos += 1;        }        let (_, i) = i.split_at(spacer_pos);        let mode = tree::EntryMode::try_from(mode).ok()?;        let (filename, i) = i.split_at(i.find_byte(0)?);        let i = &i[1..];        const HASH_LEN_FIXME: usize = 20; // TODO: 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: git_hash::oid::try_from(oid).expect("we counted exactly 20 bytes"),            },        ))    }     pub fn entry<'a, E: ParseError<&'a [u8]>>(i: &'a [u8]) -> IResult<&[u8], EntryRef<'_>, E> {        let (i, mode) = terminated(take_while_m_n(5, 6, is_digit), tag(SPACE))(i)?;        let mode = tree::EntryMode::try_from(mode)            .map_err(|invalid| nom::Err::Error(E::from_error_kind(invalid, nom::error::ErrorKind::MapRes)))?;        let (i, filename) = terminated(take_while1(|b| b != NULL[0]), tag(NULL))(i)?;        let (i, oid) = take(20u8)(i)?; // TODO: make this compatible with other hash lengths         Ok((            i,            EntryRef {                mode,                filename: filename.as_bstr(),                oid: git_hash::oid::try_from(oid).expect("we counted exactly 20 bytes"),            },        ))    }     pub fn tree<'a, E: ParseError<&'a [u8]>>(i: &'a [u8]) -> IResult<&'a [u8], TreeRef<'a>, E> {        let (i, entries) = all_consuming(many0(entry))(i)?;        Ok((i, TreeRef { entries }))    }}