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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

use diem_crypto::HashValue;

/// Swap template-type values if 'cond'=true - useful to determine left/right parameters.
pub(crate) fn swap_if<T>(first: T, second: T, cond: bool) -> (T, T) {
    if cond {
        (second, first)
    } else {
        (first, second)
    }
}

/// Return the index of the first bit that is 1 at the given depth when updates are
/// lexicographically sorted.
pub(crate) fn partition<T>(updates: &[(HashValue, T)], depth: usize) -> usize {
    // Binary search for the cut-off point where the bit at this depth turns from 0 to 1.
    // TODO: with stable partition_point: updates.partition_point(|&u| !u.0.bit(depth));
    let (mut i, mut j) = (0, updates.len());
    // Find the first index that starts with bit 1.
    while i < j {
        let mid = i + (j - i) / 2;
        if updates[mid].0.bit(depth) {
            j = mid;
        } else {
            i = mid + 1;
        }
    }
    i
}

pub(crate) enum Either<A, B> {
    A(A),
    B(B),
}

impl<A, B> Either<A, B> {
    pub fn or(cond: bool, a: A, b: B) -> Self {
        if cond {
            Either::A(a)
        } else {
            Either::B(b)
        }
    }
}