io_fill_buf.rs - mozsearch

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#![warn(rust_2018_idioms)]

#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi does not support file operations

use tempfile::NamedTempFile;

use tokio::fs::File;

use tokio::io::{AsyncBufReadExt, BufReader};

use tokio_test::assert_ok;

#[tokio::test]

async fn fill_buf_file() {

    let file = NamedTempFile::new().unwrap();

    assert_ok!(std::fs::write(file.path(), b"hello"));

    let file = assert_ok!(File::open(file.path()).await);

    let mut file = BufReader::new(file);

    let mut contents = Vec::new();

    loop {

        let consumed = {

            let buffer = assert_ok!(file.fill_buf().await);

            if buffer.is_empty() {

                break;

            contents.extend_from_slice(buffer);

            buffer.len()

};

        file.consume(consumed);

    assert_eq!(contents, b"hello");