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February 17, 2013
Gravatar of Lubos PintesPosted by Lubos PintesReply
Lubos Pintes
Gravatar of Lubos Pintes


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I am writing little program which downloads simple data file from server through HTTP.
The file is static, but updated regularly, so I am using "Range: bytes" header to optimize the traffic a bit.
After I analyzed HTTP status line and headers, I started to read the raw data through SocketStream.read(buffer).
There seems to be one single '\n' character in buffer[0] after first read. I cannot figure out why this character is appearing. It is not there when I download that file through wget.
Here is relevant part of code:
//Parse status line + headers
  string[string] header;
  auto line=ss.readLine();
  auto statusLine=line.split(" ");
  auto responseCode=to!int(statusLine[1]);
  while(true) {
    line=ss.readLine();
    if(!line.length) break;
    auto h=line.split(":");
    header[h[0].idup]=h[1].strip.idup;
  }
  int contentLength=to!uint(header["Content-Length"]);
  if(responseCode==416 && contentLength==fileSize) return; //nothing to download
  if(responseCode==200 || responseCode==216) {
    ubyte[] buffer=new ubyte[4096];
    auto first=true;
    while(contentLength>0) {
      auto bytesRead=ss.read(buffer);
      if(first) {writeln(buffer[0..20]); first=false; }
      f.rawWrite(buffer[0..bytesRead]);
      contentLength-=bytesRead;
    }
  }
March 20, 2013
Gravatar of Regan HeathPosted by Regan Heath
in reply to Lubos Pintes		Reply
Regan Heath
Gravatar of Regan Heath
Posted in reply to Lubos Pintes


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On Sun, 17 Feb 2013 16:53:23 -0000, Lubos Pintes <lubos.pintes@gmail.com> wrote:

> I am writing little program which downloads simple data file from server through HTTP.
> The file is static, but updated regularly, so I am using "Range: bytes" header to optimize the traffic a bit.
> After I analyzed HTTP status line and headers, I started to read the raw data through SocketStream.read(buffer).
> There seems to be one single '\n' character in buffer[0] after first read. I cannot figure out why this character is appearing. It is not there when I download that file through wget.
> Here is relevant part of code:
> //Parse status line + headers
>    string[string] header;
>    auto line=ss.readLine();
>    auto statusLine=line.split(" ");
>    auto responseCode=to!int(statusLine[1]);
>    while(true) {
>      line=ss.readLine();
>      if(!line.length) break;
>      auto h=line.split(":");
>      header[h[0].idup]=h[1].strip.idup;
>    }
>    int contentLength=to!uint(header["Content-Length"]);
>    if(responseCode==416 && contentLength==fileSize) return; //nothing to download
>    if(responseCode==200 || responseCode==216) {
>      ubyte[] buffer=new ubyte[4096];
>      auto first=true;
>      while(contentLength>0) {
>        auto bytesRead=ss.read(buffer);
>        if(first) {writeln(buffer[0..20]); first=false; }
>        f.rawWrite(buffer[0..bytesRead]);
>        contentLength-=bytesRead;
>      }
>    }
>

IIRC there is a blank line after headers in the HTTP protocol, that's how you know you're at the end of the headers i.e.

<status code/response>
<header>
[<header>]
<blank line>
<body>

R

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