pkg/mime: Removed mutable state from MimeMultipartTransformer

pkg/mime/lib/src/bound_multipart_stream.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+library mime.bound_multipart_stream;
+
+import 'dart:async';
+import 'dart:convert';
+
+import 'mime_shared.dart';
+import 'char_code.dart';
+
+// Bytes for '()<>@,;:\\"/[]?={} \t'.
+const _SEPARATORS = const [40, 41, 60, 62, 64, 44, 59, 58, 92, 34, 47, 91, 93,
+                           63, 61, 123, 125, 32, 9];
+
+bool _isTokenChar(int byte) {
+  return byte > 31 && byte < 128 && _SEPARATORS.indexOf(byte) == -1;
+}
+
+int _toLowerCase(int byte) {
+  const delta = CharCode.LOWER_A - CharCode.UPPER_A;
+  return (CharCode.UPPER_A <= byte && byte <= CharCode.UPPER_Z) ?
+      byte + delta : byte;
+}
+
+void _expectByteValue(int val1, int val2) {
+  if (val1 != val2) {
+    throw new MimeMultipartException("Failed to parse multipart mime 1");
+  }
+}
+
+void _expectWhitespace(int byte) {
+  if (byte != CharCode.SP && byte != CharCode.HT) {
+    throw new MimeMultipartException("Failed to parse multipart mime 2");
+  }
+}
+
+class _MimeMultipart extends MimeMultipart {
+  final Map<String, String> headers;
+  final Stream<List<int>> _stream;
+
+  _MimeMultipart(this.headers, this._stream);
+
+  StreamSubscription<List<int>> listen(void onData(List<int> data),
+                                       {void onDone(),
+                                        Function onError,
+                                        bool cancelOnError}) {
+    return _stream.listen(onData,
+                          onDone: onDone,
+                          onError: onError,
+                          cancelOnError: cancelOnError);
+  }
+}
+
+class BoundMultipartStream {
+   static const int _START = 0;
+   static const int _FIRST_BOUNDARY_ENDING = 111;
+   static const int _FIRST_BOUNDARY_END = 112;
+   static const int _BOUNDARY_ENDING = 1;
+   static const int _BOUNDARY_END = 2;
+   static const int _HEADER_START = 3;
+   static const int _HEADER_FIELD = 4;
+   static const int _HEADER_VALUE_START = 5;
+   static const int _HEADER_VALUE = 6;
+   static const int _HEADER_VALUE_FOLDING_OR_ENDING = 7;
+   static const int _HEADER_VALUE_FOLD_OR_END = 8;
+   static const int _HEADER_ENDING = 9;
+   static const int _CONTENT = 10;
+   static const int _LAST_BOUNDARY_DASH2 = 11;
+   static const int _LAST_BOUNDARY_ENDING = 12;
+   static const int _LAST_BOUNDARY_END = 13;
+   static const int _DONE = 14;
+   static const int _FAIL = 15;
+
+   final List<int> _boundary;
+   final List<int> _headerField = [];
+   final List<int> _headerValue = [];
+
+   StreamController _controller;
+
+   Stream<MimeMultipart> get stream => _controller.stream;
+
+   StreamSubscription _subscription;
+
+   StreamController _multipartController;
+   Map<String, String> _headers;
+
+   int _state = _START;
+   int _boundaryIndex = 2;
+
+   // Current index in the data buffer. If index is negative then it
+   // is the index into the artificial prefix of the boundary string.
+   int _index;
+   List<int> _buffer;
+
+   BoundMultipartStream(this._boundary, Stream<List<int>> stream) {
+     _controller = new StreamController(
+         sync: true,
+         onPause: _pauseStream,
+         onResume:_resumeStream,
+         onCancel: () {
+           _subscription.cancel();
+         },
+         onListen: () {
+           _subscription = stream.listen(
+               (data) {
+                 assert(_buffer == null);
+                 _pauseStream();
+                 _buffer = data;
+                 _index = 0;
+                 _parse();
+               },
+               onDone: () {
+                 if (_state != _DONE) {
+                   _controller.addError(
+                       new MimeMultipartException("Bad multipart ending"));
+                 }
+                 _controller.close();
+               },
+               onError: _controller.addError);
+         });
+   }
+
+   void _resumeStream() {
+     _subscription.resume();
+   }
+
+   void _pauseStream() {
+     _subscription.pause();
+   }
+
+
+   void _parse() {
+     // Number of boundary bytes to artificially place before the supplied data.
