pkg/compiler/lib/src/io/source_map_builder.dart - sdk - Git at Google

 // Copyright (c) 2012, 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.

 library;

 // ignore: implementation_imports
 import 'package:front_end/src/api_unstable/dart2js.dart' as fe;
 import 'package:kernel/ast.dart' show Location;
 import '../../compiler_api.dart'
     as api
     show CompilerOutput, OutputSink, OutputType;
 import '../util/output_util.dart';
 import '../util/util.dart';
 import 'location_provider.dart';
 import 'code_output.dart' show SourceLocationsProvider, SourceLocations;
 import 'source_information.dart' show FrameEntry, SourceLocation;

 class SourceMapBuilder {
   final String version;
   final StringSink outputSink;

   /// The URI of the source map file.
   final Uri? sourceMapUri;

   /// The URI of the target language file.
   final Uri? targetFileUri;

   final LocationProvider locationProvider;
   final List<SourceMapEntry> entries = [];

   /// Extension used to deobfuscate minified names in error messages.
   final Map<String, String> minifiedGlobalNames;
   final Map<String, String> minifiedInstanceNames;

   /// Contains mapped source locations including inlined frame mappings.
   final SourceLocations sourceLocations;

   SourceMapBuilder(
     this.version,
     this.sourceMapUri,
     this.targetFileUri,
     this.locationProvider,
     this.minifiedGlobalNames,
     this.minifiedInstanceNames,
     this.sourceLocations,
     this.outputSink,
   );

   void addMapping(int targetOffset, SourceLocation sourceLocation) {
     entries.add(SourceMapEntry(sourceLocation, targetOffset));
   }

   void printStringListOn(Iterable<String> strings) {
     bool first = true;
     outputSink.write('[');
     for (String string in strings) {
       if (!first) outputSink.write(',');
       outputSink.write('"');
       writeJsonEscapedCharsOn(string, outputSink);
       outputSink.write('"');
       first = false;
     }
     outputSink.write(']');
   }

   void build() {
     LineColumnMap<SourceMapEntry> lineColumnMap = LineColumnMap();
     for (var sourceMapEntry in entries) {
       Location kernelLocation = locationProvider.getLocation(
         sourceMapEntry.targetOffset,
       );
       int line = kernelLocation.line - 1;
       int column = kernelLocation.column - 1;
       lineColumnMap.add(line, column, sourceMapEntry);
     }

     _build(lineColumnMap);
   }

   void _build(LineColumnMap<SourceMapEntry> lineColumnMap) {
     IndexMap<Uri> uriMap = IndexMap<Uri>();
     IndexMap<String> nameMap = IndexMap<String>();

     void registerLocation(SourceLocation? sourceLocation) {
       if (sourceLocation != null) {
         if (sourceLocation.sourceUri != null) {
           uriMap.register(sourceLocation.sourceUri!);
           if (sourceLocation.sourceName != null) {
             nameMap.register(sourceLocation.sourceName!);
           }
         }
       }
     }

     lineColumnMap.forEachElement((SourceMapEntry entry) {
       registerLocation(entry.sourceLocation);
     });

     (List.of(minifiedGlobalNames.values)..sort()).forEach(nameMap.register);
     (List.of(minifiedInstanceNames.values)..sort()).forEach(nameMap.register);

     final inlinedNames = <String>[];
     sourceLocations.forEachFrameMarker((_, frame) {
       registerLocation(frame.pushLocation);
       if (frame.inlinedMethodName != null) {
         inlinedNames.add(frame.inlinedMethodName!);
       }
     });
     (inlinedNames..sort()).forEach(nameMap.register);

