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Remove unnecessary RefCell from FileSource #4157

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Remove unnecessary RefCell from FileSource #4157

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16 changes: 7 additions & 9 deletions parquet/src/util/io.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@
// specific language governing permissions and limitations
// under the License.

use std::{cell::RefCell, cmp, fmt, io::*};
use std::{cmp, fmt, io::*};

use crate::file::reader::Length;

Expand Down Expand Up @@ -47,7 +47,7 @@ impl<T: Read + Seek + Length + TryClone> ParquetReader for T {}
///
/// Designed after `arrow::io::RandomAccessFile` and `std::io::BufReader`
pub struct FileSource<R: ParquetReader> {
reader: RefCell<R>,
reader: R,
start: u64, // start position in a file
end: u64, // end position in a file
buf: Vec<u8>, // buffer where bytes read in advance are stored
Expand All @@ -71,7 +71,7 @@ impl<R: ParquetReader> fmt::Debug for FileSource<R> {
impl<R: ParquetReader> FileSource<R> {
/// Creates new file reader with start and length from a file handle
pub fn new(fd: &R, start: u64, length: usize) -> Self {
let reader = RefCell::new(fd.try_clone().unwrap());
let reader = fd.try_clone().unwrap();
Self {
reader,
start,
Expand All @@ -89,9 +89,8 @@ impl<R: ParquetReader> FileSource<R> {
// Branch using `>=` instead of the more correct `==`
// to tell the compiler that the pos..cap slice is always valid.
debug_assert!(self.buf_pos == self.buf_cap);
let mut reader = self.reader.borrow_mut();
reader.seek(SeekFrom::Start(self.start))?; // always seek to start before reading
self.buf_cap = reader.read(&mut self.buf)?;
self.reader.seek(SeekFrom::Start(self.start))?; // always seek to start before reading
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@tustvold tustvold Apr 28, 2023 •
edited
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This is technically still racy because cloned file descriptor share a seek position, but the refcell wasn't helping prevent this

self.buf_cap = self.reader.read(&mut self.buf)?;
self.buf_pos = 0;
}
Ok(&self.buf[self.buf_pos..self.buf_cap])
Expand All @@ -102,9 +101,8 @@ impl<R: ParquetReader> FileSource<R> {
self.buf_pos = 0;
self.buf_cap = 0;
// read directly into param buffer
let mut reader = self.reader.borrow_mut();
reader.seek(SeekFrom::Start(self.start))?; // always seek to start before reading
let nread = reader.read(buf)?;
self.reader.seek(SeekFrom::Start(self.start))?; // always seek to start before reading
let nread = self.reader.read(buf)?;
self.start += nread as u64;
Ok(nread)
}
Expand Down