+     int boundaryPrefix = 0;
+     // Position where content starts. Will be null if no known content
+     // start exists. Will be negative of the content starts in the
+     // boundary prefix. Will be zero or position if the content starts
+     // in the current buffer.
+     int contentStartIndex;
+
+     // Function to report content data for the current part. The data
+     // reported is from the current content start index up til the
+     // current index. As the data can be artificially prefixed with a
+     // prefix of the boundary both the content start index and index
+     // can be negative.
+     void reportData() {
+       if (contentStartIndex < 0) {
+         var contentLength = boundaryPrefix + _index - _boundaryIndex;
+         if (contentLength <= boundaryPrefix) {
+           _multipartController.add(
+               _boundary.sublist(0, contentLength));
+         } else {
+           _multipartController.add(
+               _boundary.sublist(0, boundaryPrefix));
+           _multipartController.add(
+               _buffer.sublist(0, contentLength - boundaryPrefix));
+         }
+       } else {
+         var contentEndIndex = _index - _boundaryIndex;
+         _multipartController.add(
+             _buffer.sublist(contentStartIndex, contentEndIndex));
+       }
+     }
+
+     if (_state == _CONTENT && _boundaryIndex == 0) {
+       contentStartIndex = 0;
+     } else {
+       contentStartIndex = null;
+     }
+     // The data to parse might be "artificially" prefixed with a
+     // partial match of the boundary.
+     boundaryPrefix = _boundaryIndex;
+
+     while ((_index < _buffer.length) && _state != _FAIL && _state != _DONE) {
+       if (_multipartController != null && _multipartController.isPaused) {
+         return;
+       }
+       int byte;
+       if (_index < 0) {
+         byte = _boundary[boundaryPrefix + _index];
+       } else {
+         byte = _buffer[_index];
+       }
+       switch (_state) {
+         case _START:
+           if (byte == _boundary[_boundaryIndex]) {
+             _boundaryIndex++;
+             if (_boundaryIndex == _boundary.length) {
+               _state = _FIRST_BOUNDARY_ENDING;
+               _boundaryIndex = 0;
+             }
+           } else {
+             // Restart matching of the boundary.
+             _index = _index - _boundaryIndex;
+             _boundaryIndex = 0;
+           }
+           break;
+
+         case _FIRST_BOUNDARY_ENDING:
+           if (byte == CharCode.CR) {
+             _state = _FIRST_BOUNDARY_END;
+           } else {
+             _expectWhitespace(byte);
+           }
+           break;
+
+         case _FIRST_BOUNDARY_END:
+           _expectByteValue(byte, CharCode.LF);
+           _state = _HEADER_START;
+           break;
+
+         case _BOUNDARY_ENDING:
+           if (byte == CharCode.CR) {
+             _state = _BOUNDARY_END;
+           } else if (byte == CharCode.DASH) {
+             _state = _LAST_BOUNDARY_DASH2;
+           } else {
+             _expectWhitespace(byte);
+           }
+           break;
+
+         case _BOUNDARY_END:
+           _expectByteValue(byte, CharCode.LF);
+           _multipartController.close();
+           _multipartController = null;
+           _state = _HEADER_START;
+           break;
+
+         case _HEADER_START:
+           _headers = new Map<String, String>();
+           if (byte == CharCode.CR) {
+             _state = _HEADER_ENDING;
+           } else {
+             // Start of new header field.
