Move dart2js from sdk/lib/_internal/compiler to pkg/compiler

sdk/lib/_internal/compiler/implementation/scanner/utf8_bytes_scanner.dart

-// Copyright (c) 2013, 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.
-
-part of scanner;
-
-/**
- * Scanner that reads from a UTF-8 encoded list of bytes and creates tokens
- * that points to substrings.
- */
-class Utf8BytesScanner extends ArrayBasedScanner {
-  /** The file content. */
-  List<int> bytes;
-
-  /**
-   * Points to the offset of the last byte returned by [advance].
-   *
-   * After invoking [currentAsUnicode], the [byteOffset] points to the last
-   * byte that is part of the (unicode or ASCII) character. That way, [advance]
-   * can always increase the byte offset by 1.
-   */
-  int byteOffset = -1;
-
-  /**
-   * The getter [scanOffset] is expected to return the index where the current
-   * character *starts*. In case of a non-ascii character, after invoking
-   * [currentAsUnicode], the byte offset points to the *last* byte.
-   *
-   * This field keeps track of the number of bytes for the current unicode
-   * character. For example, if bytes 7,8,9 encode one unicode character, the
-   * [byteOffset] is 9 (after invoking [currentAsUnicode]). The [scanSlack]
-   * will be 2, so that [scanOffset] returns 7.
-   */
-  int scanSlack = 0;
-
-  /**
-   * Holds the [byteOffset] value for which the current [scanSlack] is valid.
-   */
-  int scanSlackOffset = -1;
-
-  /**
-   * Returns the byte offset of the first byte that belongs to the current
-   * character.
-   */
-  int get scanOffset {
-    if (byteOffset == scanSlackOffset) {
-      return byteOffset - scanSlack;
-    } else {
-      return byteOffset;
-    }
-  }
-
-  /**
-   * The difference between the number of bytes and the number of corresponding
-   * string characters, up to the current [byteOffset].
-   */
-  int utf8Slack = 0;
-
-  /**
-   * Creates a new Utf8BytesScanner. The source file is expected to be a
-   * [Utf8BytesSourceFile] that holds a list of UTF-8 bytes. Otherwise the
-   * string text of the source file is decoded.
-   *
-   * The list of UTF-8 bytes [file.slowUtf8Bytes()] is expected to return an
-   * array whose last element is '0' to signal the end of the file. If this
-   * is not the case, the entire array is copied before scanning.
-   */
-  Utf8BytesScanner(SourceFile file, {bool includeComments: false})
-      : bytes = file.slowUtf8Bytes(),
-        super(file, includeComments) {
-    ensureZeroTermination();
-    // Skip a leading BOM.
-    if (_containsBomAt(0)) byteOffset += 3;
-  }
-
-  /**
-   * Creates a new Utf8BytesScanner from a list of UTF-8 bytes.
-   *
-   * The last element of the list is expected to be '0' to signal the end of
-   * the file. If this is not the case, the entire array is copied before
-   * scanning.
-   */
-  Utf8BytesScanner.fromBytes(this.bytes, {bool includeComments: false})
-      : super(null, includeComments) {
-    ensureZeroTermination();
-  }
-
-  void ensureZeroTermination() {
-    if (bytes.isEmpty || bytes[bytes.length - 1] != 0) {
-      // TODO(lry): abort instead of copying the array, or warn?
-      var newBytes =  new Uint8List(bytes.length + 1);
-      for (int i = 0; i < bytes.length; i++) {
-        newBytes[i] = bytes[i];
-      }
-      newBytes[bytes.length] = 0;
-      bytes = newBytes;
-    }
-  }
-
-  bool _containsBomAt(int offset) {
-    const BOM_UTF8 = const [0xEF, 0xBB, 0xBF];
-
-    return offset + 3 < bytes.length &&
-        bytes[offset] == BOM_UTF8[0] &&
-        bytes[offset + 1] == BOM_UTF8[1] &&
-        bytes[offset + 2] == BOM_UTF8[2];
-  }
-
-  int advance() => bytes[++byteOffset];
-
-  int peek() => bytes[byteOffset + 1];
-
-  /**
-   * Returns the unicode code point starting at the byte offset [startOffset]
-   * with the byte [nextByte]. If [advance] is true the current [byteOffset]
-   * is advanced to the last byte of the code point.
