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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

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/*
 * Copyright 2017 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.javascript.jscomp;

import com.google.debugging.sourcemap.SourceMapConsumerV3;
import com.google.debugging.sourcemap.SourceMapParseException;
import java.io.IOException;
import java.io.Serializable;
import javax.annotation.Nullable;

/**
 * A lazy-loaded SourceMapConsumerV3 instance.
 */
public final class SourceMapInput implements Serializable {
  private final SourceFile sourceFile;
  // No need to serialize the consumer, it will be recreated because the serialized version will
  // have cached = false.
  private transient volatile SourceMapConsumerV3 parsedSourceMap = null;
  private transient volatile boolean cached = false;

  static final DiagnosticType SOURCEMAP_RESOLVE_FAILED =
      DiagnosticType.warning("SOURCEMAP_RESOLVE_FAILED", "Failed to resolve sourcemap at {0}: {1}");

  static final DiagnosticType SOURCEMAP_PARSE_FAILED =
      DiagnosticType.warning(
          "SOURCEMAP_PARSE_FAILED", "Failed to parse malformed sourcemap in {0}: {1}");

  public SourceMapInput(SourceFile sourceFile) {
    this.sourceFile = sourceFile;
  }

  /**
   * Gets the source map, reading from disk and parsing if necessary. Returns null if the sourcemap
   * cannot be resolved or is malformed.
   */
  public synchronized @Nullable SourceMapConsumerV3 getSourceMap(ErrorManager errorManager) {
    if (!cached) {
      // Avoid re-reading or reparsing files.
      cached = true;
      String sourceMapPath = sourceFile.getOriginalPath();
      try {
        String sourceMapContents = sourceFile.getCode();
        SourceMapConsumerV3 consumer = new SourceMapConsumerV3();
        consumer.parse(sourceMapContents);
        parsedSourceMap = consumer;
      } catch (IOException e) {
        JSError error =
            JSError.make(SourceMapInput.SOURCEMAP_RESOLVE_FAILED, sourceMapPath, e.getMessage());
        errorManager.report(error.getDefaultLevel(), error);
      } catch (SourceMapParseException e) {
        JSError error =
            JSError.make(SourceMapInput.SOURCEMAP_PARSE_FAILED, sourceMapPath, e.getMessage());
        errorManager.report(error.getDefaultLevel(), error);
      }
    }
    return parsedSourceMap;
  }

  /**
   * Gets the original location of this sourcemap file on disk.
   */
  public String getOriginalPath() {
    return sourceFile.getOriginalPath();
  }
}