Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/html5lib/src/inputstream.dart

+library inputstream;
+
+import 'dart:collection';
+import 'package:utf/utf.dart';
+import 'package:source_span/source_span.dart';
+import 'char_encodings.dart';
+import 'constants.dart';
+import 'utils.dart';
+import 'encoding_parser.dart';
+
+/// Hooks to call into dart:io without directly referencing it.
+class ConsoleSupport {
+  List<int> bytesFromFile(source) => null;
+}
+
+// TODO(jmesserly): use lazy init here when supported.
+ConsoleSupport consoleSupport = new ConsoleSupport();
+
+/// Provides a unicode stream of characters to the HtmlTokenizer.
+///
+/// This class takes care of character encoding and removing or replacing
+/// incorrect byte-sequences and also provides column and line tracking.
+class HtmlInputStream {
+  /// Number of bytes to use when looking for a meta element with
+  /// encoding information.
+  static const int numBytesMeta = 512;
+
+  /// Encoding to use if no other information can be found.
+  static const String defaultEncoding = 'windows-1252';
+
+  /// The name of the character encoding.
+  String charEncodingName;
+
+  /// True if we are certain about [charEncodingName], false for tenative.
+  bool charEncodingCertain = true;
+
+  final bool generateSpans;
+
+  /// Location where the contents of the stream were found.
+  final String sourceUrl;
+
+  List<int> _rawBytes;
+
+  /// Raw UTF-16 codes, used if a Dart String is passed in.
+  Iterable<int> _rawChars;
+
+  Queue<String> errors;
+
+  SourceFile fileInfo;
+
+  List<int> _lineStarts;
+
+  List<int> _chars;
+
+  int _offset;
+
+  /// Initialises the HtmlInputStream.
+  ///
+  /// HtmlInputStream(source, [encoding]) -> Normalized stream from source
+  /// for use by html5lib.
+  ///
+  /// [source] can be either a [String] or a [List<int>] containing the raw
+  /// bytes, or a file if [consoleSupport] is initialized.
+  ///
+  /// The optional encoding parameter must be a string that indicates
+  /// the encoding.  If specified, that encoding will be used,
+  /// regardless of any BOM or later declaration (such as in a meta
+  /// element)
+  ///
+  /// [parseMeta] - Look for a <meta> element containing encoding information
+  HtmlInputStream(source, [String encoding, bool parseMeta = true,
+        this.generateSpans = false, this.sourceUrl])
+      : charEncodingName = codecName(encoding) {
+
+    if (source is String) {
+      _rawChars = toCodepoints(source);
+      charEncodingName = 'utf-8';
+      charEncodingCertain = true;
+    } else if (source is List<int>) {
+      _rawBytes = source;
+    } else {
+      // TODO(jmesserly): it's unfortunate we need to read all bytes in advance,
+      // but it's necessary because of how the UTF decoders work.
+      _rawBytes = consoleSupport.bytesFromFile(source);
+
+      if (_rawBytes == null) {
+        // TODO(jmesserly): we should accept some kind of stream API too.
+        // Unfortunately dart:io InputStream is async only, which won't work.
+        throw new ArgumentError("'source' must be a String or "
+            "List<int> (of bytes). You can also pass a RandomAccessFile if you"
+            "`import 'package:html5lib/parser_console.dart'` and call "
+            "`useConsole()`.");
+      }
+    }
+
+    // Detect encoding iff no explicit "transport level" encoding is supplied
+    if (charEncodingName == null) {
+      detectEncoding(parseMeta);
+    }
+
+    reset();
+  }
+
+  void reset() {
+    errors = new Queue<String>();
+
+    _offset = 0;
+    _lineStarts = <int>[0];
+    _chars = <int>[];
+
+    if (_rawChars == null) {
+      _rawChars = decodeBytes(charEncodingName, _rawBytes);
+    }
+
+    bool skipNewline = false;
+    for (var c in _rawChars) {
+      if (skipNewline) {
+        skipNewline = false;
+        if (c == NEWLINE) continue;
+      }
+
+      if (invalidUnicode(c)) errors.add('invalid-codepoint');
+
+      if (0xD800 <= c && c <= 0xDFFF) {
+        c = 0xFFFD;
+      } else if (c == RETURN) {
+        skipNewline = true;
+        c = NEWLINE;
+      }
+
+      _chars.add(c);
+      if (c == NEWLINE) _lineStarts.add(_chars.length);
+    }
+
+    // Free decoded characters if they aren't needed anymore.
+    if (_rawBytes != null) _rawChars = null;
+
+    // TODO(sigmund): Don't parse the file at all if spans aren't being
+    // generated.
+    fileInfo = new SourceFile.decoded(_chars, url: sourceUrl);
+  }
+
+
+  void detectEncoding([bool parseMeta = true]) {
+    // First look for a BOM
+    // This will also read past the BOM if present
+    charEncodingName = detectBOM();
+    charEncodingCertain = true;
+
+    // If there is no BOM need to look for meta elements with encoding
+    // information
+    if (charEncodingName == null && parseMeta) {
+      charEncodingName = detectEncodingMeta();
+      charEncodingCertain = false;
+    }
+    // If all else fails use the default encoding
+    if (charEncodingName == null) {
+      charEncodingCertain = false;
+      charEncodingName = defaultEncoding;
+    }
+
+    // Substitute for equivalent encodings:
+    if (charEncodingName.toLowerCase() == 'iso-8859-1') {
+      charEncodingName = 'windows-1252';
+    }
+  }
+
+  void changeEncoding(String newEncoding) {
+    if (_rawBytes == null) {
+      // We should never get here -- if encoding is certain we won't try to
+      // change it.
