iterative traversal parser

Author: swhitty

SwiftDraw/Parser.XML.Element.swift

@@ -111,33 +111,30 @@ extension XMLParser {
         return ge
     }
 
-    func parseContainerChildren(_ e: XML.Element) throws -> [DOM.GraphicsElement] {
-        guard e.name == "svg" ||
-                e.name == "clipPath" ||
-                e.name == "pattern" ||
-                e.name == "mask" ||
-                e.name == "defs" ||
-                e.name == "switch" ||
-                e.name == "g" ||
-                e.name == "a" else {
-            throw Error.invalid
-        }
+    func parseGraphicsElements(_ elements: [XML.Element]) throws -> [DOM.GraphicsElement] {
+        var result = [DOM.GraphicsElement]()
+        var stack: [(XML.Element, parent: ContainerElement?)] = elements
+            .reversed()
+            .map { ($0, parent: nil) }
+
+        while let (element, parent) = stack.popLast() {
+            guard let ge = try parseGraphicsElement(element) else {
+                continue
+            }
 
-        var children = [DOM.GraphicsElement]()
-
-        for n in e.children {
-            do {
-                if let ge = try parseGraphicsElement(n) {
-                    children.append(ge)
-                }
-            } catch let error {
-                if let parseError = parseError(for: error, parsing: n, with: options) {
-                    throw parseError
-                }
+            if var parent {
+                parent.childElements.append(ge)
+            } else {
+                result.append(ge)
             }
+
+            if let container = ge as? ContainerElement {
+                stack.append(contentsOf: element.children.reversed().map { ($0, container) })
+            }
+
         }
 
-        return children
+        return result
     }
 
     func parseError(for error: Swift.Error, parsing element: XML.Element, with options: Options) -> XMLParser.Error? {
@@ -165,19 +162,15 @@ extension XMLParser {
             throw Error.invalid
         }
 
-        let group = DOM.Group()
-        group.childElements = try parseContainerChildren(e)
-        return group
+        return DOM.Group()
     }
 
     func parseSwitch(_ e: XML.Element) throws -> DOM.Switch {
         guard e.name == "switch" else {
             throw Error.invalid
         }
 
-        let node = DOM.Switch()
-        node.childElements = try parseContainerChildren(e)
-        return node
+        return DOM.Switch()
     }
 
     func parseAttributes(_ e: XML.Element) throws -> Attributes {

SwiftDraw/Parser.XML.SVG.swift

@@ -58,7 +58,7 @@ extension XMLParser {
         let svg = DOM.SVG(width: DOM.Length(w), height: DOM.Length(h))
         svg.x = try att.parseCoordinate("x")
         svg.y = try att.parseCoordinate("y")
-        svg.childElements = try parseContainerChildren(e)
+        svg.childElements = try parseGraphicsElements(e.children)
         svg.viewBox = try parseViewBox(try att.parseString("viewBox"))
 
         svg.defs = try parseSVGDefs(e)
@@ -121,7 +121,7 @@ extension XMLParser {
         }
 
         var defs = Dictionary<String, DOM.GraphicsElement>()
-        let elements = try parseContainerChildren(e)
+        let elements = try parseGraphicsElements(e.children)
 
         for e in elements {
             guard let id = e.id else {
@@ -153,7 +153,7 @@ extension XMLParser {
         let att = try parseAttributes(e)
         let id: String = try att.parseString("id")
 
-        let children = try parseContainerChildren(e)
+        let children = try parseGraphicsElements(e.children)
         return DOM.ClipPath(id: id, childElements: children)
     }
 
@@ -176,7 +176,7 @@ extension XMLParser {
         let att = try parseAttributes(e)
         let id: String = try att.parseString("id")
 
-        let children = try parseContainerChildren(e)
+        let children = try parseGraphicsElements(e.children)
         return DOM.Mask(id: id, childElements: children)
     }
 
@@ -198,7 +198,7 @@ extension XMLParser {
 
         let att = try parseAttributes(e)
         var pattern = try parsePattern(att)
-        pattern.childElements = try parseContainerChildren(e)
+        pattern.childElements = try parseGraphicsElements(e.children)
         return pattern
     }
 }

SwiftDraw/Parser.XML.Text.swift

@@ -46,7 +46,6 @@ extension XMLParser {
     func parseAnchor(_ att: AttributeParser, element: XML.Element) throws -> DOM.Anchor? {
         let anchor = DOM.Anchor()
         anchor.href = try att.parseUrl("href")
-        anchor.childElements = try parseContainerChildren(element)
         return anchor
     }
 

SwiftDrawTests/Parser.SVGTests.swift

@@ -151,4 +151,20 @@ final class ParserSVGTests: XCTestCase {
         let circle = try XCTUnwrap(svg.firstGraphicsElement(with: "b") as? DOM.Circle)
         XCTAssertEqual(circle.id, "b")
     }
+
+    func testDeepNestingParses() async {
+        let groupOpen = String(repeating: "<g>", count: 500)
+        let groupClose = String(repeating: "</g>", count: 500)
+
+        XCTAssertNoThrow(
+            try DOM.SVG.parse(xml: #"""
+            <?xml version="1.0" encoding="UTF-8"?>
+            <svg width="64" height="64" version="1.1">
+                \#(groupOpen)
+                <circle id="b" cx="50" cy="60" r="70" />
+                \#(groupClose)
+            </svg>
+            """#)
+        )
+    }
 }