src/main/java/com/google/devtools/build/lib/syntax/StringLiteral.java

// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.syntax;

import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.skyframe.serialization.DeserializationContext;
import com.google.devtools.build.lib.skyframe.serialization.ObjectCodec;
import com.google.devtools.build.lib.skyframe.serialization.SerializationContext;
import com.google.devtools.build.lib.skyframe.serialization.SerializationException;
import com.google.protobuf.CodedInputStream;
import com.google.protobuf.CodedOutputStream;
import java.io.IOException;

/** Syntax node for a string literal. */
public final class StringLiteral extends Expression {
  String value;

  public String getValue() {
    return value;
  }

  StringLiteral(String value) {
    this.value = value;
  }

  @Override
  public void prettyPrint(Appendable buf) throws IOException {
    // TODO(adonovan): record the raw text of string (and integer) literals
    // so that we can use the syntax tree for source modification tools.
    // However, that may come with a memory cost until we start compiling
    // (at which point the cost is only transient).
    // For now, just simulate the behavior of repr(str).
    buf.append('"');
    for (int i = 0; i < value.length(); i++) {
      char c = value.charAt(i);
      switch (c) {
        case '"':
          buf.append("\\\"");
          break;
        case '\\':
          buf.append("\\\\");
          break;
        case '\r':
          buf.append("\\r");
          break;
        case '\n':
          buf.append("\\n");
          break;
        case '\t':
          buf.append("\\t");
          break;
        default:
          // The Starlark spec (and lexer) are far from complete here,
          // and it's hard to come up with a clean semantics for
          // string escapes that serves Java (UTF-16) and Go (UTF-8).
          // Clearly string literals should not contain non-printable
          // characters. For now we'll continue to pretend that all
          // non-printables are < 32, but this obviously false.
          if (c < 32) {
            buf.append(String.format("\\x%02x", (int) c));
          } else {
            buf.append(c);
          }
      }
    }
    buf.append('"');
  }

  @Override
  public void accept(NodeVisitor visitor) {
    visitor.visit(this);
  }

  @Override
  public Kind kind() {
    return Kind.STRING_LITERAL;
  }

  static final class StringLiteralCodec implements ObjectCodec<StringLiteral> {
    @Override
    public Class<? extends StringLiteral> getEncodedClass() {
      return StringLiteral.class;
    }

    @Override
    public void serialize(
        SerializationContext context, StringLiteral stringLiteral, CodedOutputStream codedOut)
        throws SerializationException, IOException {
      // The String instances referred to by StringLiterals are deduped by Parser, so therefore
      // memoization is guaranteed to be profitable.
      context.serializeWithAdHocMemoizationStrategy(
          stringLiteral.getValue(), MemoizationStrategy.MEMOIZE_AFTER, codedOut);
      context.serialize(stringLiteral.getLocation(), codedOut);
    }

    @Override
    public StringLiteral deserialize(DeserializationContext context, CodedInputStream codedIn)
        throws SerializationException, IOException {
      String value =
          context.deserializeWithAdHocMemoizationStrategy(
              codedIn, MemoizationStrategy.MEMOIZE_AFTER);
      Location location = context.deserialize(codedIn);
      StringLiteral stringLiteral = new StringLiteral(value);
      stringLiteral.setLocation(location);
      return stringLiteral;
    }
  }
}