-   */
-  int nextCodePoint(int startOffset, int nextByte, bool advance) {
-    // The number of 1s in the first byte indicate the number of bytes, at
-    // least 2.
-    int numBytes = 2;
-    int bit = 0x20;
-    while ((nextByte & bit) != 0) {
-      numBytes++;
-      bit >>= 1;
-    }
-    int end = startOffset + numBytes;
-    if (advance) {
-      byteOffset = end - 1;
-    }
-    // TODO(lry): measurably slow, decode creates first a Utf8Decoder and a
-    // _Utf8Decoder instance. Also the sublist is eagerly allocated.
-    String codePoint = UTF8.decode(bytes.sublist(startOffset, end));
-    if (codePoint.length == 0) {
-      // The UTF-8 decoder discards leading BOM characters.
-      // TODO(floitsch): don't just assume that removed characters were the
-      // BOM.
-      assert(_containsBomAt(startOffset));
-      codePoint = new String.fromCharCode(UNICODE_BOM_CHARACTER_RUNE);
-    }
-    if (codePoint.length == 1) {
-      if (advance) {
-        utf8Slack += (numBytes - 1);
-        scanSlack = numBytes - 1;
-        scanSlackOffset = byteOffset;
-      }
-      return codePoint.codeUnitAt(0);
-    } else if (codePoint.length == 2) {
-      if (advance) {
-        utf8Slack += (numBytes - 2);
-        scanSlack = numBytes - 1;
-        scanSlackOffset = byteOffset;
-        stringOffsetSlackOffset = byteOffset;
-      }
-      // In case of a surrogate pair, return a single code point.
-      return codePoint.runes.single;
-    } else {
-      throw "Invalid UTF-8 byte sequence: ${bytes.sublist(startOffset, end)}";
-    }
-  }
-
-  int lastUnicodeOffset = -1;
-  int currentAsUnicode(int next) {
-    if (next < 128) return next;
-    // Check if currentAsUnicode was already invoked.
-    if (byteOffset == lastUnicodeOffset) return next;
-    int res = nextCodePoint(byteOffset, next, true);
-    lastUnicodeOffset = byteOffset;
-    return res;
-  }
-
-  void handleUnicode(int startScanOffset) {
-    int end = byteOffset;
-    // TODO(lry): this measurably slows down the scanner for files with unicode.
-    String s = UTF8.decode(bytes.sublist(startScanOffset, end));
-    utf8Slack += (end - startScanOffset) - s.length;
-  }
-
-  /**
-   * This field remembers the byte offset of the last character decoded with
-   * [nextCodePoint] that used two code units in UTF-16.
-   *
-   * [nextCodePoint] returns a single code point for each unicode character,
-   * even if it needs two code units in UTF-16.
-   *
-   * For example, '\u{1d11e}' uses 4 bytes in UTF-8, and two code units in
-   * UTF-16. The [utf8Slack] is therefore 2. After invoking [nextCodePoint], the
-   * [byteOffset] points to the last (of 4) bytes. The [stringOffset] should
-   * return the offset of the first one, which is one position more left than
-   * the [utf8Slack].
-   */
-  int stringOffsetSlackOffset = -1;
-
-  int get stringOffset {
-    if (stringOffsetSlackOffset == byteOffset) {
-      return byteOffset - utf8Slack - 1;
-    } else {
-      return byteOffset - utf8Slack;
-    }
-  }
-
-  Token firstToken() => tokens.next;
-  Token previousToken() => tail;
-
-  void appendSubstringToken(PrecedenceInfo info, int start, bool asciiOnly,
-                            [int extraOffset = 0]) {
-    tail.next = new StringToken.fromUtf8Bytes(
-        info, bytes, start, byteOffset + extraOffset, asciiOnly, tokenStart);
-    tail = tail.next;
-  }
-
-  bool atEndOfFile() => byteOffset >= bytes.length - 1;
-}