How does H5's file domain FileReader read files in segments and upload them to the server?

This time I will show you how to segment H5 file domain FileReaderRead filesUpload to the server, H5 file domain FileReader segmentation readFile uploadto the server NotesWhat are the following? Let’s take a look at the actual cases.

Note: When uploading using Ajax, the file should not be too large, preferably less than three to four hundred megabytes, because too many consecutive Ajax requests will cause the background to crash and the data in the InputStream will be empty, especially when browsing on Google during device testing.

1. Simply read the file into Blobs in segments, and upload it to the server via ajax.

<div class="container">
    <div class="panel panel-default">
        <div class="panel-heading">分段读取文件：</div>
        <div class="panel-body">
            <input type="file" id="file" />
            <blockquote style="word-break:break-all;"></blockquote>
        </div>
    </div>
</div>

JS:

/*
* 分段读取文件为blob ，并使用ajax上传到服务器
* 分段上传exe文件会抛出异常
*/
var fileBox = document.getElementById('file');
file.onchange = function () {
    //获取文件对象
    var file = this.files[0];
    var reader = new FileReader();
    var step = 1024 * 1024;
    var total = file.size;
    var cuLoaded = 0;
    console.info("文件大小：" + file.size);
    var startTime = new Date();
    //读取一段成功
    reader.onload = function (e) {
        //处理读取的结果
        var loaded = e.loaded;
        //将分段数据上传到服务器
        uploadFile(reader.result, cuLoaded, function () {
            console.info('loaded:' + cuLoaded + 'current:' + loaded);
            //如果没有读完，继续
            cuLoaded += loaded;
            if (cuLoaded < total) {
                readBlob(cuLoaded);
            } else {
                console.log(&#39;总共用时：&#39; + (new Date().getTime() - startTime.getTime()) / 1000);
                cuLoaded = total;
            }
        });
    }
    //指定开始位置，分块读取文件
    function readBlob(start) {
        //指定开始位置和结束位置读取文件
        //console.info(&#39;start:&#39; + start);
        var blob = file.slice(start, start + step);
        reader.readAsArrayBuffer(blob);
    }
    //开始读取
    readBlob(0);
    //关键代码上传到服务器
    function uploadFile(result, startIndex, onSuccess) {
        var blob = new Blob([result]);
        //提交到服务器
        var fd = new FormData();
        fd.append(&#39;file&#39;, blob);
        fd.append(&#39;filename&#39;, file.name);
        fd.append(&#39;loaded&#39;, startIndex);
        var xhr = new XMLHttpRequest();
        xhr.open(&#39;post&#39;, &#39;../ashx/upload2.ashx&#39;, true);
        xhr.onreadystatechange = function () {
            if (xhr.readyState == 4 && xhr.status == 200) {
                // var data = eval(&#39;(&#39; + xhr.responseText + &#39;)&#39;);
                console.info(xhr.responseText);
                if (onSuccess)
                    onSuccess();
            }
        }
        //开始发送
        xhr.send(fd);
    }
}

Backend code:

/// <summary>
/// upload2 的摘要说明
/// </summary>
public class upload2 : IHttpHandler
{
    LogHelper.LogHelper _log = new LogHelper.LogHelper();
    int totalCount = 0;
    public void ProcessRequest(HttpContext context)
    {
        HttpContext _Context = context;
        //接收文件
        HttpRequest req = _Context.Request;
        if (req.Files.Count <= 0)
        {
            WriteStr("获取服务器上传文件失败");
            return;
        }
        HttpPostedFile _file = req.Files[0];
        //获取参数
        // string ext = req.Form["extention"];
        string filename = req.Form["filename"];
        //如果是int 类型当文件大的时候会出问题 最大也就是 1.9999999990686774G
        int loaded = Convert.ToInt32(req.Form["loaded"]);
        totalCount += loaded;
 
        string newname = @"F:\JavaScript_Solution\H5Solition\H5Solition\Content\TempFile\";
        newname += filename;
        //接收二级制数据并保存
        Stream stream = _file.InputStream;
        if (stream.Length <= 0)
            throw new Exception("接收的数据不能为空");
        byte[] dataOne = new byte[stream.Length];
        stream.Read(dataOne, 0, dataOne.Length);
        FileStream fs = new FileStream(newname, FileMode.Append, FileAccess.Write, FileShare.Read, 1024);
        try
        {
            fs.Write(dataOne, 0, dataOne.Length);
        }
        finally
        {
            fs.Close();
            stream.Close();
        }
        _log.WriteLine((totalCount + dataOne.Length).ToString());
        WriteStr("分段数据保存成功");
    }
    private void WriteStr(string str)
    {
        HttpContext.Current.Response.Write(str);
    }
    public bool IsReusable
    {
        get
        {
            return true;
        }
    }