     outputSink.write('{\n');
     outputSink.write('  "version": 3,\n');
     outputSink.write('  "engine": "$version",\n');
     if (sourceMapUri != null && targetFileUri != null) {
       outputSink.write(
         '  "file": '
         '"${fe.relativizeUri(sourceMapUri!, targetFileUri!, false)}",\n',
       );
     }
     outputSink.write('  "sourceRoot": "",\n');
     outputSink.write('  "sources": ');
     Iterable<String> relativeSourceUriList = const <String>[];
     if (sourceMapUri != null) {
       relativeSourceUriList = uriMap.elements.map(
         (u) => fe.relativizeUri(sourceMapUri!, u, false),
       );
     }
     printStringListOn(relativeSourceUriList);
     outputSink.write(',\n');
     outputSink.write('  "names": ');
     printStringListOn(nameMap.elements);
     outputSink.write(',\n');
     outputSink.write('  "mappings": "');
     writeEntries(lineColumnMap, uriMap, nameMap);
     outputSink.write('",\n');
     outputSink.write('  "x_org_dartlang_dart2js": {\n');
     outputSink.write('    "minified_names": {\n');
     outputSink.write('      "global": ');
     writeMinifiedNames(minifiedGlobalNames, nameMap);
     outputSink.write(',\n');
     outputSink.write('      "instance": ');
     writeMinifiedNames(minifiedInstanceNames, nameMap);
     outputSink.write('\n    },\n');
     outputSink.write('    "frames": ');
     writeFrames(uriMap, nameMap);
     outputSink.write('\n  }\n}\n');
   }

   void writeEntries(
     LineColumnMap<SourceMapEntry> entries,
     IndexMap<Uri> uriMap,
     IndexMap<String> nameMap,
   ) {
     SourceLocation? previousSourceLocation;
     int previousTargetLine = 0;
     DeltaEncoder targetColumnEncoder = DeltaEncoder();
     bool firstEntryInLine = true;
     DeltaEncoder sourceUriIndexEncoder = DeltaEncoder();
     DeltaEncoder sourceLineEncoder = DeltaEncoder();
     DeltaEncoder sourceColumnEncoder = DeltaEncoder();
     DeltaEncoder sourceNameIndexEncoder = DeltaEncoder();

     entries.forEach((int targetLine, int targetColumn, SourceMapEntry entry) {
       SourceLocation sourceLocation = entry.sourceLocation;
       if (sourceLocation == previousSourceLocation) {
         return;
       }

       if (targetLine > previousTargetLine) {
         for (int i = previousTargetLine; i < targetLine; ++i) {
           outputSink.write(';');
         }
         previousTargetLine = targetLine;
         previousSourceLocation = null;
         targetColumnEncoder.reset();
         firstEntryInLine = true;
       }

       if (!firstEntryInLine) {
         outputSink.write(',');
       }
       firstEntryInLine = false;

       targetColumnEncoder.encode(outputSink, targetColumn);

       Uri? sourceUri = sourceLocation.sourceUri;
       if (sourceUri != null) {
         sourceUriIndexEncoder.encode(outputSink, uriMap[sourceUri]!);
         sourceLineEncoder.encode(outputSink, sourceLocation.line - 1);
         sourceColumnEncoder.encode(outputSink, sourceLocation.column - 1);
       }

       String? sourceName = sourceLocation.sourceName;
       if (sourceName != null) {
         sourceNameIndexEncoder.encode(outputSink, nameMap[sourceName]!);
       }

       previousSourceLocation = sourceLocation;
     });
   }

   void writeMinifiedNames(
     Map<String, String> minifiedNames,
     IndexMap<String> nameMap,
   ) {
     bool first = true;
     outputSink.write('"');
     for (final minifiedName in List.of(minifiedNames.keys)..sort()) {
       final name = minifiedNames[minifiedName]!;
       if (!first) outputSink.write(',');
       // minifiedNames are valid JS identifiers so they don't need to be escaped
       outputSink.write(minifiedName);
       outputSink.write(',');
       outputSink.write(nameMap[name]);
       first = false;
     }
     outputSink.write('"');
   }

