feat: delayed processing of attributes

Sources/AndroidXML/Xml_Parser.swift

@@ -30,9 +30,71 @@ public struct Xml_Parser {
 		return rv
 	}
 	
+	// MARK: Iterate Elements
+	
+	/// Helper struct for delayed attribute processing
+	public struct AttributesDict {
+		private let element: XmlStartElement
+		private let lookupFn: (StringPoolRef) -> String
+		private let namespaces: [StringPoolRef: String]
+		private let nsNeedsAppend: StringPoolRef?
+		private let stringPool: StringPool
+		
+		fileprivate init(_ elem: XmlStartElement, _ pool: StringPool, lookupFn: @escaping (StringPoolRef) -> String, namespaces: [StringPoolRef : String], nsNeedsAppend: StringPoolRef?) {
+			self.element = elem
+			self.stringPool = pool
+			self.lookupFn = lookupFn
+			self.namespaces = namespaces
+			self.nsNeedsAppend = nsNeedsAppend
+		}
+		
+		/// Create new list of attributes (keeping original order)
+		public func asList() throws -> [(String, ResValue)] {
+			var rv: [(String, ResValue)] = []
+			// if tag is preceded by a namespace, apply ns-attribute
+			if let uri = nsNeedsAppend, let prefix = namespaces[uri] {
+				rv.append(("xmlns:\(prefix)", ResValue(type: .String, data: uri)))
+			}
+			// generate attributes
+			for attr in try element.attributes() {
+				var key = lookupFn(attr.name)
+				if let prefix = namespaces[attr.ns] {
+					key = prefix + ":" + key
+				}
+				rv.append((key, attr.typedValue))
+			}
+			return rv
+		}
+		
+		/// Create new dictionary of attributes (loosing original order)
+		public func asDict() throws -> [String: ResValue] {
+			var rv: [String: ResValue] = [:]
+			// if tag is preceded by a namespace, apply ns-attribute
+			if let uri = nsNeedsAppend, let prefix = namespaces[uri] {
+				rv["xmlns:\(prefix)"] = ResValue(type: .String, data: uri)
+			}
+			// generate attributes
+			for attr in try element.attributes() {
+				var key = lookupFn(attr.name)
+				if let prefix = namespaces[attr.ns] {
+					key = prefix + ":" + key
+				}
+				rv[key] = attr.typedValue
+			}
+			return rv
+		}
+		
+		/// Same as `asDict()` but calls `resolve()` on all values.
+		/// @Note String-values will contain unescaped quotes (`""`).
+		public func asDictStr() throws -> [String: String] {
+			// No `lookupFn` because attribute values are likely unique
+			try asDict().mapValues { $0.resolve(stringPool)}
+		}
+	}
+	
 	/// 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: [(String, ResValue)]) -> Void, _ end: (_ endTag: String) -> Void) throws {
+	public func iterElements(_ start: (_ startTag: String, _ attributes: AttributesDict) throws -> Void, _ end: (_ endTag: String) throws -> Void) throws {
 		// cache StringPool lookups for faster access
 		var _lookupTable: [StringPoolRef: String] = [:]
 		func lookup(_ index: StringPoolRef) -> String {
@@ -67,34 +129,25 @@ public struct Xml_Parser {
 				
 			case .XmlStartElement:
 				let elem = XmlStartElement(chunk)
-				var attrs: [(String, ResValue)] = []
+				let attrs = AttributesDict(elem, stringPool, lookupFn: lookup(_:), namespaces: namespaces, nsNeedsAppend: nsOnNextTag)
-				// if tag is preceded by a namespace, apply ns-attribute
-				if let uri = nsOnNextTag, let prefix = namespaces[uri] {
-					attrs.append(("xmlns:\(prefix)", ResValue(type: .String, data: uri)))
-				}
 				nsOnNextTag = nil
-				// generate attributes
+				try start(lookup(elem.name), attrs)
-				for attr in try elem.attributes() {
-					var key = lookup(attr.name)
-					if let prefix = namespaces[attr.ns] {
-						key = prefix + ":" + key
-					}
-					attrs.append((key, attr.typedValue))
-				}
-				start(lookup(elem.name), attrs)
 				
 			case .XmlEndElement:
-				end(lookup(XmlEndElement(chunk).name))
+				try end(lookup(XmlEndElement(chunk).name))
 				
 			default:
 				throw AXMLError("Dont know how to handle \(chunk.type) (offset: \(chunk.index(.startOfChunk)))")
 			}
 		}
 	}
-	
+}
-	// MARK: XML string
+
-	
+
-	/// Return data as XML string.
+// MARK: - XML string
+
+extension Xml_Parser {
+	/// Convenience getter to return data as XML string.
 	public func xmlString(prettyPrint: Bool = true, collapseEmptyElements: Bool = true, indent: String = "    ") throws -> String {
 		var rv = #"<?xml version="1.0" encoding="utf-8"?>"#
 		func newLine() -> String {
@@ -109,7 +162,7 @@ public struct Xml_Parser {
 				rv.append(">")
 			}
 			rv.append(newLine() + "<" + startTag)
-			for (key, attr) in attrs {
+			for (key, attr) in try attrs.asList() {
 				// yes, strings can contain quotes. Thus we must escape them.
 				// Hint: no `replace` because that is only available with Foundation
 				let val = attr.dataType == .String
@@ -138,7 +191,7 @@ public struct Xml_Parser {
 }
 
 
-// MARK: SVG converter
+// MARK: - SVG converter
 
 extension Xml_Parser {
 	/// Same as `xmlString()` but converts tag names and attribute names to SVG standard.
@@ -162,7 +215,7 @@ extension Xml_Parser {
 			if lastOpen {
 				rv.append(">")
 			}
-			var dict = attrs.reduce(into: [:]) { $0[$1.0] = $1.1 }
+			var dict = try attrs.asDict()
 			if startTag == "vector" {
 				rv.append(newLine() + #"<svg version="1.1" xmlns="http://www.w3.org/2000/svg""#)
 				if let val = dict.removeValue(forKey: "android:height") {