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Stage bignum_extract_digits

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Justin Ethier 2022-06-21 19:52:49 -07:00
parent 267137fc68
commit 28eab66ecb
1 changed files with 48 additions and 0 deletions
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48
runtime.c
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@ -2311,6 +2311,10 @@ object Cyc_length_unsafe(void *data, object l)
static int bignum_cmp_unsigned(object x, object y);
#define nmax(x, y) ((x) > (y) ? (x) : (y))
#define nmin(x, y) ((x) < (y) ? (x) : (y))
//#define percentage(n, p) ((C_long)(((double)(n) * (double)p) / 100))
char *int_to_binary(char *b, int x)
{
unsigned int i = 0x80000000, leading_zeros = 1;
@ -2488,6 +2492,50 @@ object C_bignum_simplify(object big)
}
}
/* This is currently only used by Karatsuba multiplication and
* Burnikel-Ziegler division. */
static object bignum_extract_digits(void *data, object n, object x, object start, object end)
{
if (obj_is_int(x)) { /* Needed? */
if (obj_obj2int(start) == 0 && (end == boolean_f || obj_obj2int(end) > 0))
return x;
else
return obj_int2obj(0);
} else {
uint32_t negp, size;
int istart, iend;
negp = C_bignum_negativep(x); /* Always false */
istart = obj_obj2int(start);
/* We might get passed larger values than actually fits; pad w/ zeroes */
if (end == boolean_f) iend = C_bignum_size(x);
else iend = nmin(obj_obj2int(end), C_bignum_size(x));
assert(istart >= 0);
size = iend - istart;
if (size == 0 || istart >= C_bignum_size(x)) {
return obj_int2obj(0);
} else {
object res;
uint32_t *res_digits, *x_digits;
//res = C_allocate_scratch_bignum(ptr, C_fix(size), negp, C_SCHEME_FALSE);
res = gc_alloc_bignum2(data, size);
C_bignum_sign(res) = negp;
res_digits = C_bignum_digits(res);
x_digits = C_bignum_digits(x);
/* Can't use bignum_digits_destructive_copy because that assumes
* target is at least as big as source.
*/
memcpy(res_digits, x_digits + istart, (iend - istart) * sizeof(uint32_t));
//memcpy(res_digits, x_digits + istart, C_wordstobytes(iend - istart));
return C_bignum_simplify(res);
}
}
}
//static void bignum_digits_destructive_negate(C_word result)
//{
// C_uword *scan, *end, digit, sum;