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63 lines
2.1 KiB
63 lines
2.1 KiB
#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. |
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These shouldn't have to be changed as C should guarantee that a short |
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contains at least 16 bits, but it's made changeable anyway. |
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Note: 'digit' should be able to hold 2*MASK+1, and 'twodigits' |
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should be able to hold the intermediate results in 'mul' |
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(at most (BASE-1)*(2*BASE+1) == MASK*(2*MASK+3)). |
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Also, x_sub assumes that 'digit' is an unsigned type, and overflow |
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is handled by taking the result mod 2**N for some N > SHIFT. |
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And, at some places it is assumed that MASK fits in an int, as well. |
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long_pow() requires that SHIFT be divisible by 5. */ |
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typedef unsigned short digit; |
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typedef unsigned int wdigit; /* digit widened to parameter size */ |
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#define BASE_TWODIGITS_TYPE long |
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typedef unsigned BASE_TWODIGITS_TYPE twodigits; |
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typedef BASE_TWODIGITS_TYPE stwodigits; /* signed variant of twodigits */ |
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#define SHIFT 15 |
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#define BASE ((digit)1 << SHIFT) |
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#define MASK ((int)(BASE - 1)) |
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#if SHIFT % 5 != 0 |
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#error "longobject.c requires that 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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