[BUG] Fix overflow when seeking through files

This can happen whenever the number of cells of a given resolution in a
given file is larger than (2**31-1) / 8 / nvar, where nvar is the number
of variables being tracked (e.g., for density + pressure + velocities,
that'd be 5

Author: cphyc

yt/frontends/ramses/io_utils.pyx

@@ -16,12 +16,12 @@ ctypedef np.int32_t INT32_t
 ctypedef np.int64_t INT64_t
 ctypedef np.float64_t DOUBLE_t
 
-cdef int INT32_SIZE = sizeof(np.int32_t)
-cdef int INT64_SIZE = sizeof(np.int64_t)
-cdef int DOUBLE_SIZE = sizeof(np.float64_t)
+cdef INT64_t INT32_SIZE = sizeof(np.int32_t)
+cdef INT64_t INT64_SIZE = sizeof(np.int64_t)
+cdef INT64_t DOUBLE_SIZE = sizeof(np.float64_t)
 
 
-cdef inline int skip_len(int Nskip, int record_len) noexcept nogil:
+cdef inline INT64_t skip_len(INT64_t Nskip, INT64_t record_len) noexcept nogil:
     return Nskip * (record_len * DOUBLE_SIZE + INT64_SIZE)
 
 
@@ -68,7 +68,7 @@ def read_amr(FortranFile f, dict headers,
     )
     # Initialize values
     max_level = 0
-    cdef int record_len
+    cdef INT64_t record_len
 
     for ilevel in range(nlevelmax):
         for icpu in range(ncpu_and_bound):