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cimport cqueue
cdef class Queue:
"""A queue class for C integer values.
>>> q = Queue()
>>> q.append(5)
>>> q.peek()
5
>>> q.pop()
5
"""
cdef cqueue.Queue* _c_queue
def __cinit__(self):
self._c_queue = cqueue.queue_new()
if self._c_queue is NULL:
raise MemoryError()
def __dealloc__(self):
if self._c_queue is not NULL:
cqueue.queue_free(self._c_queue)
cpdef append(self, int value):
if not cqueue.queue_push_tail(self._c_queue,
<void*> <Py_ssize_t> value):
raise MemoryError()
# The `cpdef` feature is obviously not available for the original "extend()"
# method, as the method signature is incompatible with Python argument
# types (Python does not have pointers). However, we can rename
# the C-ish "extend()" method to e.g. "extend_ints()", and write
# a new "extend()" method that provides a suitable Python interface by
# accepting an arbitrary Python iterable.
cpdef extend(self, values):
for value in values:
self.append(value)
cdef extend_ints(self, int* values, size_t count):
cdef int value
for value in values[:count]: # Slicing pointer to limit the iteration boundaries.
self.append(value)
cpdef int peek(self) except? -1:
cdef int value = <Py_ssize_t> cqueue.queue_peek_head(self._c_queue)
if value == 0:
# this may mean that the queue is empty,
# or that it happens to contain a 0 value
if cqueue.queue_is_empty(self._c_queue):
raise IndexError("Queue is empty")
return value
cpdef int pop(self) except? -1:
if cqueue.queue_is_empty(self._c_queue):
raise IndexError("Queue is empty")
return <Py_ssize_t> cqueue.queue_pop_head(self._c_queue)
def __bool__(self):
return not cqueue.queue_is_empty(self._c_queue)
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