Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
2101 lines (1965 sloc) 72.4 KB
//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 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
//
//===----------------------------------------------------------------------===//
// Implementation notes
// ====================
//
// `Dictionary` uses two storage schemes: native storage and Cocoa storage.
//
// Native storage is a hash table with open addressing and linear probing. The
// bucket array forms a logical ring (e.g., a chain can wrap around the end of
// buckets array to the beginning of it).
//
// The logical bucket array is implemented as three arrays: Key, Value, and a
// bitmap that marks valid entries. An unoccupied entry marks the end of a
// chain. There is always at least one unoccupied entry among the
// buckets. `Dictionary` does not use tombstones.
//
// In addition to the native storage, `Dictionary` can also wrap an
// `NSDictionary` in order to allow bridging `NSDictionary` to `Dictionary` in
// `O(1)`.
//
// Native dictionary storage uses a data structure like this::
//
// struct Dictionary<K,V>
// +------------------------------------------------+
// | enum Dictionary<K,V>._Variant |
// | +--------------------------------------------+ |
// | | [struct _NativeDictionary<K,V> | |
// | +---|----------------------------------------+ |
// +----/-------------------------------------------+
// /
// |
// V
// class __RawDictionaryStorage
// +-----------------------------------------------------------+
// | <isa> |
// | <refcount> |
// | _count |
// | _capacity |
// | _scale |
// | _age |
// | _seed |
// | _rawKeys |
// | _rawValue |
// | [inline bitset of occupied entries] |
// | [inline array of keys] |
// | [inline array of values] |
// +-----------------------------------------------------------+
//
// Cocoa storage uses a data structure like this:
//
// struct Dictionary<K,V>
// +----------------------------------------------+
// | enum Dictionary<K,V>._Variant |
// | +----------------------------------------+ |
// | | [ struct __CocoaDictionary | |
// | +---|------------------------------------+ |
// +----/-----------------------------------------+
// /
// |
// V
// class NSDictionary
// +--------------+
// | [refcount#1] |
// | etc. |
// +--------------+
// ^
// |
// \ struct __CocoaDictionary.Index
// +--|------------------------------------+
// | * base: __CocoaDictionary |
// | allKeys: array of all keys |
// | currentKeyIndex: index into allKeys |
// +---------------------------------------+
//
//
// The Native Kinds of Storage
// ---------------------------
//
// The native backing store is represented by three different classes:
// * `__RawDictionaryStorage`
// * `__EmptyDictionarySingleton` (extends Raw)
// * `_DictionaryStorage<K: Hashable, V>` (extends Raw)
//
// (Hereafter `Raw`, `Empty`, and `Storage`, respectively)
//
// In a less optimized implementation, `Raw` and `Empty` could be eliminated, as
// they exist only to provide special-case behaviors.
//
// `Empty` is the a type-punned empty singleton storage. Its single instance is
// created by the runtime during process startup. Because we use the same
// instance for all empty dictionaries, it cannot declare type parameters.
//
// `Storage` provides backing storage for regular native dictionaries. All
// non-empty native dictionaries use an instance of `Storage` to store their
// elements. `Storage` is a generic class with a nontrivial deinit.
//
// `Raw` is the base class for both `Empty` and `Storage`. It defines a full set
// of ivars to access dictionary contents. Like `Empty`, `Raw` is also
// non-generic; the base addresses it stores are represented by untyped raw
// pointers. The only reason `Raw` exists is to allow `_NativeDictionary` to
// treat `Empty` and `Storage` in a unified way.
//
// Storage classes don't contain much logic; `Raw` in particular is just a
// collection of ivars. `Storage` provides allocation/deinitialization logic,
// while `Empty`/`Storage` implement NSDictionary methods. All other operations
// are actually implemented by the `_NativeDictionary` and `_HashTable` structs.
//
// The `_HashTable` struct provides low-level hash table metadata operations.
// (Lookups, iteration, insertion, removal.) It owns and maintains the
// tail-allocated bitmap.
//
// `_NativeDictionary` implements the actual Dictionary operations. It
// consists of a reference to a `Raw` instance, to allow for the possibility of
// the empty singleton.
//
//
// Index Invalidation
// ------------------
//
// FIXME: decide if this guarantee is worth making, as it restricts
// collision resolution to first-come-first-serve. The most obvious alternative
// would be robin hood hashing. The Rust code base is the best
// resource on a *practical* implementation of robin hood hashing I know of:
// https://github.com/rust-lang/rust/blob/ac919fcd9d4a958baf99b2f2ed5c3d38a2ebf9d0/src/libstd/collections/hash/map.rs#L70-L178
//
// Indexing a container, `c[i]`, uses the integral offset stored in the index
// to access the elements referenced by the container. Generally, an index into
// one container has no meaning for another. However copy-on-write currently
// preserves indices under insertion, as long as reallocation doesn't occur:
//
// var (i, found) = d.find(k) // i is associated with d's storage
// if found {
// var e = d // now d is sharing its data with e
// e[newKey] = newValue // e now has a unique copy of the data
// return e[i] // use i to access e
// }
//
// The result should be a set of iterator invalidation rules familiar to anyone
// familiar with the C++ standard library. Note that because all accesses to a
// dictionary storage are bounds-checked, this scheme never compromises memory
// safety.
//
// As a safeguard against using invalid indices, Set and Dictionary maintain a
// mutation counter in their storage header (`_age`). This counter gets bumped
// every time an element is removed and whenever the contents are
// rehashed. Native indices include a copy of this counter so that index
// validation can verify it matches with current storage. This can't catch all
// misuse, because counters may match by accident; but it does make indexing a
// lot more reliable.
//
// Bridging
// ========
//
// Bridging `NSDictionary` to `Dictionary`
// ---------------------------------------
//
// FIXME(eager-bridging): rewrite this based on modern constraints.
//
// `NSDictionary` bridges to `Dictionary<NSObject, AnyObject>` in `O(1)`,
// without memory allocation.
//
// Bridging to `Dictionary<AnyHashable, AnyObject>` takes `O(n)` time, as the
// keys need to be fully rehashed after conversion to `AnyHashable`.
//
// Bridging `NSDictionary` to `Dictionary<Key, Value>` is O(1) if both Key and
// Value are bridged verbatim.
//
// Bridging `Dictionary` to `NSDictionary`
// ---------------------------------------
//
// `Dictionary<K, V>` bridges to `NSDictionary` in O(1)
// but may incur an allocation depending on the following conditions:
//
// * If the Dictionary is freshly allocated without any elements, then it
// contains the empty singleton Storage which is returned as a toll-free
// implementation of `NSDictionary`.
//
// * If both `K` and `V` are bridged verbatim, then `Dictionary<K, V>` is
// still toll-free bridged to `NSDictionary` by returning its Storage.
//
// * If the Dictionary is actually a lazily bridged NSDictionary, then that
// NSDictionary is returned.
//
// * Otherwise, bridging the `Dictionary` is done by wrapping it in a
// `_SwiftDeferredNSDictionary<K, V>`. This incurs an O(1)-sized allocation.
//
// Complete bridging of the native Storage's elements to another Storage
// is performed on first access. This is O(n) work, but is hopefully amortized
// by future accesses.
//
// This design ensures that:
// - Every time keys or values are accessed on the bridged `NSDictionary`,
// new objects are not created.
// - Accessing the same element (key or value) multiple times will return
// the same pointer.
//
// Bridging `NSSet` to `Set` and vice versa
// ----------------------------------------
//
// Bridging guarantees for `Set<Element>` are the same as for
// `Dictionary<Element, NSObject>`.
//
/// A collection whose elements are key-value pairs.
///
/// A dictionary is a type of hash table, providing fast access to the entries
/// it contains. Each entry in the table is identified using its key, which is
/// a hashable type such as a string or number. You use that key to retrieve
/// the corresponding value, which can be any object. In other languages,
/// similar data types are known as hashes or associated arrays.
///
/// Create a new dictionary by using a dictionary literal. A dictionary literal
/// is a comma-separated list of key-value pairs, in which a colon separates
/// each key from its associated value, surrounded by square brackets. You can
/// assign a dictionary literal to a variable or constant or pass it to a
/// function that expects a dictionary.
///
/// Here's how you would create a dictionary of HTTP response codes and their
/// related messages:
///
/// var responseMessages = [200: "OK",
/// 403: "Access forbidden",
/// 404: "File not found",
/// 500: "Internal server error"]
///
/// The `responseMessages` variable is inferred to have type `[Int: String]`.
