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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014-2023 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
//
//===----------------------------------------------------------------------===//
// Default implementations for common Collection requirements, adapted from the stdlib.
// FIXME: The stdlib should expose these as callable entry points.
extension Collection {
@_alwaysEmitIntoClient
internal var _defaultCount: Int {
distance(from: startIndex, to: endIndex)
}
@_alwaysEmitIntoClient
internal func _defaultDistanceForward(from start: Index, to end: Index) -> Int {
precondition(start <= end,
"Only BidirectionalCollections can have end come before start")
var start = start
var count = 0
while start != end {
count = count + 1
formIndex(after: &start)
}
return count
}
@_alwaysEmitIntoClient
internal func _defaultAdvanceForward(_ i: Index, by n: Int) -> Index {
precondition(n >= 0,
"Only BidirectionalCollections can be advanced by a negative amount")
var i = i
for _ in stride(from: 0, to: n, by: 1) {
formIndex(after: &i)
}
return i
}
@_alwaysEmitIntoClient
internal func _defaultAdvanceForward(
_ i: Index, by n: Int, limitedBy limit: Index
) -> Index? {
precondition(n >= 0,
"Only BidirectionalCollections can be advanced by a negative amount")
var i = i
for _ in stride(from: 0, to: n, by: 1) {
if i == limit {
return nil
}
formIndex(after: &i)
}
return i
}
}
extension BidirectionalCollection {
@_alwaysEmitIntoClient
internal func _defaultDistance(from start: Index, to end: Index) -> Int {
var start = start
var count = 0
if start < end {
while start != end {
count += 1
formIndex(after: &start)
}
}
else if start > end {
while start != end {
count -= 1
formIndex(before: &start)
}
}
return count
}
@_alwaysEmitIntoClient
internal func _defaultIndex(_ i: Index, offsetBy distance: Int) -> Index {
if distance >= 0 {
return _defaultAdvanceForward(i, by: distance)
}
var i = i
for _ in stride(from: 0, to: distance, by: -1) {
formIndex(before: &i)
}
return i
}
@_alwaysEmitIntoClient
internal func _defaultIndex(
_ i: Index, offsetBy distance: Int, limitedBy limit: Index
) -> Index? {
if distance >= 0 {
return _defaultAdvanceForward(i, by: distance, limitedBy: limit)
}
var i = i
for _ in stride(from: 0, to: distance, by: -1) {
if i == limit {
return nil
}
formIndex(before: &i)
}
return i
}
}
@inline(__always)
internal func _specializingCast<Input, Output>(_ value: Input, to type: Output.Type) -> Output? {
guard Input.self == Output.self else { return nil }
return _identityCast(value, to: type)
}
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