unity IO 读写文件（分段读写数据）

读取文件

读分为字符数据读取（StreamReader）和字节数据读取（FileStream）

StreamReader与FileStream区别

1. FileStream可读可写，而StreamReader只能读不能写
   2.StreamReader关闭后，与之相关的FileStream没有关闭，(通过FileStream的CanRead的测试)
   等。。。
   参考：https://www.iteye.com/blog/zhuogx-1535691

写入文件

当前文件写入非字符类型数据时，StreamWriter与BinaryWriter 存在巨大的差异。
StreamWriter 是把各种类型的数据都转化成字符，然后把字符按照一定的格式编码出来的数据写入文件
BinaryWriter 是直接把数据在内存中的真实内容写入到指定文件中

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using UnityEngine;
using UnityEngine.UI;

namespace ZYL_File
{
    public class File_IO : MonoBehaviour
    {
        private float time;
        private bool state = false;
        string path_Start = @"D:/File_Start/Content0723.rar";
        string path_End = @"D:/File_Start/www.rar";

        private int byteSize = 1024 * 1024 * 5;

        void Start()
        {
            SegRead(path_Start, path_End);
        }


        // Update is called once per frame
        void Update()
        {
        }

        /// 

        /// 超2GB文件的读取与写入
        /// 
        /// 
        /// 
        public async void SegRead(string filepath, string outpath)
        {
            if (File.Exists(outpath))
            {
                File.Delete(outpath);
            }
            File.Create(outpath).Dispose();

            FileStream fsread = new FileStream(filepath, FileMode.Open, FileAccess.Read);
            FileStream fswrite = File.OpenWrite(outpath);
            BinaryReader r = new BinaryReader(fsread);
            byte[] bs = r.ReadBytes(byteSize);

            while (bs.Length != 0)
            {
                await Task.Run(() => {
                    fswrite.Write(bs, 0, bs.Length);
                    fswrite.Flush();
                    Debug.Log("write.......");
                    //从当前流中读取指定的字节数以写入字节数组中，并将当前位置前移相应的字节数。
                    bs = r.ReadBytes(byteSize);
                    Debug.Log("进度：" + fswrite.Length * 1f / fsread.Length);
                });
            }

            fsread.Close();
            fswrite.Close();
            fsread.Dispose();
            fswrite.Dispose();
            Debug.Log("write finish");
        }


        /*
          FileStream 类操作的是字节和字节数组，而 StreamReader 或 StreamWriter 操作的是字符数据。
         */

        //-----------------------------------
        public void UseTask()
        {
            Task.Run(() =>
            {
                Test(path_Start, path_End);
                state = true;
                Debug.Log(time);
            });
        }

        //  Thread.Sleep(1000);  //延迟执行一秒

        /// 

        ///  读取和写入文件
        /// 
        /// 
        /// 
        private void Test(string path_Start, string path_End)
        {
            if (File.Exists(path_End))
            {
                File.Delete(path_End);
            }
            File.Create(path_End).Dispose();

            WriteFileData(ReadFileByte(path_Start), path_End);
        }
        /// 

        /// 读取文件
        /// 
        private byte[] ReadFileByte(string path_Start)
        {
            FileStream fileStream = new FileStream(path_Start, FileMode.Open, FileAccess.Read);  //创建读取流
            fileStream.Seek(0, SeekOrigin.Begin);
            byte[] buff = new byte[fileStream.Length];                      //创建文件长度缓冲区

            //释放文件读取流
            fileStream.Close();
            fileStream.Dispose();
            return buff;
        }
        /// 

        /// 写入文件（字节）
        /// 
        private void WriteFileData(byte[] buff, string path)
        {
            FileStream fs_Write = new FileStream(path, FileMode.Open, FileAccess.Write);
            BinaryWriter bw = new BinaryWriter(fs_Write);
            bw.Write(buff, 0, buff.Length);
            bw.Close();
            bw.Dispose();
        }

        //-----------------------------------------
        /// 

        /// 读取全部的内容(字符数据)
        /// 
        private void ReadFile()
        {
            string path_Start = @"D:/File_Start/Test.txt";
            StreamReader sr2 = new StreamReader(path_Start);
            string nextLine;

            while ((nextLine = sr2.ReadLine()) != null)
            {
                Debug.Log(nextLine + "??");
            }
            sr2.Close();
            sr2.Dispose();
        }

        //------------------------------------------
        /// 

        /// 例子一 向文件写入数据
        /// 
        private void SaveFile_Simlpe()
        {
            string path = @"D:/File_Start/Test.txt";
            StreamWriter sw1;
            if (!File.Exists(path))
            {
                sw1 = File.CreateText(path);
            }
            else
            {
                sw1 = new StreamWriter(path);
            }

            for (int i = 0; i < 100; i++)
            {
                string str = "测试" + i.ToString() + "\n";
                sw1.Write(str);
            }
            sw1.Close();
            sw1.Dispose();
        }
    }
}
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