Improve performance AttributedString Equatable conformance (#1287)

Author: jmschonfeld

Sources/FoundationEssentials/AttributedString/AttributedString+Runs.swift

@@ -278,8 +278,14 @@ extension AttributedString.Runs: BidirectionalCollection {
         precondition(i < _bounds.upperBound, "Can't advance AttributedString.Runs index beyond end")
         let (resolvedIdx, runStartIdx) = _resolve(i)
         let next = _guts.runs.index(after: resolvedIdx)
-        let currentRangeIdx = i._rangesOffset ?? _strBounds.rangeIdx(containing: i._stringIndex ?? runStartIdx)
-        let currentRange = _strBounds.ranges[currentRangeIdx]
+        let currentRangeIdx: Int
+        let currentRange: Range<BigString.Index>
+        if let cachedRangeOffset = i._rangesOffset {
+            currentRangeIdx = cachedRangeOffset
+            currentRange = _strBounds.ranges[currentRangeIdx]
+        } else {
+            (currentRange, currentRangeIdx) = _strBounds.range(containing: i._stringIndex ?? runStartIdx)
+        }
         if currentRange.upperBound.utf8Offset <= next.utf8Offset {
             let nextRangeIdx = currentRangeIdx + 1
             if nextRangeIdx == _strBounds.ranges.count {
@@ -300,7 +306,7 @@ extension AttributedString.Runs: BidirectionalCollection {
     public func index(before i: Index) -> Index {
         precondition(i > _bounds.lowerBound, "Can't step AttributedString.Runs index below start")
         let (resolvedIdx, runStartIdx) = _resolve(i)
-        let currentRangeIdx = i._rangesOffset ?? _strBounds.rangeIdx(containing: i._stringIndex ?? runStartIdx)
+        let currentRangeIdx = i._rangesOffset ?? _strBounds.range(containing: i._stringIndex ?? runStartIdx).offset
         if i == endIndex || runStartIdx.utf8Offset <= _strBounds.ranges[currentRangeIdx].lowerBound.utf8Offset {
             // The current run starts on or before our current range, look up the next range
             let previousRange = _strBounds.ranges[currentRangeIdx - 1]
@@ -394,27 +400,34 @@ extension AttributedString.Runs: BidirectionalCollection {
 
     public subscript(position: Index) -> Run {
         precondition(_bounds.contains(position), "AttributedString.Runs index is out of bounds")
-        if let strIdx = position._stringIndex {
-            precondition(_strBounds.contains(strIdx), "AttributedString.Runs index is out of bounds")
-        }
         let resolved = _resolve(position)
-        return self[_unchecked: resolved.runIndex, stringStartIdx: position._startStringIndex ?? resolved.start, stringIdx: position._stringIndex ?? resolved.start, rangeOffset: position._rangesOffset]
+        let containingRange: Range<BigString.Index>
+        let stringIdx: BigString.Index
+        if let cachedRangeOffset = position._rangesOffset {
+            containingRange = _strBounds.ranges[cachedRangeOffset]
+            if let cachedStringIdx = position._stringIndex {
+                precondition(containingRange.contains(cachedStringIdx), "AttributedString.Runs index is out of bounds")
+                stringIdx = cachedStringIdx
+            }
+        } else {
+            stringIdx = position._stringIndex ?? resolved.start
+            // No need to check that _strBounds contains stringIdx here, the below call will assert if it cannot find a range that contains the provided index
+            containingRange = _strBounds.range(containing: stringIdx).range
+        }
+        return self[_unchecked: resolved.runIndex, stringStartIdx: position._startStringIndex ?? resolved.start, stringIdx: position._stringIndex ?? resolved.start, containingRange: containingRange]
     }
 
     public subscript(position: AttributedString.Index) -> Run {
-        precondition(
-            _strBounds.contains(position._value),
-            "AttributedString index is out of bounds")
+        let containingRange = _strBounds.range(containing: position._value).range
         let r = _guts.findRun(at: position._value)
-        return self[_unchecked: r.runIndex, stringStartIdx: r.start, stringIdx: position._value]
+        return self[_unchecked: r.runIndex, stringStartIdx: r.start, stringIdx: position._value, containingRange: containingRange]
     }
 
