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Fix #54391: Use memcpy() for unaligned loads #54407

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Merged
merged 1 commit into from
Aug 4, 2023
Merged

Fix #54391: Use memcpy() for unaligned loads #54407

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60 changes: 26 additions & 34 deletions pandas/_libs/byteswap.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -10,53 +10,57 @@ from libc.stdint cimport (
uint32_t,
uint64_t,
)
from libc.string cimport memcpy


def read_float_with_byteswap(bytes data, Py_ssize_t offset, bint byteswap):
assert offset + 4 < len(data)
cdef:
const char *data_ptr = data
float res = (<float*>(data_ptr + offset))[0]
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:
res = _byteswap_float(res)
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):
assert offset + 8 < len(data)
cdef:
const char *data_ptr = data
double res = (<double*>(data_ptr + offset))[0]
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:
res = _byteswap_double(res)
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):
assert offset + 2 < len(data)
cdef:
const char *data_ptr = data
uint16_t res = (<uint16_t *>(data_ptr + offset))[0]
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):
assert offset + 4 < len(data)
cdef:
const char *data_ptr = data
uint32_t res = (<uint32_t *>(data_ptr + offset))[0]
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):
assert offset + 8 < len(data)
cdef:
const char *data_ptr = data
uint64_t res = (<uint64_t *>(data_ptr + offset))[0]
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
Expand All @@ -79,15 +83,3 @@ cdef extern from *:
uint16_t _byteswap2(uint16_t)
uint32_t _byteswap4(uint32_t)
uint64_t _byteswap8(uint64_t)


cdef float _byteswap_float(float num):
cdef uint32_t *intptr = <uint32_t *>&num
intptr[0] = _byteswap4(intptr[0])
return num


cdef double _byteswap_double(double num):
cdef uint64_t *intptr = <uint64_t *>&num
intptr[0] = _byteswap8(intptr[0])
return num