int fp_radix_size(fp_int *a, int radix, int *size)
{
int digs;
fp_int t;
fp_digit d;
*size = 0;
/* check range of the radix */
if (radix < 2 || radix > 64) {
return FP_VAL;
}
/* quick out if its zero */
if (fp_iszero(a) == 1) {
*size = 2;
return FP_OKAY;
}
fp_init_copy(&t, a);
/* if it is negative output a - */
if (t.sign == FP_NEG) {
(*size)++;
t.sign = FP_ZPOS;
}
digs = 0;
while (fp_iszero (&t) == FP_NO) {
fp_div_d (&t, (fp_digit) radix, &t, &d);
(*size)++;
}
/* append a NULL so the string is properly terminated */
(*size)++;
return FP_OKAY;
}
void fp_to_unsigned_bin(fp_int *a, unsigned char *b)
{
int x;
fp_int t;
fp_init_copy(&t, a);
x = 0;
while (fp_iszero (&t) == FP_NO) {
b[x++] = (unsigned char) (t.dp[0] & 255);
fp_div_2d (&t, 8, &t, NULL);
}
fp_reverse (b, x);
}
/* c = (a, b) */
void fp_gcd(fp_int *a, fp_int *b, fp_int *c)
{
fp_int u, v, r;
/* either zero than gcd is the largest */
if (fp_iszero (a) == 1 && fp_iszero (b) == 0) {
fp_abs (b, c);
return;
}
if (fp_iszero (a) == 0 && fp_iszero (b) == 1) {
fp_abs (a, c);
return;
}
/* optimized. At this point if a == 0 then
* b must equal zero too
*/
if (fp_iszero (a) == 1) {
fp_zero(c);
return;
}
/* sort inputs */
if (fp_cmp_mag(a, b) != FP_LT) {
fp_init_copy(&u, a);
fp_init_copy(&v, b);
} else {
fp_init_copy(&u, b);
fp_init_copy(&v, a);
}
fp_zero(&r);
while (fp_iszero(&v) == FP_NO) {
fp_mod(&u, &v, &r);
fp_copy(&v, &u);
fp_copy(&r, &v);
}
fp_copy(&u, c);
}
/* a/b => cb + d == a */
int fp_div_d(fp_int *a, fp_digit b, fp_int *c, fp_digit *d)
{
fp_int q;
fp_word w;
fp_digit t;
int ix;
/* cannot divide by zero */
if (b == 0) {
return FP_VAL;
}
/* quick outs */
if (b == 1 || fp_iszero(a) == 1) {
if (d != NULL) {
*d = 0;
}
if (c != NULL) {
fp_copy(a, c);
}
return FP_OKAY;
}
/* power of two ? */
if (s_is_power_of_two(b, &ix) == 1) {
if (d != NULL) {
*d = a->dp[0] & ((((fp_digit)1)<<ix) - 1);
}
if (c != NULL) {
fp_div_2d(a, ix, c, NULL);
}
return FP_OKAY;
}
/* no easy answer [c'est la vie]. Just division */
fp_init(&q);
q.used = a->used;
q.sign = a->sign;
w = 0;
for (ix = a->used - 1; ix >= 0; ix--) {
w = (w << ((fp_word)DIGIT_BIT)) | ((fp_word)a->dp[ix]);
if (w >= b) {
t = (fp_digit)(w / b);
w -= ((fp_word)t) * ((fp_word)b);
} else {
t = 0;
}
q.dp[ix] = (fp_digit)t;
}
if (d != NULL) {
*d = (fp_digit)w;
}
if (c != NULL) {
fp_clamp(&q);
fp_copy(&q, c);
}
return FP_OKAY;
}
int mp_format_float(FPTYPE f, char *buf, size_t buf_size, char fmt, int prec, char sign) {
char *s = buf;
if (buf_size <= FPMIN_BUF_SIZE) {
// FPMIN_BUF_SIZE is the minimum size needed to store any FP number.
// If the buffer does not have enough room for this (plus null terminator)
// then don't try to format the float.
if (buf_size >= 2) {
*s++ = '?';
}
if (buf_size >= 1) {
*s++ = '\0';
}
return buf_size >= 2;
}
if (fp_signbit(f)) {
*s++ = '-';
f = -f;
} else {
if (sign) {
*s++ = sign;
}
}
// buf_remaining contains bytes available for digits and exponent.
