Class: LIBUSB::Context

Inherits:
Object
  • Object
show all
Defined in:
lib/libusb/context.rb,
lib/libusb/eventmachine.rb

Overview

Class representing a libusb session.

Defined Under Namespace

Classes: CompletionFlag, EMPollfdHandler, Pollfd

Instance Method Summary (collapse)

Constructor Details

- (Context) initialize

Initialize libusb context.



72
73
74
75
76
77
78
79
 
# File 'lib/libusb/context.rb', line 72

def initialize
  m = FFI::MemoryPointer.new :pointer
  res = Call.libusb_init(m)
  LIBUSB.raise_error res, "in libusb_init" if res!=0
  @ctx = m.read_pointer
  @on_pollfd_added = nil
  @on_pollfd_removed = nil
end

Instance Method Details

- (Object) debug=(level)

Set message verbosity.

  • Level 0: no messages ever printed by the library (default)

  • Level 1: error messages are printed to stderr

  • Level 2: warning and error messages are printed to stderr

  • Level 3: informational messages are printed to stdout, warning and error messages are printed to stderr

The default level is 0, which means no messages are ever printed. If you choose to increase the message verbosity level, ensure that your application does not close the stdout/stderr file descriptors.

You are advised to set level 3. libusb is conservative with its message logging and most of the time, will only log messages that explain error conditions and other oddities. This will help you debug your software.

If the LIBUSB_DEBUG environment variable was set when libusb was initialized, this method does nothing: the message verbosity is fixed to the value in the environment variable.

If libusb was compiled without any message logging, this method does nothing: you'll never get any messages.

If libusb was compiled with verbose debug message logging, this method does nothing: you'll always get messages from all levels.

Parameters:

  • level (Fixnum) —

    debug level to set



115
116
117
 
# File 'lib/libusb/context.rb', line 115

def debug=(level)
  Call.libusb_set_debug(@ctx, level)
end

- (Array<LIBUSB::Device>) devices(filter_hash = {})

Obtain a list of devices currently attached to the USB system, optionally matching certain criteria.

Examples:

# Return all devices of vendor 0x0ab1 where idProduct is 3 or 4:
context.device :idVendor=>0x0ab1, :idProduct=>[0x0003, 0x0004]

Parameters:

  • filter_hash (Hash) (defaults to: {}) —

    A number of criteria can be defined in key-value pairs. Only devices that equal all given criterions will be returned. If a criterion is not specified or its value is nil, any device will match that criterion. The following criteria can be filtered:

    • :idVendor, :idProduct (FixNum) for matching vendor/product ID,

    • :bClass, :bSubClass, :bProtocol (FixNum) for the device type - Devices using CLASS_PER_INTERFACE will match, if any of the interfaces match.

    • :bcdUSB, :bcdDevice, :bMaxPacketSize0 (FixNum) for the USB and device release numbers.

    Criteria can also specified as Array of several alternative values.

Returns:



195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
 
# File 'lib/libusb/context.rb', line 195

def devices(filter_hash={})
  device_list.select do |dev|
    ( !filter_hash[:bClass] || (dev.bDeviceClass==CLASS_PER_INTERFACE ?
                         dev.settings.map(&:bInterfaceClass).&([filter_hash[:bClass]].flatten).any? :
                         [filter_hash[:bClass]].flatten.include?(dev.bDeviceClass))) &&
    ( !filter_hash[:bSubClass] || (dev.bDeviceClass==CLASS_PER_INTERFACE ?
                         dev.settings.map(&:bInterfaceSubClass).&([filter_hash[:bSubClass]].flatten).any? :
                         [filter_hash[:bSubClass]].flatten.include?(dev.bDeviceSubClass))) &&
    ( !filter_hash[:bProtocol] || (dev.bDeviceClass==CLASS_PER_INTERFACE ?
                         dev.settings.map(&:bInterfaceProtocol).&([filter_hash[:bProtocol]].flatten).any? :
                         [filter_hash[:bProtocol]].flatten.include?(dev.bDeviceProtocol))) &&
    ( !filter_hash[:bMaxPacketSize0] || [filter_hash[:bMaxPacketSize0]].flatten.include?(dev.bMaxPacketSize0) ) &&
    ( !filter_hash[:idVendor] || [filter_hash[:idVendor]].flatten.include?(dev.idVendor) ) &&
    ( !filter_hash[:idProduct] || [filter_hash[:idProduct]].flatten.include?(dev.idProduct) ) &&
    ( !filter_hash[:bcdUSB] || [filter_hash[:bcdUSB]].flatten.include?(dev.bcdUSB) ) &&
    ( !filter_hash[:bcdDevice] || [filter_hash[:bcdDevice]].flatten.include?(dev.bcdDevice) )
  end
end

