Working with Buffered streams

[Bradley Smith]

There is a bug in the Stream class. If you mix, readLine() and 
read(ubyte[]) calls to a stream, readLine() may not appear to perform as 
documented. As documented, readLine() stop at "some combination of 
carriage return [CR] and line feed [LF]". However, this is not 
necessarily true. If the stream is non-seekable, readLine() will stop at 
CR and set a prevCr flag indicating that a LF should be consumed on the 
next read. However, this only takes place in the getc() method and 
methods using getc(). Some methods, like read(ubyte[]), read the stream 
directly and the prevCr flag is not processed.

At first, I thought this might just be odd behavior rather than a bug, 
but I decided that it is a bug. In order to understand how to use the 
stream effectively, one must understand the implementation details. One 
must know that the behavior for seekable streams is different that 
non-seekable streams, and adjust the client code accordingly. For this 
reason, it should be considered a bug.

The workaround this bug is to check the first character of a 
non-seekable stream after reading with readLine(). For example:

       if(!ss.seekable) {
         ss.read(b);
         if (b[0] != '\n') {
           s.write(b);
         }
       }
       while(ss.read(b) != 0){
         s.write(b);
       }

Thanks,
   Bradley

Lorenzo Villani wrote:
> Ok, this is a very noob-ish question :)
> 
> I'm writing a simple HTTP file downloader (you can find it attached to this post) but I have some troubles getting a proper file after transfer. (eg: local downloaded file is corrupted). Can someone help me? (Please note that i'm new to this language :D )
> 
> 
> ------------------------------------------------------------------------
> 
> import std.file;
> import std.string;
> import std.stdio;
> import std.stream;
> import std.socketstream;
> import std.socket;
> 
> class HttpDownload {	
> 	public:
> 		this() {}
> 		
> 		void downloadFile(char[] domain, char[] dir, char[] file, int port = 80) {
> 			Socket sock = new TcpSocket(new InternetAddress(domain, port));
> 			SocketStream ss = new SocketStream(sock);
> 			
> 			// we prepare the request
> 			if ( port != 80 )
> 				domain = domain ~ ":" ~ cast(char)port;
> 			
> 			char[] request = "GET " ~ dir ~ "/" ~ file ~ " HTTP/1.1\r\n"
> 				~ "Connection: Keep-Alive\r\n"
> 				~ "User-Agent: Mozilla 5.0\r\n"
> 				~ "Host: " ~ domain ~ "\r\n"
> 				~ "\r\n";
> 			
> 			// we send the request
> 			ss.writeString(request);
> 			
> 			// this for removes the HTTP header and looks for a positive response
> 			// from the webserver
> 			for(;;) {
> 				char[] response = ss.readLine();
> 				char[] RESPONSE = "HTTP/1.1 ";
> 				
> 				if(!response.length) {
> 					break;
> 				} else {
> 					if (response.length > RESPONSE.length && !icmp(RESPONSE, response[0 .. RESPONSE.length])) {
> 						char[] code;
> 						code = response[RESPONSE.length .. response.length];
> 						int i = ifind(code, "200 OK");
> 						if ( i != -1 ) {
> 							writefln("---> Received a 200 OK");
> 						} else {
> 							throw new Exception("Webserver has replied with an error");
> 							return;
> 						}
> 					}
> 				}
> 			}
> 			
> 			// write file
> 			BufferedFile s = new BufferedFile();
> 			s.create(getcwd() ~ "/" ~ file);
> 			ubyte[1] b;
> 			while(ss.read(b) != 0){
> 				s.write(b);
> 			}
> 			ss.close();
> 			s.close();
> 		}
> }
> 
> int main() {
> 	HttpDownload download = new HttpDownload();
> 	download.downloadFile("www.capponcino.it", "/tremulous/dl/pk3", "highrise-b4.pk3", 80);
> 	return 0;
> }