Function read_to_string_at

src/fs/file_io_ext.rs:1058–1076

(file: &std::fs::File, buf: &mut String, offset: u64)

}

fn read_to_string_at(file: &std::fs::File, buf: &mut String, offset: u64) -> io::Result<usize> {
    let len = match file.metadata()?.len().checked_sub(offset) {
        None => return Ok(0),
        Some(len) => len,
    };

    // This temporary buffer is theoretically unnecessary, but eliminating it
    // currently involves a bunch of `unsafe`.
    let mut tmp = vec![0_u8; len.try_into().unwrap_or(usize::MAX)];
    FileIoExt::read_exact_at(file, &mut tmp, offset)?;
    let s = String::from_utf8(tmp).map_err(|_| {
        io::Error::new(
            io::ErrorKind::InvalidData,
            "stream did not contain valid UTF-8",
        )
    })?;
    buf.push_str(&s);
    Ok(len as usize)
}

fn _file_io_ext_can_be_trait_object(_: &dyn FileIoExt) {}