// Sources/SwiftProtobuf/MathUtils.swift - Generally useful mathematical functions

//

// Copyright (c) 2014 - 2017 Apple Inc. and the project authors

// Licensed under Apache License v2.0 with Runtime Library Exception

//

// See LICENSE.txt for license information:

// https://github.com/apple/swift-protobuf/blob/main/LICENSE.txt

//

// -----------------------------------------------------------------------------

///

/// Generally useful mathematical and arithmetic functions.

///

// -----------------------------------------------------------------------------

#if canImport(FoundationEssentials)

import FoundationEssentials

#else

import Foundation

#endif

/// Remainder in standard modular arithmetic (modulo). This coincides with (%)

/// when a > 0.

///

/// - Parameters:

///   - a: The dividend. Can be positive, 0 or negative.

///   - b: The divisor. This must be positive, and is an error if 0 or negative.

/// - Returns: The unique value r such that 0 <= r < b and b * q + r = a for some q.

internal func mod<T: SignedInteger>(_ a: T, _ b: T) -> T {

    assert(b > 0)

    let r = a % b

    return r >= 0 ? r : r + b

}

/// Quotient in standard modular arithmetic (Euclidean division). This coincides

/// with (/) when a > 0.

///

/// - Parameters:

///   - a: The dividend. Can be positive, 0 or negative.

///   - b: The divisor. This must be positive, and is an error if 0 or negative.

/// - Returns: The unique value q such that for some 0 <= r < b, b * q + r = a.

internal func div<T: SignedInteger>(_ a: T, _ b: T) -> T {

    assert(b > 0)

    return a >= 0 ? a / b : (a + 1) / b - 1

}