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