-    internal subscript(_unchecked i: _InternalRuns.Index, stringStartIdx stringStartIdx: BigString.Index, stringIdx stringIdx: BigString.Index, rangeOffset rangeOffset: Int? = nil) -> Run {
+    internal subscript(_unchecked i: _InternalRuns.Index, stringStartIdx stringStartIdx: BigString.Index, stringIdx stringIdx: BigString.Index, containingRange containingRange: Range<BigString.Index>) -> Run {
         let run = _guts.runs[i]
         // Clamp the run into the bounds of self, using relative calculations.
-        let range = _strBounds.ranges[rangeOffset ?? _strBounds.rangeIdx(containing: stringIdx)]
-        let lowerBound = Swift.max(stringStartIdx, range.lowerBound)
-        let upperUTF8 = Swift.min(stringStartIdx.utf8Offset + run.length, range.upperBound.utf8Offset)
+        let lowerBound = Swift.max(stringStartIdx, containingRange.lowerBound)
+        let upperUTF8 = Swift.min(stringStartIdx.utf8Offset + run.length, containingRange.upperBound.utf8Offset)
         let upperBound = _guts.string.utf8.index(stringIdx, offsetBy: upperUTF8 - stringIdx.utf8Offset)
         return Run(_attributes: run.attributes, Range(uncheckedBounds: (lowerBound, upperBound)), _guts)
     }
@@ -428,8 +441,7 @@ extension AttributedString.Runs {
             _strBounds.contains(position._value),
             "AttributedString index is out of bounds")
         let r = _guts.findRun(at: position._value)
-        let rangeIdx = _strBounds.rangeIdx(containing: position._value)
-        let range = _strBounds.ranges[rangeIdx]
+        let (range, rangeIdx) = _strBounds.range(containing: position._value)
         let strIdx = Swift.max(range.lowerBound, r.start)
         return Index(_runIndex: r.runIndex, startStringIndex: r.start, stringIndex: strIdx, rangeOffset: rangeIdx, withinDiscontiguous: _isDiscontiguous)
     }
@@ -484,13 +496,10 @@ extension AttributedString.Runs {
         constraints: Set<AttributeRunBoundaries?>,
         endOfCurrent: Bool
     ) -> AttributedString.Index {
-        precondition(
-            self._strBounds.contains(i._value),
-            "AttributedString index is out of bounds")
+        // _strBounds.range(containing:) below validates that i._value is within the bounds of this slice
         precondition(!attributeNames.isEmpty)
         let r = _guts.findRun(at: i._value)
-        let currentRangeIdx = _strBounds.rangeIdx(containing: i._value)
-        let currentRange = _strBounds.ranges[currentRangeIdx]
+        let (currentRange, currentRangeIdx) = _strBounds.range(containing: i._value)
 
         guard constraints.count != 1 || constraints.contains(nil) else {
             // We have a single constraint and attributes are guaranteed to be consistent between constraint boundaries
@@ -540,18 +549,15 @@ extension AttributedString.Runs {
         constraints: Set<AttributeRunBoundaries?>,
         endOfPrevious: Bool
     ) -> AttributedString.Index {
-        precondition(
-            _strBounds.contains(i._value) || i._value == endIndex._stringIndex,
-            "AttributedString index is out of bounds")
+        // _strBounds.range(containing:) below validates that i._value is within the bounds of this slice
         precondition(!attributeNames.isEmpty)
         var currentRangeIdx: Int
         var currentRange: Range<BigString.Index>
         if i._value == endIndex._stringIndex {
             currentRangeIdx = _strBounds.ranges.count
             currentRange = Range(uncheckedBounds: (endIndex._stringIndex!, endIndex._stringIndex!))
         } else {
-            currentRangeIdx = _strBounds.rangeIdx(containing: i._value)
-            currentRange = _strBounds.ranges[currentRangeIdx]
+            (currentRange, currentRangeIdx) = _strBounds.range(containing: i._value)
         }
         var currentStringIdx = i._value
         if currentRange.lowerBound == i._value {
@@ -585,15 +591,13 @@ extension AttributedString.Runs {
         attributeNames: [String],
         constraints: Set<AttributeRunBoundaries?>
     ) -> (index: AttributedString.Index, runIndex: AttributedString._InternalRuns.Index) {
-        precondition(
-            _strBounds.contains(i._value) || i._value == endIndex._stringIndex,
-            "AttributedString index is out of bounds")
+        // _strBounds.range(containing:) below validates that i._value is within the bounds of this slice
         precondition(!attributeNames.isEmpty)
         let r = _guts.findRun(at: i._value)
         if r.runIndex.offset == endIndex._runOffset {
             return (i, r.runIndex)
         }
-        let currentRange = _strBounds.ranges[_strBounds.rangeIdx(containing: i._value)]
+        let currentRange = _strBounds.range(containing: i._value).range
 
         guard constraints.count != 1 || constraints.contains(nil) else {
             let nextIndex = _guts.string.unicodeScalars.index(after: i._value)
@@ -719,20 +723,20 @@ extension BigSubstring.UnicodeScalarView {
 }
 
