56 lines
1.5 KiB
C
56 lines
1.5 KiB
C
/* LibTomPoly, Polynomial Basis Math -- Tom St Denis
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*
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* LibTomPoly is a public domain library that provides
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* polynomial basis arithmetic support. It relies on
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* LibTomMath for large integer support.
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*
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* This library is free for all purposes without any
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* express guarantee that it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://poly.libtomcrypt.org
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*/
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#include <tompoly.h>
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int pb_readraw(pb_poly *a, unsigned char *buf, int len)
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{
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int terms, x, y, z, err;
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/* zero poly */
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pb_zero(a);
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/* must be at least four bytes */
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if (len < 4) {
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return MP_VAL;
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}
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/* number of terms */
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terms = ((unsigned)buf[0]) | ((unsigned)buf[1]<<8);
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y = 2;
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/* grow to the right size */
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if (a->alloc < terms) {
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if ((err = pb_grow(a, terms)) != MP_OKAY) {
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return err;
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}
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}
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/* read characteristic */
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z = ((unsigned)buf[y]) | ((unsigned)buf[y+1]<<8); y += 2;
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if (z + y > len) { return MP_VAL; }
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if ((err = mp_read_signed_bin(&(a->characteristic), buf+y, z)) != MP_OKAY) { return err; }
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y += z;
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/* read terms */
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for (x = 0; x < terms; x++) {
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z = ((unsigned)buf[y]) | ((unsigned)buf[y+1]<<8); y += 2;
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if (z + y > len) { return MP_VAL; }
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if ((err = mp_read_signed_bin(&(a->characteristic), buf+y, z)) != MP_OKAY) { return err; }
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y += z;
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}
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return MP_OKAY;
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}
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