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Merge pull request #6435 from SparkiDev/sp_int_count_bits_cleanup

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SP int: cleanup sp_count_bits
This commit is contained in:
David Garske
2023-05-24 15:11:12 -07:00
committed by GitHub
parent 1218cfb7f2 622375b47e
commit e3be76b238
1 changed files with 38 additions and 51 deletions
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89
wolfcrypt/src/sp_int.c
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@ -5473,76 +5473,63 @@ int sp_is_bit_set(const sp_int* a, unsigned int b)
*/ */
int sp_count_bits(const sp_int* a) int sp_count_bits(const sp_int* a)
{ {
int n = 0; int n = -1;
/* Check parameter. */ /* Check parameter. */
if (a != NULL) { if ((a != NULL) && (a->used > 0)) {
/* Get index of last word. */ /* Get index of last word. */
n = (int)(a->used - 1); n = (int)(a->used - 1);
/* Don't count leading zeros. */ /* Don't count leading zeros. */
while ((n >= 0) && (a->dp[n] == 0)) { while ((n >= 0) && (a->dp[n] == 0)) {
n--; n--;
} }
/* -1 indicates SP integer value was zero. */ }
if (n < 0) {
n = 0; /* -1 indicates SP integer value was zero. */
} if (n < 0) {
else { n = 0;
#ifdef SP_ASM_HI_BIT_SET_IDX }
else {
/* Get the most significant word. */
sp_int_digit d = a->dp[n];
/* Count of bits up to last word. */
n *= SP_WORD_SIZE;
#ifdef SP_ASM_HI_BIT_SET_IDX
{
sp_int_digit hi; sp_int_digit hi;
sp_int_digit d;
/* Get the most significant word. */
d = a->dp[n];
/* Count of bits up to last word. */
n *= SP_WORD_SIZE;
/* Get index of highest set bit. */ /* Get index of highest set bit. */
SP_ASM_HI_BIT_SET_IDX(d, hi); SP_ASM_HI_BIT_SET_IDX(d, hi);
/* Add bits up to and including index. */ /* Add bits up to and including index. */
n += (int)hi + 1; n += (int)hi + 1;
#elif defined(SP_ASM_LZCNT) }
#elif defined(SP_ASM_LZCNT)
{
sp_int_digit lz; sp_int_digit lz;
sp_int_digit d;
/* Get the most significant word. */
d = a->dp[n];
/* Count of bits up to last word. */
n *= SP_WORD_SIZE;
/* Count number of leading zeros in highest non-zero digit. */ /* Count number of leading zeros in highest non-zero digit. */
SP_ASM_LZCNT(d, lz); SP_ASM_LZCNT(d, lz);
/* Add non-leading zero bits count. */ /* Add non-leading zero bits count. */
n += SP_WORD_SIZE - (int)lz; n += SP_WORD_SIZE - (int)lz;
#else
sp_int_digit d;
/* Get the most significant word. */
d = a->dp[n];
/* Count of bits up to last word. */
n *= SP_WORD_SIZE;
/* Check if top word has more than half the bits set. */
if (d > SP_HALF_MAX) {
/* Set count to a full last word. */
n += SP_WORD_SIZE;
/* Don't count leading zero bits. */
while ((d & ((sp_int_digit)1 << (SP_WORD_SIZE - 1))) == 0) {
n--;
d <<= 1;
}
}
else {
/* Add to count until highest set bit is shifted out. */
while (d != 0) {
n++;
d >>= 1;
}
}
#endif
} }
#else
/* Check if top word has more than half the bits set. */
if (d > SP_HALF_MAX) {
/* Set count to a full last word. */
n += SP_WORD_SIZE;
/* Don't count leading zero bits. */
while ((d & ((sp_int_digit)1 << (SP_WORD_SIZE - 1))) == 0) {
n--;
d <<= 1;
}
}
else {
/* Add to count until highest set bit is shifted out. */
while (d != 0) {
n++;
d >>= 1;
}
}
#endif
} }
return n; return n;