diff --git a/CoreFoundation/Parsing.subproj/CFXMLInterface.c b/CoreFoundation/Parsing.subproj/CFXMLInterface.c
index 65e277fef7..0dac7dd401 100644
--- a/CoreFoundation/Parsing.subproj/CFXMLInterface.c
+++ b/CoreFoundation/Parsing.subproj/CFXMLInterface.c
@@ -1,6 +1,6 @@
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information
@@ -8,7 +8,7 @@
 //
 
 /*	CFXMLInterface.c
-	Copyright (c) 2015 Apple Inc. and the Swift project authors
+	Copyright (c) 2020 Apple Inc. and the Swift project authors
  */
 
 #include <CoreFoundation/CFRuntime.h>
@@ -210,7 +210,8 @@ void _CFXMLInterfaceCtxtUseOptions(_CFXMLInterfaceParserContext ctx, CFIndex opt
 }
 
 int _CFXMLInterfaceParseChunk(_CFXMLInterfaceParserContext ctxt, const char *chunk, int size, int terminate) {
-    return xmlParseChunk(ctxt, chunk, size, terminate);
+    int ret = xmlParseChunk(ctxt, chunk, size, terminate);
+    return ret == XML_ERR_DOCUMENT_END && terminate ? XML_ERR_OK : ret;
 }
 
 void _CFXMLInterfaceStopParser(_CFXMLInterfaceParserContext ctx) {
diff --git a/Sources/FoundationXML/XMLParser.swift b/Sources/FoundationXML/XMLParser.swift
index 7acc76b852..232f96093f 100644
--- a/Sources/FoundationXML/XMLParser.swift
+++ b/Sources/FoundationXML/XMLParser.swift
@@ -1,6 +1,6 @@
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information
@@ -486,8 +486,9 @@ open class XMLParser : NSObject {
         return false
     }
 
-    internal func parseData(_ data: Data) -> Bool {
+    internal func parseData(_ data: Data, lastChunkOfData: Bool = false) -> Bool {
         _CFXMLInterfaceSetStructuredErrorFunc(interface, _structuredErrorFunc)
+        defer { _CFXMLInterfaceSetStructuredErrorFunc(interface, nil) }
 
         let handler: _CFXMLInterfaceSAXHandler? = (delegate != nil ? _handler : nil)
         let unparsedData: Data
@@ -504,7 +505,7 @@ open class XMLParser : NSObject {
             // If we have not received 4 bytes, save the bomChunk for next pass
             if bomChunk.count < 4 {
                 _bomChunk = bomChunk
-                return false
+                return true
             }
             // Prepare options (substitute entities, recover on errors)
             var options = _kCFXMLInterfaceRecover | _kCFXMLInterfaceNoEnt
@@ -520,6 +521,12 @@ open class XMLParser : NSObject {
                 let bytes = rawBuffer.baseAddress!.assumingMemoryBound(to: CChar.self)
                 _parserContext = _CFXMLInterfaceCreatePushParserCtxt(handler, interface, bytes, 4, nil)
             }
+            guard _parserContext != nil else {
+                if _parserError == nil {
+                    _parserError = NSError(domain: XMLParser.errorDomain, code: ErrorCode.outOfMemoryError.rawValue)
+                }
+                return false
+            };
             _CFXMLInterfaceCtxtUseOptions(_parserContext, options)
             // Prepare the remaining data for parsing
             let dataRange = bomChunk.indices
@@ -532,57 +539,54 @@ open class XMLParser : NSObject {
 
         let parseResult = unparsedData.withUnsafeBytes { (rawBuffer: UnsafeRawBufferPointer) -> Int32 in
             let bytes = rawBuffer.baseAddress!.assumingMemoryBound(to: CChar.self)
-            return _CFXMLInterfaceParseChunk(_parserContext, bytes, Int32(unparsedData.count), 0)
+            return _CFXMLInterfaceParseChunk(_parserContext, bytes, Int32(unparsedData.count), lastChunkOfData ? 1 : 0)
         }
 
         let result = _handleParseResult(parseResult)
-        _CFXMLInterfaceSetStructuredErrorFunc(interface, nil)
         return result
     }
 
