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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
internal extension RangeExpression {
func clampedLowerAndUpperBounds(_ boundary: Range<Int>) -> (lower: Int?, upper: Int?) {
var lower: Int?
var upper: Int?
switch self {
case let self as Range<Int>:
let clamped = self.clamped(to: boundary)
lower = clamped.lowerBound
upper = clamped.upperBound
case let self as ClosedRange<Int>:
let clamped = self.clamped(to: ClosedRange(boundary))
lower = clamped.lowerBound
upper = clamped.upperBound
case let self as PartialRangeFrom<Int>:
lower = max(self.lowerBound, boundary.lowerBound)
upper = nil
case let self as PartialRangeThrough<Int>:
lower = nil
upper = min(self.upperBound, boundary.upperBound)
case let self as PartialRangeUpTo<Int>:
lower = nil
let (val, overflow) = self.upperBound.subtractingReportingOverflow(1)
if overflow { // So small that we have no choice but treating self as PartialRangeThrough
upper = min(self.upperBound, boundary.upperBound)
} else {
upper = min(val, boundary.upperBound)
}
default:
lower = nil
upper = nil
}
if lower != nil {
lower = min(lower!, boundary.upperBound)
}
if upper != nil {
upper = max(upper!, boundary.lowerBound)
}
return (lower: lower, upper: upper)
}
}
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