public DownloaderResult Download(Uri url, DownloaderOptions options)
{
var head = CreateRequest(url, options);
head.Method = "HEAD";
var headResponse = (HttpWebResponse)head.GetResponse();
headResponse.Close();
if (this.IsRedirect(headResponse)) {
var target = headResponse.Headers[HttpResponseHeader.Location];
if (target.IsNullOrEmpty())
throw new Exception("Response is a redirect, but location header was not set.");
return Download(new Uri(target), options);
}
if (headResponse.StatusCode != HttpStatusCode.OK)
throw new NotSupportedException(string.Format("HEAD request returned a response code {0}: {1} that is currently not supported.", headResponse.StatusCode, headResponse.StatusDescription));
while (true) {
try {
return Download(url, headResponse, options);
}
catch (DownloadException ex) {
this.logger.LogError("Download error {0}, retrying.", ex.Message);
}
}
}
private static HttpWebRequest CreateRequest(Uri url, DownloaderOptions options)
{
var request = (HttpWebRequest)WebRequest.Create(url);
request.Credentials = options.Credentials;
request.AllowAutoRedirect = false;
return request;
}
private DownloaderResult Download(Uri url, HttpWebResponse headResponse, DownloaderOptions options)
{
var fullLength = headResponse.ContentLength;
var fileName = GetFileName(headResponse);
var file = this.mapPath(url, fileName);
file.Directory.Create();
logger.LogMessage("-> {0}", file.FullName);
var get = CreateRequest(url, options);
get.Method = "GET";
var lengthDownloadedBefore = 0L;
var fileMode = FileMode.Append;
if (file.Exists && file.Length > 0) {
if (file.Length == fullLength) {
this.logger.LogMessage("File is already fully downloaded.");
return new DownloaderResult(url, file, headResponse.ContentType);
}
if (file.Length < fullLength) {
this.logger.LogMessage("File already exists, requesting range {0}-{1}.", file.Length, headResponse.ContentLength);
get.AddRange(file.Length, fullLength);
lengthDownloadedBefore = file.Length;
}
else if (fullLength <= 0) {
this.logger.LogWarning("File already exists, but server did not provide length, so it will be fully redownloaded.");
fileMode = FileMode.Create;
}
else {
this.logger.LogWarning("File already exists, but it is larger than file on server, so it will be fully redownloaded. ");
fileMode = FileMode.Create;
}
}
var response = get.GetResponse();
var downloadedTotal = 0L;
using (response)
using (var fileStream = file.Open(fileMode, FileAccess.Write, FileShare.Read))
using (var webStream = response.GetResponseStream()) {
var buffer = new byte[1024];
var time = new Stopwatch();
time.Start();
while (true) {
int count;
try {
count = webStream.Read(buffer, 0, buffer.Length);
}
catch (IOException ex) {
throw new DownloadException(ex.Message, ex);
}
if (count == 0)
break;
downloadedTotal += count;
fileStream.Write(buffer, 0, count);
options.ReportProgress(new DownloaderProgress {
File = file,
BytesDownloadedBefore = lengthDownloadedBefore,
BytesDownloaded = downloadedTotal,
BytesTotal = fullLength,
TimeElapsed = time.Elapsed
});
}
}
this.logger.LogMessage("Download completed.");
var contentType = new ContentType(headResponse.ContentType);
return new DownloaderResult(url, file, contentType.MediaType);
}