Add discover feature

Includes example script demonstrating how to use the discover()
function and its callbacks.

README.md

@@ -2,11 +2,6 @@
 
 Python bindings for liblxi.
 
-## Features
-
-The python bindings implements all of the liblxi API except the discover
-functions.
-
 ## Requirements
 
 Make sure you have python3 and liblxi installed.
@@ -35,17 +30,33 @@ pkg install liblxi python3
 
 ## Run the example code
 
+Note:
+
+If it fails to find the liblxi library you can try preload it with the specific
+path to the library. For example:
+
+```
+LD_PRELOAD=$HOME/opt/lib/liblxi.so python3 send_receive.py 192.168.0.157
+```
+
+### Send and receive example
+
 Run the example test script with the IP of your instrument as argument:
 ```
-$ python3 test.py 192.168.0.157
+$ PYTHONPATH=. python3 ./examples/send_receive.py 192.168.0.157
 Sent 5 bytes
 Sent command: *IDN?
 Received 49 bytes
 Received message: Rohde&Schwarz,RTB2004,1333.1005k04/113192,02.400
 ```
 
-If it fails to find the liblxi library you can try preload it like so:
+### Discover example
 
+Search for instruments:
 ```
-LD_PRELOAD=/usr/lib/liblxi.so python3 test.py 192.168.0.157
+PYTHONPATH=. python3 ./examples/discover.py
+Broadcasting on lo using address 127.0.0.1
+Broadcasting on enxe4b97a86fdad using address 192.168.0.255
+   Found Rohde&Schwarz,NGM202,3638.4472k03/101403,03.068 00A8F863604 on address 192.168.0.107
+Broadcasting on virbr0 using address 192.168.122.255
 ```

examples/discover.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+
+# liblxi-python discover example script
+
+import lxi
+
+
+# Callback functions which are called during discovery
+
+def broadcast(address, interface):
+    address = str(address, 'ascii')
+    interface = str(interface, 'ascii')
+    print("Broadcasting on " + interface + " using address " + address)
+    return
+
+def device(address, id):
+    address = str(address, 'ascii')
+    id = str(id, 'ascii')
+    print("   Found " + id + " on address " + address)
+    return
+
+def service(address, id, service, port):
+    address = str(address, 'ascii')
+    id = str(id, 'ascii')
+    service = str(service, 'ascii')
+    port = str(port)
+    print("Found " + id + " on address " + address)
+    print(" " + service + " service on port " + port)
+
+# Initialize library
+lxi.init()
+
+# Search for devices
+timeout = 1000
+info = lxi.lxi_info_class()
+info.broadcast = broadcast
+info.device = device
+info.service = service
+
+device = lxi.discover(info, timeout, lxi.discover_protocol.DISCOVER_VXI11)
+# device = lxi.discover(info, timeout, lxi.discover_protocol.DISCOVER_MDNS)
+

lxi.py

@@ -29,7 +29,7 @@
 #
 
 #
-# Python bindings for liblxi (work in progress)
+# Python bindings for liblxi
 #
 
 from ctypes import *
@@ -56,11 +56,40 @@
 
 # Load the library
 lib = cdll.LoadLibrary(liblxi)
-  
+
 # Define functions
 def init():
     lib.lxi_init()
 
+# Define types
+class LXI_INFO(Structure):
+    _fields_ = [("broadcast", CFUNCTYPE(None, c_char_p, c_char_p )),
+                ("device", CFUNCTYPE(None, c_char_p, c_char_p)),
+                ("service", CFUNCTYPE(None, c_char_p, c_char_p, c_char_p, c_int))]
+
+class lxi_info_class:
+    def broadcast(self, address, interface):
+        return
+
+    def device(self, address, id):
+        return
+
+    def service(self, address, id, service, port):
+        return
+
+def discover(info: lxi_info_class, timeout: int, type: int):
+    lib.lxi_discover.argtypes = c_void_p, c_int, c_int
+    lib.lxi_discover.restype = c_int
+    BROADCAST_FUNC = CFUNCTYPE(None, c_char_p, c_char_p)
+    broadcast_func = BROADCAST_FUNC(info.broadcast)
+    DEVICE_FUNC = CFUNCTYPE(None, c_char_p, c_char_p)
+    device_func = DEVICE_FUNC(info.device)
+    SERVICE_FUNC = CFUNCTYPE(None, c_char_p, c_char_p, c_char_p, c_int)
+    service_func = SERVICE_FUNC(info.service)
+    c_info_p = pointer(LXI_INFO(broadcast_func, device_func, service_func))
+    status = lib.lxi_discover(c_info_p, c_int(timeout), c_int(type))
+    return status
+
 def connect(address, port: int, name, timeout: int, protocol: int):
     lib.lxi_connect.argtypes = c_char_p, c_int, c_char_p, c_int, c_int
     lib.lxi_connect.restype = c_int
@@ -96,3 +125,10 @@ def __init__(self):
         self.RAW = 1
 
 protocol = _protocol_()
+
+class _discover_protocol_:
+    def __init__(self):
+        self.DISCOVER_VXI11 = 0
+        self.DISCOVER_MDNS = 1
+
+discover_protocol = _discover_protocol_()