char *BN_bn2hex(const BIGNUM *bn) {
int width = bn_minimal_width(bn);
char *buf = OPENSSL_malloc(1 /* leading '-' */ + 1 /* zero is non-empty */ +
width * BN_BYTES * 2 + 1 /* trailing NUL */);
if (buf == NULL) {
OPENSSL_PUT_ERROR(BN, ERR_R_MALLOC_FAILURE);
return NULL;
}
char *p = buf;
if (bn->neg) {
*(p++) = '-';
}
if (BN_is_zero(bn)) {
*(p++) = '0';
}
int z = 0;
for (int i = width - 1; i >= 0; i--) {
for (int j = BN_BITS2 - 8; j >= 0; j -= 8) {
// strip leading zeros
int v = ((int)(bn->d[i] >> (long)j)) & 0xff;
if (z || v != 0) {
*(p++) = hextable[v >> 4];
*(p++) = hextable[v & 0x0f];
z = 1;
}
}
}
int BN_abs_is_word(const BIGNUM *bn, BN_ULONG w) {
switch (bn_minimal_width(bn)) {
case 1:
return bn->d[0] == w;
case 0:
return w == 0;
default:
return 0;
}
}
int BN_is_pow2(const BIGNUM *bn) {
int width = bn_minimal_width(bn);
if (width == 0 || bn->neg) {
return 0;
}
for (int i = 0; i < width - 1; i++) {
if (bn->d[i] != 0) {
return 0;
}
}
return 0 == (bn->d[width-1] & (bn->d[width-1] - 1));
}
int BN_sub_word(BIGNUM *a, BN_ULONG w) {
int i;
// degenerate case: w is zero
if (!w) {
return 1;
}
// degenerate case: a is zero
if (BN_is_zero(a)) {
i = BN_set_word(a, w);
if (i != 0) {
BN_set_negative(a, 1);
}
return i;
}
// handle 'a' when negative
if (a->neg) {
a->neg = 0;
i = BN_add_word(a, w);
a->neg = 1;
return i;
}
if ((bn_minimal_width(a) == 1) && (a->d[0] < w)) {
a->d[0] = w - a->d[0];
a->neg = 1;
return 1;
}
i = 0;
for (;;) {
if (a->d[i] >= w) {
a->d[i] -= w;
break;
} else {
a->d[i] -= w;
i++;
w = 1;
}
}
if ((a->d[i] == 0) && (i == (a->width - 1))) {
a->width--;
}
return 1;
}
int BN_is_zero(const BIGNUM *bn) {
return bn_minimal_width(bn) == 0;
}
int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
int max, min, dif;
register BN_ULONG t1, t2, *ap, *bp, *rp;
int i, carry;
max = bn_minimal_width(a);
min = bn_minimal_width(b);
dif = max - min;
if (dif < 0) // hmm... should not be happening
{
OPENSSL_PUT_ERROR(BN, BN_R_ARG2_LT_ARG3);
return 0;
}
if (!bn_wexpand(r, max)) {
return 0;
}
ap = a->d;
bp = b->d;
rp = r->d;
carry = 0;
for (i = min; i != 0; i--) {
t1 = *(ap++);
t2 = *(bp++);
if (carry) {
carry = (t1 <= t2);
t1 -= t2 + 1;
} else {
carry = (t1 < t2);
t1 -= t2;
}
*(rp++) = t1;
}
if (carry) // subtracted
{
if (!dif) {
// error: a < b
return 0;
}
while (dif) {
dif--;
t1 = *(ap++);
t2 = t1 - 1;
*(rp++) = t2;
if (t1) {
break;
}
}
}
if (dif > 0 && rp != ap) {
OPENSSL_memcpy(rp, ap, sizeof(*rp) * dif);
}
r->width = max;
r->neg = 0;
bn_set_minimal_width(r);
return 1;
}
