cranpose-core 0.9.11

Composition runtime and reactive state for Cranpose
Documentation 
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#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub(in crate::slot) enum CheckedU32Delta {
    Add(u32),
    Sub(u32),
}

impl CheckedU32Delta {
    #[inline]
    pub(in crate::slot) fn from_i64(delta: i64, field: &'static str) -> Self {
        if delta >= 0 {
            Self::Add(
                u32::try_from(delta).unwrap_or_else(|_| panic_u32_delta_out_of_range(field, delta)),
            )
        } else {
            Self::Sub(
                u32::try_from(delta.unsigned_abs())
                    .unwrap_or_else(|_| panic_u32_delta_out_of_range(field, delta)),
            )
        }
    }

    #[inline]
    fn as_i64(self) -> i64 {
        match self {
            Self::Add(delta) => i64::from(delta),
            Self::Sub(delta) => -i64::from(delta),
        }
    }
}

#[inline]
pub(crate) fn checked_usize_to_u32(value: usize, field: &'static str) -> u32 {
    u32::try_from(value).unwrap_or_else(|_| panic_usize_out_of_range(field, "u32 storage", value))
}

#[inline]
pub(in crate::slot) fn checked_usize_to_i64(value: usize, field: &'static str) -> i64 {
    i64::try_from(value)
        .unwrap_or_else(|_| panic_usize_out_of_range(field, "i64 mutation delta", value))
}

#[cold]
#[inline(never)]
fn panic_usize_out_of_range(field: &'static str, limit: &'static str, value: usize) -> ! {
    panic!("{field} exceeds {limit} limit: {value}");
}

#[inline]
pub(in crate::slot) fn checked_u32_delta(
    value: u32,
    delta: CheckedU32Delta,
    min: u32,
    field: &'static str,
) -> u32 {
    if let Some(updated) = try_checked_u32_delta(value, delta, min) {
        return updated;
    }
    match delta {
        CheckedU32Delta::Add(delta) => {
            value
                .checked_add(delta)
                .unwrap_or_else(|| panic_u32_delta_overflow(field, value, delta));
        }
        CheckedU32Delta::Sub(delta) => {
            value
                .checked_sub(delta)
                .unwrap_or_else(|| panic_u32_delta_below_min(field, value, -i64::from(delta), min));
        }
    }
    panic_u32_delta_below_min(field, value, delta.as_i64(), min);
}

#[inline]
fn try_checked_u32_delta(value: u32, delta: CheckedU32Delta, min: u32) -> Option<u32> {
    let updated = match delta {
        CheckedU32Delta::Add(delta) => value.checked_add(delta)?,
        CheckedU32Delta::Sub(delta) => value.checked_sub(delta)?,
    };
    (updated >= min).then_some(updated)
}

#[cold]
#[inline(never)]
fn panic_u32_delta_out_of_range(field: &'static str, delta: i64) -> ! {
    panic!("{field} delta exceeds u32 storage limit: {delta}");
}

/// Shifts every value by `delta`, as [`checked_u32_delta`] shifts one, with
/// one check after the walk where that checks each value.
pub(in crate::slot) fn shift_u32_values<'a>(
    values: impl Iterator<Item = &'a mut u32>,
    delta: CheckedU32Delta,
    field: &'static str,
) {
    let overflowed = match delta {
        CheckedU32Delta::Add(delta) => values.fold(false, |overflowed, value| {
            let (shifted, overflow) = value.overflowing_add(delta);
            *value = shifted;
            overflowed | overflow
        }),
        CheckedU32Delta::Sub(delta) => values.fold(false, |overflowed, value| {
            let (shifted, overflow) = value.overflowing_sub(delta);
            *value = shifted;
            overflowed | overflow
        }),
    };
    if overflowed {
        panic_u32_shift_overflow(field, delta);
    }
}

#[cold]
#[inline(never)]
fn panic_u32_shift_overflow(field: &'static str, delta: CheckedU32Delta) -> ! {
    panic!("{field} shift by {delta:?} left the u32 range");
}

#[cold]
#[inline(never)]
fn panic_u32_delta_overflow(field: &'static str, value: u32, delta: u32) -> ! {
    panic!("{field} mutation overflow: {value} + {delta}");
}

#[cold]
#[inline(never)]
fn panic_u32_delta_below_min(
    field: &'static str,
    value: u32,
    delta: impl Into<i64>,
    min: u32,
) -> ! {
    let delta = delta.into();
    panic!("{field} cannot become smaller than {min}: {value} + {delta}");
}

#[cfg(test)]
#[path = "tests/checked_tests.rs"]
mod tests;