YooAsset/Assets/YooAsset/Runtime/DownloadSystem/Downloader/DownloadHandlerFileRange.cs

using System;
using System.IO;
using UnityEngine;
using UnityEngine.Networking;

namespace YooAsset
{
	/// <summary>
	/// 支持Unity2018版本的断点续传下载器
	/// </summary>
	internal class DownloadHandlerFileRange : DownloadHandlerScript
	{
		private string _fileSavePath;
		private long _fileTotalSize;
		private UnityWebRequest _webRequest;
		private FileStream _fileStream;

		private long _localFileSize = 0;
		private long _curFileSize = 0;


		public DownloadHandlerFileRange(string fileSavePath, long fileTotalSize, UnityWebRequest webRequest) : base(new byte[1024 * 1024])
		{
			_fileSavePath = fileSavePath;
			_fileTotalSize = fileTotalSize;
			_webRequest = webRequest;

			if (File.Exists(fileSavePath))
			{
				FileInfo fileInfo = new FileInfo(fileSavePath);
				_localFileSize = fileInfo.Length;
			}

			_fileStream = new FileStream(_fileSavePath, FileMode.Append, FileAccess.Write);
			_curFileSize = _localFileSize;
		}
		protected override bool ReceiveData(byte[] data, int dataLength)
		{
			if (data == null || dataLength == 0 || _webRequest.responseCode >= 400)
				return false;

			if (_fileStream == null)
				return false;

			_fileStream.Write(data, 0, dataLength);
			_curFileSize += dataLength;
			return true;
		}

		/// <summary>
		/// UnityWebRequest.downloadHandler.data
		/// </summary>
		protected override byte[] GetData()
		{
			return null;
		}

		/// <summary>
		/// UnityWebRequest.downloadHandler.text
		/// </summary>
		protected override string GetText()
		{
			return null;
		}

		/// <summary>
		/// UnityWebRequest.downloadProgress
		/// </summary>
		protected override float GetProgress()
		{
			return _fileTotalSize == 0 ? 0 : ((float)_curFileSize) / _fileTotalSize;
		}

		/// <summary>
		/// 释放下载句柄
		/// </summary>
		public void Cleanup()
		{
			if (_fileStream != null)
			{
				_fileStream.Flush();
				_fileStream.Dispose();
				_fileStream = null;
			}
		}
	}
}