lib/src/bound_multipart_stream.dart - mime - Git at Google

 // 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.

 import 'dart:async';
 import 'dart:convert';

 import 'char_code.dart' as char_code;
 import 'mime_shared.dart';

 /// Bytes for '()<>@,;:\\"/[]?={} \t'.
 const _separators = {
   40, 41, 60, 62, 64, 44, 59, 58, 92, 34, 47, 91, 93, 63, 61, 123, 125, 32, 9 //
 };

 bool _isTokenChar(int byte) =>
     byte > 31 && byte < 128 && !_separators.contains(byte);

 int _toLowerCase(int byte) {
   const delta = char_code.lowerA - char_code.upperA;
   return (char_code.upperA <= byte && byte <= char_code.upperZ)
       ? byte + delta
       : byte;
 }

 void _expectByteValue(int val1, int val2) {
   if (val1 != val2) {
     throw MimeMultipartException('Failed to parse multipart mime 1');
   }
 }

 void _expectWhitespace(int byte) {
   if (byte != char_code.sp && byte != char_code.ht) {
     throw MimeMultipartException('Failed to parse multipart mime 2');
   }
 }

 class _MimeMultipart extends MimeMultipart {
   @override
   final Map<String, String> headers;
   final Stream<List<int>> _stream;

   _MimeMultipart(this.headers, this._stream);

   @override
   StreamSubscription<List<int>> listen(
     void Function(List<int> data)? onData, {
     void Function()? onDone,
     Function? onError,
     bool? cancelOnError,
   }) =>
       _stream.listen(
         onData,
         onDone: onDone,
         onError: onError,
         cancelOnError: cancelOnError,
       );
 }

 class BoundMultipartStream {
   static const int _startCode = 0;
   static const int _boundaryEndingCode = 1;
   static const int _boundaryEndCode = 2;
   static const int _headerStartCode = 3;
   static const int _headerFieldCode = 4;
   static const int _headerValueStartCode = 5;
   static const int _headerValueCode = 6;
   static const int _headerValueFoldingOrEndingCode = 7;
   static const int _headerValueFoldOrEndCode = 8;
   static const int _headerEndingCode = 9;
   static const int _contentCode = 10;
   static const int _lastBoundaryDash2Code = 11;
   static const int _lastBoundaryEndingCode = 12;
   static const int _lastBoundaryEndCode = 13;
   static const int _doneCode = 14;
   static const int _failCode = 15;

   final List<int> _boundary;
   final List<int> _headerField = [];
   final List<int> _headerValue = [];

   // The following states belong to `_controller`, state changes will not be
   // immediately acted upon but rather only after the current
   // `_multipartController` is done.
   static const int _controllerStateIdle = 0;
   static const int _controllerStateActive = 1;
   static const int _controllerStatePaused = 2;
   static const int _controllerStateCanceled = 3;

   int _controllerState = _controllerStateIdle;

   final _controller = StreamController<MimeMultipart>(sync: true);

   Stream<MimeMultipart> get stream => _controller.stream;

   late StreamSubscription _subscription;

   StreamController<List<int>>? _multipartController;
   Map<String, String>? _headers;

   int _state = _startCode;
   int _boundaryIndex = 2;

   /// Current index into [_buffer].
   ///
   /// If index is negative then it is the index into the artificial prefix of
   /// the boundary string.
   int _index = 0;
   List<int> _buffer = _placeholderBuffer;

   BoundMultipartStream(this._boundary, Stream<List<int>> stream) {
     _controller
       ..onPause = _pauseStream
       ..onResume = _resumeStream
       ..onCancel = () {
         _controllerState = _controllerStateCanceled;
         _tryPropagateControllerState();
       }
       ..onListen = () {
         _controllerState = _controllerStateActive;
         _subscription = stream.listen((data) {
           assert(_buffer == _placeholderBuffer);
           _subscription.pause();
           _buffer = data;
           _index = 0;
           _parse();
         }, onDone: () {
           if (_state != _doneCode) {
             _controller
                 .addError(MimeMultipartException('Bad multipart ending'));
           }
           _controller.close();
         }, onError: _controller.addError);
       };
   }