/// The `Key` type of the dictionary is `Int`, and the `Value` type of the
/// dictionary is `String`.
///
/// To create a dictionary with no key-value pairs, use an empty dictionary
/// literal (`[:]`).
///
/// var emptyDict: [String: String] = [:]
///
/// Any type that conforms to the `Hashable` protocol can be used as a
/// dictionary's `Key` type, including all of Swift's basic types. You can use
/// your own custom types as dictionary keys by making them conform to the
/// `Hashable` protocol.
///
/// Getting and Setting Dictionary Values
/// =====================================
///
/// The most common way to access values in a dictionary is to use a key as a
/// subscript. Subscripting with a key takes the following form:
///
/// print(responseMessages[200])
/// // Prints "Optional("OK")"
///
/// Subscripting a dictionary with a key returns an optional value, because a
/// dictionary might not hold a value for the key that you use in the
/// subscript.
///
/// The next example uses key-based subscripting of the `responseMessages`
/// dictionary with two keys that exist in the dictionary and one that does
/// not.
///
/// let httpResponseCodes = [200, 403, 301]
/// for code in httpResponseCodes {
/// if let message = responseMessages[code] {
/// print("Response \(code): \(message)")
/// } else {
/// print("Unknown response \(code)")
/// }
/// }
/// // Prints "Response 200: OK"
/// // Prints "Response 403: Access Forbidden"
/// // Prints "Unknown response 301"
///
/// You can also update, modify, or remove keys and values from a dictionary
/// using the key-based subscript. To add a new key-value pair, assign a value
/// to a key that isn't yet a part of the dictionary.
///
/// responseMessages[301] = "Moved permanently"
/// print(responseMessages[301])
/// // Prints "Optional("Moved permanently")"
///
/// Update an existing value by assigning a new value to a key that already
/// exists in the dictionary. If you assign `nil` to an existing key, the key
/// and its associated value are removed. The following example updates the
/// value for the `404` code to be simply "Not found" and removes the
/// key-value pair for the `500` code entirely.
///
/// responseMessages[404] = "Not found"
/// responseMessages[500] = nil
/// print(responseMessages)
/// // Prints "[301: "Moved permanently", 200: "OK", 403: "Access forbidden", 404: "Not found"]"
///
/// In a mutable `Dictionary` instance, you can modify in place a value that
/// you've accessed through a keyed subscript. The code sample below declares a
/// dictionary called `interestingNumbers` with string keys and values that
/// are integer arrays, then sorts each array in-place in descending order.
///
/// var interestingNumbers = ["primes": [2, 3, 5, 7, 11, 13, 17],
/// "triangular": [1, 3, 6, 10, 15, 21, 28],
/// "hexagonal": [1, 6, 15, 28, 45, 66, 91]]
/// for key in interestingNumbers.keys {
/// interestingNumbers[key]?.sort(by: >)
/// }
///
/// print(interestingNumbers["primes"]!)
/// // Prints "[17, 13, 11, 7, 5, 3, 2]"
///
/// Iterating Over the Contents of a Dictionary
/// ===========================================
///
/// Every dictionary is an unordered collection of key-value pairs. You can
/// iterate over a dictionary using a `for`-`in` loop, decomposing each
/// key-value pair into the elements of a tuple.
///
/// let imagePaths = ["star": "/glyphs/star.png",
/// "portrait": "/images/content/portrait.jpg",
/// "spacer": "/images/shared/spacer.gif"]
///
/// for (name, path) in imagePaths {
/// print("The path to '\(name)' is '\(path)'.")
/// }
/// // Prints "The path to 'star' is '/glyphs/star.png'."
/// // Prints "The path to 'portrait' is '/images/content/portrait.jpg'."
/// // Prints "The path to 'spacer' is '/images/shared/spacer.gif'."
///
/// The order of key-value pairs in a dictionary is stable between mutations
/// but is otherwise unpredictable. If you need an ordered collection of
/// key-value pairs and don't need the fast key lookup that `Dictionary`
/// provides, see the `KeyValuePairs` type for an alternative.
///
/// You can search a dictionary's contents for a particular value using the
/// `contains(where:)` or `firstIndex(where:)` methods supplied by default
/// implementation. The following example checks to see if `imagePaths` contains
/// any paths in the `"/glyphs"` directory:
///
/// let glyphIndex = imagePaths.firstIndex(where: { $0.value.hasPrefix("/glyphs") })
/// if let index = glyphIndex {
/// print("The '\(imagePaths[index].key)' image is a glyph.")
/// } else {
/// print("No glyphs found!")
/// }
/// // Prints "The 'star' image is a glyph.")
///
/// Note that in this example, `imagePaths` is subscripted using a dictionary
/// index. Unlike the key-based subscript, the index-based subscript returns
/// the corresponding key-value pair as a non-optional tuple.
///
/// print(imagePaths[glyphIndex!])
/// // Prints "("star", "/glyphs/star.png")"
///
/// A dictionary's indices stay valid across additions to the dictionary as
/// long as the dictionary has enough capacity to store the added values
/// without allocating more buffer. When a dictionary outgrows its buffer,
/// existing indices may be invalidated without any notification.
///
/// When you know how many new values you're adding to a dictionary, use the
/// `init(minimumCapacity:)` initializer to allocate the correct amount of
/// buffer.
///
/// Bridging Between Dictionary and NSDictionary
/// ============================================
///
/// You can bridge between `Dictionary` and `NSDictionary` using the `as`
/// operator. For bridging to be possible, the `Key` and `Value` types of a
/// dictionary must be classes, `@objc` protocols, or types that bridge to
/// Foundation types.
///
/// Bridging from `Dictionary` to `NSDictionary` always takes O(1) time and
/// space. When the dictionary's `Key` and `Value` types are neither classes
/// nor `@objc` protocols, any required bridging of elements occurs at the
/// first access of each element. For this reason, the first operation that
/// uses the contents of the dictionary may take O(*n*).
///
/// Bridging from `NSDictionary` to `Dictionary` first calls the `copy(with:)`
/// method (`- copyWithZone:` in Objective-C) on the dictionary to get an
/// immutable copy and then performs additional Swift bookkeeping work that
/// takes O(1) time. For instances of `NSDictionary` that are already
/// immutable, `copy(with:)` usually returns the same dictionary in O(1) time;
/// otherwise, the copying performance is unspecified. The instances of
/// `NSDictionary` and `Dictionary` share buffer using the same copy-on-write
/// optimization that is used when two instances of `Dictionary` share
/// buffer.
@frozen
public struct Dictionary<Key: Hashable, Value> {
/// The element type of a dictionary: a tuple containing an individual
/// key-value pair.
public typealias Element = (key: Key, value: Value)
@usableFromInline
internal var _variant: _Variant
@inlinable
internal init(_native: __owned _NativeDictionary<Key, Value>) {
_variant = _Variant(native: _native)
}
#if _runtime(_ObjC)
@inlinable
internal init(_cocoa: __owned __CocoaDictionary) {
_variant = _Variant(cocoa: _cocoa)
}
/// Private initializer used for bridging.
///
/// Only use this initializer when both conditions are true:
///
/// * it is statically known that the given `NSDictionary` is immutable;
/// * `Key` and `Value` are bridged verbatim to Objective-C (i.e.,
/// are reference types).
@inlinable
public // SPI(Foundation)
init(_immutableCocoaDictionary: __owned AnyObject) {
_internalInvariant(
_isBridgedVerbatimToObjectiveC(Key.self) &&
_isBridgedVerbatimToObjectiveC(Value.self),
"""
Dictionary can be backed by NSDictionary buffer only when both Key \
and Value are bridged verbatim to Objective-C
""")
self.init(_cocoa: __CocoaDictionary(_immutableCocoaDictionary))
}
#endif
/// Creates an empty dictionary.
@inlinable
public init() {
self.init(_native: _NativeDictionary())
}
/// Creates an empty dictionary with preallocated space for at least the
/// specified number of elements.
///
/// Use this initializer to avoid intermediate reallocations of a dictionary's
/// storage buffer when you know how many key-value pairs you are adding to a
/// dictionary after creation.
