Memoize hashValue in Diff.swift

devxoul · kzaher · commit c385cbe166de · 2019-04-09T18:38:22.000+02:00
diff --git a/Sources/Differentiator/Diff.swift b/Sources/Differentiator/Diff.swift
@@ -129,13 +129,15 @@ public enum Diff {
     private struct OptimizedIdentity<E: Hashable> : Hashable {
 
         let identity: UnsafePointer<E>
+        private let cachedHashValue: Int
 
         init(_ identity: UnsafePointer<E>) {
             self.identity = identity
+            self.cachedHashValue = identity.pointee.hashValue
         }
 
         func hash(into hasher: inout Hasher) {
-          hasher.combine(self.identity.pointee.hashValue)
+          hasher.combine(self.cachedHashValue)
         }
 
         static func == (lhs: OptimizedIdentity<E>, rhs: OptimizedIdentity<E>) -> Bool {

Original file line number	Diff line number	Diff line change
`@@ -129,13 +129,15 @@ public enum Diff {`
`129`	`129`	`private struct OptimizedIdentity<E: Hashable> : Hashable {`
`130`	`130`
`131`	`131`	`let identity: UnsafePointer<E>`
	`132`	`+ private let cachedHashValue: Int`
`132`	`133`
`133`	`134`	`init(_ identity: UnsafePointer<E>) {`
`134`	`135`	`self.identity = identity`
	`136`	`+ self.cachedHashValue = identity.pointee.hashValue`
`135`	`137`	`}`
`136`	`138`
`137`	`139`	`func hash(into hasher: inout Hasher) {`
`138`		`- hasher.combine(self.identity.pointee.hashValue)`
	`140`	`+ hasher.combine(self.cachedHashValue)`
`139`	`141`	`}`
`140`	`142`
`141`	`143`	`static func == (lhs: OptimizedIdentity<E>, rhs: OptimizedIdentity<E>) -> Bool {`