   void writeFrames(IndexMap<Uri> uriMap, IndexMap<String> nameMap) {
     var offsetEncoder = DeltaEncoder();
     var uriEncoder = DeltaEncoder();
     var lineEncoder = DeltaEncoder();
     var columnEncoder = DeltaEncoder();
     var nameEncoder = DeltaEncoder();
     outputSink.write('"');
     sourceLocations.forEachFrameMarker((int offset, FrameEntry entry) {
       offsetEncoder.encode(outputSink, offset);
       if (entry.isPush) {
         SourceLocation location = entry.pushLocation!;
         uriEncoder.encode(outputSink, uriMap[location.sourceUri!]!);
         lineEncoder.encode(outputSink, location.line - 1);
         columnEncoder.encode(outputSink, location.column - 1);
         nameEncoder.encode(outputSink, nameMap[entry.inlinedMethodName!]!);
       } else {
         // ; and , are not used by VLQ so we can distinguish them in the
         // encoding, this is the same reason they are used in the mappings
         // field.
         outputSink.write(entry.isEmptyPop ? ";" : ",");
       }
     });
     outputSink.write('"');
   }

   /// Returns the source map tag to put at the end a .js file in [fileUri] to
   /// make it point to the source map file in [sourceMapUri].
   static String generateSourceMapTag(Uri? sourceMapUri, Uri? fileUri) {
     if (sourceMapUri != null && fileUri != null) {
       String sourceMapFileName = fe.relativizeUri(fileUri, sourceMapUri, false);
       return '''

 //# sourceMappingURL=$sourceMapFileName
 ''';
     }
     return '';
   }

   /// Generates source map files for all [SourceLocations] in
   /// [sourceLocationsProvider] for the .js code in [locationProvider]
   /// [sourceMapUri] is used to relativizes the URIs of the referenced source
   /// files and the target [fileUri]. [name] and [outputProvider] are used to
   /// create the [api.OutputSink] for the source map text.
   static void outputSourceMap(
     SourceLocationsProvider sourceLocationsProvider,
     LocationProvider locationProvider,
     Map<String, String> minifiedGlobalNames,
     Map<String, String> minifiedInstanceNames,
     String name,
     Uri? sourceMapUri,
     Uri? fileUri,
     api.CompilerOutput compilerOutput,
   ) {
     // Create a source file for the compilation output. This allows using
     // [:getLine:] to transform offsets to line numbers in [SourceMapBuilder].
     int index = 0;
     for (var sourceLocations in sourceLocationsProvider.sourceLocations) {
       String extension = 'js.map';
       if (index > 0) {
         if (name == '') {
           name = fileUri != null ? fileUri.pathSegments.last : 'out.js';
           extension = 'map.${sourceLocations.name}';
         } else {
           extension = 'js.map.${sourceLocations.name}';
         }
       }
       final outputSink = BufferedStringSinkWrapper(
         compilerOutput.createOutputSink(
           name,
           extension,
           api.OutputType.sourceMap,
         ),
       );
       SourceMapBuilder sourceMapBuilder = SourceMapBuilder(
         sourceLocations.name,
         sourceMapUri,
         fileUri,
         locationProvider,
         minifiedGlobalNames,
         minifiedInstanceNames,
         sourceLocations,
         outputSink,
       );
       sourceLocations.forEachSourceLocation(sourceMapBuilder.addMapping);
       sourceMapBuilder.build();
       sourceLocations.close();
       outputSink.close();
       index++;
     }
   }
 }

 /// Encoder for value deltas in VLQ format.
 class DeltaEncoder {
   /// The last emitted value of the encoder.
   int _value = 0;

   /// Reset the encoder to its initial state.
   void reset() {
     _value = 0;
   }