- (Object) eventmachine_register

Register libusb's file descriptors and timeouts to EventMachine.

Examples:

require 'libusb/eventmachine'
context = LIBUSB::Context.new
EventMachine.run do
  context.eventmachine_register
end

See Also:



34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
 
# File 'lib/libusb/eventmachine.rb', line 34

def eventmachine_register
  @eventmachine_attached_fds = {}
  @eventmachine_timer = nil

  pollfds = self.pollfds
  if pollfds
    pollfds.each do |pollfd|
      eventmachine_add_pollfd(pollfd)
    end

    self.on_pollfd_added do |pollfd|
      eventmachine_add_pollfd(pollfd)
    end

    self.on_pollfd_removed do |pollfd|
      eventmachine_rm_pollfd(pollfd)
    end
  else
    # Libusb pollfd API is not available on this platform.
    # Use simple polling timer, instead:
    EventMachine.add_periodic_timer(0.01) do
      @eventmachine_timer = self.handle_events 0
    end
  end
end

- (Object) eventmachine_unregister 



60
61
62
63
64
65
 
# File 'lib/libusb/eventmachine.rb', line 60

def eventmachine_unregister
  @eventmachine_timer.cancel if @eventmachine_timer
  @eventmachine_attached_fds.each do |fd, watcher|
    watcher.detach
  end
end

- (Object) exit

Deinitialize libusb.

Should be called after closing all open devices and before your application terminates.



84
85
86
 
# File 'lib/libusb/context.rb', line 84

def exit
  Call.libusb_exit(@ctx)
end

- (Object) handle_events(timeout = nil, completion_flag = nil)

Handle any pending events in blocking mode.

This method must be called when libusb is running asynchronous transfers. This gives libusb the opportunity to reap pending transfers, invoke callbacks, etc.

If a zero timeout is passed, this function will handle any already-pending events and then immediately return in non-blocking style.

If a non-zero timeout is passed and no events are currently pending, this method will block waiting for events to handle up until the specified timeout. If an event arrives or a signal is raised, this method will return early.

If the parameter completion_flag is used, then after obtaining the event handling lock this function will return immediately if the flag is set to completed. This allows for race free waiting for the completion of a specific transfer. See source of Transfer#submit_and_wait for a use case of completion_flag.

Parameters:

  • timeout (Integer, nil) (defaults to: nil) —

    the maximum time (in millseconds) to block waiting for events, or 0 for non-blocking mode

  • completion_flag (Context::CompletionFlag, nil) (defaults to: nil) —

    CompletionFlag to check



155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
 
# File 'lib/libusb/context.rb', line 155

def handle_events(timeout=nil, completion_flag=nil)
  if completion_flag && !completion_flag.is_a?(Context::CompletionFlag)
    raise ArgumentError, "completion_flag is not a CompletionFlag"
  end
  if timeout
    timeval = Call::Timeval.new
    timeval.in_ms = timeout
    res = if Call.respond_to?(:libusb_handle_events_timeout_completed)
      Call.libusb_handle_events_timeout_completed(@ctx, timeval, completion_flag)
    else
      Call.libusb_handle_events_timeout(@ctx, timeval)
    end
  else
    res = if Call.respond_to?(:libusb_handle_events_completed)
      Call.libusb_handle_events_completed(@ctx, completion_flag )
    else
      Call.libusb_handle_events(@ctx)
    end
  end
  LIBUSB.raise_error res, "in libusb_handle_events" if res<0
end

- (Float?) next_timeout

Determine the next internal timeout that libusb needs to handle.

