protobuf/src/ProtocolBuffers/TextGenerator.cs

#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://github.com/jskeet/dotnet-protobufs/
// Original C++/Java/Python code:
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#endregion

using System;
using System.IO;
using System.Text;

namespace Google.ProtocolBuffers {

  /// <summary>
  /// Helper class to control indentation. Used for TextFormat and by ProtoGen.
  /// </summary>
  public sealed class TextGenerator {

    /// <summary>
    /// The string to use at the end of each line. We assume that "Print" is only called using \n
    /// to indicate a line break; that's what we use to detect when we need to indent etc, and
    /// *just* the \n is replaced with the contents of lineBreak.
    /// </summary>
    private readonly string lineBreak;

    /// <summary>
    /// Writer to write formatted text to.
    /// </summary>
    private readonly TextWriter writer;

    /// <summary>
    /// Keeps track of whether the next piece of text should be indented
    /// </summary>
    bool atStartOfLine = true;

    /// <summary>
    /// Keeps track of the current level of indentation
    /// </summary>
    readonly StringBuilder indent = new StringBuilder();

    /// <summary>
    /// Creates a generator writing to the given writer. The writer
    /// is not closed by this class.
    /// </summary>
    public TextGenerator(TextWriter writer, string lineBreak) {
      this.writer = writer;
      this.lineBreak = lineBreak;
    }

    /// <summary>
    /// Indents text by two spaces. After calling Indent(), two spaces
    /// will be inserted at the beginning of each line of text. Indent() may
    /// be called multiple times to produce deeper indents.
    /// </summary>
    public void Indent() {
      indent.Append("  ");
    }

    /// <summary>
    /// Reduces the current indent level by two spaces.
    /// </summary>
    public void Outdent() {
      if (indent.Length == 0) {
        throw new InvalidOperationException("Too many calls to Outdent()");
      }
      indent.Length -= 2;
    }

    public void WriteLine(string text) {
      Print(text);
      Print("\n");
    }

    public void WriteLine(string format, params object[] args) {
      WriteLine(string.Format(format, args));
    }

    public void WriteLine() {
      WriteLine("");
    }

    /// <summary>
    /// Prints the given text to the output stream, indenting at line boundaries.
    /// </summary>
    /// <param name="text"></param>
    public void Print(string text) {
      int pos = 0;

      for (int i = 0; i < text.Length; i++) {
        if (text[i] == '\n') {
          // Strip off the \n from what we write
          Write(text.Substring(pos, i - pos));
          Write(lineBreak);
          pos = i + 1;
          atStartOfLine = true;
        }
      }
      Write(text.Substring(pos));
    }

    public void Write(string format, params object[] args) {
      Write(string.Format(format, args));
    }
    
    private void Write(string data) {
      if (data.Length == 0) {
        return;
      }
      if (atStartOfLine) {
        atStartOfLine = false;
        writer.Write(indent);
      }
      writer.Write(data);
    }
  }
}