use crate::{error::*, flag::*};
use core::{cmp, convert::TryFrom};
pub fn calc_seek_offset_usize(
cur_offset: usize,
pos: isize,
whence: usize,
buf_len: usize,
) -> Result<isize> {
let cur_offset = isize::try_from(cur_offset).or_else(|_| Err(Error::new(EOVERFLOW)))?;
let buf_len = isize::try_from(buf_len).or_else(|_| Err(Error::new(EOVERFLOW)))?;
calc_seek_offset_isize(cur_offset, pos, whence, buf_len)
}
pub fn calc_seek_offset_isize(
cur_offset: isize,
pos: isize,
whence: usize,
buf_len: isize,
) -> Result<isize> {
let new_offset = match whence {
SEEK_CUR => pos.checked_add(cur_offset),
SEEK_END => pos.checked_add(buf_len),
SEEK_SET => Some(pos),
_ => None,
};
match new_offset {
Some(new_offset) if new_offset < 0 => Err(Error::new(EINVAL)),
Some(new_offset) => Ok(cmp::min(new_offset, buf_len)),
None => Err(Error::new(EOVERFLOW)),
}
}