Optimize object key lookup through reducing String initialization

Package.swift

@@ -14,7 +14,12 @@ let package = Package(
         .library(
             name: "IkigaJSON",
             targets: ["IkigaJSON"]
-        )
+        ),
+        // Embedded Swift compatible library - no Foundation or NIO dependencies
+        .library(
+            name: "IkigaJSONCore",
+            targets: ["_JSONCore"]
+        ),
     ],
     dependencies: [
         // Dependencies declare other packages that this package depends on.
@@ -24,7 +29,11 @@ let package = Package(
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
         // Targets can depend on other targets in this package, and on products in packages which this package depends on.
         .target(
-            name: "_JSONCore"
+            name: "_JSONCore",
+            swiftSettings: [
+                // Enable strict concurrency for Embedded Swift compatibility
+                .enableExperimentalFeature("StrictConcurrency"),
+            ]
         ),
         .target(
             name: "_NIOJSON",

Sources/_JSONCore/Errors.swift

@@ -114,13 +114,11 @@ public enum JSONParserError: Error, Sendable {
     case unexpectedToken(line: Int, column: Int, token: UInt8, reason: Reason)
 }
 
-public struct TypeConversionError<F: FixedWidthInteger & Sendable>: Error {
-    let from: F
-    let to: Any.Type
+public struct TypeConversionError<F: FixedWidthInteger & Sendable, T>: Error, Sendable {
+    public let from: F
 
-    public init(from: F, to: Any.Type) {
+    public init(from: F, to: T.Type) {
         self.from = from
-        self.to = to
     }
 }
 

Sources/_JSONCore/Parser/JSONParser+Parsing.swift

@@ -99,7 +99,7 @@ extension JSONTokenizer {
             }
 
             try skipWhitespace() // needed because of the comma
-            try scanStringLiteral()
+            try scanObjectKey()
             try skipWhitespace()
 
             guard nextByte() == .colon else {
@@ -280,4 +280,66 @@ extension JSONTokenizer {
 
         throw JSONParserError.missingData(line: line, column: column)
     }
+
+    /// Scans an object key (string) and computes its hash for fast lookup
+    @_optimize(speed)
+    @inlinable
+    mutating func scanObjectKey() throws(JSONParserError) {
+        if currentByte != .quote {
+            throw JSONParserError.unexpectedToken(line: line, column: column, token: currentByte, reason: .expectedObjectKey)
+        }
+
+        var currentIndex: Int = 1
+        var didEscape = false
+        defer { advance(currentIndex) }
+
+        while currentIndex < count {
+            defer { currentIndex = currentIndex &+ 1 }
+
+            let byte = self[currentIndex]
+
+            if byte == .quote {
+                var escaped = false
+
+                if didEscape {
+                    var backwardsOffset = currentIndex &- 1
+
+                    escapeLoop: while backwardsOffset >= 1 {
+                        defer { backwardsOffset = backwardsOffset &- 1 }
+
+                        if self[backwardsOffset] == .backslash {
+                            escaped = !escaped
+                        } else {
+                            break escapeLoop
+                        }
+                    }
+                }
+
+                if !escaped {
+                    let start = JSONSourcePosition(byteIndex: currentOffset)
+                    let stringToken = JSONToken.String(
+                        start: start,
+                        byteLength: currentIndex &+ 1,
+                        usesEscaping: didEscape
+                    )
+
+                    // Compute hash of key bytes (excluding quotes)
+                    // Key content starts at offset 1 (after opening quote)
+                    // and ends just before `currentIndex` (which points to the closing quote).
+                    var hash: UInt32 = 2166136261  // FNV offset basis
+                    for i in 1..<currentIndex {
+                        hash ^= UInt32(self[i])
+                        hash &*= 16777619  // FNV prime
+                    }
+
+                    destination.objectKeyFound(stringToken, hash: hash)
+                    return
+                }
+            } else if byte == .backslash {
+                didEscape = true
+            }
+        }
+
+        throw JSONParserError.missingData(line: line, column: column)
+    }
 }

Sources/_JSONCore/Parser/JSONTokenizerDestination.swift

@@ -13,6 +13,17 @@ public protocol JSONTokenizerDestination {
     mutating func nullFound(_ null: JSONToken.Null)
     mutating func stringFound(_ string: JSONToken.String)
     mutating func numberFound(_ number: JSONToken.Number)
+
+    /// Called when an object key is found, with a pre-computed hash of the key bytes.
+    /// Default implementation calls `stringFound()` for backward compatibility.
+    mutating func objectKeyFound(_ string: JSONToken.String, hash: UInt32)
+}
+
+extension JSONTokenizerDestination {
+    @inlinable
+    public mutating func objectKeyFound(_ string: JSONToken.String, hash: UInt32) {
+        stringFound(string)
+    }
 }
 
 public enum JSONToken: Sendable, Hashable {