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102 lines
3.8 KiB
C
102 lines
3.8 KiB
C
#ifndef Py_LONGINTREPR_H
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#define Py_LONGINTREPR_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* This is published for the benefit of "friend" marshal.c only. */
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/* Parameters of the long integer representation. There are two different
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sets of parameters: one set for 30-bit digits, stored in an unsigned 32-bit
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integer type, and one set for 15-bit digits with each digit stored in an
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unsigned short. The value of PYLONG_BITS_IN_DIGIT, defined either at
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configure time or in pyport.h, is used to decide which digit size to use.
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Type 'digit' should be able to hold 2*PyLong_BASE-1, and type 'twodigits'
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should be an unsigned integer type able to hold all integers up to
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PyLong_BASE*PyLong_BASE-1. x_sub assumes that 'digit' is an unsigned type,
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and that overflow is handled by taking the result modulo 2**N for some N >
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PyLong_SHIFT. The majority of the code doesn't care about the precise
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value of PyLong_SHIFT, but there are some notable exceptions:
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- long_pow() requires that PyLong_SHIFT be divisible by 5
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- PyLong_{As,From}ByteArray require that PyLong_SHIFT be at least 8
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- long_hash() requires that PyLong_SHIFT is *strictly* less than the number
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of bits in an unsigned long, as do the PyLong <-> long (or unsigned long)
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conversion functions
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- the long <-> size_t/Py_ssize_t conversion functions expect that
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PyLong_SHIFT is strictly less than the number of bits in a size_t
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- the marshal code currently expects that PyLong_SHIFT is a multiple of 15
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- NSMALLNEGINTS and NSMALLPOSINTS should be small enough to fit in a single
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digit; with the current values this forces PyLong_SHIFT >= 9
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The values 15 and 30 should fit all of the above requirements, on any
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platform.
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*/
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#if PYLONG_BITS_IN_DIGIT == 30
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#if !(defined HAVE_UINT64_T && defined HAVE_UINT32_T && \
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defined HAVE_INT64_T && defined HAVE_INT32_T)
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#error "30-bit long digits requested, but the necessary types are not available on this platform"
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#endif
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typedef PY_UINT32_T digit;
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typedef PY_INT32_T sdigit; /* signed variant of digit */
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typedef PY_UINT64_T twodigits;
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typedef PY_INT64_T stwodigits; /* signed variant of twodigits */
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#define PyLong_SHIFT 30
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#define _PyLong_DECIMAL_SHIFT 9 /* max(e such that 10**e fits in a digit) */
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#define _PyLong_DECIMAL_BASE ((digit)1000000000) /* 10 ** DECIMAL_SHIFT */
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#elif PYLONG_BITS_IN_DIGIT == 15
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typedef unsigned short digit;
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typedef short sdigit; /* signed variant of digit */
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typedef unsigned long twodigits;
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typedef long stwodigits; /* signed variant of twodigits */
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#define PyLong_SHIFT 15
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#define _PyLong_DECIMAL_SHIFT 4 /* max(e such that 10**e fits in a digit) */
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#define _PyLong_DECIMAL_BASE ((digit)10000) /* 10 ** DECIMAL_SHIFT */
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#else
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#error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
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#endif
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#define PyLong_BASE ((digit)1 << PyLong_SHIFT)
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#define PyLong_MASK ((digit)(PyLong_BASE - 1))
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#if PyLong_SHIFT % 5 != 0
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#error "longobject.c requires that PyLong_SHIFT be divisible by 5"
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#endif
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/* Long integer representation.
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The absolute value of a number is equal to
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SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
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Negative numbers are represented with ob_size < 0;
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zero is represented by ob_size == 0.
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In a normalized number, ob_digit[abs(ob_size)-1] (the most significant
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digit) is never zero. Also, in all cases, for all valid i,
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0 <= ob_digit[i] <= MASK.
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The allocation function takes care of allocating extra memory
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so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.
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CAUTION: Generic code manipulating subtypes of PyVarObject has to
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aware that longs abuse ob_size's sign bit.
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*/
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struct _longobject {
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PyObject_VAR_HEAD
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digit ob_digit[1];
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};
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PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t);
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/* Return a copy of src. */
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PyAPI_FUNC(PyObject *) _PyLong_Copy(PyLongObject *src);
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#ifdef __cplusplus
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}
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#endif
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#endif /* !Py_LONGINTREPR_H */
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