+             _headerField.add(_toLowerCase(byte));
+             _state = _HEADER_FIELD;
+           }
+           break;
+
+         case _HEADER_FIELD:
+           if (byte == CharCode.COLON) {
+             _state = _HEADER_VALUE_START;
+           } else {
+             if (!_isTokenChar(byte)) {
+               throw new MimeMultipartException("Invalid header field name");
+             }
+             _headerField.add(_toLowerCase(byte));
+           }
+           break;
+
+         case _HEADER_VALUE_START:
+           if (byte == CharCode.CR) {
+             _state = _HEADER_VALUE_FOLDING_OR_ENDING;
+           } else if (byte != CharCode.SP && byte != CharCode.HT) {
+             // Start of new header value.
+             _headerValue.add(byte);
+             _state = _HEADER_VALUE;
+           }
+           break;
+
+         case _HEADER_VALUE:
+           if (byte == CharCode.CR) {
+             _state = _HEADER_VALUE_FOLDING_OR_ENDING;
+           } else {
+             _headerValue.add(byte);
+           }
+           break;
+
+         case _HEADER_VALUE_FOLDING_OR_ENDING:
+           _expectByteValue(byte, CharCode.LF);
+           _state = _HEADER_VALUE_FOLD_OR_END;
+           break;
+
+         case _HEADER_VALUE_FOLD_OR_END:
+           if (byte == CharCode.SP || byte == CharCode.HT) {
+             _state = _HEADER_VALUE_START;
+           } else {
+             String headerField = UTF8.decode(_headerField);
+             String headerValue = UTF8.decode(_headerValue);
+             _headers[headerField.toLowerCase()] = headerValue;
+             _headerField.clear();
+             _headerValue.clear();
+             if (byte == CharCode.CR) {
+               _state = _HEADER_ENDING;
+             } else {
+               // Start of new header field.
+               _headerField.add(_toLowerCase(byte));
+               _state = _HEADER_FIELD;
+             }
+           }
+           break;
+
+         case _HEADER_ENDING:
+           _expectByteValue(byte, CharCode.LF);
+           _multipartController = new StreamController(
+               sync: true,
+               onPause: () {
+                 _pauseStream();
+               },
+               onResume: () {
+                 _resumeStream();
+                 _parse();
+               });
+           _controller.add(
+               new _MimeMultipart(_headers, _multipartController.stream));
+           _headers = null;
+           _state = _CONTENT;
+           contentStartIndex = _index + 1;
+           break;
+
+         case _CONTENT:
+           if (byte == _boundary[_boundaryIndex]) {
+             _boundaryIndex++;
+             if (_boundaryIndex == _boundary.length) {
+               if (contentStartIndex != null) {
+                 _index++;
+                 reportData();
+                 _index--;
+               }
+               _multipartController.close();
+               _boundaryIndex = 0;
+               _state = _BOUNDARY_ENDING;
+             }
+           } else {
+             // Restart matching of the boundary.
+             _index = _index - _boundaryIndex;
+             if (contentStartIndex == null) contentStartIndex = _index;
+             _boundaryIndex = 0;
+           }
+           break;
+
+         case _LAST_BOUNDARY_DASH2:
+           _expectByteValue(byte, CharCode.DASH);
+           _state = _LAST_BOUNDARY_ENDING;
+           break;
+
+         case _LAST_BOUNDARY_ENDING:
+           if (byte == CharCode.CR) {
+             _state = _LAST_BOUNDARY_END;
+           } else {
+             _expectWhitespace(byte);
+           }
+           break;
+
+         case _LAST_BOUNDARY_END:
+           _expectByteValue(byte, CharCode.LF);
+           _multipartController.close();
+           _multipartController = null;
+           _state = _DONE;
+           break;
+
+         default:
+           // Should be unreachable.
+           assert(false);
+           break;
+       }
+
+       // Move to the next byte.
+       _index++;
+     }
+
+     // Report any known content.
+     if (_state == _CONTENT && contentStartIndex != null) {
+       reportData();
+     }
+
+     // Resume if at end.
+     if (_index == _buffer.length) {
+       _buffer = null;
+       _index = null;
+       _resumeStream();
+     }
+   }
+}