-    internal func parseFromStream() -> Bool {
+    internal func parseFrom(_ stream : InputStream) -> Bool {
         var result = true
-        XMLParser.setCurrentParser(self)
-        defer { XMLParser.setCurrentParser(nil) }
-        if let stream = _stream {
-            stream.open()
-            defer { stream.close() }
-            let buffer = malloc(_chunkSize)!.bindMemory(to: UInt8.self, capacity: _chunkSize)
-            defer { free(buffer) }
-            var len = stream.read(buffer, maxLength: _chunkSize)
-            if len != -1 {
-                while len > 0 {
-                    let data = Data(bytesNoCopy: buffer, count: len, deallocator: .none)
-                    result = parseData(data)
-                    len = stream.read(buffer, maxLength: _chunkSize)
-                }
-            } else {
+
+        guard let buffer = malloc(_chunkSize)?.bindMemory(to: UInt8.self, capacity: _chunkSize) else { return false }
+        defer { free(buffer) }
+
+        stream.open()
+        defer { stream.close() }
+        parseLoop: while result {
+            switch stream.read(buffer, maxLength: _chunkSize) {
+            case let len where len > 0:
+                let data = Data(bytesNoCopy: buffer, count: len, deallocator: .none)
+                result = parseData(data)
+            case 0:
+                result = parseData(Data(), lastChunkOfData: true)
+                break parseLoop
+            default: // See SR-13516, should be `case ..<0:`
                 result = false
-            }
-        } else if var data = _data {
-            let buffer = malloc(_chunkSize)!.bindMemory(to: UInt8.self, capacity: _chunkSize)
-            defer { free(buffer) }
-            var range = NSRange(location: 0, length: min(_chunkSize, data.count))
-            while result {
-                let chunk = data.withUnsafeMutableBytes { (rawBuffer: UnsafeMutableRawBufferPointer) -> Data in
-                    let ptr = rawBuffer.baseAddress!.advanced(by: range.location)
-                    return Data(bytesNoCopy: ptr, count: range.length, deallocator: .none)
-                }
-                result = parseData(chunk)
-                if range.location + range.length >= data.count {
-                    break
+                if _parserError == nil {
+                    _parserError = stream.streamError
                 }
-                range = NSRange(location: range.location + range.length, length: min(_chunkSize, data.count - (range.location + range.length)))
+
+                break parseLoop
             }
-        } else {
-            result = false
         }
+
         return result
     }
     
     // called to start the event-driven parse. Returns YES in the event of a successful parse, and NO in case of error.
     open func parse() -> Bool {
-        return parseFromStream()
+        XMLParser.setCurrentParser(self)
+        defer { XMLParser.setCurrentParser(nil) }
+
+        if _stream != nil {
+            return parseFrom(_stream!)
+        } else if _data != nil {
+            return parseData(_data!, lastChunkOfData: true)
+        }
+
+        return false
     }
     
     // called by the delegate to stop the parse. The delegate will get an error message sent to it.
diff --git a/Tests/Foundation/Tests/TestXMLParser.swift b/Tests/Foundation/Tests/TestXMLParser.swift
index 240dc1f9c1..e013829339 100644
--- a/Tests/Foundation/Tests/TestXMLParser.swift
+++ b/Tests/Foundation/Tests/TestXMLParser.swift
@@ -95,6 +95,7 @@ class TestXMLParser : XCTestCase {
             .foundCharacters("bar"),
             .didEndElement("foo", uri, namespaces ? "foo" : nil),
             .didEndElement("test", uri, namespaces ? "test" : nil),
+            .endDocument,
         ]
     }