// It is buf_size minus room for the sign and null byte.
int buf_remaining = buf_size - 1 - (s - buf);
if (fp_isspecial(f)) {
char uc = fmt & 0x20;
if (fp_isinf(f)) {
*s++ = 'I' ^ uc;
*s++ = 'N' ^ uc;
*s++ = 'F' ^ uc;
goto ret;
} else if (fp_isnan(f)) {
*s++ = 'N' ^ uc;
*s++ = 'A' ^ uc;
*s++ = 'N' ^ uc;
ret:
*s = '\0';
return s - buf;
}
}
if (prec < 0) {
prec = 6;
}
char e_char = 'E' | (fmt & 0x20); // e_char will match case of fmt
fmt |= 0x20; // Force fmt to be lowercase
char org_fmt = fmt;
if (fmt == 'g' && prec == 0) {
prec = 1;
}
int e, e1;
int dec = 0;
char e_sign = '\0';
int num_digits = 0;
const FPTYPE *pos_pow = g_pos_pow;
const FPTYPE *neg_pow = g_neg_pow;
if (fp_iszero(f)) {
e = 0;
if (fmt == 'f') {
// Truncate precision to prevent buffer overflow
if (prec + 2 > buf_remaining) {
prec = buf_remaining - 2;
}
num_digits = prec + 1;
} else {
// Truncate precision to prevent buffer overflow
if (prec + 6 > buf_remaining) {
prec = buf_remaining - 6;
}
if (fmt == 'e') {
e_sign = '+';
}
}
} else if (fp_isless1(f)) {
// We need to figure out what an integer digit will be used
// in case 'f' is used (or we revert other format to it below).
// As we just tested number to be <1, this is obviously 0,
// but we can round it up to 1 below.
char first_dig = '0';
if (f >= FPROUND_TO_ONE) {
first_dig = '1';
}
// Build negative exponent
for (e = 0, e1 = FPDECEXP; e1; e1 >>= 1, pos_pow++, neg_pow++) {
if (*neg_pow > f) {
e += e1;
f *= *pos_pow;
}
}
char e_sign_char = '-';
if (fp_isless1(f) && f >= FPROUND_TO_ONE) {
f = FPCONST(1.0);
if (e == 0) {
e_sign_char = '+';
}
} else if (fp_isless1(f)) {
e++;
f *= FPCONST(10.0);
}
// If the user specified 'g' format, and e is <= 4, then we'll switch
// to the fixed format ('f')
if (fmt == 'f' || (fmt == 'g' && e <= 4)) {
fmt = 'f';
dec = -1;
*s++ = first_dig;
if (org_fmt == 'g') {
prec += (e - 1);
}
// truncate precision to prevent buffer overflow
if (prec + 2 > buf_remaining) {
prec = buf_remaining - 2;
}
num_digits = prec;
if (num_digits) {
*s++ = '.';
while (--e && num_digits) {
*s++ = '0';
num_digits--;
}
}
} else {
// For e & g formats, we'll be printing the exponent, so set the
// sign.
e_sign = e_sign_char;
dec = 0;
if (prec > (buf_remaining - FPMIN_BUF_SIZE)) {
prec = buf_remaining - FPMIN_BUF_SIZE;
if (fmt == 'g') {
prec++;
}
}
}
} else {
// Build positive exponent
for (e = 0, e1 = FPDECEXP; e1; e1 >>= 1, pos_pow++, neg_pow++) {
/* a/b => cb + d == a */
int fp_div(fp_int *a, fp_int *b, fp_int *c, fp_int *d)
{
fp_int q, x, y, t1, t2;
int n, t, i, norm, neg;
/* is divisor zero ? */
if (fp_iszero (b) == 1) {
return FP_VAL;
}
/* if a < b then q=0, r = a */
if (fp_cmp_mag (a, b) == FP_LT) {
if (d != NULL) {
fp_copy (a, d);
}
if (c != NULL) {
fp_zero (c);
}
return FP_OKAY;
}
fp_init(&q);
q.used = a->used + 2;
fp_init(&t1);
fp_init(&t2);
fp_init_copy(&x, a);
fp_init_copy(&y, b);
/* fix the sign */
neg = (a->sign == b->sign) ? FP_ZPOS : FP_NEG;
