AtkTextNodeBufferWrapper.cs

// <copyright file="AtkTextNodeBufferWrapper.cs" company="lokinmodar">
// Copyright (c) lokinmodar. All rights reserved.
// Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License license.
// </copyright>

using System;
using System.Runtime.InteropServices;
using System.Text;

namespace Echoglossian
{
  /// <summary>
  /// Provides a wrapper for managing a UTF-8 encoded text buffer using unmanaged memory.
  /// </summary>
  internal unsafe class AtkTextNodeBufferWrapper
  {
    private byte* strBuffer;
    private int bufferLen;

    /// <summary>
    /// Gets the buffer containing the UTF-8 encoded string.
    /// </summary>
    public byte* GetBuffer => this.strBuffer;

    /// <summary>
    /// Sets the buffer to the UTF-8 representation of the given string.
    /// The buffer is reallocated if it doesn't already exist or is too small.
    /// </summary>
    /// <param name="text">The string to be encoded and stored in the buffer.</param>
    public void SetBuffer(string text)
    {
      // Get the length of the string as UTF-8 bytes
      int strLen = Encoding.UTF8.GetByteCount(text);

      // Reallocate buffer if it doesn't already exist or is too small
      if (this.strBuffer == null || strLen + 1 > this.bufferLen)
      {
        NativeMemory.Free(this.strBuffer);
        this.strBuffer = (byte*)NativeMemory.Alloc((nuint)(strLen + 1)); // Need one extra byte for the null terminator
        this.bufferLen = strLen + 1;
      }

      // Wrap buffer in a span to use GetBytes
      Span<byte> bufferSpan = new(this.strBuffer, strLen + 1);

      // Convert string to UTF-8 and store in buffer
      Encoding.UTF8.GetBytes(text, bufferSpan);

      // Add null terminator to the end of the string
      bufferSpan[strLen] = 0;
    }

    /// <summary>
    /// Frees the previously allocated buffer.
    /// </summary>
    public void FreeBuffer()
    {
      NativeMemory.Free(this.strBuffer);
      this.bufferLen = 0;
    }
  }
}