   void _resumeStream() {
     assert(_controllerState == _controllerStatePaused);
     _controllerState = _controllerStateActive;
     _tryPropagateControllerState();
   }

   void _pauseStream() {
     _controllerState = _controllerStatePaused;
     _tryPropagateControllerState();
   }

   void _tryPropagateControllerState() {
     if (_multipartController == null) {
       switch (_controllerState) {
         case _controllerStateActive:
           if (_subscription.isPaused) _subscription.resume();
           break;
         case _controllerStatePaused:
           if (!_subscription.isPaused) _subscription.pause();
           break;
         case _controllerStateCanceled:
           _subscription.cancel();
           break;
         default:
           throw StateError('This code should never be reached.');
       }
     }
   }

   void _parse() {
     // Number of boundary bytes to artificially place before the supplied data.
     // The data to parse might be 'artificially' prefixed with a
     // partial match of the boundary.
     var boundaryPrefix = _boundaryIndex;
     // 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.
     var contentStartIndex =
         _state == _contentCode && _boundaryIndex == 0 ? 0 : null;

     // 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));
       }
     }

     while (
         _index < _buffer.length && _state != _failCode && _state != _doneCode) {
       var byte =
           _index < 0 ? _boundary[boundaryPrefix + _index] : _buffer[_index];
       switch (_state) {
         case _startCode:
           if (byte == _boundary[_boundaryIndex]) {
             _boundaryIndex++;
             if (_boundaryIndex == _boundary.length) {
               _state = _boundaryEndingCode;
               _boundaryIndex = 0;
             }
           } else {
             // Restart matching of the boundary.
             _index = _index - _boundaryIndex;
             _boundaryIndex = 0;
           }
           break;

         case _boundaryEndingCode:
           if (byte == char_code.cr) {
             _state = _boundaryEndCode;
           } else if (byte == char_code.dash) {
             _state = _lastBoundaryDash2Code;
           } else {
             _expectWhitespace(byte);
           }
           break;

         case _boundaryEndCode:
           _expectByteValue(byte, char_code.lf);
           _multipartController?.close();
           if (_multipartController != null) {
             _multipartController = null;
             _tryPropagateControllerState();
           }
           _state = _headerStartCode;
           break;

         case _headerStartCode:
           _headers = <String, String>{};
           if (byte == char_code.cr) {
             _state = _headerEndingCode;
           } else {
             // Start of new header field.
             _headerField.add(_toLowerCase(byte));
             _state = _headerFieldCode;
           }
           break;

         case _headerFieldCode:
           if (byte == char_code.colon) {
             _state = _headerValueStartCode;
           } else {
             if (!_isTokenChar(byte)) {
               throw MimeMultipartException('Invalid header field name');
             }
             _headerField.add(_toLowerCase(byte));
           }
           break;

         case _headerValueStartCode:
           if (byte == char_code.cr) {
             _state = _headerValueFoldingOrEndingCode;
           } else if (byte != char_code.sp && byte != char_code.ht) {
             // Start of new header value.
             _headerValue.add(byte);
             _state = _headerValueCode;
           }
           break;

         case _headerValueCode:
           if (byte == char_code.cr) {
             _state = _headerValueFoldingOrEndingCode;
           } else {
             _headerValue.add(byte);
           }
           break;

         case _headerValueFoldingOrEndingCode:
           _expectByteValue(byte, char_code.lf);
           _state = _headerValueFoldOrEndCode;
           break;

         case _headerValueFoldOrEndCode:
           if (byte == char_code.sp || byte == char_code.ht) {
             _state = _headerValueStartCode;
           } else {
             var headerField = utf8.decode(_headerField);
             var headerValue = utf8.decode(_headerValue);
             _headers![headerField.toLowerCase()] = headerValue;
             _headerField.clear();
             _headerValue.clear();
             if (byte == char_code.cr) {
               _state = _headerEndingCode;
             } else {
               // Start of new header field.
               _headerField.add(_toLowerCase(byte));
               _state = _headerFieldCode;
             }
           }
           break;

