blob: ad80fa00093184e3bea79adb2a30cd6417d688b7 [file] [log] [blame]
// 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 builder object useful for creating source maps programatically.
library source_maps.builder;
// TODO(sigmund): add a builder for multi-section mappings.
import 'dart:json' as json;
import 'dart:collection';
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) {
if (targetFile == null) {
throw new ArgumentError('targetFile cannot be null');
_entries.add(new Entry(source,
new FileLocation(targetFile, targetOffset), identifier));
/// Adds an entry mapping [target] to [source].
void addSpan(Span source, Span target) {
var name = source.isIdentifier ? source.text : null;
_entries.add(new Entry(source.start, target.start, name));
void addLocation(Location source, Location target, String identifier) {
_entries.add(new Entry(source, target, identifier));
/// 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.
for (var entry in _entries) {
int nextLine =;
if (nextLine > line) {
for (int i = line; i < nextLine; ++i) {
line = nextLine;
column = 0;
first = true;
if (!first) buff.write(',');
first = false;
column = _append(buff, column,;
if (entry.source == null) continue;
srcUrlId = _append(buff, srcUrlId,
_indexOf(_urls, entry.source.sourceUrl));
srcLine = _append(buff, srcLine, entry.source.line);
srcColumn = _append(buff, srcColumn, entry.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;
/// Encodes all mappings added to this builder as a json string.
String toJson(String fileUrl) => json.stringify(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.
class Entry implements Comparable {
/// Span denoting the original location in the input source file
final Location source;
/// Span indicating the corresponding location in the target file.
final Location target;
/// An identifier name, when this location is the start of an identifier.
final String identifierName;
Entry(this.source,, this.identifierName);
/// Implements [Comparable] to ensure that entries are ordered by their
/// location in the target file. We sort primarily by the target offset
/// because source map files are encoded by printing each mapping in order as
/// they appear in the target file.
int compareTo(Entry other) {
int res = target.compareTo(;
if (res != 0) return res;
res = source.sourceUrl.compareTo(other.source.sourceUrl);
if (res != 0) return res;
return source.compareTo(other.source);