revert ccalendar, just implement shift_months cases

Author: jbrockmendel

pandas/_libs/tslibs/ccalendar.pxd

@@ -17,12 +17,14 @@ np.import_array()
 
 from util cimport is_string_object, is_integer_object
 
-from ccalendar cimport get_days_in_month, monthrange
+from pandas._libs.tslib import monthrange
+
 from conversion cimport tz_convert_single, pydt_to_i8
 from frequencies cimport get_freq_code
 from nattype cimport NPY_NAT
 from np_datetime cimport (pandas_datetimestruct,
-                          dtstruct_to_dt64, dt64_to_dtstruct)
+                          dtstruct_to_dt64, dt64_to_dtstruct,
+                          is_leapyear, days_per_month_table)
 
 # ---------------------------------------------------------------------
 # Constants
@@ -450,6 +452,11 @@ class BaseOffset(_BaseOffset):
 # ----------------------------------------------------------------------
 # RelativeDelta Arithmetic
 
+@cython.wraparound(False)
+@cython.boundscheck(False)
+cdef inline int get_days_in_month(int year, int month) nogil:
+    return days_per_month_table[is_leapyear(year)][month - 1]
+
 
 cdef inline int year_add_months(pandas_datetimestruct dts, int months) nogil:
     """new year number after shifting pandas_datetimestruct number of months"""

pandas/_libs/tslibs/ccalendar.pyx

@@ -343,7 +343,6 @@ class CheckSDist(sdist_class):
                  'pandas/_libs/window.pyx',
                  'pandas/_libs/sparse.pyx',
                  'pandas/_libs/parsers.pyx',
-                 'pandas/_libs/tslibs/ccalendar.pyx',
                  'pandas/_libs/tslibs/strptime.pyx',
                  'pandas/_libs/tslibs/np_datetime.pyx',
                  'pandas/_libs/tslibs/timedeltas.pyx',
@@ -559,8 +558,6 @@ def pxd(name):
                      '_libs/tslibs/nattype'],
         'depends': tseries_depends,
         'sources': np_datetime_sources},
-    '_libs.tslibs.ccalendar': {
-        'pyxfile': '_libs/tslibs/ccalendar'},
     '_libs.tslibs.conversion': {
         'pyxfile': '_libs/tslibs/conversion',
         'pxdfiles': ['_libs/src/util',
@@ -587,7 +584,6 @@ def pxd(name):
     '_libs.tslibs.offsets': {
         'pyxfile': '_libs/tslibs/offsets',
         'pxdfiles': ['_libs/src/util',
-                     '_libs/tslibs/ccalendar',
                      '_libs/tslibs/conversion',
                      '_libs/tslibs/frequencies',
                      '_libs/tslibs/nattype'],