///
/// - Parameter minimumCapacity: The minimum number of key-value pairs that
/// the newly created dictionary should be able to store without
/// reallocating its storage buffer.
public // FIXME(reserveCapacity): Should be inlinable
init(minimumCapacity: Int) {
_variant = _Variant(native: _NativeDictionary(capacity: minimumCapacity))
}
/// Creates a new dictionary from the key-value pairs in the given sequence.
///
/// You use this initializer to create a dictionary when you have a sequence
/// of key-value tuples with unique keys. Passing a sequence with duplicate
/// keys to this initializer results in a runtime error. If your
/// sequence might have duplicate keys, use the
/// `Dictionary(_:uniquingKeysWith:)` initializer instead.
///
/// The following example creates a new dictionary using an array of strings
/// as the keys and the integers in a countable range as the values:
///
/// let digitWords = ["one", "two", "three", "four", "five"]
/// let wordToValue = Dictionary(uniqueKeysWithValues: zip(digitWords, 1...5))
/// print(wordToValue["three"]!)
/// // Prints "3"
/// print(wordToValue)
/// // Prints "["three": 3, "four": 4, "five": 5, "one": 1, "two": 2]"
///
/// - Parameter keysAndValues: A sequence of key-value pairs to use for
/// the new dictionary. Every key in `keysAndValues` must be unique.
/// - Returns: A new dictionary initialized with the elements of
/// `keysAndValues`.
/// - Precondition: The sequence must not have duplicate keys.
@inlinable
public init<S: Sequence>(
uniqueKeysWithValues keysAndValues: __owned S
) where S.Element == (Key, Value) {
if let d = keysAndValues as? Dictionary<Key, Value> {
self = d
return
}
var native = _NativeDictionary<Key, Value>(
capacity: keysAndValues.underestimatedCount)
// '_MergeError.keyCollision' is caught and handled with an appropriate
// error message one level down, inside native.merge(_:...). We throw an
// error instead of calling fatalError() directly because we want the
// message to include the duplicate key, and the closure only has access to
// the conflicting values.
try! native.merge(
keysAndValues,
isUnique: true,
uniquingKeysWith: { _, _ in throw _MergeError.keyCollision })
self.init(_native: native)
}
/// Creates a new dictionary from the key-value pairs in the given sequence,
/// using a combining closure to determine the value for any duplicate keys.
///
/// You use this initializer to create a dictionary when you have a sequence
/// of key-value tuples that might have duplicate keys. As the dictionary is
/// built, the initializer calls the `combine` closure with the current and
/// new values for any duplicate keys. Pass a closure as `combine` that
/// returns the value to use in the resulting dictionary: The closure can
/// choose between the two values, combine them to produce a new value, or
/// even throw an error.
///
/// The following example shows how to choose the first and last values for
/// any duplicate keys:
///
/// let pairsWithDuplicateKeys = [("a", 1), ("b", 2), ("a", 3), ("b", 4)]
///
/// let firstValues = Dictionary(pairsWithDuplicateKeys,
/// uniquingKeysWith: { (first, _) in first })
/// // ["b": 2, "a": 1]
///
/// let lastValues = Dictionary(pairsWithDuplicateKeys,
/// uniquingKeysWith: { (_, last) in last })
/// // ["b": 4, "a": 3]
///
/// - Parameters:
/// - keysAndValues: A sequence of key-value pairs to use for the new
/// dictionary.
/// - combine: A closure that is called with the values for any duplicate
/// keys that are encountered. The closure returns the desired value for
/// the final dictionary.
@inlinable
public init<S: Sequence>(
_ keysAndValues: __owned S,
uniquingKeysWith combine: (Value, Value) throws -> Value
) rethrows where S.Element == (Key, Value) {
var native = _NativeDictionary<Key, Value>(
capacity: keysAndValues.underestimatedCount)
try native.merge(keysAndValues, isUnique: true, uniquingKeysWith: combine)
self.init(_native: native)
}
/// Creates a new dictionary whose keys are the groupings returned by the
/// given closure and whose values are arrays of the elements that returned
/// each key.
///
/// The arrays in the "values" position of the new dictionary each contain at
/// least one element, with the elements in the same order as the source
/// sequence.
///
/// The following example declares an array of names, and then creates a
/// dictionary from that array by grouping the names by first letter:
///
/// let students = ["Kofi", "Abena", "Efua", "Kweku", "Akosua"]
/// let studentsByLetter = Dictionary(grouping: students, by: { $0.first! })
/// // ["E": ["Efua"], "K": ["Kofi", "Kweku"], "A": ["Abena", "Akosua"]]
///
/// The new `studentsByLetter` dictionary has three entries, with students'
/// names grouped by the keys `"E"`, `"K"`, and `"A"`.
///
/// - Parameters:
/// - values: A sequence of values to group into a dictionary.
/// - keyForValue: A closure that returns a key for each element in
/// `values`.
@inlinable
public init<S: Sequence>(
grouping values: __owned S,
by keyForValue: (S.Element) throws -> Key
) rethrows where Value == [S.Element] {
try self.init(_native: _NativeDictionary(grouping: values, by: keyForValue))
}
}
//
// All APIs below should dispatch to `_variant`, without doing any
// additional processing.
//
extension Dictionary: Sequence {
/// Returns an iterator over the dictionary's key-value pairs.
///
/// Iterating over a dictionary yields the key-value pairs as two-element
/// tuples. You can decompose the tuple in a `for`-`in` loop, which calls
/// `makeIterator()` behind the scenes, or when calling the iterator's
/// `next()` method directly.
///
/// let hues = ["Heliotrope": 296, "Coral": 16, "Aquamarine": 156]
/// for (name, hueValue) in hues {
/// print("The hue of \(name) is \(hueValue).")
/// }
/// // Prints "The hue of Heliotrope is 296."
/// // Prints "The hue of Coral is 16."
/// // Prints "The hue of Aquamarine is 156."
///
/// - Returns: An iterator over the dictionary with elements of type
/// `(key: Key, value: Value)`.
@inlinable
@inline(__always)
public __consuming func makeIterator() -> Iterator {
return _variant.makeIterator()
}
}
// This is not quite Sequence.filter, because that returns [Element], not Self
extension Dictionary {
/// Returns a new dictionary containing the key-value pairs of the dictionary
/// that satisfy the given predicate.
///
/// - Parameter isIncluded: A closure that takes a key-value pair as its
/// argument and returns a Boolean value indicating whether the pair
/// should be included in the returned dictionary.
/// - Returns: A dictionary of the key-value pairs that `isIncluded` allows.
@inlinable
@available(swift, introduced: 4.0)
public __consuming func filter(
_ isIncluded: (Element) throws -> Bool
) rethrows -> [Key: Value] {
// FIXME(performance): Try building a bitset of elements to keep, so that we
// eliminate rehashings during insertion.
var result = _NativeDictionary<Key, Value>()
for element in self {
if try isIncluded(element) {
result.insertNew(key: element.key, value: element.value)
}
}
return Dictionary(_native: result)
}
}
extension Dictionary: Collection {
public typealias SubSequence = Slice<Dictionary>
/// The position of the first element in a nonempty dictionary.
///
/// If the collection is empty, `startIndex` is equal to `endIndex`.
///
/// - Complexity: Amortized O(1) if the dictionary does not wrap a bridged
/// `NSDictionary`. If the dictionary wraps a bridged `NSDictionary`, the
/// performance is unspecified.
@inlinable
public var startIndex: Index {
return _variant.startIndex
}
/// The dictionary's "past the end" position---that is, the position one
/// greater than the last valid subscript argument.
///
/// If the collection is empty, `endIndex` is equal to `startIndex`.
///
/// - Complexity: Amortized O(1) if the dictionary does not wrap a bridged
/// `NSDictionary`; otherwise, the performance is unspecified.
@inlinable
public var endIndex: Index {
return _variant.endIndex
}
@inlinable
public func index(after i: Index) -> Index {
return _variant.index(after: i)
}
@inlinable
public func formIndex(after i: inout Index) {
_variant.formIndex(after: &i)
}
/// Returns the index for the given key.
///
/// If the given key is found in the dictionary, this method returns an index
/// into the dictionary that corresponds with the key-value pair.
///
/// let countryCodes = ["BR": "Brazil", "GH": "Ghana", "JP": "Japan"]
/// let index = countryCodes.index(forKey: "JP")
///
/// print("Country code for \(countryCodes[index!].value): '\(countryCodes[index!].key)'.")
/// // Prints "Country code for Japan: 'JP'."
