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big: Add pow.

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This commit is contained in:
Jeroen van Rijn
2021-08-11 20:59:51 +02:00
parent c3a4d7dda2
commit d953e40fb3
3 changed files with 54 additions and 7 deletions
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core/math/big/log.odin
+46 -4
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@@ -9,7 +9,7 @@ package big
The code started out as an idiomatic source port of libTomMath, which is in the public domain, with thanks.
*/
log_n_int :: proc(a: ^Int, base: DIGIT) -> (log: int, err: Error) {
int_log :: proc(a: ^Int, base: DIGIT) -> (res: int, err: Error) {
if base < 2 || DIGIT(base) > _DIGIT_MAX {
return -1, .Invalid_Argument;
}
@@ -35,7 +35,7 @@ log_n_int :: proc(a: ^Int, base: DIGIT) -> (log: int, err: Error) {
Fast path for `Int`s that fit within a single `DIGIT`.
*/
if a.used == 1 {
return log_n_digit(a.digit[0], DIGIT(base));
return log(a.digit[0], DIGIT(base));
}
// if (MP_HAS(S_MP_LOG)) {
@@ -45,7 +45,49 @@ log_n_int :: proc(a: ^Int, base: DIGIT) -> (log: int, err: Error) {
return -1, .Unimplemented;
}
log_n :: proc{log_n_int, log_n_digit};
log :: proc { int_log, int_log_digit, };
/*
Calculate c = a**b using a square-multiply algorithm.
*/
int_pow :: proc(dest, base: ^Int, power: int) -> (err: Error) {
if err = clear_if_uninitialized(dest); err != .None { return err; }
if err = clear_if_uninitialized(base); err != .None { return err; }
// if ((err = mp_init_copy(&g, a)) != MP_OKAY) {
// return err;
// }
// /* set initial result */
// mp_set(c, 1uL);
// while (b > 0) {
// /* if the bit is set multiply */
// if ((b & 1) != 0) {
// if ((err = mp_mul(c, &g, c)) != MP_OKAY) {
// goto LBL_ERR;
// }
// }
// /* square */
// if (b > 1) {
// if ((err = mp_sqr(&g, &g)) != MP_OKAY) {
// goto LBL_ERR;
// }
// }
// /* shift to next bit */
// b >>= 1;
// }
// LBL_ERR:
// mp_clear(&g);
// return err;
return err;
}
pow :: proc { int_pow, };
/*
Returns the log2 of an `Int`, provided `base` is a power of two.
@@ -79,7 +121,7 @@ small_pow :: proc(base: _WORD, exponent: _WORD) -> (result: _WORD) {
return result;
}
log_n_digit :: proc(a: DIGIT, base: DIGIT) -> (log: int, err: Error) {
int_log_digit :: proc(a: DIGIT, base: DIGIT) -> (log: int, err: Error) {
/*
If the number is smaller than the base, it fits within a fraction.
Therefore, we return 0.