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big: Add pow.

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This commit is contained in:
Jeroen van Rijn
2021-07-23 22:47:44 +02:00
parent c3a4d7dda2
commit d953e40fb3
3 changed files with 54 additions and 7 deletions
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7
core/math/big/basic.odin
View File

@@ -516,7 +516,7 @@ int_mul_digit :: proc(dest, src: ^Int, multiplier: DIGIT) -> (err: Error) {
}
if is_power_of_two(int(multiplier)) {
ix: int;
if ix, err = log_n(multiplier, 2); err != .None { return err; }
if ix, err = log(multiplier, 2); err != .None { return err; }
return shl(dest, src, ix);
}
@@ -648,6 +648,11 @@ int_mul :: proc(dest, src, multiplier: ^Int) -> (err: Error) {
mul :: proc { int_mul, int_mul_digit, };
sqr :: proc(dest, src: ^Int) -> (err: Error) {
return mul(dest, src, src);
}
/*
==========================
Low-level routines

50
core/math/big/log.odin
View File

@@ -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.

4
core/math/big/radix.odin
View File

@@ -207,7 +207,7 @@ itoa_raw :: proc(a: ^Int, radix: i8, buffer: []u8, size := int(-1), zero_termina
shift, count: int;
// mask := _WORD(radix - 1);
shift, err = log_n(DIGIT(radix), 2);
shift, err = log(DIGIT(radix), 2);
count, err = count_bits(a);
digit: _WORD;
@@ -263,7 +263,7 @@ radix_size :: proc(a: ^Int, radix: i8, zero_terminate := false) -> (size: int, e
digit = a.digit,
};
if size, err = log_n(t, DIGIT(radix)); err != .None {
if size, err = log(t, DIGIT(radix)); err != .None {
return 0, err;
}