[Rust] Implement Length and TryClone traits for Cursor<Vec<u8>> in reader.rs

[asfimport]

Currently Length and TryClone are implemented for Cursor<&'a [u8]> in src/file/reader.rs

Attempting to create a cursor from a Vec...

fn test_cursor_and_file_has_the_same_behaviour() {
  let mut buf: Vec<u8> = Vec::new();        
  get_test_file("alltypes_plain.parquet")            
    .read_to_end(&mut buf)            
    .unwrap();        
  let cursor = Cursor::new(buf.as_slice());
...

 

results in:

`buf` does not live long enough

borrowed value does not live long enough 
rustc(E0597)
reader.rs(681, 34): borrowed value does not live long enough
reader.rs(681, 34): argument requires that `buf` is borrowed for `'static`
reader.rs(691, 5): `buf` dropped here while still borrowed

 

Implementing Length and TryClone for Cursor<Vec> would allow for:

fn test_cursor_and_file_has_the_same_behaviour() {        
  let mut buf: Vec<u8> = Vec::new();        
  get_test_file("alltypes_plain.parquet")            
    .read_to_end(&mut buf)            
    .unwrap();        
  let cursor = Cursor::new(buf);
  let read_from_cursor = SerializedFileReader::new(cursor).unwrap();
...

Otherwise, buf: Vec must be declared static in order to initialize a SerializedFileReader from a Cursor.

I'm new to rust so perhaps this is the intended behavior, but if not I'm happy to submit a PR for this

 

Reporter: David Kegley / @dbkegley

PRs and other links:

• GitHub Pull Request #6376

_{Note: This issue was originally created as ARROW-7768. Please see the migration documentation for further details.}

[asfimport]

Chao Sun / @sunchao:
Issue resolved by pull request 6376
#6376