   /// Writes the VLQ of delta between [value] and the last emitted value into
   /// [output] and updates the last emitted value of the encoder.
   void encode(StringSink output, int value) {
     _value = encodeVLQ(output, value, _value);
   }

   static const int vlqBaseShift = 5;
   static const int vlqBaseMask = (1 << 5) - 1;
   static const int vlqContinuationBit = 1 << 5;
   static const int vlqContinuationMask = 1 << 5;
   static const String base64Digits =
       'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmn'
       'opqrstuvwxyz0123456789+/';

   /// Writes the VLQ of delta between [value] and [offset] into [output] and
   /// return [value].
   static int encodeVLQ(StringSink output, int value, int offset) {
     int delta = value - offset;
     int signBit = 0;
     if (delta < 0) {
       signBit = 1;
       delta = -delta;
     }
     delta = (delta << 1) | signBit;
     do {
       int digit = delta & vlqBaseMask;
       delta >>= vlqBaseShift;
       if (delta > 0) {
         digit |= vlqContinuationBit;
       }
       output.write(base64Digits[digit]);
     } while (delta > 0);
     return value;
   }
 }

 class SourceMapEntry {
   SourceLocation sourceLocation;
   int targetOffset;

   SourceMapEntry(this.sourceLocation, this.targetOffset);
 }

 /// Map from line/column pairs to lists of [T] elements.
 class LineColumnMap<T> {
   final Map<int, Map<int, List<T>>> _map = {};

   /// Returns the list of elements associated with ([line],[column]).
   List<T> _getList(int line, int column) {
     Map<int, List<T>> lineMap = _map[line] ??= {};
     return lineMap[column] ??= [];
   }

   /// Adds [element] to the end of the list of elements associated with
   /// ([line],[column]).
   void add(int line, int column, T element) {
     _getList(line, column).add(element);
   }

   /// Adds [element] to the beginning of the list of elements associated with
   /// ([line],[column]).
   void addFirst(int line, int column, T element) {
     _getList(line, column).insert(0, element);
   }

   /// Calls [f] with the line number for each line with associated elements.
   ///
   /// [f] is called in increasing line order.
   void forEachLine(void Function(int line) f) {
     List<int> lines = _map.keys.toList()..sort();
     lines.forEach(f);
   }

   /// Returns the elements for the first the column in [line] that has
   /// associated elements.
   List<T>? getFirstElementsInLine(int line) {
     Map<int, List<T>>? lineMap = _map[line];
     if (lineMap == null) return null;
     List<int> columns = lineMap.keys.toList()..sort();
     return lineMap[columns.first];
   }

   /// Calls [f] for each column with associated elements in [line].
   ///
   /// [f] is called in increasing column order.
   void forEachColumn(int line, void Function(int column, List<T> elements) f) {
     Map<int, List<T>>? lineMap = _map[line];
     if (lineMap != null) {
       List<int> columns = lineMap.keys.toList()..sort();
       for (var column in columns) {
         f(column, lineMap[column]!);
       }
     }
   }

   /// Calls [f] for each line/column/element triplet in the map.
   ///
   /// [f] is called in increasing line, column, element order.
   void forEach(void Function(int line, int column, T element) f) {
     List<int> lines = _map.keys.toList()..sort();
     for (int line in lines) {
       Map<int, List<T>> lineMap = _map[line]!;
       List<int> columns = lineMap.keys.toList()..sort();
       for (int column in columns) {
         for (var e in lineMap[column]!) {
           f(line, column, e);
         }
       }
     }
   }

   /// Calls [f] for each element associated in the map.
   ///
   /// [f] is called in increasing line, column, element order.
   void forEachElement(void Function(T element) f) {
     forEach((line, column, element) => f(element));
   }
 }

 /// Map from [T] elements to assigned indices.
 class IndexMap<T> {
   Map<T, int> map = {};

   /// Register [element] and returns its index.
   int register(T element) {
     return map.putIfAbsent(element, () => map.length);
   }

   /// Returns the index of [element].
   int? operator [](T element) => map[element];