 extension RangeSet {
-    fileprivate func rangeIdx(containing index: Bound) -> Int {
+    fileprivate func range(containing index: Bound) -> (range: Range<Bound>, offset: Int) {
         var start = 0
         var end = self.ranges.count
         while start < end {
             let middle = (start + end) / 2
             let value = self.ranges[middle]
             if value.contains(index) {
-                return middle
+                return (value, middle)
             } else if index < value.lowerBound {
                 end = middle
             } else {
                 start = middle + 1
             }
         }
-        preconditionFailure("Internal Inconsistency: Provided index \(index) is out of bounds")
+        preconditionFailure("AttributedString.Runs index is out of bounds")
     }
 }

Sources/FoundationEssentials/AttributedString/AttributedStringAttributeStorage.swift

@@ -13,8 +13,8 @@
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 extension AttributedString {
     internal struct _AttributeValue : Hashable, CustomStringConvertible, Sendable {
-        typealias RawValue = any Sendable & Hashable
-        let rawValue: RawValue
+        private typealias RawValue = any Sendable & Hashable
+        private let _rawValue: RawValue
 
         // FIXME: If these are always tied to keys, then why are we caching these
         // FIXME: on each individual value? Move them to a separate
@@ -24,21 +24,14 @@ extension AttributedString {
         let inheritedByAddedText: Bool
         let invalidationConditions: Set<AttributeInvalidationCondition>?
 
-        var description: String { String(describing: rawValue) }
+        var description: String { String(describing: _rawValue) }
 
         init<K: AttributedStringKey>(_ value: K.Value, for key: K.Type) where K.Value : Sendable {
-            rawValue = value
+            _rawValue = value
             runBoundaries = K.runBoundaries
             inheritedByAddedText = K.inheritedByAddedText
             invalidationConditions = K.invalidationConditions
         }
-        
-        private init<K: AttributedStringKey>(checkingValue value: RawValue, for key: K.Type) where K.Value : Sendable {
-            guard let trueValue = value as? K.Value else {
-                fatalError("\(#function) called with non-matching attribute value type")
-            }
-            self.init(trueValue, for: K.self)
-        }
 
         var isInvalidatedOnTextChange: Bool {
             invalidationConditions?.contains(.textChanged) ?? false
@@ -61,35 +54,27 @@ extension AttributedString {
         func rawValue<K: AttributedStringKey>(
             as key: K.Type
         ) -> K.Value where K.Value: Sendable {
-            rawValue as! K.Value
+            func extractValue<RealValue>(_ value: RealValue) -> K.Value {
+                assert(RealValue.self == K.Value.self, "_AttributeValue raw value can only be retrieved with a key whose value matches the stored attribute value (stored type \(RealValue.self) does not match key value type \(K.Value.self))")
+                return _identityCast(value, to: K.Value.self)
+            }
+            return _openExistential(self._rawValue, do: extractValue)
         }
 
-        static func ==(lhs: Self, rhs: Self) -> Bool {
-            Self.__equalAttributes(lhs.rawValue, rhs.rawValue)
+        static func ==(left: Self, right: Self) -> Bool {
+            func openEquatableLHS<LeftValue: Hashable & Sendable>(_ leftValue: LeftValue) -> Bool {
+                func openEquatableRHS<RightValue: Hashable & Sendable>(_ rightValue: RightValue) -> Bool {
+                    assert(LeftValue.self == RightValue.self, "Two _AttributeValues can only be compared if they are of the same attribute value type")
+                    let rightValueAsLeft = _identityCast(rightValue, to: LeftValue.self)
+                    return rightValueAsLeft == leftValue
+                }
+                return openEquatableRHS(right._rawValue)
+            }
+            return openEquatableLHS(left._rawValue)
         }
 
         func hash(into hasher: inout Hasher) {
-            rawValue.hash(into: &hasher)
-        }
-
-        private static func __equalAttributes(_ lhs: RawValue?, _ rhs: RawValue?) -> Bool {
-            switch (lhs, rhs) {
-            case (.none, .none):
-                return true
-            case (.none, .some(_)):
-                return false
-            case (.some(_), .none):
-                return false
-            case (.some(let lhs), .some(let rhs)):
-                func openEquatable<LHS: Equatable>(_ equatableLHS: LHS) -> Bool {
-                    if let equatableRHS = rhs as? LHS {
-                        return equatableLHS == equatableRHS
-                    } else {
-                        return false
-                    }
-                }
-                return openEquatable(lhs)
-            }
+            _rawValue.hash(into: &hasher)
         }
     }
 }