///
/// - Parameter key: The key to find in the dictionary.
/// - Returns: The index for `key` and its associated value if `key` is in
/// the dictionary; otherwise, `nil`.
@inlinable
@inline(__always)
public func index(forKey key: Key) -> Index? {
// Complexity: amortized O(1) for native dictionary, O(*n*) when wrapping an
// NSDictionary.
return _variant.index(forKey: key)
}
/// Accesses the key-value pair at the specified position.
///
/// This subscript takes an index into the dictionary, instead of a key, and
/// returns the corresponding key-value pair as a tuple. When performing
/// collection-based operations that return an index into a dictionary, use
/// this subscript with the resulting value.
///
/// For example, to find the key for a particular value in a dictionary, use
/// the `firstIndex(where:)` method.
///
/// let countryCodes = ["BR": "Brazil", "GH": "Ghana", "JP": "Japan"]
/// if let index = countryCodes.firstIndex(where: { $0.value == "Japan" }) {
/// print(countryCodes[index])
/// print("Japan's country code is '\(countryCodes[index].key)'.")
/// } else {
/// print("Didn't find 'Japan' as a value in the dictionary.")
/// }
/// // Prints "("JP", "Japan")"
/// // Prints "Japan's country code is 'JP'."
///
/// - Parameter position: The position of the key-value pair to access.
/// `position` must be a valid index of the dictionary and not equal to
/// `endIndex`.
/// - Returns: A two-element tuple with the key and value corresponding to
/// `position`.
@inlinable
public subscript(position: Index) -> Element {
return _variant.lookup(position)
}
/// The number of key-value pairs in the dictionary.
///
/// - Complexity: O(1).
@inlinable
public var count: Int {
return _variant.count
}
//
// `Sequence` conformance
//
/// A Boolean value that indicates whether the dictionary is empty.
///
/// Dictionaries are empty when created with an initializer or an empty
/// dictionary literal.
///
/// var frequencies: [String: Int] = [:]
/// print(frequencies.isEmpty)
/// // Prints "true"
@inlinable
public var isEmpty: Bool {
return count == 0
}
}
extension Dictionary {
/// Accesses the value associated with the given key for reading and writing.
///
/// This *key-based* subscript returns the value for the given key if the key
/// is found in the dictionary, or `nil` if the key is not found.
///
/// The following example creates a new dictionary and prints the value of a
/// key found in the dictionary (`"Coral"`) and a key not found in the
/// dictionary (`"Cerise"`).
///
/// var hues = ["Heliotrope": 296, "Coral": 16, "Aquamarine": 156]
/// print(hues["Coral"])
/// // Prints "Optional(16)"
/// print(hues["Cerise"])
/// // Prints "nil"
///
/// When you assign a value for a key and that key already exists, the
/// dictionary overwrites the existing value. If the dictionary doesn't
/// contain the key, the key and value are added as a new key-value pair.
///
/// Here, the value for the key `"Coral"` is updated from `16` to `18` and a
/// new key-value pair is added for the key `"Cerise"`.
///
/// hues["Coral"] = 18
/// print(hues["Coral"])
/// // Prints "Optional(18)"
///
/// hues["Cerise"] = 330
/// print(hues["Cerise"])
/// // Prints "Optional(330)"
///
/// If you assign `nil` as the value for the given key, the dictionary
/// removes that key and its associated value.
///
/// In the following example, the key-value pair for the key `"Aquamarine"`
/// is removed from the dictionary by assigning `nil` to the key-based
/// subscript.
///
/// hues["Aquamarine"] = nil
/// print(hues)
/// // Prints "["Coral": 18, "Heliotrope": 296, "Cerise": 330]"
///
/// - Parameter key: The key to find in the dictionary.
/// - Returns: The value associated with `key` if `key` is in the dictionary;
/// otherwise, `nil`.
@inlinable
public subscript(key: Key) -> Value? {
get {
return _variant.lookup(key)
}
set(newValue) {
if let x = newValue {
_variant.setValue(x, forKey: key)
} else {
removeValue(forKey: key)
}
}
_modify {
defer { _fixLifetime(self) }
yield &_variant[key]
}
}
}
extension Dictionary: ExpressibleByDictionaryLiteral {
/// Creates a dictionary initialized with a dictionary literal.
///
/// Do not call this initializer directly. It is called by the compiler to
/// handle dictionary literals. To use a dictionary literal as the initial
/// value of a dictionary, enclose a comma-separated list of key-value pairs
/// in square brackets.
///
/// For example, the code sample below creates a dictionary with string keys
/// and values.
///
/// let countryCodes = ["BR": "Brazil", "GH": "Ghana", "JP": "Japan"]
/// print(countryCodes)
/// // Prints "["BR": "Brazil", "JP": "Japan", "GH": "Ghana"]"
///
/// - Parameter elements: The key-value pairs that will make up the new
/// dictionary. Each key in `elements` must be unique.
@inlinable
@_effects(readonly)
@_semantics("optimize.sil.specialize.generic.size.never")
public init(dictionaryLiteral elements: (Key, Value)...) {
let native = _NativeDictionary<Key, Value>(capacity: elements.count)
for (key, value) in elements {
let (bucket, found) = native.find(key)
_precondition(!found, "Dictionary literal contains duplicate keys")
native._insert(at: bucket, key: key, value: value)
}
self.init(_native: native)
}
}
extension Dictionary {
/// Accesses the value with the given key. If the dictionary doesn't contain
/// the given key, accesses the provided default value as if the key and
/// default value existed in the dictionary.
///
/// Use this subscript when you want either the value for a particular key
/// or, when that key is not present in the dictionary, a default value. This
/// example uses the subscript with a message to use in case an HTTP response
/// code isn't recognized:
///
/// var responseMessages = [200: "OK",
/// 403: "Access forbidden",
/// 404: "File not found",
/// 500: "Internal server error"]
///
/// let httpResponseCodes = [200, 403, 301]
/// for code in httpResponseCodes {
/// let message = responseMessages[code, default: "Unknown response"]
/// print("Response \(code): \(message)")
/// }
/// // Prints "Response 200: OK"
/// // Prints "Response 403: Access Forbidden"
/// // Prints "Response 301: Unknown response"
///
/// When a dictionary's `Value` type has value semantics, you can use this
/// subscript to perform in-place operations on values in the dictionary.
/// The following example uses this subscript while counting the occurrences
/// of each letter in a string:
///
/// let message = "Hello, Elle!"
/// var letterCounts: [Character: Int] = [:]
/// for letter in message {
/// letterCounts[letter, defaultValue: 0] += 1
/// }
/// // letterCounts == ["H": 1, "e": 2, "l": 4, "o": 1, ...]
///
/// When `letterCounts[letter, defaultValue: 0] += 1` is executed with a
/// value of `letter` that isn't already a key in `letterCounts`, the
/// specified default value (`0`) is returned from the subscript,
/// incremented, and then added to the dictionary under that key.
///
/// - Note: Do not use this subscript to modify dictionary values if the
/// dictionary's `Value` type is a class. In that case, the default value
/// and key are not written back to the dictionary after an operation.
///
/// - Parameters:
/// - key: The key the look up in the dictionary.
/// - defaultValue: The default value to use if `key` doesn't exist in the
/// dictionary.
/// - Returns: The value associated with `key` in the dictionary`; otherwise,
/// `defaultValue`.
@inlinable
public subscript(
key: Key, default defaultValue: @autoclosure () -> Value
) -> Value {
@inline(__always)
get {
return _variant.lookup(key) ?? defaultValue()
}
@inline(__always)
_modify {
let (bucket, found) = _variant.mutatingFind(key)
let native = _variant.asNative
if !found {
let value = defaultValue()
native._insert(at: bucket, key: key, value: value)
}
let address = native._values + bucket.offset
defer { _fixLifetime(self) }
yield &address.pointee
}
}
/// Returns a new dictionary containing the keys of this dictionary with the
/// values transformed by the given closure.
///
/// - Parameter transform: A closure that transforms a value. `transform`
/// accepts each value of the dictionary as its parameter and returns a
/// transformed value of the same or of a different type.
/// - Returns: A dictionary containing the keys and transformed values of
/// this dictionary.
///
/// - Complexity: O(*n*), where *n* is the length of the dictionary.
