1 files changed, 79 insertions, 0 deletions
diff --git a/glucometerutils/support/hiddevice.py b/glucometerutils/support/hiddevice.py
new file mode 100644
index 0000000..a3f2776
--- /dev/null
+++ b/glucometerutils/support/hiddevice.py
@@ -0,0 +1,79 @@
+"""Common routines and base driver class for HID-based meters.
+"""
+
+__author__ = 'Diego Elio Pettenò'
+__email__ = 'flameeyes@flameeyes.eu'
+__copyright__ = 'Copyright © 2017, Diego Elio Pettenò'
+__license__ = 'MIT'
+
+import logging
+import os
+
+from glucometerutils import exceptions
+
+
+class HidDevice(object):
+    """A device speaking USB HID protocol driver base.
+
+    This class does not implement an actual driver by itself, but provides an
+    easier access to the boilerplate code required for speaking USB HID.
+
+    This helper wraps around an optional dependency on hidapi library: if
+    present the driver will auto-detect the device, if not the device path needs
+    to be provided and should point to a device implementing Linux's hidraw
+    interface.
+
+    The following constants can be set by the actual drivers:
+
+      USB_VENDOR_ID: (int) USB vendor ID for the device.
+      USB_PRODUCT_ID: (int) USB product ID for the device.
+
+    If the VID/PID pair is not provided, the driver will require a device path
+    to be used.
+    """
+
+    USB_VENDOR_ID = None
+    USB_PRODUCT_ID = None
+
+    def __init__(self, device):
+        if None in (self.USB_VENDOR_ID, self.USB_PRODUCT_ID) and not device:
+            raise exceptions.CommandLineError(
+                '--device parameter is required, should point to a /dev/hidraw '
+                'device node representing the meter.')
+
+        # If the user passed a device path that does not exist, raise an
+        # error. This is to avoid writing to a file instead of to a device node.
+        if device and not os.path.exists(device):
+            raise exceptions.ConnectionFailed(
+                message='Path %s does not exist.' % device)
+
+        # If the user passed a device, try opening it.
+        if device:
+            self.handle_ = open(device, 'w+b')
+        else:
+            logging.info(
+                'No --device parameter provided, using hidapi library.')
+            try:
+                import hid
+                self.handle_ = hid.device()
+                self.handle_.open(self.USB_VENDOR_ID, self.USB_PRODUCT_ID)
+            except ImportError:
+                raise exceptions.ConnectionFailed(
+                    message='Missing requied "hidapi" module.')
+            except OSError as e:
+                raise exceptions.ConnectionFailed(
+                    message='Unable to connect to meter: %s.' % e)
+
+    def _write(self, report):
+        """Writes a report to the HID handle."""
+
+        if self.handle_.write(report) < 0:
+            raise exceptions.CommandError()
+
+    def _read(self, size=64):
+        """Read a report from the HID handle.
+
+        This is important as it handles the one incompatible interface between
+        hidraw devices and hidapi handles.
+        """
+        return bytes(self.handle_.read(size))