Moving logic for writing source maps from SourceMapBuilder into the Mapping class.

pkg/source_maps/lib/builder.dart

Index: pkg/source_maps/lib/builder.dart
diff --git a/pkg/source_maps/lib/builder.dart b/pkg/source_maps/lib/builder.dart
index ef22e3123720dcdf9d726c85662ac3b06c24cd61..cd30ccb94941fd4b2ec57872e3be7a8e3daef716 100644
--- a/pkg/source_maps/lib/builder.dart
+++ b/pkg/source_maps/lib/builder.dart
@@ -7,25 +7,16 @@ library source_maps.builder;
 
 // TODO(sigmund): add a builder for multi-section mappings.
 
-import 'dart:collection';
 import 'dart:convert';
 
+import 'parser.dart';
 import 'span.dart';
-import 'src/vlq.dart';
 
 /// Builds a source map given a set of mappings.
 class SourceMapBuilder {
 
   final List<Entry> _entries = <Entry>[];
 
-  /// Indices associated with file urls that will be part of the source map. We
-  /// use a linked hash-map so that `_urls.keys[_urls[u]] == u`
-  final Map<String, int> _urls = new LinkedHashMap<String, int>();
-
-  /// Indices associated with identifiers that will be part of the source map.
-  /// We use a linked hash-map so that `_names.keys[_names[n]] == n`
-  final Map<String, int> _names = new LinkedHashMap<String, int>();
-
   /// Adds an entry mapping the [targetOffset] to [source].
   void addFromOffset(Location source,
       SourceFile targetFile, int targetOffset, String identifier) {
@@ -48,78 +39,11 @@ class SourceMapBuilder {
 
   /// Encodes all mappings added to this builder as a json map.
   Map build(String fileUrl) {
-    var buff = new StringBuffer();
-    var line = 0;
-    var column = 0;
-    var srcLine = 0;
-    var srcColumn = 0;
-    var srcUrlId = 0;
-    var srcNameId = 0;
-    var first = true;
-
-    // The encoding needs to be sorted by the target offsets.
-    _entries.sort();
-    for (var entry in _entries) {
-      int nextLine = entry.target.line;
-      if (nextLine > line) {
-        for (int i = line; i < nextLine; ++i) {
-          buff.write(';');
-        }
-        line = nextLine;
-        column = 0;
-        first = true;
-      }
-
-      if (!first) buff.write(',');
-      first = false;
-      column = _append(buff, column, entry.target.column);
-
-      // Encoding can be just the column offset if there is no source
-      // information.
-      var source = entry.source;
-      if (source == null) continue;
-      var newUrlId = _indexOf(_urls, source.sourceUrl);
-
-      srcUrlId = _append(buff, srcUrlId, newUrlId);
-      srcLine = _append(buff, srcLine, source.line);
-      srcColumn = _append(buff, srcColumn, source.column);
-
-      if (entry.identifierName == null) continue;
-      srcNameId = _append(buff, srcNameId,
-          _indexOf(_names, entry.identifierName));
-    }
-
-    var result = {
-      'version': 3,
-      'sourceRoot': '',
-      'sources': _urls.keys.toList(),
-      'names' : _names.keys.toList(),
-      'mappings' : buff.toString()
-    };
-    if (fileUrl != null) {
-      result['file'] = fileUrl;
-    }
-    return result;
+    return new SingleMapping.fromEntries(this._entries, fileUrl).toJson();
   }
 
   /// Encodes all mappings added to this builder as a json string.
   String toJson(String fileUrl) => JSON.encode(build(fileUrl));
-
-  /// Get the index of [value] in [map], or create one if it doesn't exist.
-  int _indexOf(Map<String, int> map, String value) {
-    return map.putIfAbsent(value, () {
-      int index = map.length;
-      map[value] = index;
-      return index;
-    });
-  }
-
-  /// Appends to [buff] a VLQ encoding of [newValue] using the difference
-  /// between [oldValue] and [newValue]
-  static int _append(StringBuffer buff, int oldValue, int newValue) {
-    buff.writeAll(encodeVlq(newValue - oldValue));
-    return newValue;
-  }
 }
 
 /// An entry in the source map builder.