@inlinable
public func mapValues<T>(
_ transform: (Value) throws -> T
) rethrows -> Dictionary<Key, T> {
return try Dictionary<Key, T>(_native: _variant.mapValues(transform))
}
/// Returns a new dictionary containing only the key-value pairs that have
/// non-`nil` values as the result of transformation by the given closure.
///
/// Use this method to receive a dictionary with non-optional values when
/// your transformation produces optional values.
///
/// In this example, note the difference in the result of using `mapValues`
/// and `compactMapValues` with a transformation that returns an optional
/// `Int` value.
///
/// let data = ["a": "1", "b": "three", "c": "///4///"]
///
/// let m: [String: Int?] = data.mapValues { str in Int(str) }
/// // ["a": 1, "b": nil, "c": nil]
///
/// let c: [String: Int] = data.compactMapValues { str in Int(str) }
/// // ["a": 1]
///
/// - Parameter transform: A closure that transforms a value. `transform`
/// accepts each value of the dictionary as its parameter and returns an
/// optional transformed value of the same or of a different type.
/// - Returns: A dictionary containing the keys and non-`nil` transformed
/// values of this dictionary.
///
/// - Complexity: O(*m* + *n*), where *n* is the length of the original
/// dictionary and *m* is the length of the resulting dictionary.
@inlinable
public func compactMapValues<T>(
_ transform: (Value) throws -> T?
) rethrows -> Dictionary<Key, T> {
let result: _NativeDictionary<Key, T> =
try self.reduce(into: _NativeDictionary<Key, T>()) { (result, element) in
if let value = try transform(element.value) {
result.insertNew(key: element.key, value: value)
}
}
return Dictionary<Key, T>(_native: result)
}
/// Updates the value stored in the dictionary for the given key, or adds a
/// new key-value pair if the key does not exist.
///
/// Use this method instead of key-based subscripting when you need to know
/// whether the new value supplants the value of an existing key. If the
/// value of an existing key is updated, `updateValue(_:forKey:)` returns
/// the original value.
///
/// var hues = ["Heliotrope": 296, "Coral": 16, "Aquamarine": 156]
///
/// if let oldValue = hues.updateValue(18, forKey: "Coral") {
/// print("The old value of \(oldValue) was replaced with a new one.")
/// }
/// // Prints "The old value of 16 was replaced with a new one."
///
/// If the given key is not present in the dictionary, this method adds the
/// key-value pair and returns `nil`.
///
/// if let oldValue = hues.updateValue(330, forKey: "Cerise") {
/// print("The old value of \(oldValue) was replaced with a new one.")
/// } else {
/// print("No value was found in the dictionary for that key.")
/// }
/// // Prints "No value was found in the dictionary for that key."
///
/// - Parameters:
/// - value: The new value to add to the dictionary.
/// - key: The key to associate with `value`. If `key` already exists in
/// the dictionary, `value` replaces the existing associated value. If
/// `key` isn't already a key of the dictionary, the `(key, value)` pair
/// is added.
/// - Returns: The value that was replaced, or `nil` if a new key-value pair
/// was added.
@inlinable
@discardableResult
public mutating func updateValue(
_ value: __owned Value,
forKey key: Key
) -> Value? {
return _variant.updateValue(value, forKey: key)
}
/// Merges the key-value pairs in the given sequence into the dictionary,
/// using a combining closure to determine the value for any duplicate keys.
///
/// Use the `combine` closure to select a value to use in the updated
/// dictionary, or to combine existing and new values. As the key-value
/// pairs are merged with the dictionary, the `combine` closure is called
/// with the current and new values for any duplicate keys that are
/// encountered.
///
/// This example shows how to choose the current or new values for any
/// duplicate keys:
///
/// var dictionary = ["a": 1, "b": 2]
///
/// // Keeping existing value for key "a":
/// dictionary.merge(zip(["a", "c"], [3, 4])) { (current, _) in current }
/// // ["b": 2, "a": 1, "c": 4]
///
/// // Taking the new value for key "a":
/// dictionary.merge(zip(["a", "d"], [5, 6])) { (_, new) in new }
/// // ["b": 2, "a": 5, "c": 4, "d": 6]
///
/// - Parameters:
/// - other: A sequence of key-value pairs.
/// - combine: A closure that takes the current and new values for any
/// duplicate keys. The closure returns the desired value for the final
/// dictionary.
@inlinable
public mutating func merge<S: Sequence>(
_ other: __owned S,
uniquingKeysWith combine: (Value, Value) throws -> Value
) rethrows where S.Element == (Key, Value) {
try _variant.merge(other, uniquingKeysWith: combine)
}
/// Merges the given dictionary into this dictionary, using a combining
/// closure to determine the value for any duplicate keys.
///
/// Use the `combine` closure to select a value to use in the updated
/// dictionary, or to combine existing and new values. As the key-values
/// pairs in `other` are merged with this dictionary, the `combine` closure
/// is called with the current and new values for any duplicate keys that
/// are encountered.
///
/// This example shows how to choose the current or new values for any
/// duplicate keys:
///
/// var dictionary = ["a": 1, "b": 2]
///
/// // Keeping existing value for key "a":
/// dictionary.merge(["a": 3, "c": 4]) { (current, _) in current }
/// // ["b": 2, "a": 1, "c": 4]
///
/// // Taking the new value for key "a":
/// dictionary.merge(["a": 5, "d": 6]) { (_, new) in new }
/// // ["b": 2, "a": 5, "c": 4, "d": 6]
///
/// - Parameters:
/// - other: A dictionary to merge.
/// - combine: A closure that takes the current and new values for any
/// duplicate keys. The closure returns the desired value for the final
/// dictionary.
@inlinable
public mutating func merge(
_ other: __owned [Key: Value],
uniquingKeysWith combine: (Value, Value) throws -> Value
) rethrows {
try _variant.merge(
other.lazy.map { ($0, $1) }, uniquingKeysWith: combine)
}
/// Creates a dictionary by merging key-value pairs in a sequence into the
/// dictionary, using a combining closure to determine the value for
/// duplicate keys.
///
/// Use the `combine` closure to select a value to use in the returned
/// dictionary, or to combine existing and new values. As the key-value
/// pairs are merged with the dictionary, the `combine` closure is called
/// with the current and new values for any duplicate keys that are
/// encountered.
///
/// This example shows how to choose the current or new values for any
/// duplicate keys:
///
/// let dictionary = ["a": 1, "b": 2]
/// let newKeyValues = zip(["a", "b"], [3, 4])
///
/// let keepingCurrent = dictionary.merging(newKeyValues) { (current, _) in current }
/// // ["b": 2, "a": 1]
/// let replacingCurrent = dictionary.merging(newKeyValues) { (_, new) in new }
/// // ["b": 4, "a": 3]
///
/// - Parameters:
/// - other: A sequence of key-value pairs.
/// - combine: A closure that takes the current and new values for any
/// duplicate keys. The closure returns the desired value for the final
/// dictionary.
/// - Returns: A new dictionary with the combined keys and values of this
/// dictionary and `other`.
@inlinable
public __consuming func merging<S: Sequence>(
_ other: __owned S,
uniquingKeysWith combine: (Value, Value) throws -> Value
) rethrows -> [Key: Value] where S.Element == (Key, Value) {
var result = self
try result._variant.merge(other, uniquingKeysWith: combine)
return result
}
/// Creates a dictionary by merging the given dictionary into this
/// dictionary, using a combining closure to determine the value for
/// duplicate keys.
///
/// Use the `combine` closure to select a value to use in the returned
/// dictionary, or to combine existing and new values. As the key-value
/// pairs in `other` are merged with this dictionary, the `combine` closure
/// is called with the current and new values for any duplicate keys that
/// are encountered.
///
/// This example shows how to choose the current or new values for any
/// duplicate keys:
///
/// let dictionary = ["a": 1, "b": 2]
/// let otherDictionary = ["a": 3, "b": 4]
///
/// let keepingCurrent = dictionary.merging(otherDictionary)
/// { (current, _) in current }
/// // ["b": 2, "a": 1]
/// let replacingCurrent = dictionary.merging(otherDictionary)
/// { (_, new) in new }
/// // ["b": 4, "a": 3]
///
/// - Parameters:
/// - other: A dictionary to merge.
/// - combine: A closure that takes the current and new values for any
/// duplicate keys. The closure returns the desired value for the final
/// dictionary.
/// - Returns: A new dictionary with the combined keys and values of this
/// dictionary and `other`.
