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nathan130200/FileDownloader.cs

Forked from yasirkula/FileDownloader.cs
Created December 17, 2017 14:32
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C# Download Public File From Google Drive™ (works for large files as well)
Raw
FileDownloader.cs
using System;
using System.IO;
using System.Net;
public static class FileDownloader
{
private const string GOOGLE_DRIVE_DOMAIN = "drive.google.com";
private const string GOOGLE_DRIVE_DOMAIN2 = "https://drive.google.com";
// Normal example: FileDownloader.DownloadFileFromURLToPath( "http://example.com/file/download/link", @"C:\file.txt" );
// Drive example: FileDownloader.DownloadFileFromURLToPath( "http://drive.google.com/file/d/FILEID/view?usp=sharing", @"C:\file.txt" );
public static FileInfo DownloadFileFromURLToPath( string url, string path )
{
if( url.StartsWith( GOOGLE_DRIVE_DOMAIN ) || url.StartsWith( GOOGLE_DRIVE_DOMAIN2 ) )
return DownloadGoogleDriveFileFromURLToPath( url, path );
else
return DownloadFileFromURLToPath( url, path, null );
}
private static FileInfo DownloadFileFromURLToPath( string url, string path, WebClient webClient )
{
try
{
if( webClient == null )
{
using( webClient = new WebClient() )
{
webClient.DownloadFile( url, path );
return new FileInfo( path );
}
}
else
{
webClient.DownloadFile( url, path );
return new FileInfo( path );
}
}
catch( WebException )
{
return null;
}
}
// Downloading large files from Google Drive prompts a warning screen and
// requires manual confirmation. Consider that case and try to confirm the download automatically
// if warning prompt occurs
private static FileInfo DownloadGoogleDriveFileFromURLToPath( string url, string path )
{
// You can comment the statement below if the provided url is guaranteed to be in the following format:
// https://drive.google.com/uc?id=FILEID&export=download
url = GetGoogleDriveDownloadLinkFromUrl( url );
using( CookieAwareWebClient webClient = new CookieAwareWebClient() )
{
FileInfo downloadedFile;
// Sometimes Drive returns an NID cookie instead of a download_warning cookie at first attempt,
// but works in the second attempt
for( int i = 0; i < 2; i++ )
{
downloadedFile = DownloadFileFromURLToPath( url, path, webClient );
if( downloadedFile == null )
return null;
// Confirmation page is around 50KB, shouldn't be larger than 60KB
if( downloadedFile.Length > 60000 )
return downloadedFile;
// Downloaded file might be the confirmation page, check it
string content;
using( var reader = downloadedFile.OpenText() )
{
// Confirmation page starts with <!DOCTYPE html>, which can be preceeded by a newline
char[] header = new char[20];
int readCount = reader.ReadBlock( header, 0, 20 );
if( readCount < 20 || !( new string( header ).Contains( "<!DOCTYPE html>" ) ) )
return downloadedFile;
content = reader.ReadToEnd();
}
int linkIndex = content.LastIndexOf( "href=\"/uc?" );
if( linkIndex < 0 )
return downloadedFile;
linkIndex += 6;
int linkEnd = content.IndexOf( '"', linkIndex );
if( linkEnd < 0 )
return downloadedFile;
url = "https://drive.google.com" + content.Substring( linkIndex, linkEnd - linkIndex ).Replace( "&amp;", "&" );
}
downloadedFile = DownloadFileFromURLToPath( url, path, webClient );
return downloadedFile;
}
}
// Handles 3 kinds of links (they can be preceeded by https://):
// - drive.google.com/open?id=FILEID
// - drive.google.com/file/d/FILEID/view?usp=sharing
// - drive.google.com/uc?id=FILEID&export=download
public static string GetGoogleDriveDownloadLinkFromUrl( string url )
{
int index = url.IndexOf( "id=" );
int closingIndex;
if( index > 0 )
{
index += 3;
closingIndex = url.IndexOf( '&', index );
if( closingIndex < 0 )
closingIndex = url.Length;
}
else
{
index = url.IndexOf( "file/d/" );
if( index < 0 ) // url is not in any of the supported forms
return string.Empty;
index += 7;
closingIndex = url.IndexOf( '/', index );
if( closingIndex < 0 )
{
closingIndex = url.IndexOf( '?', index );
if( closingIndex < 0 )
closingIndex = url.Length;
}
}
return string.Format( "https://drive.google.com/uc?id={0}&export=download", url.Substring( index, closingIndex - index ) );
}
}
// Web client used for Google Drive
public class CookieAwareWebClient : WebClient
{
private class CookieContainer
{
Dictionary<string, string> _cookies;
public string this[Uri url]
{
get
{
string cookie;
if( _cookies.TryGetValue( url.Host, out cookie ) )
return cookie;
return null;
}
set
{
_cookies[url.Host] = value;
}
}
public CookieContainer()
{
_cookies = new Dictionary<string, string>();
}
}
private CookieContainer cookies;
public CookieAwareWebClient() : base()
{
cookies = new CookieContainer();
}
protected override WebRequest GetWebRequest( Uri address )
{
WebRequest request = base.GetWebRequest( address );
if( request is HttpWebRequest )
{
string cookie = cookies[address];
if( cookie != null )
( (HttpWebRequest) request ).Headers.Set( "cookie", cookie );
}
return request;
}
protected override WebResponse GetWebResponse( WebRequest request, IAsyncResult result )
{
WebResponse response = base.GetWebResponse( request, result );
string[] cookies = response.Headers.GetValues( "Set-Cookie" );
if( cookies != null && cookies.Length > 0 )
{
string cookie = "";
foreach( string c in cookies )
cookie += c;
this.cookies[response.ResponseUri] = cookie;
}
return response;
}
protected override WebResponse GetWebResponse( WebRequest request )
{
WebResponse response = base.GetWebResponse( request );
string[] cookies = response.Headers.GetValues( "Set-Cookie" );
if( cookies != null && cookies.Length > 0 )
{
string cookie = "";
foreach( string c in cookies )
cookie += c;
this.cookies[response.ResponseUri] = cookie;
}
return response;
}
}
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