C# 文件句柄IntPtr快速保存

1.新版本

        /// <summary>
        /// 文件保存
        /// </summary>
        /// <param name="intPtr">文件源句柄</param>
        /// <param name="fileSize">图像大小，例如 1 * 1024 * 1024，写入1MB</param>
        /// <param name="savePath">保存路径</param>
        public unsafe static void SaveImageFromIntPtr(IntPtr intPtr, int fileSize, string savePath)
        {
            using FileStream fileStream = new FileStream(savePath, FileMode.Create, FileAccess.Write);
            using var writer = new BinaryWriter(fileStream);
            writer.Write(new Span<byte>((void*)intPtr, fileSize));
        }

2.老版本

        /// <summary>
        /// 文件保存
        /// </summary>
        /// <param name="intPtr">文件源句柄</param>
        /// <param name="fileSize"></