@inlinable
public __consuming func merging(
_ other: __owned [Key: Value],
uniquingKeysWith combine: (Value, Value) throws -> Value
) rethrows -> [Key: Value] {
var result = self
try result.merge(other, uniquingKeysWith: combine)
return result
}
/// Removes and returns the key-value pair at the specified index.
///
/// Calling this method invalidates any existing indices for use with this
/// dictionary.
///
/// - Parameter index: The position of the key-value pair to remove. `index`
/// must be a valid index of the dictionary, and must not equal the
/// dictionary's end index.
/// - Returns: The key-value pair that correspond to `index`.
///
/// - Complexity: O(*n*), where *n* is the number of key-value pairs in the
/// dictionary.
@inlinable
@discardableResult
public mutating func remove(at index: Index) -> Element {
return _variant.remove(at: index)
}
/// Removes the given key and its associated value from the dictionary.
///
/// If the key is found in the dictionary, this method returns the key's
/// associated value. On removal, this method invalidates all indices with
/// respect to the dictionary.
///
/// var hues = ["Heliotrope": 296, "Coral": 16, "Aquamarine": 156]
/// if let value = hues.removeValue(forKey: "Coral") {
/// print("The value \(value) was removed.")
/// }
/// // Prints "The value 16 was removed."
///
/// If the key isn't found in the dictionary, `removeValue(forKey:)` returns
/// `nil`.
///
/// if let value = hues.removeValueForKey("Cerise") {
/// print("The value \(value) was removed.")
/// } else {
/// print("No value found for that key.")
/// }
/// // Prints "No value found for that key.""
///
/// - Parameter key: The key to remove along with its associated value.
/// - Returns: The value that was removed, or `nil` if the key was not
/// present in the dictionary.
///
/// - Complexity: O(*n*), where *n* is the number of key-value pairs in the
/// dictionary.
@inlinable
@discardableResult
public mutating func removeValue(forKey key: Key) -> Value? {
return _variant.removeValue(forKey: key)
}
/// Removes all key-value pairs from the dictionary.
///
/// Calling this method invalidates all indices with respect to the
/// dictionary.
///
/// - Parameter keepCapacity: Whether the dictionary should keep its
/// underlying buffer. If you pass `true`, the operation preserves the
/// buffer capacity that the collection has, otherwise the underlying
/// buffer is released. The default is `false`.
///
/// - Complexity: O(*n*), where *n* is the number of key-value pairs in the
/// dictionary.
@inlinable
public mutating func removeAll(keepingCapacity keepCapacity: Bool = false) {
// The 'will not decrease' part in the documentation comment is worded very
// carefully. The capacity can increase if we replace Cocoa dictionary with
// native dictionary.
_variant.removeAll(keepingCapacity: keepCapacity)
}
}
extension Dictionary {
/// A collection containing just the keys of the dictionary.
///
/// When iterated over, keys appear in this collection in the same order as
/// they occur in the dictionary's key-value pairs. Each key in the keys
/// collection has a unique value.
///
/// let countryCodes = ["BR": "Brazil", "GH": "Ghana", "JP": "Japan"]
/// print(countryCodes)
/// // Prints "["BR": "Brazil", "JP": "Japan", "GH": "Ghana"]"
///
/// for k in countryCodes.keys {
/// print(k)
/// }
/// // Prints "BR"
/// // Prints "JP"
/// // Prints "GH"
@inlinable
@available(swift, introduced: 4.0)
public var keys: Keys {
// FIXME(accessors): Provide a _read
get {
return Keys(_dictionary: self)
}
}
/// A collection containing just the values of the dictionary.
///
/// When iterated over, values appear in this collection in the same order as
/// they occur in the dictionary's key-value pairs.
///
/// let countryCodes = ["BR": "Brazil", "GH": "Ghana", "JP": "Japan"]
/// print(countryCodes)
/// // Prints "["BR": "Brazil", "JP": "Japan", "GH": "Ghana"]"
///
/// for v in countryCodes.values {
/// print(v)
/// }
/// // Prints "Brazil"
/// // Prints "Japan"
/// // Prints "Ghana"
@inlinable
@available(swift, introduced: 4.0)
public var values: Values {
// FIXME(accessors): Provide a _read
get {
return Values(_dictionary: self)
}
_modify {
var values = Values(_variant: _Variant(dummy: ()))
swap(&values._variant, &_variant)
defer { self._variant = values._variant }
yield &values
}
}
/// A view of a dictionary's keys.
@frozen
public struct Keys
: Collection, Equatable,
CustomStringConvertible, CustomDebugStringConvertible {
public typealias Element = Key
public typealias SubSequence = Slice<Dictionary.Keys>
@usableFromInline
internal var _variant: Dictionary<Key, Value>._Variant
@inlinable
internal init(_dictionary: __owned Dictionary) {
self._variant = _dictionary._variant
}
// Collection Conformance
// ----------------------
@inlinable
public var startIndex: Index {
return _variant.startIndex
}
@inlinable
public var endIndex: Index {
return _variant.endIndex
}
@inlinable
public func index(after i: Index) -> Index {
return _variant.index(after: i)
}
@inlinable
public func formIndex(after i: inout Index) {
_variant.formIndex(after: &i)
}
@inlinable
public subscript(position: Index) -> Element {
return _variant.key(at: position)
}
// Customization
// -------------
/// The number of keys in the dictionary.
///
/// - Complexity: O(1).
@inlinable
public var count: Int {
return _variant.count
}
@inlinable
public var isEmpty: Bool {
return count == 0
}
@inlinable
@inline(__always)
public func _customContainsEquatableElement(_ element: Element) -> Bool? {
return _variant.contains(element)
}
@inlinable
@inline(__always)
public func _customIndexOfEquatableElement(_ element: Element) -> Index?? {
return Optional(_variant.index(forKey: element))
}
@inlinable
@inline(__always)
public func _customLastIndexOfEquatableElement(_ element: Element) -> Index?? {
// The first and last elements are the same because each element is unique.
return _customIndexOfEquatableElement(element)
}
@inlinable
public static func ==(lhs: Keys, rhs: Keys) -> Bool {
// Equal if the two dictionaries share storage.
#if _runtime(_ObjC)
if
lhs._variant.isNative,
rhs._variant.isNative,
lhs._variant.asNative._storage === rhs._variant.asNative._storage
{
return true
}
if
!lhs._variant.isNative,
!rhs._variant.isNative,
lhs._variant.asCocoa.object === rhs._variant.asCocoa.object
{
return true
}
#else
if lhs._variant.asNative._storage === rhs._variant.asNative._storage {
return true
}
#endif
// Not equal if the dictionaries are different sizes.
if lhs.count != rhs.count {
return false
}
// Perform unordered comparison of keys.
for key in lhs {
if !rhs.contains(key) {
return false
}
}
return true
}
public var description: String {
return _makeCollectionDescription()
}
public var debugDescription: String {
return _makeCollectionDescription(withTypeName: "Dictionary.Keys")
}
}
/// A view of a dictionary's values.
@frozen
public struct Values
: MutableCollection, CustomStringConvertible, CustomDebugStringConvertible {
public typealias Element = Value
@usableFromInline
internal var _variant: Dictionary<Key, Value>._Variant
@inlinable
internal init(_variant: __owned Dictionary<Key, Value>._Variant) {
self._variant = _variant
}
@inlinable
internal init(_dictionary: __owned Dictionary) {
self._variant = _dictionary._variant
}
// Collection Conformance
// ----------------------
@inlinable
public var startIndex: Index {
return _variant.startIndex
}
@inlinable
public var endIndex: Index {
return _variant.endIndex
}
@inlinable
public func index(after i: Index) -> Index {
return _variant.index(after: i)
}
@inlinable
public func formIndex(after i: inout Index) {
_variant.formIndex(after: &i)
}
@inlinable
public subscript(position: Index) -> Element {
// FIXME(accessors): Provide a _read
get {
return _variant.value(at: position)
}
_modify {
let native = _variant.ensureUniqueNative()
let bucket = native.validatedBucket(for: position)
let address = native._values + bucket.offset
defer { _fixLifetime(self) }
yield &address.pointee
}
}
// Customization
// -------------
/// The number of values in the dictionary.
///
/// - Complexity: O(1).
