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core/irrt: refactor out slice::indices and range::len

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lyken 2024-08-23 10:00:51 +08:00
parent 3782791323
commit 5c68ef00ac
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GPG Key ID: 3BD5FC6AC8325DD8
1 changed files with 60 additions and 42 deletions
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102
nac3core/irrt/irrt/slice.hpp
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@ -7,6 +7,19 @@
namespace
{
namespace range
{
template <typename T> T len(T start, T stop, T step)
{
// Reference: https://github.com/python/cpython/blob/9dbd12375561a393eaec4b21ee4ac568a407cdb0/Objects/rangeobject.c#L933
if (step > 0 && start < stop)
return 1 + (stop - 1 - start) / step;
else if (step < 0 && start > stop)
return 1 + (start - 1 - stop) / (-step);
else
return 0;
}
} // namespace range
/**
* @brief A Python range.
@ -22,15 +35,8 @@ template <typename T> struct Range
*/
template <typename SizeT> T len()
{
// Reference: https://github.com/python/cpython/blob/9dbd12375561a393eaec4b21ee4ac568a407cdb0/Objects/rangeobject.c#L933
debug_assert(SizeT, step != 0);
if (step > 0 && start < stop)
return 1 + (stop - 1 - start) / step;
else if (step < 0 && start > stop)
return 1 + (start - 1 - stop) / (-step);
else
return 0;
return range::len(start, stop, step);
}
};
@ -75,6 +81,50 @@ template <typename T> T resolve_index_in_length(T length, T index)
return -1;
}
}
/**
* @brief Resolve a slice as a range.
*
* In Python, this would be `range(*slice(start, stop, step).indices(length))`.
*/
template <typename T>
void indices(bool start_defined, T start, bool stop_defined, T stop, bool step_defined, T step, T length,
T *range_start, T *range_stop, T *range_step)
{
// Reference: https://github.com/python/cpython/blob/main/Objects/sliceobject.c#L388
*range_step = step_defined ? step : 1;
bool step_is_negative = *range_step < 0;
T lower, upper;
if (step_is_negative)
{
lower = -1;
upper = length - 1;
}
else
{
lower = 0;
upper = length;
}
if (start_defined)
{
*range_start = start < 0 ? max(lower, start + length) : min(upper, start);
}
else
{
*range_start = step_is_negative ? upper : lower;
}
if (stop_defined)
{
*range_stop = stop < 0 ? max(lower, stop + length) : min(upper, stop);
}
else
{
*range_stop = step_is_negative ? lower : upper;
}
}
} // namespace slice
/**
@ -132,40 +182,8 @@ template <typename T> struct Slice
debug_assert(SizeT, length >= 0);
Range<T> result;
result.step = step_defined ? step : 1;
bool step_is_negative = result.step < 0;
T lower, upper;
if (step_is_negative)
{
lower = -1;
upper = length - 1;
}
else
{
lower = 0;
upper = length;
}
if (start_defined)
{
result.start = start < 0 ? max(lower, start + length) : min(upper, start);
}
else
{
result.start = step_is_negative ? upper : lower;
}
if (stop_defined)
{
result.stop = stop < 0 ? max(lower, stop + length) : min(upper, stop);
}
else
{
result.stop = step_is_negative ? lower : upper;
}
slice::indices(start_defined, start, stop_defined, stop, step_defined, step, length, &result.start,
&result.stop, &result.step);
return result;
}