Make SDK summary writing available to analyzer clients.

pkg/analyzer/tool/summary/build_sdk_summaries.dart

 import 'dart:io';
 
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:analyzer/src/summary/flat_buffers.dart' as fb;
 import 'package:analyzer/src/summary/summary_file_builder.dart';
 
 main(List<String> args) {
   if (args.length < 1) {
     _printUsage();
     exitCode = 1;
@@ skipping 11 matching lines @@
     if (!FileSystemEntity.isDirectorySync(outputDirectoryPath)) {
       print("'$outputDirectoryPath' is not a directory.");
       _printUsage();
       exitCode = 1;
       return;
     }
     //
     // Prepare results.
     //
     String sdkPath = args.length > 2 ? args[2] : null;
-    _Output output = _buildMultipleOutputs(sdkPath, includeSpec);
+    SummaryOutput output = _buildMultipleOutputs(sdkPath, includeSpec);
     if (output == null) {
       exitCode = 1;
       return;
     }
     //
     // Write results.
     //
     if (includeSpec) {
       output.spec.writeMultiple(outputDirectoryPath, 'spec');
     }
     output.strong.writeMultiple(outputDirectoryPath, 'strong');
   } else if (command == 'single-output' &&
       args.length >= 2 &&
       args.length <= 3) {
     String outputPath = args[1];
     String sdkPath = args.length > 2 ? args[2] : null;
     //
     // Prepare results.
     //
-    _Output output = _buildMultipleOutputs(sdkPath, true);
+    SummaryOutput output = _buildMultipleOutputs(sdkPath, true);
     if (output == null) {
       exitCode = 1;
       return;
     }
+
     //
     // Write results.
     //
-    fb.Builder builder = new fb.Builder();
-    fb.Offset specSumOffset = builder.writeListUint8(output.spec.sum);
-    fb.Offset specIndexOffset = builder.writeListUint8(output.spec.index);
-    fb.Offset strongSumOffset = builder.writeListUint8(output.strong.sum);
-    fb.Offset strongIndexOffset = builder.writeListUint8(output.strong.index);
-    builder.startTable();
-    builder.addOffset(_FIELD_SPEC_SUM, specSumOffset);
-    builder.addOffset(_FIELD_SPEC_INDEX, specIndexOffset);
-    builder.addOffset(_FIELD_STRONG_SUM, strongSumOffset);
-    builder.addOffset(_FIELD_STRONG_INDEX, strongIndexOffset);
-    fb.Offset offset = builder.endTable();
-    new File(outputPath)
-        .writeAsBytesSync(builder.finish(offset), mode: FileMode.WRITE_ONLY);
+    output.write(outputPath);
   } else if (command == 'extract-spec-sum' && args.length == 3) {
     String inputPath = args[1];
     String outputPath = args[2];
-    _extractSingleOutput(inputPath, _FIELD_SPEC_SUM, outputPath);
+    _extractSingleOutput(inputPath, FIELD_SPEC_SUM, outputPath);
   } else if (command == 'extract-spec-index' && args.length == 3) {
     String inputPath = args[1];
     String outputPath = args[2];
-    _extractSingleOutput(inputPath, _FIELD_SPEC_INDEX, outputPath);
+    _extractSingleOutput(inputPath, FIELD_SPEC_INDEX, outputPath);
   } else if (command == 'extract-strong-sum' && args.length == 3) {
     String inputPath = args[1];
     String outputPath = args[2];
-    _extractSingleOutput(inputPath, _FIELD_STRONG_SUM, outputPath);
+    _extractSingleOutput(inputPath, FIELD_STRONG_SUM, outputPath);
   } else if (command == 'extract-strong-index' && args.length == 3) {
     String inputPath = args[1];
     String outputPath = args[2];
-    _extractSingleOutput(inputPath, _FIELD_STRONG_INDEX, outputPath);
+    _extractSingleOutput(inputPath, FIELD_STRONG_INDEX, outputPath);
   } else {
     _printUsage();
     exitCode = 1;
     return;
   }
 }
 
 /**
  * The name of the SDK summaries builder application.
  */
 const BINARY_NAME = "build_sdk_summaries";
 
-const int _FIELD_SPEC_INDEX = 1;
-const int _FIELD_SPEC_SUM = 0;
-const int _FIELD_STRONG_INDEX = 3;
-const int _FIELD_STRONG_SUM = 2;
-
-_Output _buildMultipleOutputs(String sdkPath, bool includeSpec) {
+SummaryOutput _buildMultipleOutputs(String sdkPath, bool includeSpec) {
   //
   // Validate the SDK path.
   //
   if (sdkPath != null) {
     if (!FileSystemEntity.isDirectorySync('$sdkPath/lib')) {
       print("'$sdkPath/lib' does not exist.");
       _printUsage();
       return null;
     }
   } else {
     sdkPath = DirectoryBasedDartSdk.defaultSdkDirectory.getAbsolutePath();
   }
 
   //
   // Build spec and strong outputs.
   //
   BuilderOutput spec = includeSpec ? _buildOutput(sdkPath, false) : null;
   BuilderOutput strong = _buildOutput(sdkPath, true);
-  return new _Output(spec, strong);
+  return new SummaryOutput(spec, strong);
 }
 
 BuilderOutput _buildOutput(String sdkPath, bool strongMode) {
   String modeName = strongMode ? 'strong' : 'spec';
   print('Generating $modeName mode summary and index.');
   Stopwatch sw = new Stopwatch()..start();
   BuilderOutput output = new SummaryBuilder.forSdk(sdkPath, strongMode).build();
   print('\tDone in ${sw.elapsedMilliseconds} ms.');
   return output;
 }
@@ skipping 26 matching lines @@
   print('    Generate a single file with summary and index.');
   print('  extract-spec-sum input_file output_file');
   print('    Extract the spec-mode summary file.');
   print('  extract-strong-sum input_file output_file');
   print('    Extract the strong-mode summary file.');
   print('  extract-spec-index input_file output_file');
   print('    Extract the spec-mode index file.');
   print('  extract-strong-index input_file output_file');
   print('    Extract the strong-mode index file.');
 }
-
-class _Output {
-  final BuilderOutput spec;
-  final BuilderOutput strong;
-
-  _Output(this.spec, this.strong);
-}