@inlinable
public var count: Int {
return _variant.count
}
@inlinable
public var isEmpty: Bool {
return count == 0
}
public var description: String {
return _makeCollectionDescription()
}
public var debugDescription: String {
return _makeCollectionDescription(withTypeName: "Dictionary.Values")
}
@inlinable
public mutating func swapAt(_ i: Index, _ j: Index) {
guard i != j else { return }
#if _runtime(_ObjC)
if !_variant.isNative {
_variant = .init(native: _NativeDictionary(_variant.asCocoa))
}
#endif
let isUnique = _variant.isUniquelyReferenced()
let native = _variant.asNative
let a = native.validatedBucket(for: i)
let b = native.validatedBucket(for: j)
_variant.asNative.swapValuesAt(a, b, isUnique: isUnique)
}
}
}
extension Dictionary.Keys {
@frozen
public struct Iterator: IteratorProtocol {
@usableFromInline
internal var _base: Dictionary<Key, Value>.Iterator
@inlinable
@inline(__always)
internal init(_ base: Dictionary<Key, Value>.Iterator) {
self._base = base
}
@inlinable
@inline(__always)
public mutating func next() -> Key? {
#if _runtime(_ObjC)
if case .cocoa(let cocoa) = _base._variant {
_base._cocoaPath()
guard let cocoaKey = cocoa.nextKey() else { return nil }
return _forceBridgeFromObjectiveC(cocoaKey, Key.self)
}
#endif
return _base._asNative.nextKey()
}
}
@inlinable
@inline(__always)
public __consuming func makeIterator() -> Iterator {
return Iterator(_variant.makeIterator())
}
}
extension Dictionary.Values {
@frozen
public struct Iterator: IteratorProtocol {
@usableFromInline
internal var _base: Dictionary<Key, Value>.Iterator
@inlinable
@inline(__always)
internal init(_ base: Dictionary<Key, Value>.Iterator) {
self._base = base
}
@inlinable
@inline(__always)
public mutating func next() -> Value? {
#if _runtime(_ObjC)
if case .cocoa(let cocoa) = _base._variant {
_base._cocoaPath()
guard let (_, cocoaValue) = cocoa.next() else { return nil }
return _forceBridgeFromObjectiveC(cocoaValue, Value.self)
}
#endif
return _base._asNative.nextValue()
}
}
@inlinable
@inline(__always)
public __consuming func makeIterator() -> Iterator {
return Iterator(_variant.makeIterator())
}
}
extension Dictionary: Equatable where Value: Equatable {
@inlinable
public static func == (lhs: [Key: Value], rhs: [Key: Value]) -> Bool {
#if _runtime(_ObjC)
switch (lhs._variant.isNative, rhs._variant.isNative) {
case (true, true):
return lhs._variant.asNative.isEqual(to: rhs._variant.asNative)
case (false, false):
return lhs._variant.asCocoa.isEqual(to: rhs._variant.asCocoa)
case (true, false):
return lhs._variant.asNative.isEqual(to: rhs._variant.asCocoa)
case (false, true):
return rhs._variant.asNative.isEqual(to: lhs._variant.asCocoa)
}
#else
return lhs._variant.asNative.isEqual(to: rhs._variant.asNative)
#endif
}
}
extension Dictionary: Hashable where Value: Hashable {
/// Hashes the essential components of this value by feeding them into the
/// given hasher.
///
/// - Parameter hasher: The hasher to use when combining the components
/// of this instance.
@inlinable
public func hash(into hasher: inout Hasher) {
var commutativeHash = 0
for (k, v) in self {
// Note that we use a copy of our own hasher here. This makes hash values
// dependent on its state, eliminating static collision patterns.
var elementHasher = hasher
elementHasher.combine(k)
elementHasher.combine(v)
commutativeHash ^= elementHasher._finalize()
}
hasher.combine(commutativeHash)
}
}
extension Dictionary: _HasCustomAnyHashableRepresentation
where Value: Hashable {
public __consuming func _toCustomAnyHashable() -> AnyHashable? {
return AnyHashable(_box: _DictionaryAnyHashableBox(self))
}
}
internal struct _DictionaryAnyHashableBox<Key: Hashable, Value: Hashable>
: _AnyHashableBox {
internal let _value: Dictionary<Key, Value>
internal let _canonical: Dictionary<AnyHashable, AnyHashable>
internal init(_ value: __owned Dictionary<Key, Value>) {
self._value = value
self._canonical = value as Dictionary<AnyHashable, AnyHashable>
}
internal var _base: Any {
return _value
}
internal var _canonicalBox: _AnyHashableBox {
return _DictionaryAnyHashableBox<AnyHashable, AnyHashable>(_canonical)
}
internal func _isEqual(to other: _AnyHashableBox) -> Bool? {
guard
let other = other as? _DictionaryAnyHashableBox<AnyHashable, AnyHashable>
else {
return nil
}
return _canonical == other._value
}
internal var _hashValue: Int {
return _canonical.hashValue
}
internal func _hash(into hasher: inout Hasher) {
_canonical.hash(into: &hasher)
}
internal func _rawHashValue(_seed: Int) -> Int {
return _canonical._rawHashValue(seed: _seed)
}
internal func _unbox<T: Hashable>() -> T? {
return _value as? T
}
internal func _downCastConditional<T>(
into result: UnsafeMutablePointer<T>
) -> Bool {
guard let value = _value as? T else { return false }
result.initialize(to: value)
return true
}
}
extension Collection {
// Utility method for KV collections that wish to implement
// CustomStringConvertible and CustomDebugStringConvertible using a bracketed
// list of elements.
// FIXME: Doesn't use the withTypeName argument yet
internal func _makeKeyValuePairDescription<K, V>(
withTypeName type: String? = nil
) -> String where Element == (key: K, value: V) {
if self.isEmpty {
return "[:]"
}
var result = "["
var first = true
for (k, v) in self {
if first {
first = false
} else {
result += ", "
}
debugPrint(k, terminator: "", to: &result)
result += ": "
debugPrint(v, terminator: "", to: &result)
}
result += "]"
return result
}
}
extension Dictionary: CustomStringConvertible, CustomDebugStringConvertible {
/// A string that represents the contents of the dictionary.
public var description: String {
return _makeKeyValuePairDescription()
}
/// A string that represents the contents of the dictionary, suitable for
/// debugging.
public var debugDescription: String {
return _makeKeyValuePairDescription()
}
}
@usableFromInline
@frozen
internal enum _MergeError: Error {
case keyCollision
}
extension Dictionary {
/// The position of a key-value pair in a dictionary.
///
/// Dictionary has two subscripting interfaces:
///
/// 1. Subscripting with a key, yielding an optional value:
///
/// v = d[k]!
///
/// 2. Subscripting with an index, yielding a key-value pair:
///
/// (k, v) = d[i]
@frozen
public struct Index {
// Index for native dictionary is efficient. Index for bridged NSDictionary
// is not, because neither NSEnumerator nor fast enumeration support moving
// backwards. Even if they did, there is another issue: NSEnumerator does
// not support NSCopying, and fast enumeration does not document that it is
// safe to copy the state. So, we cannot implement Index that is a value
// type for bridged NSDictionary in terms of Cocoa enumeration facilities.
@frozen
@usableFromInline
internal enum _Variant {
case native(_HashTable.Index)
#if _runtime(_ObjC)
case cocoa(__CocoaDictionary.Index)
#endif
}
@usableFromInline
internal var _variant: _Variant
@inlinable
@inline(__always)
internal init(_variant: __owned _Variant) {
self._variant = _variant
}
@inlinable
@inline(__always)
internal init(_native index: _HashTable.Index) {
self.init(_variant: .native(index))
}
#if _runtime(_ObjC)
@inlinable
@inline(__always)
internal init(_cocoa index: __owned __CocoaDictionary.Index) {
self.init(_variant: .cocoa(index))
}
#endif
}
}
extension Dictionary.Index {
#if _runtime(_ObjC)
@usableFromInline @_transparent
internal var _guaranteedNative: Bool {
return _canBeClass(Key.self) == 0 || _canBeClass(Value.self) == 0
}
// Allow the optimizer to consider the surrounding code unreachable if Element
// is guaranteed to be native.
