Alle Dateien aus dem Pythonkurs
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"""
The following are faster versions of struct.unpack that avoid the overhead of Python
function calls.
In the SAS7BDAT parser, they may be called up to (n_rows * n_cols) times.
"""
from cython cimport Py_ssize_t
from libc.stdint cimport (
uint16_t,
uint32_t,
uint64_t,
)
from libc.string cimport memcpy
def read_float_with_byteswap(bytes data, Py_ssize_t offset, bint byteswap):
cdef uint32_t value
assert offset + sizeof(value) < len(data)
cdef const void *ptr = <unsigned char*>(data) + offset
memcpy(&value, ptr, sizeof(value))
if byteswap:
value = _byteswap4(value)
cdef float res
memcpy(&res, &value, sizeof(res))
return res
def read_double_with_byteswap(bytes data, Py_ssize_t offset, bint byteswap):
cdef uint64_t value
assert offset + sizeof(value) < len(data)
cdef const void *ptr = <unsigned char*>(data) + offset
memcpy(&value, ptr, sizeof(value))
if byteswap:
value = _byteswap8(value)
cdef double res
memcpy(&res, &value, sizeof(res))
return res
def read_uint16_with_byteswap(bytes data, Py_ssize_t offset, bint byteswap):
cdef uint16_t res
assert offset + sizeof(res) < len(data)
memcpy(&res, <const unsigned char*>(data) + offset, sizeof(res))
if byteswap:
res = _byteswap2(res)
return res
def read_uint32_with_byteswap(bytes data, Py_ssize_t offset, bint byteswap):
cdef uint32_t res
assert offset + sizeof(res) < len(data)
memcpy(&res, <const unsigned char*>(data) + offset, sizeof(res))
if byteswap:
res = _byteswap4(res)
return res
def read_uint64_with_byteswap(bytes data, Py_ssize_t offset, bint byteswap):
cdef uint64_t res
assert offset + sizeof(res) < len(data)
memcpy(&res, <const unsigned char*>(data) + offset, sizeof(res))
if byteswap:
res = _byteswap8(res)
return res
# Byteswapping
cdef extern from *:
"""
#ifdef _MSC_VER
#define _byteswap2 _byteswap_ushort
#define _byteswap4 _byteswap_ulong
#define _byteswap8 _byteswap_uint64
#else
#define _byteswap2 __builtin_bswap16
#define _byteswap4 __builtin_bswap32
#define _byteswap8 __builtin_bswap64
#endif
"""
uint16_t _byteswap2(uint16_t)
uint32_t _byteswap4(uint32_t)
uint64_t _byteswap8(uint64_t)