code: /*
   * Copyright (C) 2010 Google Inc.
   *
   * 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 tools.com.google.gson.internal;
  
  import tools.com.google.gson.JsonElement;
  import tools.com.google.gson.JsonIOException;
  import tools.com.google.gson.JsonNull;
  import tools.com.google.gson.JsonParseException;
  import tools.com.google.gson.JsonSyntaxException;
  import tools.com.google.gson.internal.bind.TypeAdapters;
  import tools.com.google.gson.stream.JsonReader;
  import tools.com.google.gson.stream.JsonWriter;
  import tools.com.google.gson.stream.MalformedJsonException;
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.Writer;
  
  /**
   * Reads and writes GSON parse trees over streams.
   */
  public final class Streams {
    private Streams() {
      throw new UnsupportedOperationException();
    }
  
    /**
     * Takes a reader in any state and returns the next value as a JsonElement.
     */
    public static JsonElement parse(JsonReader reader) throws JsonParseException {
      boolean isEmpty = true;
      try {
        reader.peek();
        isEmpty = false;
        return TypeAdapters.JSON_ELEMENT.read(reader);
      } catch (EOFException e) {
        /*
         * For compatibility with JSON 1.5 and earlier, we return a JsonNull for
         * empty documents instead of throwing.
         */
        if (isEmpty) {
          return JsonNull.INSTANCE;
        }
        // The stream ended prematurely so it is likely a syntax error.
        throw new JsonSyntaxException(e);
      } catch (MalformedJsonException e) {
        throw new JsonSyntaxException(e);
      } catch (IOException e) {
        throw new JsonIOException(e);
      } catch (NumberFormatException e) {
        throw new JsonSyntaxException(e);
      }
    }
  
    /**
     * Writes the JSON element to the writer, recursively.
     */
    public static void write(JsonElement element, JsonWriter writer) throws IOException {
      TypeAdapters.JSON_ELEMENT.write(writer, element);
    }
  
    public static Writer writerForAppendable(Appendable appendable) {
      return appendable instanceof Writer ? (Writer) appendable : new AppendableWriter(appendable);
    }
  
    /**
     * Adapts an {@link Appendable} so it can be passed anywhere a {@link Writer}
     * is used.
     */
    private static final class AppendableWriter extends Writer {
      private final Appendable appendable;
      private final CurrentWrite currentWrite = new CurrentWrite();
  
      AppendableWriter(Appendable appendable) {
        this.appendable = appendable;
      }
  
      @Override public void write(char[] chars, int offset, int length) throws IOException {
        currentWrite.chars = chars;
        appendable.append(currentWrite, offset, offset + length);
      }
  
      @Override public void write(int i) throws IOException {
        appendable.append((char) i);
      }
  
      @Override public void flush() {}
      @Override public void close() {}
  
      /**
       * A mutable char sequence pointing at a single char[].
       */
      static class CurrentWrite implements CharSequence {
        char[] chars;
        public int length() {
          return chars.length;
        }
        public char charAt(int i) {
          return chars[i];
        }
        public CharSequence subSequence(int start, int end) {
          return new String(chars, start, end - start);
        }
      }
    }
  
  }
  