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