| 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091929394959697 |
- package goja
- // ported from https://gist.github.com/orlp/3551590
- var highest_bit_set = [256]byte{
- 0, 1, 2, 2, 3, 3, 3, 3,
- 4, 4, 4, 4, 4, 4, 4, 4,
- 5, 5, 5, 5, 5, 5, 5, 5,
- 5, 5, 5, 5, 5, 5, 5, 5,
- 6, 6, 6, 6, 6, 6, 6, 6,
- 6, 6, 6, 6, 6, 6, 6, 6,
- 6, 6, 6, 6, 6, 6, 6, 6,
- 6, 6, 6, 6, 6, 6, 6, 255, // anything past 63 is a guaranteed overflow with base > 1
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255,
- }
- func ipow(base, exp int64) (result int64) {
- result = 1
- switch highest_bit_set[byte(exp)] {
- case 255: // we use 255 as an overflow marker and return 0 on overflow/underflow
- if base == 1 {
- return 1
- }
- if base == -1 {
- return 1 - 2*(exp&1)
- }
- return 0
- case 6:
- if exp&1 != 0 {
- result *= base
- }
- exp >>= 1
- base *= base
- fallthrough
- case 5:
- if exp&1 != 0 {
- result *= base
- }
- exp >>= 1
- base *= base
- fallthrough
- case 4:
- if exp&1 != 0 {
- result *= base
- }
- exp >>= 1
- base *= base
- fallthrough
- case 3:
- if exp&1 != 0 {
- result *= base
- }
- exp >>= 1
- base *= base
- fallthrough
- case 2:
- if exp&1 != 0 {
- result *= base
- }
- exp >>= 1
- base *= base
- fallthrough
- case 1:
- if exp&1 != 0 {
- result *= base
- }
- fallthrough
- default:
- return result
- }
- }
|
