windows file format device independent bitmap dib / bmp decoding and encoding
Diffstat (limited to 'src/until.rs')
| -rw-r--r-- | src/until.rs | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/src/until.rs b/src/until.rs new file mode 100644 index 0000000..45f2491 --- /dev/null +++ b/src/until.rs @@ -0,0 +1,42 @@ +//! “Lifted” from itertools +pub struct UntilDone<'a, I, E: 'a> { + error: &'a mut Result<(), E>, + iter: I, +} + +impl<'a, I, T, E> Iterator for UntilDone<'a, I, E> +where + I: Iterator<Item = Result<T, E>>, +{ + type Item = T; + + fn next(&mut self) -> Option<Self::Item> { + match self.iter.next() { + Some(Ok(x)) => Some(x), + Some(Err(e)) => { + *self.error = Err(e); + None + } + None => None, + } + } +} + +pub trait Until<T> { + /// “Lift” a function of the values of an iterator so that it can process + /// an iterator of `Result` values instead. + fn until_done<E, R>(self, f: impl FnOnce(UntilDone<Self, E>) -> R) -> Result<R, E>; +} + +impl<T, I: Iterator<Item = T>> Until<T> for I { + fn until_done<E, R>(self, f: impl FnOnce(UntilDone<Self, E>) -> R) -> Result<R, E> { + let mut error = Ok(()); + + let result = f(UntilDone { + error: &mut error, + iter: self, + }); + + error.map(|_| result) + } +} |