   /// Returns the indexed elements.
   Iterable<T> get elements => map.keys;
 }
	// Copyright (c) 2012, 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.

	library;

	// ignore: implementation_imports
	import 'package:front_end/src/api_unstable/dart2js.dart' as fe;
	import 'package:kernel/ast.dart' show Location;
	import '../../compiler_api.dart'
	as api
	show CompilerOutput, OutputSink, OutputType;
	import '../util/output_util.dart';
	import '../util/util.dart';
	import 'location_provider.dart';
	import 'code_output.dart' show SourceLocationsProvider, SourceLocations;
	import 'source_information.dart' show FrameEntry, SourceLocation;

	class SourceMapBuilder {
	final String version;
	final StringSink outputSink;

	/// The URI of the source map file.
	final Uri? sourceMapUri;

	/// The URI of the target language file.
	final Uri? targetFileUri;

	final LocationProvider locationProvider;
	final List<SourceMapEntry> entries = [];

	/// Extension used to deobfuscate minified names in error messages.
	final Map<String, String> minifiedGlobalNames;
	final Map<String, String> minifiedInstanceNames;

	/// Contains mapped source locations including inlined frame mappings.
	final SourceLocations sourceLocations;

	SourceMapBuilder(
	this.version,
	this.sourceMapUri,
	this.targetFileUri,
	this.locationProvider,
	this.minifiedGlobalNames,
	this.minifiedInstanceNames,
	this.sourceLocations,
	this.outputSink,
	);

	void addMapping(int targetOffset, SourceLocation sourceLocation) {
	entries.add(SourceMapEntry(sourceLocation, targetOffset));
	}

	void printStringListOn(Iterable<String> strings) {
	bool first = true;
	outputSink.write('[');
	for (String string in strings) {
	if (!first) outputSink.write(',');
	outputSink.write('"');
	writeJsonEscapedCharsOn(string, outputSink);
	outputSink.write('"');
	first = false;
	}
	outputSink.write(']');
	}

	void build() {
	LineColumnMap<SourceMapEntry> lineColumnMap = LineColumnMap();
	for (var sourceMapEntry in entries) {
	Location kernelLocation = locationProvider.getLocation(
	sourceMapEntry.targetOffset,
	);
	int line = kernelLocation.line - 1;
	int column = kernelLocation.column - 1;
	lineColumnMap.add(line, column, sourceMapEntry);
	}

	_build(lineColumnMap);
	}

	void _build(LineColumnMap<SourceMapEntry> lineColumnMap) {
	IndexMap<Uri> uriMap = IndexMap<Uri>();
	IndexMap<String> nameMap = IndexMap<String>();

	void registerLocation(SourceLocation? sourceLocation) {
	if (sourceLocation != null) {
	if (sourceLocation.sourceUri != null) {
	uriMap.register(sourceLocation.sourceUri!);
	if (sourceLocation.sourceName != null) {
	nameMap.register(sourceLocation.sourceName!);
	}
	}
	}
	}

	lineColumnMap.forEachElement((SourceMapEntry entry) {
	registerLocation(entry.sourceLocation);
	});

	(List.of(minifiedGlobalNames.values)..sort()).forEach(nameMap.register);
	(List.of(minifiedInstanceNames.values)..sort()).forEach(nameMap.register);

	final inlinedNames = <String>[];
	sourceLocations.forEachFrameMarker((_, frame) {
	registerLocation(frame.pushLocation);
	if (frame.inlinedMethodName != null) {
	inlinedNames.add(frame.inlinedMethodName!);
	}
	});
	(inlinedNames..sort()).forEach(nameMap.register);

