ref: move StringPool cache into StringPool

Sources/AndroidXML/StringPool.swift

@@ -53,6 +53,7 @@ public struct StringPool {
 		let dataString: Index
 		let dataStyle: Index
 	}
+	private var _lookupTable: [StringPoolRef: String] = [:]
 	
 	init(_ idx: Index, _ bytes: RawBytes) throws {
 		self.init(try ChunkHeader(idx, bytes, expect: .StringPool))
@@ -81,6 +82,9 @@ public struct StringPool {
 	/// Retrieve string for given `StringPoolRef` index
 	public func getString(_ idx: StringPoolRef) -> String {
 		precondition(idx < stringCount, "Index out of bounds for string-pool string[\(idx) > \(stringCount)]")
+		if let cached = _lookupTable[idx] {
+			return cached
+		}
 		let offset = header._bytes.int32(_offset.indicesString + Index(idx) * 4)
 		let dataOffset = _offset.dataString + Index(offset)
 		return flags.contains(.Utf8)
@@ -95,4 +99,15 @@ public struct StringPool {
 		let dataOffset = _offset.dataStyle + Index(offset)
 		return StringPoolSpan(dataOffset, header._bytes)
 	}
+	
+	/// Performs `getString()` and caches the results in a lookup-table.
+	/// For memory-efficiency you should use this only on keys which are expected to repeat.
+	public mutating func getStringCached(_ index: StringPoolRef) -> String {
+		if let cached = _lookupTable[index] {
+			return cached
+		}
+		let val = self.getString(index)
+		_lookupTable[index] = val
+		return val
+	}
 }

Sources/AndroidXML/Xml_Parser.swift

@@ -95,15 +95,9 @@ public struct Xml_Parser {
 	/// Iterate over whole tree and call `start` and `end` blocks for each element.
 	/// Each `start` block contains the `tag` name and its attribute `(name, value)` pairs.
 	public func iterElements(_ start: (_ startTag: String, _ attributes: AttributesDict) throws -> Void, _ end: (_ endTag: String) throws -> Void) throws {
-		// cache StringPool lookups for faster access
+		var pool = stringPool
-		var _lookupTable: [StringPoolRef: String] = [:]
 		func lookup(_ index: StringPoolRef) -> String {
-			if let cached = _lookupTable[index] {
+			pool.getStringCached(index)
-				return cached
-			}
-			let val = stringPool.getString(index)
-			_lookupTable[index] = val
-			return val
 		}
 		// cache namespace prefix strings
 		var namespaces: [StringPoolRef: String] = [:]
@@ -120,7 +114,7 @@ public struct Xml_Parser {
 				
 			case .XmlStartNamespace:
 				let ns = XmlNamespace(chunk)
-				namespaces[ns.uri] = lookup(ns.prefix)
+				namespaces[ns.uri] = pool.getStringCached(ns.prefix)
 				nsOnNextTag = ns.uri
 				
 			case .XmlEndNamespace:
@@ -131,10 +125,10 @@ public struct Xml_Parser {
 				let elem = XmlStartElement(chunk)
 				let attrs = AttributesDict(elem, stringPool, lookupFn: lookup(_:), namespaces: namespaces, nsNeedsAppend: nsOnNextTag)
 				nsOnNextTag = nil
-				try start(lookup(elem.name), attrs)
+				try start(pool.getStringCached(elem.name), attrs)
 				
 			case .XmlEndElement:
-				try end(lookup(XmlEndElement(chunk).name))
+				try end(pool.getStringCached(XmlEndElement(chunk).name))
 				
 			default:
 				throw AXMLError("Dont know how to handle \(chunk.type) (offset: \(chunk.index(.startOfChunk)))")