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WebSVN – planix.SVN – Blame – /os/branches/feature_unix/sys/src/libmp/port/mpaux.c – Rev 2

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#include "os.h"
2 
#include <mp.h>
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#include "dat.h"
4 
 
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static mpdigit _mptwodata[1] = { 2 };
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static mpint _mptwo =
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{
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	1,
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	1,
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	1,
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	_mptwodata,
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	MPstatic
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};
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mpint *mptwo = &_mptwo;
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static mpdigit _mponedata[1] = { 1 };
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static mpint _mpone =
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{
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	1,
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	1,
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	1,
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	_mponedata,
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	MPstatic
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};
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mpint *mpone = &_mpone;
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static mpdigit _mpzerodata[1] = { 0 };
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static mpint _mpzero =
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{
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	1,
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	1,
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	0,
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	_mpzerodata,
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	MPstatic
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};
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mpint *mpzero = &_mpzero;
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static int mpmindigits = 33;
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// set minimum digit allocation
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void
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mpsetminbits(int n)
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{
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	if(n < 0)
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		sysfatal("mpsetminbits: n < 0");
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	if(n == 0)
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		n = 1;
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	mpmindigits = DIGITS(n);
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}
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// allocate an n bit 0'd number
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mpint*
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mpnew(int n)
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{
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	mpint *b;
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	if(n < 0)
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		sysfatal("mpsetminbits: n < 0");
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	b = mallocz(sizeof(mpint), 1);
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	setmalloctag(b, getcallerpc(&n));
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	if(b == nil)
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		sysfatal("mpnew: %r");
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	n = DIGITS(n);
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	if(n < mpmindigits)
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		n = mpmindigits;
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	b->p = (mpdigit*)mallocz(n*Dbytes, 1);
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	if(b->p == nil)
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		sysfatal("mpnew: %r");
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	b->size = n;
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	b->sign = 1;
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	return b;
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}
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// guarantee at least n significant bits
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void
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mpbits(mpint *b, int m)
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{
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	int n;
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	n = DIGITS(m);
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	if(b->size >= n){
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		if(b->top >= n)
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			return;
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		memset(&b->p[b->top], 0, Dbytes*(n - b->top));
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		b->top = n;
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		return;
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	}
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	b->p = (mpdigit*)realloc(b->p, n*Dbytes);
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	if(b->p == nil)
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		sysfatal("mpbits: %r");
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	memset(&b->p[b->top], 0, Dbytes*(n - b->top));
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	b->size = n;
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	b->top = n;
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}
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void
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mpfree(mpint *b)
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{
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	if(b == nil)
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		return;
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	if(b->flags & MPstatic)
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		sysfatal("freeing mp constant");
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	memset(b->p, 0, b->size*Dbytes);	// information hiding
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	free(b->p);
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	free(b);
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}
109 
 
110 
void
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mpnorm(mpint *b)
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{
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	int i;
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	for(i = b->top-1; i >= 0; i--)
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		if(b->p[i] != 0)
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			break;
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	b->top = i+1;
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	if(b->top == 0)
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		b->sign = 1;
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}
122 
 
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mpint*
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mpcopy(mpint *old)
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{
126 
	mpint *new;
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128 
	new = mpnew(Dbits*old->size);
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	new->top = old->top;
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	new->sign = old->sign;
131 
	memmove(new->p, old->p, Dbytes*old->top);
132 
	return new;
133 
}
134 
 
135 
void
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mpassign(mpint *old, mpint *new)
137 
{
138 
	mpbits(new, Dbits*old->top);
139 
	new->sign = old->sign;
140 
	new->top = old->top;
141 
	memmove(new->p, old->p, Dbytes*old->top);
142 
}
143 
 
144 
// number of significant bits in mantissa
145 
int
146 
mpsignif(mpint *n)
147 
{
148 
	int i, j;
149 
	mpdigit d;
150 
 
151 
	if(n->top == 0)
152 
		return 0;
153 
	for(i = n->top-1; i >= 0; i--){
154 
		d = n->p[i];
155 
		for(j = Dbits-1; j >= 0; j--){
156 
			if(d & (((mpdigit)1)<<j))
157 
				return i*Dbits + j + 1;
158 
		}
159 
	}
160 
	return 0;
161 
}
162 
 
163 
// k, where n = 2**k * q for odd q
164 
int
165 
mplowbits0(mpint *n)
166 
{
167 
	int k, bit, digit;
168 
	mpdigit d;
169 
 
170 
	if(n->top==0)
171 
		return 0;
172 
	k = 0;
173 
	bit = 0;
174 
	digit = 0;
175 
	d = n->p[0];
176 
	for(;;){
177 
		if(d & (1<<bit))
178 
			break;
179 
		k++;
180 
		bit++;
181 
		if(bit==Dbits){
182 
			if(++digit >= n->top)
183 
				return 0;
184 
			d = n->p[digit];
185 
			bit = 0;
186 
		}
187 
	}
188 
	return k;
189 
}
190