	outputSink.write('{\n');
	outputSink.write(' "version": 3,\n');
	outputSink.write(' "engine": "$version",\n');
	if (sourceMapUri != null && targetFileUri != null) {
	outputSink.write(
	' "file": '
	'"${fe.relativizeUri(sourceMapUri!, targetFileUri!, false)}",\n',
	);
	}
	outputSink.write(' "sourceRoot": "",\n');
	outputSink.write(' "sources": ');
	Iterable<String> relativeSourceUriList = const <String>[];
	if (sourceMapUri != null) {
	relativeSourceUriList = uriMap.elements.map(
	(u) => fe.relativizeUri(sourceMapUri!, u, false),
	);
	}
	printStringListOn(relativeSourceUriList);
	outputSink.write(',\n');
	outputSink.write(' "names": ');
	printStringListOn(nameMap.elements);
	outputSink.write(',\n');
	outputSink.write(' "mappings": "');
	writeEntries(lineColumnMap, uriMap, nameMap);
	outputSink.write('",\n');
	outputSink.write(' "x_org_dartlang_dart2js": {\n');
	outputSink.write(' "minified_names": {\n');
	outputSink.write(' "global": ');
	writeMinifiedNames(minifiedGlobalNames, nameMap);
	outputSink.write(',\n');
	outputSink.write(' "instance": ');
	writeMinifiedNames(minifiedInstanceNames, nameMap);
	outputSink.write('\n },\n');
	outputSink.write(' "frames": ');
	writeFrames(uriMap, nameMap);
	outputSink.write('\n }\n}\n');
	}

	void writeEntries(
	LineColumnMap<SourceMapEntry> entries,
	IndexMap<Uri> uriMap,
	IndexMap<String> nameMap,
	) {
	SourceLocation? previousSourceLocation;
	int previousTargetLine = 0;
	DeltaEncoder targetColumnEncoder = DeltaEncoder();
	bool firstEntryInLine = true;
	DeltaEncoder sourceUriIndexEncoder = DeltaEncoder();
	DeltaEncoder sourceLineEncoder = DeltaEncoder();
	DeltaEncoder sourceColumnEncoder = DeltaEncoder();
	DeltaEncoder sourceNameIndexEncoder = DeltaEncoder();

	entries.forEach((int targetLine, int targetColumn, SourceMapEntry entry) {
	SourceLocation sourceLocation = entry.sourceLocation;
	if (sourceLocation == previousSourceLocation) {
	return;
	}

	if (targetLine > previousTargetLine) {
	for (int i = previousTargetLine; i < targetLine; ++i) {
	outputSink.write(';');
	}
	previousTargetLine = targetLine;
	previousSourceLocation = null;
	targetColumnEncoder.reset();
	firstEntryInLine = true;
	}

	if (!firstEntryInLine) {
	outputSink.write(',');
	}
	firstEntryInLine = false;

	targetColumnEncoder.encode(outputSink, targetColumn);

	Uri? sourceUri = sourceLocation.sourceUri;
	if (sourceUri != null) {
	sourceUriIndexEncoder.encode(outputSink, uriMap[sourceUri]!);
	sourceLineEncoder.encode(outputSink, sourceLocation.line - 1);
	sourceColumnEncoder.encode(outputSink, sourceLocation.column - 1);
	}

	String? sourceName = sourceLocation.sourceName;
	if (sourceName != null) {
	sourceNameIndexEncoder.encode(outputSink, nameMap[sourceName]!);
	}

	previousSourceLocation = sourceLocation;
	});
	}

	void writeMinifiedNames(
	Map<String, String> minifiedNames,
	IndexMap<String> nameMap,
	) {
	bool first = true;
	outputSink.write('"');
	for (final minifiedName in List.of(minifiedNames.keys)..sort()) {
	final name = minifiedNames[minifiedName]!;
	if (!first) outputSink.write(',');
	// minifiedNames are valid JS identifiers so they don't need to be escaped
	outputSink.write(minifiedName);
	outputSink.write(',');
	outputSink.write(nameMap[name]);
	first = false;
	}
	outputSink.write('"');
	}