@usableFromInline @_transparent
internal func _cocoaPath() {
if _guaranteedNative {
_conditionallyUnreachable()
}
}
@inlinable
@inline(__always)
internal mutating func _isUniquelyReferenced() -> Bool {
defer { _fixLifetime(self) }
var handle = _asCocoa.handleBitPattern
return handle == 0 || _isUnique_native(&handle)
}
@usableFromInline @_transparent
internal var _isNative: Bool {
switch _variant {
case .native:
return true
case .cocoa:
_cocoaPath()
return false
}
}
#endif
@usableFromInline @_transparent
internal var _asNative: _HashTable.Index {
switch _variant {
case .native(let nativeIndex):
return nativeIndex
#if _runtime(_ObjC)
case .cocoa:
_preconditionFailure(
"Attempting to access Dictionary elements using an invalid index")
#endif
}
}
#if _runtime(_ObjC)
@usableFromInline
internal var _asCocoa: __CocoaDictionary.Index {
@_transparent
get {
switch _variant {
case .native:
_preconditionFailure(
"Attempting to access Dictionary elements using an invalid index")
case .cocoa(let cocoaIndex):
return cocoaIndex
}
}
_modify {
guard case .cocoa(var cocoa) = _variant else {
_preconditionFailure(
"Attempting to access Dictionary elements using an invalid index")
}
let dummy = _HashTable.Index(bucket: _HashTable.Bucket(offset: 0), age: 0)
_variant = .native(dummy)
defer { _variant = .cocoa(cocoa) }
yield &cocoa
}
}
#endif
}
extension Dictionary.Index: Equatable {
@inlinable
public static func == (
lhs: Dictionary<Key, Value>.Index,
rhs: Dictionary<Key, Value>.Index
) -> Bool {
switch (lhs._variant, rhs._variant) {
case (.native(let lhsNative), .native(let rhsNative)):
return lhsNative == rhsNative
#if _runtime(_ObjC)
case (.cocoa(let lhsCocoa), .cocoa(let rhsCocoa)):
lhs._cocoaPath()
return lhsCocoa == rhsCocoa
default:
_preconditionFailure("Comparing indexes from different dictionaries")
#endif
}
}
}
extension Dictionary.Index: Comparable {
@inlinable
public static func < (
lhs: Dictionary<Key, Value>.Index,
rhs: Dictionary<Key, Value>.Index
) -> Bool {
switch (lhs._variant, rhs._variant) {
case (.native(let lhsNative), .native(let rhsNative)):
return lhsNative < rhsNative
#if _runtime(_ObjC)
case (.cocoa(let lhsCocoa), .cocoa(let rhsCocoa)):
lhs._cocoaPath()
return lhsCocoa < rhsCocoa
default:
_preconditionFailure("Comparing indexes from different dictionaries")
#endif
}
}
}
extension Dictionary.Index: Hashable {
public // FIXME(cocoa-index): Make inlinable
func hash(into hasher: inout Hasher) {
#if _runtime(_ObjC)
guard _isNative else {
hasher.combine(1 as UInt8)
hasher.combine(_asCocoa._offset)
return
}
hasher.combine(0 as UInt8)
hasher.combine(_asNative.bucket.offset)
#else
hasher.combine(_asNative.bucket.offset)
#endif
}
}
extension Dictionary {
/// An iterator over the members of a `Dictionary<Key, Value>`.
@frozen
public struct Iterator {
// Dictionary has a separate IteratorProtocol and Index because of
// efficiency and implementability reasons.
//
// Native dictionaries have efficient indices.
// Bridged NSDictionary instances don't.
//
// Even though fast enumeration is not suitable for implementing
// Index, which is multi-pass, it is suitable for implementing a
// IteratorProtocol, which is being consumed as iteration proceeds.
@usableFromInline
@frozen
internal enum _Variant {
case native(_NativeDictionary<Key, Value>.Iterator)
#if _runtime(_ObjC)
case cocoa(__CocoaDictionary.Iterator)
#endif
}
@usableFromInline
internal var _variant: _Variant
@inlinable
internal init(_variant: __owned _Variant) {
self._variant = _variant
}
@inlinable
internal init(_native: __owned _NativeDictionary<Key, Value>.Iterator) {
self.init(_variant: .native(_native))
}
#if _runtime(_ObjC)
@inlinable
internal init(_cocoa: __owned __CocoaDictionary.Iterator) {
self.init(_variant: .cocoa(_cocoa))
}
#endif
}
}
extension Dictionary.Iterator {
#if _runtime(_ObjC)
@usableFromInline @_transparent
internal var _guaranteedNative: Bool {
return _canBeClass(Key.self) == 0 || _canBeClass(Value.self) == 0
}
/// Allow the optimizer to consider the surrounding code unreachable if
/// Dictionary<Key, Value> is guaranteed to be native.
@usableFromInline @_transparent
internal func _cocoaPath() {
if _guaranteedNative {
_conditionallyUnreachable()
}
}
@usableFromInline @_transparent
internal var _isNative: Bool {
switch _variant {
case .native:
return true
case .cocoa:
_cocoaPath()
return false
}
}
#endif
@usableFromInline @_transparent
internal var _asNative: _NativeDictionary<Key, Value>.Iterator {
get {
switch _variant {
case .native(let nativeIterator):
return nativeIterator
#if _runtime(_ObjC)
case .cocoa:
_internalInvariantFailure("internal error: does not contain a native index")
#endif
}
}
set {
self._variant = .native(newValue)
}
}
#if _runtime(_ObjC)
@usableFromInline @_transparent
internal var _asCocoa: __CocoaDictionary.Iterator {
get {
switch _variant {
case .native:
_internalInvariantFailure("internal error: does not contain a Cocoa index")
case .cocoa(let cocoa):
return cocoa
}
}
}
#endif
}
extension Dictionary.Iterator: IteratorProtocol {
/// Advances to the next element and returns it, or `nil` if no next element
/// exists.
///
/// Once `nil` has been returned, all subsequent calls return `nil`.
@inlinable
@inline(__always)
public mutating func next() -> (key: Key, value: Value)? {
#if _runtime(_ObjC)
guard _isNative else {
if let (cocoaKey, cocoaValue) = _asCocoa.next() {
let nativeKey = _forceBridgeFromObjectiveC(cocoaKey, Key.self)
let nativeValue = _forceBridgeFromObjectiveC(cocoaValue, Value.self)
return (nativeKey, nativeValue)
}
return nil
}
#endif
return _asNative.next()
}
}
extension Dictionary.Iterator: CustomReflectable {
/// A mirror that reflects the iterator.
public var customMirror: Mirror {
return Mirror(
self,
children: EmptyCollection<(label: String?, value: Any)>())
}
}
extension Dictionary: CustomReflectable {
/// A mirror that reflects the dictionary.
public var customMirror: Mirror {
let style = Mirror.DisplayStyle.dictionary
return Mirror(self, unlabeledChildren: self, displayStyle: style)
}
}
extension Dictionary {
/// Removes and returns the first key-value pair of the dictionary if the
/// dictionary isn't empty.
///
/// The first element of the dictionary is not necessarily the first element
/// added. Don't expect any particular ordering of key-value pairs.
///
/// - Returns: The first key-value pair of the dictionary if the dictionary
/// is not empty; otherwise, `nil`.
///
/// - Complexity: Averages to O(1) over many calls to `popFirst()`.
@inlinable
public mutating func popFirst() -> Element? {
guard !isEmpty else { return nil }
return remove(at: startIndex)
}
/// The total number of key-value pairs that the dictionary can contain without
/// allocating new storage.
@inlinable
public var capacity: Int {
return _variant.capacity
}
/// Reserves enough space to store the specified number of key-value pairs.
///
/// If you are adding a known number of key-value pairs to a dictionary, use this
/// method to avoid multiple reallocations. This method ensures that the
/// dictionary has unique, mutable, contiguous storage, with space allocated
/// for at least the requested number of key-value pairs.
///
/// Calling the `reserveCapacity(_:)` method on a dictionary with bridged
/// storage triggers a copy to contiguous storage even if the existing
/// storage has room to store `minimumCapacity` key-value pairs.
///
/// - Parameter minimumCapacity: The requested number of key-value pairs to
/// store.
public // FIXME(reserveCapacity): Should be inlinable
mutating func reserveCapacity(_ minimumCapacity: Int) {
_variant.reserveCapacity(minimumCapacity)
_internalInvariant(self.capacity >= minimumCapacity)
}
}
public typealias DictionaryIndex<Key: Hashable, Value> =
Dictionary<Key, Value>.Index
public typealias DictionaryIterator<Key: Hashable, Value> =
Dictionary<Key, Value>.Iterator
You can’t perform that action at this time.