x.sign = y.sign = FP_ZPOS;
/* normalize both x and y, ensure that y >= b/2, [b == 2**DIGIT_BIT] */
norm = fp_count_bits(&y) % DIGIT_BIT;
if (norm < (int)(DIGIT_BIT-1)) {
norm = (DIGIT_BIT-1) - norm;
fp_mul_2d (&x, norm, &x);
fp_mul_2d (&y, norm, &y);
} else {
norm = 0;
}
/* note hac does 0 based, so if used==5 then its 0,1,2,3,4, e.g. use 4 */
n = x.used - 1;
t = y.used - 1;
/* while (x >= y*b**n-t) do { q[n-t] += 1; x -= y*b**{n-t} } */
fp_lshd (&y, n - t); /* y = y*b**{n-t} */
while (fp_cmp (&x, &y) != FP_LT) {
++(q.dp[n - t]);
fp_sub (&x, &y, &x);
}
/* reset y by shifting it back down */
fp_rshd (&y, n - t);
/* step 3. for i from n down to (t + 1) */
for (i = n; i >= (t + 1); i--) {
if (i > x.used) {
continue;
}
/* step 3.1 if xi == yt then set q{i-t-1} to b-1,
* otherwise set q{i-t-1} to (xi*b + x{i-1})/yt */
if (x.dp[i] == y.dp[t]) {
q.dp[i - t - 1] = ((((fp_word)1) << DIGIT_BIT) - 1);
} else {
fp_word tmp;
tmp = ((fp_word) x.dp[i]) << ((fp_word) DIGIT_BIT);
tmp |= ((fp_word) x.dp[i - 1]);
tmp /= ((fp_word) y.dp[t]);
q.dp[i - t - 1] = (fp_digit) (tmp);
}
/* while (q{i-t-1} * (yt * b + y{t-1})) >
xi * b**2 + xi-1 * b + xi-2
do q{i-t-1} -= 1;
*/
q.dp[i - t - 1] = (q.dp[i - t - 1] + 1);
do {
q.dp[i - t - 1] = (q.dp[i - t - 1] - 1);
/* find left hand */
fp_zero (&t1);
t1.dp[0] = (t - 1 < 0) ? 0 : y.dp[t - 1];
t1.dp[1] = y.dp[t];
t1.used = 2;
fp_mul_d (&t1, q.dp[i - t - 1], &t1);
/* find right hand */
t2.dp[0] = (i - 2 < 0) ? 0 : x.dp[i - 2];
t2.dp[1] = (i - 1 < 0) ? 0 : x.dp[i - 1];
t2.dp[2] = x.dp[i];
t2.used = 3;
} while (fp_cmp_mag(&t1, &t2) == FP_GT);
/* step 3.3 x = x - q{i-t-1} * y * b**{i-t-1} */
fp_mul_d (&y, q.dp[i - t - 1], &t1);
fp_lshd (&t1, i - t - 1);
fp_sub (&x, &t1, &x);
/* if x < 0 then { x = x + y*b**{i-t-1}; q{i-t-1} -= 1; } */
if (x.sign == FP_NEG) {
fp_copy (&y, &t1);
fp_lshd (&t1, i - t - 1);
fp_add (&x, &t1, &x);
q.dp[i - t - 1] = q.dp[i - t - 1] - 1;
}
}
/* now q is the quotient and x is the remainder
* [which we have to normalize]
*/
/* get sign before writing to c */
x.sign = x.used == 0 ? FP_ZPOS : a->sign;
if (c != NULL) {
fp_clamp (&q);
fp_copy (&q, c);
c->sign = neg;
}
if (d != NULL) {
fp_div_2d (&x, norm, &x, NULL);
/* the following is a kludge, essentially we were seeing the right remainder but
with excess digits that should have been zero
*/
for (i = b->used; i < x.used; i++) {
x.dp[i] = 0;
}
fp_clamp(&x);
fp_copy (&x, d);
}
return FP_OKAY;
}
/* c = 1/a (mod b) for odd b only */
int fp_invmod(fp_int *a, fp_int *b, fp_int *c)
{
fp_int x, y, u, v, B, D;
int neg;
/* 2. [modified] b must be odd */
if (fp_iseven (b) == FP_YES) {
return fp_invmod_slow(a,b,c);
}
/* init all our temps */
fp_init(&x); fp_init(&y);
fp_init(&u); fp_init(&v);
fp_init(&B); fp_init(&D);
/* x == modulus, y == value to invert */
fp_copy(b, &x);
/* we need y = |a| */
fp_abs(a, &y);
/* 3. u=x, v=y, A=1, B=0, C=0,D=1 */
fp_copy(&x, &u);
fp_copy(&y, &v);
fp_set (&D, 1);
top:
