Support using prefixes with 0xff as the last byte.

This changes the logic for computing the range_end of a prefix so that
it works even if the prefix ends with one or more 0xff bytes

Author: tmccombs

etcd3/client.py

@@ -295,7 +295,7 @@ def get_prefix_response(self, key_prefix, **kwargs):
 
         range_request = self._build_get_range_request(
             key=key_prefix,
-            range_end=utils.increment_last_byte(utils.to_bytes(key_prefix)),
+            range_end=utils.prefix_range_end(utils.to_bytes(key_prefix)),
             **kwargs
         )
 
@@ -518,7 +518,7 @@ def delete_prefix(self, prefix):
         """Delete a range of keys with a prefix in etcd."""
         delete_request = self._build_delete_request(
             prefix,
-            range_end=utils.increment_last_byte(utils.to_bytes(prefix))
+            range_end=utils.prefix_range_end(utils.to_bytes(prefix))
         )
         return self.kvstub.DeleteRange(
             delete_request,
@@ -586,7 +586,7 @@ def add_watch_prefix_callback(self, key_prefix, callback, **kwargs):
         :returns: watch_id. Later it could be used for cancelling watch.
         """
         kwargs['range_end'] = \
-            utils.increment_last_byte(utils.to_bytes(key_prefix))
+            utils.prefix_range_end(utils.to_bytes(key_prefix))
 
         return self.add_watch_callback(key_prefix, callback, **kwargs)
 
@@ -665,7 +665,7 @@ def watch_prefix_response(self, key_prefix, **kwargs):
         :returns: tuple of ``responses_iterator`` and ``cancel``.
         """
         kwargs['range_end'] = \
-            utils.increment_last_byte(utils.to_bytes(key_prefix))
+            utils.prefix_range_end(utils.to_bytes(key_prefix))
         return self.watch_response(key_prefix, **kwargs)
 
     def watch_prefix(self, key_prefix, **kwargs):
@@ -677,7 +677,7 @@ def watch_prefix(self, key_prefix, **kwargs):
         :returns: tuple of ``events_iterator`` and ``cancel``.
         """
         kwargs['range_end'] = \
-            utils.increment_last_byte(utils.to_bytes(key_prefix))
+            utils.prefix_range_end(utils.to_bytes(key_prefix))
         return self.watch(key_prefix, **kwargs)
 
     @_handle_errors
@@ -730,7 +730,7 @@ def watch_prefix_once_response(self, key_prefix, timeout=None, **kwargs):
         will raise ``WatchTimedOut`` exception.
         """
         kwargs['range_end'] = \
-            utils.increment_last_byte(utils.to_bytes(key_prefix))
+            utils.prefix_range_end(utils.to_bytes(key_prefix))
         return self.watch_once_response(key_prefix, timeout=timeout, **kwargs)
 
     def watch_prefix_once(self, key_prefix, timeout=None, **kwargs):
@@ -741,7 +741,7 @@ def watch_prefix_once(self, key_prefix, timeout=None, **kwargs):
         will raise ``WatchTimedOut`` exception.
         """
         kwargs['range_end'] = \
-            utils.increment_last_byte(utils.to_bytes(key_prefix))
+            utils.prefix_range_end(utils.to_bytes(key_prefix))
         return self.watch_once(key_prefix, timeout=timeout, **kwargs)
 
     @_handle_errors

etcd3/utils.py

@@ -1,6 +1,10 @@
-def increment_last_byte(byte_string):
-    s = bytearray(byte_string)
-    s[-1] = s[-1] + 1
+def prefix_range_end(prefix):
+    """Create a bytestring that can be used as a range_end for a prefix."""
+    s = bytearray(prefix)
+    for i in reversed(range(len(s))):
+        if s[i] < 0xff:
+            s[i] = s[i] + 1
+            break
     return bytes(s)
 
 

tests/test_etcd3.py

@@ -555,7 +555,7 @@ def test_nested_transactions(self, etcd):
     def test_transaction_range_conditions(self, etcd):
         etcdctl('put', '/doot/key1', 'dootdoot')
         etcdctl('put', '/doot/key2', 'notdootdoot')
-        range_end = utils.increment_last_byte(utils.to_bytes('/doot/'))
+        range_end = utils.prefix_range_end(utils.to_bytes('/doot/'))
         compare = [etcd.transactions.value('/doot/', range_end) == 'dootdoot']
         status, _ = etcd.transaction(compare=compare, success=[], failure=[])
         assert not status
@@ -980,8 +980,11 @@ def test_disarm_alarm(self, etcd):
 
 
 class TestUtils(object):
-    def test_increment_last_byte(self):
-        assert etcd3.utils.increment_last_byte(b'foo') == b'fop'
+    def test_prefix_range_end(self):
+        assert etcd3.utils.prefix_range_end(b'foo') == b'fop'
+        assert etcd3.utils.prefix_range_end(b'ab\xff') == b'ac\xff'
+        assert (etcd3.utils.prefix_range_end(b'a\xff\xff\xff\xff\xff')
+                == b'b\xff\xff\xff\xff\xff')
 
     def test_to_bytes(self):
         assert isinstance(etcd3.utils.to_bytes(b'doot'), bytes) is True

tox.ini

@@ -44,7 +44,7 @@ exclude =  .venv,.git,.tox,dist,docs,*lib/python*,*egg,build,etcd3/etcdrpc/
 application-import-names = etcd3
 max-complexity = 10
 # TODO add docstrings for public methods, modules, etc
-ignore = D1
+ignore = D1, W503
 
 [travis]
 python = 3.6: py36, flake8