2. The segment reads the file as a blob, and uploads it to the server using ajax, adding the stop and continue function operations

<div class="container">
    <div class="panel panel-default">
        <div class="panel-heading">分段读取文件：</div>
        <div class="panel-body">
            <input type="file" id="file" />
            <br />
            <input type="button" value="中止" onclick="stop();" />&emsp;
            <input type="button" value="继续" onclick="containue();" />
            <br />
            <progress id="progressOne" max="100" value="0" style="width:400px;"></progress>
            <blockquote id="Status" style="word-break:break-all;"></blockquote>
        </div>
    </div>
</div>

JS:

/*
* 分段读取文件为blob ，并使用ajax上传到服务器
* 使用Ajax方式提交上传数据文件大小应该有限值，最好500MB以内
* 原因短时间过多的ajax请求，Asp.Net后台会崩溃获取上传的分块数据为空
* 取代方式，长连接或WebSocket
*/
var fileBox = document.getElementById('file');
var reader = null;  //读取操作对象
var step = 1024 * 1024 * 3.5;  //每次读取文件大小
var cuLoaded = 0; //当前已经读取总数
var file = null; //当前读取的文件对象
var enableRead = true;//标识是否可以读取文件
fileBox.onchange = function () {
    //获取文件对象
    file = this.files[0];
    var total = file.size;
    console.info("文件大小：" + file.size);
    var startTime = new Date();
    reader = new FileReader();
    //读取一段成功
    reader.onload = function (e) {
        //处理读取的结果
        var result = reader.result;
        var loaded = e.loaded;
        if (enableRead == false)
            return false;
        //将分段数据上传到服务器
        uploadFile(result, cuLoaded, function () {
            console.info('loaded:' + cuLoaded + '----current:' + loaded);
            //如果没有读完，继续
            cuLoaded += loaded;
            if (cuLoaded < total) {
                readBlob(cuLoaded);
            } else {
                console.log(&#39;总共用时：&#39; + (new Date().getTime() - startTime.getTime()) / 1000);
                cuLoaded = total;
            }
            //显示结果进度
            var percent = (cuLoaded / total) * 100;
            document.getElementById(&#39;Status&#39;).innerText = percent;
            document.getElementById(&#39;progressOne&#39;).value = percent;
        });
    }
    //开始读取
    readBlob(0);
    //关键代码上传到服务器
    function uploadFile(result, startIndex, onSuccess) {
        var blob = new Blob([result]);
        //提交到服务器
        var fd = new FormData();
        fd.append(&#39;file&#39;, blob);
        fd.append(&#39;filename&#39;, file.name);
        fd.append(&#39;loaded&#39;, startIndex);
        var xhr = new XMLHttpRequest();
        xhr.open(&#39;post&#39;, &#39;../ashx/upload2.ashx&#39;, true);
        xhr.onreadystatechange = function () {
            if (xhr.readyState == 4 && xhr.status == 200) {
                if (onSuccess)
                    onSuccess();
            } else if (xhr.status == 500) {
                //console.info(&#39;请求出错，&#39; + xhr.responseText);
                setTimeout(function () {
                    containue();
                }, 1000);
            }
        }
        //开始发送
        xhr.send(fd);
    }
}
//指定开始位置，分块读取文件
function readBlob(start) {
    //指定开始位置和结束位置读取文件
    var blob = file.slice(start, start + step);
    reader.readAsArrayBuffer(blob);
}
//中止
function stop() {
    //中止读取操作
    console.info(&#39;中止，cuLoaded：&#39; + cuLoaded);
    enableRead = false;
    reader.abort();
}
//继续
function containue() {
    console.info(&#39;继续，cuLoaded：&#39; + cuLoaded);
    enableRead = true;
    readBlob(cuLoaded);
}

The background code is the same as above

I believe I have read these cases You have mastered the method. For more exciting information, please pay attention to other related articles on the php Chinese website!

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