You only need to use this function if you are calling poll() or select() or similar on libusb's file descriptors yourself - you do not need to use it if you are calling #handle_events directly.

You should call this function in your main loop in order to determine how long to wait for select() or poll() to return results. libusb needs to be called into at this timeout, so you should use it as an upper bound on your select() or poll() call.

When the timeout has expired, call into #handle_events (perhaps in non-blocking mode) so that libusb can handle the timeout.

This function may return zero. If this is the case, it indicates that libusb has a timeout that has already expired so you should call #handle_events immediately. A return code of nil indicates that there are no pending timeouts.

On some platforms, this function will always returns nil (no pending timeouts). See libusb's notes on time-based events.

Returns:

  • (Float, nil) —

    the timeout in seconds



262
263
264
265
266
267
 
# File 'lib/libusb/context.rb', line 262

def next_timeout
  timeval = Call::Timeval.new
  res = Call.libusb_get_next_timeout @ctx, timeval
  LIBUSB.raise_error res, "in libusb_get_next_timeout" if res<0
  res == 1 ? timeval.in_s : nil
end

- (Object) on_pollfd_added {|pollfd| ... }

Register a notification block for file descriptor additions.

This block will be invoked for every new file descriptor that libusb uses as an event source.

Note that file descriptors may have been added even before you register these notifiers (e.g. at #initialize time).

Yield Parameters:

  • pollfd (Pollfd) —

    The added file descriptor is yielded to the block



278
279
280
281
282
283
284
 
# File 'lib/libusb/context.rb', line 278

def on_pollfd_added &block
  @on_pollfd_added = proc do |fd, events, _|
    pollfd = Pollfd.new fd, events
    block.call pollfd
  end
  Call.libusb_set_pollfd_notifiers @ctx, @on_pollfd_added, @on_pollfd_removed, nil
end

- (Object) on_pollfd_removed {|pollfd| ... }

Register a notification block for file descriptor removals.

This block will be invoked for every removed file descriptor that libusb uses as an event source.

Note that the removal notifier may be called during #exit (e.g. when it is closing file descriptors that were opened and added to the poll set at #initialize time). If you don't want this, overwrite the notifier immediately before calling #exit.

Yield Parameters:

  • pollfd (Pollfd) —

    The removed file descriptor is yielded to the block



297
298
299
300
301
302
303
 
# File 'lib/libusb/context.rb', line 297

def on_pollfd_removed &block
  @on_pollfd_removed = proc do |fd, _|
    pollfd = Pollfd.new fd
    block.call pollfd
  end
  Call.libusb_set_pollfd_notifiers @ctx, @on_pollfd_added, @on_pollfd_removed, nil
end

- (Array<Pollfd>) pollfds

Retrieve a list of file descriptors that should be polled by your main loop as libusb event sources.

As file descriptors are a Unix-specific concept, this function is not available on Windows and will always return nil.

Returns:

  • (Array<Pollfd>) —

    list of Pollfd objects, nil on error, nil on platforms where the functionality is not available



224
225
226
227
228
229
230
231
232
233
234
235
236
237
 
# File 'lib/libusb/context.rb', line 224

def pollfds
  ppPollfds = Call.libusb_get_pollfds(@ctx)
  return nil if ppPollfds.null?
  offs = 0
  pollfds = []
  while !(pPollfd=ppPollfds.get_pointer(offs)).null?
    pollfd = Call::Pollfd.new pPollfd
    pollfds << Pollfd.new(pollfd[:fd], pollfd[:events])
    offs += FFI.type_size :pointer
  end
  # ppPollfds has to be released by free() -> give the GC this job
  ppPollfds.autorelease = true
  pollfds
end