Necko walkthrough: take data protocol as example

1. NECKO WALKTHROUGH
(Data Protocol)
Tommy Kuo [:KuoE0]
kuoe0@mozilla.com
2015.04.23 @Mozilla Taiwan

2. Outline
• Create protocol channel
• Listener interface
• Open protocol channel
• Data transaction

3. Protocol

4. URI Syntax
<scheme name> : <hierarchical part> [ ? <query> ] [ # <fragment> ]
http : //google.com/search ? q=Mozilla
https : //www.facebook.com/pages/郝神好神/871866229523862
file : ///Downloads/郝神好帥.jpg
about : config
mailto : kuoe0@mozilla.com
data : text/html;charset=utf-8;base64,6YOd56We5aW95bil
line : //shop/detail/xxx

5. Data Protocol
data:[<MIME-type>][;charset=<encoding>][;base64],<data>
A very simple protocol.

6. data:text/html;charset=utf-8;base64,6YOd56We5aW95bil

7. data:text/html;charset=utf-8;base64,6YOd56We5aW95bil
After base64 decoding…

8. Create Protocol Channel

9. handleCommand
openUILinkIn
openLinkIn
loadURIWithFlags (tabbrowser)
loadURIWithFlags (browser)
LoadURI(char16_t*, …)
LoadURIWithOptions
LoadURI(nsIURI*, …)
InternalLoad
DoURILoad
DoChannelLoad
NS_NewURI
NS_NewChannelInternal
Browser UI
(XUL)
DocShell Necko
GetProtocolHandler
GetProtocolHandler
nsIURI
nsIChannel
NewURI
NewChannel2

10. GetProtocolHandler
1. Get protocol handler if it is cached.
2. Lookup in ‘about:config’ to check internal support.
3. For internal protocol, get internal protocol hander
service and cache it.
4. For external protocol, get default external protocol
handler service.
netwerk/base/nsIOService.cpp#406

11. data:text/html;charset=utf-8;base64,6YOd56We5aW95bil
GetProtocolHandler
nsDataHandler
nsSimpleURI nsDataChannel
NewURI() NewChannel2()

12. Protocol Handler API
Format the URI Create the channel Get flags
NewChannel2(…)
NewProxiedChannel2(…)
NewURI(…) GetProtocolFlags(…)

13. Protocol Handler
Internal External
lookup in /netwerk/protocol/ lookup in about:config

14. Internal protocol handler in /netwerk/protocol/

15. External protocol handler in about:config

16. Listener Interface

17. nsIStreamListener
• onStartRequest()
• Called to signify the beginning of an asynchronous request.
• onStopRequest()
• Called to signify the end of an asynchronous request.
• onDataAvailable()
• This method is called when the next chunk of data for the
ongoing request may be read without blocking the calling
thread.

18. nsInputStreamPump… nsDataChannelnsHtml5StreamParser
OnStartRequest
OnStartRequest
OnStartRequest
OnDataAvailable
OnDataAvailable
OnDataAvailable
Read / ReadSegment
OnStopRequest
OnStopRequest
OnStopRequest

19. Open Protocol Channel

20. Initialize & Start

21. nsDataChannel
nsPipeInputStreamInitialize Stream & Pump
nsInputStreamPump
(event dispatcher)
(data source) notify on ready
create create

22. nsDocumentOpenInfo
nsDataChannel
nsInputStreamPump
Setup Listener Chain
listen
listen
notify
notify

23. Start Waiting nsInputStreamPump
nsDataChannel
nsPipeInputStream
AsyncRead()
AsyncWait()OnInputStreamReady()

24. Data Transaction

25. IDLE START
STOP TRANSFER
State of nsInputStreamPump
Must be in main thread!!

26. OnStateStart

27. OnStateStart

28. Create Content Viewer
nsDocShell
nsHTMLDocument
nsDocumentViewer
load

29. Set Content Listener
nsHtml5StreamParser
nsHtml5StreamListener
nsDocumentOpenInfo
listen
listen
notify
notify

30. nsDocumentOpenInfoCall OnStartRequest()
nsDataChannel
nsInputStreamPump
nsHtml5StreamParser
nsHtml5StreamListener
listen notify
listen notify
listen notify
listen notify

31. OnStateTransfer

32. OnStateTransfer

33. nsDocumentOpenInfoCall OnDataAvailable()
nsDataChannel
nsInputStreamPump
nsHtml5StreamParser
nsHtml5StreamListener
listen notify
listen notify
listen notify
listen notify

34. Read Data
nsPipeInputStream
Read/ReadSegment
nsHtml5StreamParser

35. nsPipeInputStream
data segment
nsHtml5StreamParser
parser buffer
temporal buffer
Call Read() in Main Thread
copy
dispatch to parser thread

36. nsPipeInputStream
data segment
nsHtml5StreamParser
parser buffer
Call ReadSegment() in Parser Thread
copy

37. OnStateStop

38. OnStateStop

39. nsDocumentOpenInfoCall OnStopRequest()
nsDataChannel
nsInputStreamPump
nsHtml5StreamParser
nsHtml5StreamListener
listen notify
listen notify
listen notify
listen notify

40. Thank you!