         case _headerEndingCode:
           _expectByteValue(byte, char_code.lf);
           _multipartController = StreamController(
               sync: true,
               onListen: () {
                 if (_subscription.isPaused) _subscription.resume();
               },
               onPause: _subscription.pause,
               onResume: _subscription.resume);
           _controller
               .add(_MimeMultipart(_headers!, _multipartController!.stream));
           _headers = null;
           _state = _contentCode;
           contentStartIndex = _index + 1;
           break;

         case _contentCode:
           if (byte == _boundary[_boundaryIndex]) {
             _boundaryIndex++;
             if (_boundaryIndex == _boundary.length) {
               if (contentStartIndex != null) {
                 _index++;
                 reportData();
                 _index--;
               }
               _multipartController!.close();
               _multipartController = null;
               _tryPropagateControllerState();
               _boundaryIndex = 0;
               _state = _boundaryEndingCode;
             }
           } else {
             // Restart matching of the boundary.
             _index = _index - _boundaryIndex;
             contentStartIndex ??= _index;
             _boundaryIndex = 0;
           }
           break;

         case _lastBoundaryDash2Code:
           _expectByteValue(byte, char_code.dash);
           _state = _lastBoundaryEndingCode;
           break;

         case _lastBoundaryEndingCode:
           if (byte == char_code.cr) {
             _state = _lastBoundaryEndCode;
           } else {
             _expectWhitespace(byte);
           }
           break;

         case _lastBoundaryEndCode:
           _expectByteValue(byte, char_code.lf);
           _multipartController?.close();
           if (_multipartController != null) {
             _multipartController = null;
             _tryPropagateControllerState();
           }
           _state = _doneCode;
           break;

         default:
           // Should be unreachable.
           assert(false);
           break;
       }

       // Move to the next byte.
       _index++;
     }

     // Report any known content.
     if (_state == _contentCode && contentStartIndex != null) {
       reportData();
     }

     // Resume if at end.
     if (_index == _buffer.length) {
       _buffer = _placeholderBuffer;
       _index = 0;
       _subscription.resume();
     }
   }
 }

 // Used as a placeholder instead of having a nullable buffer.
 const _placeholderBuffer = <int>[];
	// 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.

	import 'dart:async';
	import 'dart:convert';

	import 'char_code.dart' as char_code;
	import 'mime_shared.dart';

	/// Bytes for '()<>@,;:\\"/[]?={} \t'.
	const _separators = {
	40, 41, 60, 62, 64, 44, 59, 58, 92, 34, 47, 91, 93, 63, 61, 123, 125, 32, 9 //
	};

	bool _isTokenChar(int byte) =>
	byte > 31 && byte < 128 && !_separators.contains(byte);

	int _toLowerCase(int byte) {
	const delta = char_code.lowerA - char_code.upperA;
	return (char_code.upperA <= byte && byte <= char_code.upperZ)
	? byte + delta
	: byte;
	}

	void _expectByteValue(int val1, int val2) {
	if (val1 != val2) {
	throw MimeMultipartException('Failed to parse multipart mime 1');
	}
	}

	void _expectWhitespace(int byte) {
	if (byte != char_code.sp && byte != char_code.ht) {
	throw MimeMultipartException('Failed to parse multipart mime 2');
	}
	}

	class _MimeMultipart extends MimeMultipart {
	@override
	final Map<String, String> headers;
	final Stream<List<int>> _stream;

	_MimeMultipart(this.headers, this._stream);

	@override
	StreamSubscription<List<int>> listen(
	void Function(List<int> data)? onData, {
	void Function()? onDone,
	Function? onError,
	bool? cancelOnError,
	}) =>
	_stream.listen(
	onData,
	onDone: onDone,
	onError: onError,
	cancelOnError: cancelOnError,
	);
	}

	class BoundMultipartStream {
	static const int _startCode = 0;
	static const int _boundaryEndingCode = 1;
	static const int _boundaryEndCode = 2;
	static const int _headerStartCode = 3;
	static const int _headerFieldCode = 4;
	static const int _headerValueStartCode = 5;
	static const int _headerValueCode = 6;
	static const int _headerValueFoldingOrEndingCode = 7;
	static const int _headerValueFoldOrEndCode = 8;
	static const int _headerEndingCode = 9;
	static const int _contentCode = 10;
	static const int _lastBoundaryDash2Code = 11;
	static const int _lastBoundaryEndingCode = 12;
	static const int _lastBoundaryEndCode = 13;
	static const int _doneCode = 14;
	static const int _failCode = 15;

	final List<int> _boundary;
	final List<int> _headerField = [];
	final List<int> _headerValue = [];

