Move source maps package to the dart repo, so it can be used by other internal

pkg/source_maps/lib/printer.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.
+
+/// Contains a code printer that generates code by recording the source maps.
+library source_maps.printer;
+
+import 'dart:utf' show stringToCodepoints;
+import 'builder.dart';
+import 'span.dart';
+
+const int _LF = 10;
+const int _CR = 13;
+
+/// A printer that keeps track of offset locations and records source maps
+/// locations.
+class Printer {
+  final String filename;
+  final StringBuffer _buff = new StringBuffer();
+  final SourceMapBuilder _maps = new SourceMapBuilder();
+  String get text => _buff.toString();
+  String get map => _maps.toJson(filename);
+
+  /// Current source location mapping.
+  Location _loc;
+
+  /// Current line in the buffer;
+  int _line = 0;
+
+  /// Current column in the buffer.
+  int _column = 0;
+
+  Printer(this.filename);
+
+  /// Add [str] contents to the output, tracking new lines to track correct
+  /// positions for span locations. When [projectMarks] is true, this method
+  /// adds a source map location on each new line, projecting that every new
+  /// line in the target file (printed here) corresponds to a new line in the
+  /// source file.
+  void add(String str, {projectMarks: false}) {
+    var chars = stringToCodepoints(str);
+    var length = chars.length;
+    for (int i = 0; i < length; i++) {
+      var c = chars[i];
+      if (c == _LF || (c == _CR && (i + 1 == length || chars[i + 1] != _LF))) {
+        // Return not followed by line-feed is treated as a new line.
+        _line++;
+        _column = 0;
+        if (projectMarks && _loc != null) {
+          if (_loc is FixedLocation) {
+            mark(new FixedLocation(0, _loc.sourceUrl, _loc.line + 1, 0));
+          } else if (_loc is FileLocation) {
+            var file = (_loc as FileLocation).file;
+            mark(new FileLocation(file, file.getOffset(_loc.line + 1, 0)));
+          }
+        }
+      } else {
+        _column++;
+      }
+    }
+    _buff.write(str);
+  }
+
+
+  /// Append a [total] number of spaces in the target file. Typically used for
+  /// formatting indentation.
+  void addSpaces(int total) {
+    for (int i = 0; i < total; i++) _buff.write(' ');
+    _column += total;
+  }
+
+  /// Marks that the current point in the target file corresponds to the [mark]
+  /// in the source file, which can be either a [Location] or a [Span]. When the
+  /// mark is an identifier's Span, this also records the name of the identifier
+  /// in the source map information.
+  void mark(mark) {
+    var loc;
+    var identifier = null;
+    if (mark is Location) {
+      loc = mark;
+    } else if (mark is Span) {
+      loc = mark.start;
+      if (mark.isIdentifier) identifier = mark.text;
+    }
+    _maps.addLocation(loc,
+        new FixedLocation(_buff.length, null, _line, _column), identifier);
+    _loc = loc;
+  }
+}