	void writeFrames(IndexMap<Uri> uriMap, IndexMap<String> nameMap) {
	var offsetEncoder = DeltaEncoder();
	var uriEncoder = DeltaEncoder();
	var lineEncoder = DeltaEncoder();
	var columnEncoder = DeltaEncoder();
	var nameEncoder = DeltaEncoder();
	outputSink.write('"');
	sourceLocations.forEachFrameMarker((int offset, FrameEntry entry) {
	offsetEncoder.encode(outputSink, offset);
	if (entry.isPush) {
	SourceLocation location = entry.pushLocation!;
	uriEncoder.encode(outputSink, uriMap[location.sourceUri!]!);
	lineEncoder.encode(outputSink, location.line - 1);
	columnEncoder.encode(outputSink, location.column - 1);
	nameEncoder.encode(outputSink, nameMap[entry.inlinedMethodName!]!);
	} else {
	// ; and , are not used by VLQ so we can distinguish them in the
	// encoding, this is the same reason they are used in the mappings
	// field.
	outputSink.write(entry.isEmptyPop ? ";" : ",");
	}
	});
	outputSink.write('"');
	}

	/// Returns the source map tag to put at the end a .js file in [fileUri] to
	/// make it point to the source map file in [sourceMapUri].
	static String generateSourceMapTag(Uri? sourceMapUri, Uri? fileUri) {
	if (sourceMapUri != null && fileUri != null) {
	String sourceMapFileName = fe.relativizeUri(fileUri, sourceMapUri, false);
	return '''

	//# sourceMappingURL=$sourceMapFileName
	''';
	}
	return '';
	}

	/// Generates source map files for all [SourceLocations] in
	/// [sourceLocationsProvider] for the .js code in [locationProvider]
	/// [sourceMapUri] is used to relativizes the URIs of the referenced source
	/// files and the target [fileUri]. [name] and [outputProvider] are used to
	/// create the [api.OutputSink] for the source map text.
	static void outputSourceMap(
	SourceLocationsProvider sourceLocationsProvider,
	LocationProvider locationProvider,
	Map<String, String> minifiedGlobalNames,
	Map<String, String> minifiedInstanceNames,
	String name,
	Uri? sourceMapUri,
	Uri? fileUri,
	api.CompilerOutput compilerOutput,
	) {
	// Create a source file for the compilation output. This allows using
	// [:getLine:] to transform offsets to line numbers in [SourceMapBuilder].
	int index = 0;
	for (var sourceLocations in sourceLocationsProvider.sourceLocations) {
	String extension = 'js.map';
	if (index > 0) {
	if (name == '') {
	name = fileUri != null ? fileUri.pathSegments.last : 'out.js';
	extension = 'map.${sourceLocations.name}';
	} else {
	extension = 'js.map.${sourceLocations.name}';
	}
	}
	final outputSink = BufferedStringSinkWrapper(
	compilerOutput.createOutputSink(
	name,
	extension,
	api.OutputType.sourceMap,
	),
	);
	SourceMapBuilder sourceMapBuilder = SourceMapBuilder(
	sourceLocations.name,
	sourceMapUri,
	fileUri,
	locationProvider,
	minifiedGlobalNames,
	minifiedInstanceNames,
	sourceLocations,
	outputSink,
	);
	sourceLocations.forEachSourceLocation(sourceMapBuilder.addMapping);
	sourceMapBuilder.build();
	sourceLocations.close();
	outputSink.close();
	index++;
	}
	}
	}

	/// Encoder for value deltas in VLQ format.
	class DeltaEncoder {
	/// The last emitted value of the encoder.
	int _value = 0;

	/// Reset the encoder to its initial state.
	void reset() {
	_value = 0;
	}

	/// Writes the VLQ of delta between [value] and the last emitted value into
	/// [output] and updates the last emitted value of the encoder.
	void encode(StringSink output, int value) {
	_value = encodeVLQ(output, value, _value);
	}

	static const int vlqBaseShift = 5;
	static const int vlqBaseMask = (1 << 5) - 1;
	static const int vlqContinuationBit = 1 << 5;
	static const int vlqContinuationMask = 1 << 5;
	static const String base64Digits =
	'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmn'
	'opqrstuvwxyz0123456789+/';

