wsi-rs 0.5.1

wsi-rs whole-slide image reader
Documentation 
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use crate::error::WsiError;

pub(crate) fn expect_exact_count<T>(
    values: Vec<T>,
    expected: usize,
    context: &'static str,
) -> Result<Vec<T>, WsiError> {
    if values.len() != expected {
        return Err(WsiError::BackendContract {
            context,
            expected,
            actual: values.len(),
        });
    }
    Ok(values)
}

pub(crate) fn exactly_one<T>(values: Vec<T>, context: &'static str) -> Result<T, WsiError> {
    let mut values = expect_exact_count(values, 1, context)?;
    Ok(values.pop().expect("length checked above"))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn exactly_one_accepts_one_and_rejects_other_cardinalities() {
        assert_eq!(exactly_one(vec![7], "test").expect("one item"), 7);
        for values in [Vec::<u8>::new(), vec![1, 2]] {
            assert!(matches!(
                exactly_one(values, "test"),
                Err(WsiError::BackendContract { .. })
            ));
        }
    }
}