	// The following states belong to `_controller`, state changes will not be
	// immediately acted upon but rather only after the current
	// `_multipartController` is done.
	static const int _controllerStateIdle = 0;
	static const int _controllerStateActive = 1;
	static const int _controllerStatePaused = 2;
	static const int _controllerStateCanceled = 3;

	int _controllerState = _controllerStateIdle;

	final _controller = StreamController<MimeMultipart>(sync: true);

	Stream<MimeMultipart> get stream => _controller.stream;

	late StreamSubscription _subscription;

	StreamController<List<int>>? _multipartController;
	Map<String, String>? _headers;

	int _state = _startCode;
	int _boundaryIndex = 2;

	/// Current index into [_buffer].
	///
	/// If index is negative then it is the index into the artificial prefix of
	/// the boundary string.
	int _index = 0;
	List<int> _buffer = _placeholderBuffer;

	BoundMultipartStream(this._boundary, Stream<List<int>> stream) {
	_controller
	..onPause = _pauseStream
	..onResume = _resumeStream
	..onCancel = () {
	_controllerState = _controllerStateCanceled;
	_tryPropagateControllerState();
	}
	..onListen = () {
	_controllerState = _controllerStateActive;
	_subscription = stream.listen((data) {
	assert(_buffer == _placeholderBuffer);
	_subscription.pause();
	_buffer = data;
	_index = 0;
	_parse();
	}, onDone: () {
	if (_state != _doneCode) {
	_controller
	.addError(MimeMultipartException('Bad multipart ending'));
	}
	_controller.close();
	}, onError: _controller.addError);
	};
	}

	void _resumeStream() {
	assert(_controllerState == _controllerStatePaused);
	_controllerState = _controllerStateActive;
	_tryPropagateControllerState();
	}

	void _pauseStream() {
	_controllerState = _controllerStatePaused;
	_tryPropagateControllerState();
	}

	void _tryPropagateControllerState() {
	if (_multipartController == null) {
	switch (_controllerState) {
	case _controllerStateActive:
	if (_subscription.isPaused) _subscription.resume();
	break;
	case _controllerStatePaused:
	if (!_subscription.isPaused) _subscription.pause();
	break;
	case _controllerStateCanceled:
	_subscription.cancel();
	break;
	default:
	throw StateError('This code should never be reached.');
	}
	}
	}

	void _parse() {
	// Number of boundary bytes to artificially place before the supplied data.
	// The data to parse might be 'artificially' prefixed with a
	// partial match of the boundary.
	var boundaryPrefix = _boundaryIndex;
	// 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.
	var contentStartIndex =
	_state == _contentCode && _boundaryIndex == 0 ? 0 : null;

	// 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));
	}
	}

	while (
	_index < _buffer.length && _state != _failCode && _state != _doneCode) {
	var byte =
	_index < 0 ? _boundary[boundaryPrefix + _index] : _buffer[_index];
	switch (_state) {
	case _startCode:
	if (byte == _boundary[_boundaryIndex]) {
	_boundaryIndex++;
	if (_boundaryIndex == _boundary.length) {
	_state = _boundaryEndingCode;
	_boundaryIndex = 0;
	}
	} else {
	// Restart matching of the boundary.
	_index = _index - _boundaryIndex;
	_boundaryIndex = 0;
	}
	break;

	case _boundaryEndingCode:
	if (byte == char_code.cr) {
	_state = _boundaryEndCode;
	} else if (byte == char_code.dash) {
	_state = _lastBoundaryDash2Code;
	} else {
	_expectWhitespace(byte);
	}
	break;

