remove unnecessary unsafe block code in Buffer's read_more method

[asder8215]

Out of curiosity, I was taking a look at the BufReader's peek() method and ended up checking out the code for Buffer's read_more() method. For reference, this is original code of Buffer's read_more() method.

    /// Read more bytes into the buffer without discarding any of its contents
    pub fn read_more(&mut self, mut reader: impl Read) -> io::Result<usize> {
        let mut buf = BorrowedBuf::from(&mut self.buf[self.filled..]);
        let old_init = self.initialized - self.filled;
        unsafe {
             buf.set_init(old_init);
        }
        reader.read_buf(buf.unfilled())?;
        self.filled += buf.len();
        self.initialized += buf.init_len() - old_init;
        Ok(buf.len())
    }

I think the unsafe block in the read_more() might be unused because I was taking a look into what reader.read_buf() does and it seems to already be setting the BorrowBuf's init field to another value.

fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<()> {
        default_read_buf(|b| self.read(b), buf)
}

pub(crate) fn default_read_buf<F>(read: F, mut cursor: BorrowedCursor<'_>) -> Result<()>
where
    F: FnOnce(&mut [u8]) -> Result<usize>,
{
    let n = read(cursor.ensure_init().init_mut())?;
    cursor.advance(n);
    Ok(())
}

/// Initializes all bytes in the cursor.
#[inline]
pub fn ensure_init(&mut self) -> &mut Self {
    // SAFETY: always in bounds and we never uninitialize these bytes.
    let uninit = unsafe { self.buf.buf.get_unchecked_mut(self.buf.init..) };

    // SAFETY: 0 is a valid value for MaybeUninit<u8> and the length matches the allocation
    // since it is comes from a slice reference.
    unsafe {
        ptr::write_bytes(uninit.as_mut_ptr(), 0, uninit.len());
    }
    self.buf.init = self.buf.capacity();

    self
}

It seems like the init field is reassigned inside the ensure_init() function, which would make the buf.set_init(old_init) code not useful. I know that the buf.unfilled() that is passed into reader.read_buf() is a BorrowedCursor<'this>, but as far as I am aware, a BorrowCursor<'this> is a wrapper around the unfilled portion of BorrowedBuf<'_>:

#[derive(Debug)]
pub struct BorrowedCursor<'a> {
    /// The underlying buffer.
    // Safety invariant: we treat the type of buf as covariant in the lifetime of `BorrowedBuf` when
    // we create a `BorrowedCursor`. This is only safe if we never replace `buf` by assigning into
    // it, so don't do that!
    buf: &'a mut BorrowedBuf<'a>,
}

If I'm understanding things correctly, I believe it's fine to get rid of the unsafe block code in this function.

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[rust-log-analyzer]

The job pr-check-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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REPOSITORY                                   TAG       IMAGE ID       CREATED      SIZE
ghcr.io/dependabot/dependabot-updater-core   latest    63ba4a2ff346   9 days ago   775MB
=> Removing docker images...
Deleted Images:
untagged: ghcr.io/dependabot/dependabot-updater-core:latest
untagged: ghcr.io/dependabot/dependabot-updater-core@sha256:830c840ea4b8c27b6919bdd47c017030adeb538f226e1cdfd386490a622b9218
deleted: sha256:63ba4a2ff3467a98ac6c8610fece2cdc9893e2af6c18111e57618f8949749b82
deleted: sha256:77617fa265a7311b1c0502e01ff6157d25228d91f6cddc21d7901eb440d0adee
deleted: sha256:0bd8abdbb1f7c0453b4bc76cce6ecf0a3b9e4b5d0c8ceeb63652e91a63cab4a1
deleted: sha256:4e9913397e051a70593edc1662de159778ce1bf65132295639da0e119913b53f
deleted: sha256:3e54edb2fef4b1c1393a2928bfa1017c22cc578f5f3eef677580662e8d2e79ea
---
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap (line 72) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,RandomState>::new (line 264) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,RandomState>::with_capacity (line 283) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,RandomState>::from (line 1503) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::capacity (line 445) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::clear (line 819) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::contains_key (line 1220) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::drain (line 721) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::entry (line 959) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::get (line 987) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::extract_if (line 761) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::get_disjoint_mut (line 1077) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::get_disjoint_mut (line 1119) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::hasher (line 837) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::get_key_value (line 1017) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::get_disjoint_unchecked_mut (line 1162) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::get_mut (line 1247) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::insert (line 1280) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::into_iter (line 2052) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::into_keys (line 491) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::into_values (line 586) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::is_empty (line 698) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::iter (line 618) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::keys (line 461) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::iter_mut (line 648) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::len (line 681) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::remove (line 1339) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::reserve (line 870) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::remove_entry (line 1367) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::retain (line 792) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::shrink_to (line 937) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::shrink_to_fit (line 913) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::try_insert (line 1309) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::try_reserve (line 895) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::values (line 523) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S,A>::values_mut (line 552) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S>::with_capacity_and_hasher (line 383) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::HashMap<K,V,S>::with_hasher (line 351) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::IntoKeys (line 1842) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::IntoIter (line 1610) ... ok
test library/std/src/collections/hash/map.rs - collections::hash::map::IntoValues (line 1876) ... ok
---
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,RandomState>::new (line 142) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,RandomState>::with_capacity (line 161) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::capacity (line 313) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,RandomState>::from (line 1180) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::clear (line 490) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::contains (line 758) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::drain (line 398) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::difference (line 630) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::entry (line 861) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::extract_if (line 434) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::get (line 783) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::get_or_insert (line 805) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::hasher (line 508) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::get_or_insert_with (line 829) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::insert (line 983) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::into_iter (line 1642) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::is_disjoint (line 903) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::intersection (line 697) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::is_empty (line 375) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::iter (line 329) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::is_subset (line 929) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::is_superset (line 951) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::len (line 357) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::reserve (line 541) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::remove (line 1030) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::replace (line 1004) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::retain (line 465) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::shrink_to (line 607) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::shrink_to_fit (line 584) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::symmetric_difference (line 660) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::take (line 1058) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::try_reserve (line 567) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S,A>::union (line 726) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S>::with_capacity_and_hasher (line 255) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::HashSet<T,S>::with_hasher (line 223) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::Intersection (line 1506) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::Iter (line 1391) ... ok
test library/std/src/collections/hash/set.rs - collections::hash::set::IntoIter (line 1421) ... ok

[asder8215]

I'm not sure if the pr-check-2 is a fault of this PR because the error output isn't related to the change I'm making.