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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Collections open source project
//
// Copyright (c) 2021 - 2024 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
//
//===----------------------------------------------------------------------===//
extension OrderedDictionary: Encodable where Key: Encodable, Value: Encodable {
/// Encodes the contents of this dictionary into the given encoder.
///
/// The dictionary's contents are encoded as alternating key-value pairs in
/// an unkeyed container.
///
/// This function throws an error if any values are invalid for the given
/// encoder's format.
///
/// - Note: Unlike the standard `Dictionary` type, ordered dictionaries
/// always encode themselves into an unkeyed container, because
/// `Codable`'s keyed containers do not guarantee that they preserve the
/// ordering of the items they contain. (And in popular encoding formats,
/// keyed containers tend to map to unordered data structures -- e.g.,
/// JSON's "object" construct is explicitly unordered.)
///
/// - Parameter encoder: The encoder to write data to.
@inlinable
public func encode(to encoder: Encoder) throws {
// Encode contents as an array of alternating key-value pairs.
var container = encoder.unkeyedContainer()
for (key, value) in self {
try container.encode(key)
try container.encode(value)
}
}
}
extension OrderedDictionary: Decodable where Key: Decodable, Value: Decodable {
/// Creates a new dictionary by decoding from the given decoder.
///
/// `OrderedDictionary` expects its contents to be encoded as alternating
/// key-value pairs in an unkeyed container.
///
/// This initializer throws an error if reading from the decoder fails, or
/// if the decoded contents are not in the expected format.
///
/// - Note: Unlike the standard `Dictionary` type, ordered dictionaries
/// always encode themselves into an unkeyed container, because
/// `Codable`'s keyed containers do not guarantee that they preserve the
/// ordering of the items they contain. (And in popular encoding formats,
/// keyed containers tend to map to unordered data structures -- e.g.,
/// JSON's "object" construct is explicitly unordered.)
///
/// - Parameter decoder: The decoder to read data from.
@inlinable
public init(from decoder: Decoder) throws {
// We expect to be encoded as an array of alternating key-value pairs.
var container = try decoder.unkeyedContainer()
self.init()
while !container.isAtEnd {
let key = try container.decode(Key.self)
let (index, bucket) = self._keys._find(key)
guard index == nil else {
let context = DecodingError.Context(
codingPath: container.codingPath,
debugDescription: "Duplicate key at offset \(container.currentIndex - 1)")
throw DecodingError.dataCorrupted(context)
}
guard !container.isAtEnd else {
throw DecodingError.dataCorrupted(
DecodingError.Context(
codingPath: container.codingPath,
debugDescription: "Unkeyed container reached end before value in key-value pair"
)
)
}
let value = try container.decode(Value.self)
_keys._appendNew(key, in: bucket)
_values.append(value)
}
_checkInvariants()
}
}
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