Graham MacDonald
33 lines
1.4 KiB
Rust
33 lines
1.4 KiB
Rust
use core::cmp;
|
|
use core::convert::TryFrom;
|
|
use crate::error::*;
|
|
use crate::flag::*;
|
|
|
|
/// Helper for seek calls
|
|
/// In most cases it's easier to use a usize to track the offset and buffer size internally,
|
|
/// but the seek interface uses isize. This wrapper ensures EOVERFLOW errors are returned
|
|
/// as appropriate if the value in the usize can't fit in the isize.
|
|
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)
|
|
}
|
|
|
|
/// Helper for seek calls
|
|
/// Result is guaranteed to be positive.
|
|
/// EOVERFLOW returned if the arguments would cause an overflow.
|
|
/// EINVAL returned if the new offset is out of bounds.
|
|
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))
|
|
}
|
|
} |