/* 4. while u is even do */
while (fp_iseven (&u) == FP_YES) {
/* 4.1 u = u/2 */
fp_div_2 (&u, &u);
/* 4.2 if B is odd then */
if (fp_isodd (&B) == FP_YES) {
fp_sub (&B, &x, &B);
}
/* B = B/2 */
fp_div_2 (&B, &B);
}
/* 5. while v is even do */
while (fp_iseven (&v) == FP_YES) {
/* 5.1 v = v/2 */
fp_div_2 (&v, &v);
/* 5.2 if D is odd then */
if (fp_isodd (&D) == FP_YES) {
/* D = (D-x)/2 */
fp_sub (&D, &x, &D);
}
/* D = D/2 */
fp_div_2 (&D, &D);
}
/* 6. if u >= v then */
if (fp_cmp (&u, &v) != FP_LT) {
/* u = u - v, B = B - D */
fp_sub (&u, &v, &u);
fp_sub (&B, &D, &B);
} else {
/* v - v - u, D = D - B */
fp_sub (&v, &u, &v);
fp_sub (&D, &B, &D);
}
/* if not zero goto step 4 */
if (fp_iszero (&u) == FP_NO) {
goto top;
}
/* now a = C, b = D, gcd == g*v */
/* if v != 1 then there is no inverse */
if (fp_cmp_d (&v, 1) != FP_EQ) {
return FP_VAL;
}
/* b is now the inverse */
neg = a->sign;
while (D.sign == FP_NEG) {
fp_add (&D, b, &D);
}
fp_copy (&D, c);
c->sign = neg;
return FP_OKAY;
}
static int fp_invmod_slow (fp_int * a, fp_int * b, fp_int * c)
{
fp_int x, y, u, v, A, B, C, D;
int res;
/* b cannot be negative */
if (b->sign == FP_NEG || fp_iszero(b) == 1) {
return FP_VAL;
}
/* init temps */
fp_init(&x); fp_init(&y);
fp_init(&u); fp_init(&v);
fp_init(&A); fp_init(&B);
fp_init(&C); fp_init(&D);
/* x = a, y = b */
if ((res = fp_mod(a, b, &x)) != FP_OKAY) {
return res;
}
fp_copy(b, &y);
/* 2. [modified] if x,y are both even then return an error! */
if (fp_iseven (&x) == 1 && fp_iseven (&y) == 1) {
return FP_VAL;
}
/* 3. u=x, v=y, A=1, B=0, C=0,D=1 */
fp_copy (&x, &u);
fp_copy (&y, &v);
fp_set (&A, 1);
fp_set (&D, 1);
top:
/* 4. while u is even do */
while (fp_iseven (&u) == 1) {
/* 4.1 u = u/2 */
fp_div_2 (&u, &u);
/* 4.2 if A or B is odd then */
if (fp_isodd (&A) == 1 || fp_isodd (&B) == 1) {
/* A = (A+y)/2, B = (B-x)/2 */
fp_add (&A, &y, &A);
fp_sub (&B, &x, &B);
}
/* A = A/2, B = B/2 */
fp_div_2 (&A, &A);
fp_div_2 (&B, &B);
}
/* 5. while v is even do */
while (fp_iseven (&v) == 1) {
/* 5.1 v = v/2 */
fp_div_2 (&v, &v);
/* 5.2 if C or D is odd then */
if (fp_isodd (&C) == 1 || fp_isodd (&D) == 1) {
/* C = (C+y)/2, D = (D-x)/2 */
fp_add (&C, &y, &C);
fp_sub (&D, &x, &D);
}
/* C = C/2, D = D/2 */
fp_div_2 (&C, &C);
fp_div_2 (&D, &D);
}
/* 6. if u >= v then */
if (fp_cmp (&u, &v) != FP_LT) {
/* u = u - v, A = A - C, B = B - D */
fp_sub (&u, &v, &u);
fp_sub (&A, &C, &A);
fp_sub (&B, &D, &B);
} else {
/* v - v - u, C = C - A, D = D - B */
fp_sub (&v, &u, &v);
fp_sub (&C, &A, &C);
fp_sub (&D, &B, &D);
}
/* if not zero goto step 4 */
if (fp_iszero (&u) == 0)
goto top;
/* now a = C, b = D, gcd == g*v */
/* if v != 1 then there is no inverse */
if (fp_cmp_d (&v, 1) != FP_EQ) {
return FP_VAL;
}
/* if its too low */
while (fp_cmp_d(&C, 0) == FP_LT) {
fp_add(&C, b, &C);
}
/* too big */
while (fp_cmp_mag(&C, b) != FP_LT) {
fp_sub(&C, b, &C);
}
/* C is now the inverse */
fp_copy(&C, c);
return FP_OKAY;
}
