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b5e522e200
Previously, the snapshot file was recomputed on every build. We now record checksums for all snapshot inputs (which are catalogued in the snapshot dependencies file output alongside the snapshot) and only rebuild if the checksum for any input file (or the previous output file) has changed.
64 lines
2.2 KiB
Dart
64 lines
2.2 KiB
Dart
// Copyright 2017 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'dart:async';
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import 'dart:convert' show JSON;
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import 'package:crypto/crypto.dart' show md5;
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import 'file_system.dart';
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/// A collection of checksums for a set of input files.
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///
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/// This class can be used during build actions to compute a checksum of the
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/// build action inputs, and if unchanged from the previous build, skip the
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/// build step. This assumes that build outputs are strictly a product of the
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/// input files.
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class Checksum {
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Checksum.fromFiles(Set<String> inputPaths) : _checksums = <String, String>{} {
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final Iterable<File> files = inputPaths.map(fs.file);
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final Iterable<File> missingInputs = files.where((File file) => !file.existsSync());
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if (missingInputs.isNotEmpty)
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throw new ArgumentError('Missing input files:\n' + missingInputs.join('\n'));
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for (File file in files) {
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final List<int> bytes = file.readAsBytesSync();
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_checksums[file.path] = md5.convert(bytes).toString();
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}
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}
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Checksum.fromJson(String json) : _checksums = JSON.decode(json);
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final Map<String, String> _checksums;
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String toJson() => JSON.encode(_checksums);
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@override
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bool operator==(dynamic other) {
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return other is Checksum &&
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_checksums.length == other._checksums.length &&
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_checksums.keys.every((String key) => _checksums[key] == other._checksums[key]);
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}
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@override
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int get hashCode => _checksums.hashCode;
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}
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/// Parses a VM snapshot dependency file.
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///
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/// Snapshot dependency files are a single line mapping the output snapshot to a
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/// space-separated list of input files used to generate that output. e.g,
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///
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/// outfile : file1.dart file2.dart file3.dart
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Future<Set<String>> readDepfile(String depfilePath) async {
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// Depfile format:
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// outfile1 outfile2 : file1.dart file2.dart file3.dart
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final String contents = await fs.file(depfilePath).readAsString();
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final String dependencies = contents.split(': ')[1];
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return dependencies
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.split(' ')
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.map((String path) => path.trim())
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.where((String path) => path.isNotEmpty)
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.toSet();
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}
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