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HTTP/FTP fetch content as a range of lines asynchronously.

auto byLineAsync(Conn, Terminator, Char, PostUnit) (
  const(char)[] url,
  const(PostUnit)[] postData,
  KeepTerminator keepTerminator = No.keepTerminator,
  Terminator terminator = '\n',
  size_t transmitBuffers = 10,
  Conn conn = Conn()
if (isCurlConn!Conn && isSomeChar!Char && isSomeChar!Terminator);

auto byLineAsync(Conn, Terminator, Char) (
  const(char)[] url,
  KeepTerminator keepTerminator = No.keepTerminator,
  Terminator terminator = '\n',
  size_t transmitBuffers = 10,
  Conn conn = Conn()

A range of lines is returned immediately and the request that fetches the lines is performed in another thread. If the method or other request properties is to be customized then set the conn parameter with a HTTP/FTP instance that has these properties set.

If postData is non-null the method will be set to post for HTTP requests.

The background thread will buffer up to transmitBuffers number of lines before it stops receiving data from network. When the main thread reads the lines from the range it frees up buffers and allows for the background thread to receive more data from the network.

If no data is available and the main thread accesses the range it will block until data becomes available. An exception to this is the wait(Duration) method on the LineInputRange. This method will wait at maximum for the specified duration and return true if data is available.


import, std.stdio;
// Get some pages in the background
auto range1 = byLineAsync("");
auto range2 = byLineAsync("");
foreach (line; byLineAsync(""))

// Lines already fetched in the background and ready
foreach (line; range1) writeln(line);
foreach (line; range2) writeln(line);
import, std.stdio;
// Get a line in a background thread and wait in
// main thread for 2 seconds for it to arrive.
auto range3 = byLineAsync("");
if (range3.wait(dur!"seconds"(2)))
    writeln("No line received after 2 seconds!");


url The url to receive content from
postData Data to HTTP Post
keepTerminator Yes.keepTerminator signals that the line terminator should be returned as part of the lines in the range.
terminator The character that terminates a line
transmitBuffers The number of lines buffered asynchronously
conn The connection to use e.g. HTTP or FTP.


A range of Char[] with the content of the resource pointer to by the URL.


Jonas Drewsen. Some of the SMTP code contributed by Jimmy Cao.


Boost License 1.0.