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33 lines
687 B
Go
33 lines
687 B
Go
package puddle
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import "unsafe"
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type ints interface {
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int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64
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}
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// log2Int returns log2 of an integer. This function panics if val < 0. For val
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// == 0, returns 0.
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func log2Int[T ints](val T) uint8 {
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if val <= 0 {
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panic("log2 of non-positive number does not exist")
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}
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return log2IntRange(val, 0, uint8(8*unsafe.Sizeof(val)))
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}
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func log2IntRange[T ints](val T, begin, end uint8) uint8 {
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length := end - begin
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if length == 1 {
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return begin
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}
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delim := begin + length/2
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mask := T(1) << delim
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if mask > val {
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return log2IntRange(val, begin, delim)
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} else {
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return log2IntRange(val, delim, end)
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}
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}
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