protected async Task <IMailWriteReference> CreateWriteReference(
string sender,
CancellationToken token,
IEnumerable <string> recipients,
Func <string, string> getTempPathFromName,
Func <string, string> getPathFromName)
{
IEnumerable <string> targetRecipients = recipients;
string mailName = Guid.NewGuid().ToString("D");
string tempPath = getTempPathFromName(mailName);
string targetPath = getPathFromName(mailName);
// ReSharper disable AssignNullToNotNullAttribute
Directory.CreateDirectory(Path.GetDirectoryName(targetPath));
Directory.CreateDirectory(Path.GetDirectoryName(tempPath));
// ReSharper restore AssignNullToNotNullAttribute
using (Sharable <FileStream> shared =
Sharable.Create(File.Open(tempPath, FileMode.CreateNew, FileAccess.Write, FileShare.Read)))
{
FileStream stream = shared.Peek();
IEnumerable <string> enumerable = targetRecipients.ToList();
// Save room for header length
using (var writer = new StreamWriter(stream, new UTF8Encoding(false), 1024, true))
{
await writer.WriteLineAsync($"{HeaderLengthHeader}000000000");
await writer.WriteLineAsync($"FROM:{sender}");
foreach (string recipient in enumerable)
{
token.ThrowIfCancellationRequested();
await writer.WriteLineAsync($"TO:{recipient}");
}
await writer.FlushAsync();
var location = (int)stream.Position;
stream.Seek(0, SeekOrigin.Begin);
await writer.FlushAsync();
await writer.WriteLineAsync($"{HeaderLengthHeader}{location:D9}");
await writer.FlushAsync();
stream.Seek(location, SeekOrigin.Begin);
}
return(new WriteReference(
mailName,
tempPath,
targetPath,
sender,
enumerable,
new StreamSpan(shared.TakeValue()),
this));
}
}
public async Task <IMailReadReference> OpenReadAsync(IMailReference reference, CancellationToken token)
{
var mailReference = reference as Reference;
if (mailReference == null)
{
throw new ArgumentNullException(nameof(reference));
}
using (Sharable <FileStream> stream = Sharable.Create(File.OpenRead(mailReference.Path)))
{
string sender;
var recipients = new List <string>();
FileStream streamImpl = stream.Peek();
// 23 ASCII characters, up to 1 GB in size, should be sufficient
// Header-Legnth:000000000
string headerSizeHeader = Encoding.ASCII.GetString(await streamImpl.ReadExactlyAsync(23, token));
if (!headerSizeHeader.StartsWith(HeaderLengthHeader))
{
throw new FormatException($"Invalid mail file format, expected {HeaderLengthHeader} line");
}
if (!int.TryParse(headerSizeHeader.Substring(HeaderLengthHeader.Length), out int headerSize) || headerSize <= 0)
{
throw new FormatException($"Invalid mail file format, {HeaderLengthHeader} is not a valid number");
}
using (var reader = new StreamReader(new StreamSpan(streamImpl, 0, headerSize), Encoding.UTF8, false, 1, true))
{
// This should be the "new line" at the end of the Header-Length we've already consumed
// so all that is left is the rest of the line (which is empty).
// If it's not, then we didn't read what we thought we read, bail
string blankLine = await reader.ReadLineAsync();
if (!string.IsNullOrEmpty(blankLine))
{
throw new FormatException($"Invalid mail file format, {HeaderLengthHeader} is improperly formatted");
}
string fromLine = await reader.ReadLineAsync();
if (!fromLine.StartsWith("FROM:"))
{
throw new FormatException("Invalid mail file format, expected FROM line");
}
sender = fromLine.Substring(5);
string line = null;
while (await reader.TryReadLineAsync(l => line = l, token))
{
if (line.StartsWith("TO:"))
{
recipients.Add(line.Substring(3));
continue;
}
throw new FormatException("Invalid mail file format, expected TO: line or Begin Message");
}
}
return(new ReadReference(
mailReference.Id,
sender,
recipients,
mailReference.Path,
new StreamSpan(stream.TakeValue()),
this));
}
}