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GH-101291: Add low level, unstable API for pylong (GH-101685)

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Co-authored-by: Petr Viktorin <encukou@gmail.com>
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Mark Shannon 2023-05-21 14:45:48 +01:00 • committed by GitHub
parent ab71acd67b
commit 93923793f6
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8 changed files with 139 additions and 20 deletions
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35
Include/internal/pycore_long.h
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@ -118,6 +118,21 @@ PyAPI_FUNC(char*) _PyLong_FormatBytesWriter(
#define SIGN_NEGATIVE 2
#define NON_SIZE_BITS 3
/* The functions _PyLong_IsCompact and _PyLong_CompactValue are defined
* in Include/cpython/longobject.h, since they need to be inline.
*
* "Compact" values have at least one bit to spare,
* so that addition and subtraction can be performed on the values
* without risk of overflow.
*
* The inline functions need tag bits.
* For readability, rather than do `#define SIGN_MASK _PyLong_SIGN_MASK`
* we define them to the numbers in both places and then assert that
* they're the same.
*/
static_assert(SIGN_MASK == _PyLong_SIGN_MASK, "SIGN_MASK does not match _PyLong_SIGN_MASK");
static_assert(NON_SIZE_BITS == _PyLong_NON_SIZE_BITS, "NON_SIZE_BITS does not match _PyLong_NON_SIZE_BITS");
/* All *compact" values are guaranteed to fit into
* a Py_ssize_t with at least one bit to spare.
* In other words, for 64 bit machines, compact
@ -131,11 +146,6 @@ _PyLong_IsNonNegativeCompact(const PyLongObject* op) {
return op->long_value.lv_tag <= (1 << NON_SIZE_BITS);
}
static inline int
_PyLong_IsCompact(const PyLongObject* op) {
assert(PyLong_Check(op));
return op->long_value.lv_tag < (2 << NON_SIZE_BITS);
}
static inline int
_PyLong_BothAreCompact(const PyLongObject* a, const PyLongObject* b) {
@ -144,21 +154,6 @@ _PyLong_BothAreCompact(const PyLongObject* a, const PyLongObject* b) {
return (a->long_value.lv_tag | b->long_value.lv_tag) < (2 << NON_SIZE_BITS);
}
/* Returns a *compact* value, iff `_PyLong_IsCompact` is true for `op`.
*
* "Compact" values have at least one bit to spare,
* so that addition and subtraction can be performed on the values
* without risk of overflow.
*/
static inline Py_ssize_t
_PyLong_CompactValue(const PyLongObject *op)
{
assert(PyLong_Check(op));
assert(_PyLong_IsCompact(op));
Py_ssize_t sign = 1 - (op->long_value.lv_tag & SIGN_MASK);
return sign * (Py_ssize_t)op->long_value.ob_digit[0];
}
static inline bool
_PyLong_IsZero(const PyLongObject *op)
{