/// <summary>
/// The actual functionality to download with optional hash verification
/// subclasses that wish to return the contents of the downloaded file
/// or do something else with it can override this instead of RunWithReturn.
/// </summary>
/// <param name="success"></param>
/// <returns></returns>
protected virtual NPath RunDownload(bool success)
{
Exception exception = null;
var attempts = 0;
bool result = false;
var partialFile = TargetDirectory.Combine(Filename + ".partial");
TargetDirectory.EnsureDirectoryExists();
do
{
exception = null;
if (Token.IsCancellationRequested)
{
break;
}
try
{
Logger.Trace($"Download of {Url} to {Destination} Attempt {attempts + 1} of {RetryCount + 1}");
using (var destinationStream = fileSystem.OpenWrite(partialFile, FileMode.Append))
{
result = Downloader.Download(Logger, Url, destinationStream,
(value, total) =>
{
UpdateProgress(value, total);
return(!Token.IsCancellationRequested);
});
}
if (result)
{
partialFile.Move(Destination);
}
}
catch (Exception ex)
{
exception = ex;
result = false;
}
} while (!result && attempts++ < RetryCount);
if (!result)
{
Token.ThrowIfCancellationRequested();
throw new DownloadException("Error downloading file", exception);
}
return(Destination);
}
async Task DownloadAsync(HttpClient httpClient, CancellationToken cancellationToken)
{
var response = (await httpClient.GetAsync(
SourceUri,
HttpCompletionOption.ResponseHeadersRead,
cancellationToken)).EnsureSuccessStatusCode();
cancellationToken.ThrowIfCancellationRequested();
ActualSourceUri = response.Content.Headers.ContentLocation ?? SourceUri;
TotalBytes = (ulong)response.Content.Headers.ContentLength.GetValueOrDefault();
var _targetFile = TargetDirectory.Combine(Path.GetFileName(ActualSourceUri.LocalPath));
using (var hash = MD5.Create())
using (var sourceStream = await response.Content.ReadAsStreamAsync().ConfigureAwait(false))
using (var outputStream = CreateOutputStream(ref _targetFile)) {
cancellationToken.ThrowIfCancellationRequested();
TargetFile = _targetFile;
var buffer = new byte [bufferSize];
int read;
while ((read = await sourceStream
.ReadAsync(buffer, 0, buffer.Length, cancellationToken)
.ConfigureAwait(false)) != 0)
{
cancellationToken.ThrowIfCancellationRequested();
await outputStream
.WriteAsync(buffer, 0, read, cancellationToken)
.ConfigureAwait(false);
hash.TransformBlock(buffer, 0, read, buffer, 0);
ProgressBytes += (ulong)read;
Progress = TotalBytes == 0 ? 0.0 : ProgressBytes / (double)TotalBytes;
}
hash.TransformFinalBlock(buffer, 0, 0);
await outputStream
.FlushAsync(cancellationToken)
.ConfigureAwait(false);
var fileLength = new FileInfo(TargetFile).Length;
if (fileLength != (long)TotalBytes)
{
throw new DamagedDownloadException(
$"expected {TotalBytes} bytes for {TargetFile} " +
$"but size on disk is {fileLength} bytes");
}
if (Md5Hash != null)
{
var actualHash = hash.Hash.ToHexString();
if (!String.Equals(Md5Hash, actualHash, StringComparison.OrdinalIgnoreCase))
{
throw new DamagedDownloadException(
$"checksum ({actualHash}) for {TargetFile} does " +
$"not match expected checksum {Md5Hash}");
}
}
}
}
