41 lines
577 B
C
41 lines
577 B
C
#include "os.h"
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#include <mp.h>
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#include "dat.h"
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// convert a big-endian byte array (most significant byte first) to an mpint
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mpint*
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betomp(uchar *p, uint n, mpint *b)
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{
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int m, s;
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mpdigit x;
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if(b == nil)
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b = mpnew(0);
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// dump leading zeros
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while(*p == 0 && n > 1){
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p++;
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n--;
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}
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// get the space
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mpbits(b, n*8);
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b->top = DIGITS(n*8);
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m = b->top-1;
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// first digit might not be Dbytes long
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s = ((n-1)*8)%Dbits;
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x = 0;
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for(; n > 0; n--){
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x |= ((mpdigit)(*p++)) << s;
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s -= 8;
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if(s < 0){
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b->p[m--] = x;
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s = Dbits-8;
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x = 0;
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}
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}
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return b;
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}
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