	/// Writes the VLQ of delta between [value] and [offset] into [output] and
	/// return [value].
	static int encodeVLQ(StringSink output, int value, int offset) {
	int delta = value - offset;
	int signBit = 0;
	if (delta < 0) {
	signBit = 1;
	delta = -delta;
	}
	delta = (delta << 1) \| signBit;
	do {
	int digit = delta & vlqBaseMask;
	delta >>= vlqBaseShift;
	if (delta > 0) {
	digit \|= vlqContinuationBit;
	}
	output.write(base64Digits[digit]);
	} while (delta > 0);
	return value;
	}
	}

	class SourceMapEntry {
	SourceLocation sourceLocation;
	int targetOffset;

	SourceMapEntry(this.sourceLocation, this.targetOffset);
	}

	/// Map from line/column pairs to lists of [T] elements.
	class LineColumnMap<T> {
	final Map<int, Map<int, List<T>>> _map = {};

	/// Returns the list of elements associated with ([line],[column]).
	List<T> _getList(int line, int column) {
	Map<int, List<T>> lineMap = _map[line] ??= {};
	return lineMap[column] ??= [];
	}

	/// Adds [element] to the end of the list of elements associated with
	/// ([line],[column]).
	void add(int line, int column, T element) {
	_getList(line, column).add(element);
	}

	/// Adds [element] to the beginning of the list of elements associated with
	/// ([line],[column]).
	void addFirst(int line, int column, T element) {
	_getList(line, column).insert(0, element);
	}

	/// Calls [f] with the line number for each line with associated elements.
	///
	/// [f] is called in increasing line order.
	void forEachLine(void Function(int line) f) {
	List<int> lines = _map.keys.toList()..sort();
	lines.forEach(f);
	}

	/// Returns the elements for the first the column in [line] that has
	/// associated elements.
	List<T>? getFirstElementsInLine(int line) {
	Map<int, List<T>>? lineMap = _map[line];
	if (lineMap == null) return null;
	List<int> columns = lineMap.keys.toList()..sort();
	return lineMap[columns.first];
	}

	/// Calls [f] for each column with associated elements in [line].
	///
	/// [f] is called in increasing column order.
	void forEachColumn(int line, void Function(int column, List<T> elements) f) {
	Map<int, List<T>>? lineMap = _map[line];
	if (lineMap != null) {
	List<int> columns = lineMap.keys.toList()..sort();
	for (var column in columns) {
	f(column, lineMap[column]!);
	}
	}
	}

	/// Calls [f] for each line/column/element triplet in the map.
	///
	/// [f] is called in increasing line, column, element order.
	void forEach(void Function(int line, int column, T element) f) {
	List<int> lines = _map.keys.toList()..sort();
	for (int line in lines) {
	Map<int, List<T>> lineMap = _map[line]!;
	List<int> columns = lineMap.keys.toList()..sort();
	for (int column in columns) {
	for (var e in lineMap[column]!) {
	f(line, column, e);
	}
	}
	}
	}

	/// Calls [f] for each element associated in the map.
	///
	/// [f] is called in increasing line, column, element order.
	void forEachElement(void Function(T element) f) {
	forEach((line, column, element) => f(element));
	}
	}

	/// Map from [T] elements to assigned indices.
	class IndexMap<T> {
	Map<T, int> map = {};

	/// Register [element] and returns its index.
	int register(T element) {
	return map.putIfAbsent(element, () => map.length);
	}

	/// Returns the index of [element].
	int? operator [](T element) => map[element];

	/// Returns the indexed elements.
	Iterable<T> get elements => map.keys;
	}