	case _boundaryEndCode:
	_expectByteValue(byte, char_code.lf);
	_multipartController?.close();
	if (_multipartController != null) {
	_multipartController = null;
	_tryPropagateControllerState();
	}
	_state = _headerStartCode;
	break;

	case _headerStartCode:
	_headers = <String, String>{};
	if (byte == char_code.cr) {
	_state = _headerEndingCode;
	} else {
	// Start of new header field.
	_headerField.add(_toLowerCase(byte));
	_state = _headerFieldCode;
	}
	break;

	case _headerFieldCode:
	if (byte == char_code.colon) {
	_state = _headerValueStartCode;
	} else {
	if (!_isTokenChar(byte)) {
	throw MimeMultipartException('Invalid header field name');
	}
	_headerField.add(_toLowerCase(byte));
	}
	break;

	case _headerValueStartCode:
	if (byte == char_code.cr) {
	_state = _headerValueFoldingOrEndingCode;
	} else if (byte != char_code.sp && byte != char_code.ht) {
	// Start of new header value.
	_headerValue.add(byte);
	_state = _headerValueCode;
	}
	break;

	case _headerValueCode:
	if (byte == char_code.cr) {
	_state = _headerValueFoldingOrEndingCode;
	} else {
	_headerValue.add(byte);
	}
	break;

	case _headerValueFoldingOrEndingCode:
	_expectByteValue(byte, char_code.lf);
	_state = _headerValueFoldOrEndCode;
	break;

	case _headerValueFoldOrEndCode:
	if (byte == char_code.sp \|\| byte == char_code.ht) {
	_state = _headerValueStartCode;
	} else {
	var headerField = utf8.decode(_headerField);
	var headerValue = utf8.decode(_headerValue);
	_headers![headerField.toLowerCase()] = headerValue;
	_headerField.clear();
	_headerValue.clear();
	if (byte == char_code.cr) {
	_state = _headerEndingCode;
	} else {
	// Start of new header field.
	_headerField.add(_toLowerCase(byte));
	_state = _headerFieldCode;
	}
	}
	break;

	case _headerEndingCode:
	_expectByteValue(byte, char_code.lf);
	_multipartController = StreamController(
	sync: true,
	onListen: () {
	if (_subscription.isPaused) _subscription.resume();
	},
	onPause: _subscription.pause,
	onResume: _subscription.resume);
	_controller
	.add(_MimeMultipart(_headers!, _multipartController!.stream));
	_headers = null;
	_state = _contentCode;
	contentStartIndex = _index + 1;
	break;

	case _contentCode:
	if (byte == _boundary[_boundaryIndex]) {
	_boundaryIndex++;
	if (_boundaryIndex == _boundary.length) {
	if (contentStartIndex != null) {
	_index++;
	reportData();
	_index--;
	}
	_multipartController!.close();
	_multipartController = null;
	_tryPropagateControllerState();
	_boundaryIndex = 0;
	_state = _boundaryEndingCode;
	}
	} else {
	// Restart matching of the boundary.
	_index = _index - _boundaryIndex;
	contentStartIndex ??= _index;
	_boundaryIndex = 0;
	}
	break;

	case _lastBoundaryDash2Code:
	_expectByteValue(byte, char_code.dash);
	_state = _lastBoundaryEndingCode;
	break;

	case _lastBoundaryEndingCode:
	if (byte == char_code.cr) {
	_state = _lastBoundaryEndCode;
	} else {
	_expectWhitespace(byte);
	}
	break;

	case _lastBoundaryEndCode:
	_expectByteValue(byte, char_code.lf);
	_multipartController?.close();
	if (_multipartController != null) {
	_multipartController = null;
	_tryPropagateControllerState();
	}
	_state = _doneCode;
	break;

	default:
	// Should be unreachable.
	assert(false);
	break;
	}

	// Move to the next byte.
	_index++;
	}

	// Report any known content.
	if (_state == _contentCode && contentStartIndex != null) {
	reportData();
	}

	// Resume if at end.
	if (_index == _buffer.length) {
	_buffer = _placeholderBuffer;
	_index = 0;
	_subscription.resume();
	}
	}
	}

	// Used as a placeholder instead of having a nullable buffer.
	const _placeholderBuffer = <int>[];