+      throw new StateError('cannot change encoding when parsing a String.');
+    }
+
+    newEncoding = codecName(newEncoding);
+    if (const ['utf-16', 'utf-16-be', 'utf-16-le'].contains(newEncoding)) {
+      newEncoding = 'utf-8';
+    }
+    if (newEncoding == null) {
+      return;
+    } else if (newEncoding == charEncodingName) {
+      charEncodingCertain = true;
+    } else {
+      charEncodingName = newEncoding;
+      charEncodingCertain = true;
+      _rawChars = null;
+      reset();
+      throw new ReparseException(
+          'Encoding changed from $charEncodingName to $newEncoding');
+    }
+  }
+
+  /// Attempts to detect at BOM at the start of the stream. If
+  /// an encoding can be determined from the BOM return the name of the
+  /// encoding otherwise return null.
+  String detectBOM() {
+    // Try detecting the BOM using bytes from the string
+    if (hasUtf8Bom(_rawBytes)) {
+      return 'utf-8';
+    }
+    // Note: we don't need to remember whether it was big or little endian
+    // because the decoder will do that later. It will also eat the BOM for us.
+    if (hasUtf16Bom(_rawBytes)) {
+      return 'utf-16';
+    }
+    if (hasUtf32Bom(_rawBytes)) {
+      return 'utf-32';
+    }
+    return null;
+  }
+
+  /// Report the encoding declared by the meta element.
+  String detectEncodingMeta() {
+    var parser = new EncodingParser(slice(_rawBytes, 0, numBytesMeta));
+    var encoding = parser.getEncoding();
+
+    if (const ['utf-16', 'utf-16-be', 'utf-16-le'].contains(encoding)) {
+      encoding = 'utf-8';
+    }
+
+    return encoding;
+  }
+
+  /// Returns the current offset in the stream, i.e. the number of codepoints
+  /// since the start of the file.
+  int get position => _offset;
+
+  /// Read one character from the stream or queue if available. Return
+  /// EOF when EOF is reached.
+  String char() {
+    if (_offset >= _chars.length) return EOF;
+    return new String.fromCharCodes([_chars[_offset++]]);
+  }
+
+  String peekChar() {
+    if (_offset >= _chars.length) return EOF;
+    return new String.fromCharCodes([_chars[_offset]]);
+  }
+
+  /// Returns a string of characters from the stream up to but not
+  /// including any character in 'characters' or EOF.
+  String charsUntil(String characters, [bool opposite = false]) {
+    int start = _offset;
+    String c;
+    while ((c = peekChar()) != null && characters.contains(c) == opposite) {
+      _offset++;
+    }
+
+    return new String.fromCharCodes(_chars.sublist(start, _offset));
+  }
+
+  void unget(String ch) {
+    // Only one character is allowed to be ungotten at once - it must
+    // be consumed again before any further call to unget
+    if (ch != null) {
+      _offset--;
+      assert(peekChar() == ch);
+    }
+  }
+}
+
+
+// TODO(jmesserly): the Python code used a regex to check for this. But
+// Dart doesn't let you create a regexp with invalid characters.
+bool invalidUnicode(int c) {
+  if (0x0001 <= c && c <= 0x0008) return true;
+  if (0x000E <= c && c <= 0x001F) return true;
+  if (0x007F <= c && c <= 0x009F) return true;
+  if (0xD800 <= c && c <= 0xDFFF) return true;
+  if (0xFDD0 <= c && c <= 0xFDEF) return true;
+  switch (c) {
+    case 0x000B: case 0xFFFE: case 0xFFFF: case 0x01FFFE: case 0x01FFFF:
+    case 0x02FFFE: case 0x02FFFF: case 0x03FFFE: case 0x03FFFF:
+    case 0x04FFFE: case 0x04FFFF: case 0x05FFFE: case 0x05FFFF:
+    case 0x06FFFE: case 0x06FFFF: case 0x07FFFE: case 0x07FFFF:
+    case 0x08FFFE: case 0x08FFFF: case 0x09FFFE: case 0x09FFFF:
+    case 0x0AFFFE: case 0x0AFFFF: case 0x0BFFFE: case 0x0BFFFF:
+    case 0x0CFFFE: case 0x0CFFFF: case 0x0DFFFE: case 0x0DFFFF:
+    case 0x0EFFFE: case 0x0EFFFF: case 0x0FFFFE: case 0x0FFFFF:
+    case 0x10FFFE: case 0x10FFFF:
+      return true;
+  }
+  return false;
+}
+
+/// Return the python codec name corresponding to an encoding or null if the
+/// string doesn't correspond to a valid encoding.
+String codecName(String encoding) {
+  final asciiPunctuation = new RegExp(
+      "[\u0009-\u000D\u0020-\u002F\u003A-\u0040\u005B-\u0060\u007B-\u007E]");
+
+  if (encoding == null) return null;
+  var canonicalName = encoding.replaceAll(asciiPunctuation, '').toLowerCase();
+  return encodings[canonicalName];
+}