| // 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; |
| } |