+/* Here follows specialised variants of bn_add_words() and
+ bn_sub_words(). They have the property performing operations on
+ arrays of different sizes. The sizes of those arrays is expressed through
+ cl, which is the common length ( basicall, min(len(a),len(b)) ), and dl,
+ which is the delta between the two lengths, calculated as len(a)-len(b).
+ All lengths are the number of BN_ULONGs... For the operations that require
+ a result array as parameter, it must have the length cl+abs(dl).
+ These functions should probably end up in bn_asm.c as soon as there are
+ assembler counterparts for the systems that use assembler files. */
+
+BN_ULONG bn_sub_part_words(BN_ULONG *r,
+ const BN_ULONG *a, const BN_ULONG *b,
+ int cl, int dl)
+ {
+ BN_ULONG c, t;
+
+ assert(cl >= 0);
+ c = bn_sub_words(r, a, b, cl);
+
+ if (dl == 0)
+ return c;
+
+ r += cl;
+ a += cl;
+ b += cl;
+
+ if (dl < 0)
+ {
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_sub_part_words %d + %d (dl < 0, c = %d)\n", cl, dl, c);
+#endif
+ for (;;)
+ {
+ t = b[0];
+ r[0] = (0-t-c)&BN_MASK2;
+ if (t != 0) c=1;
+ if (++dl >= 0) break;
+
+ t = b[1];
+ r[1] = (0-t-c)&BN_MASK2;
+ if (t != 0) c=1;
+ if (++dl >= 0) break;
+
+ t = b[2];
+ r[2] = (0-t-c)&BN_MASK2;
+ if (t != 0) c=1;
+ if (++dl >= 0) break;
+
+ t = b[3];
+ r[3] = (0-t-c)&BN_MASK2;
+ if (t != 0) c=1;
+ if (++dl >= 0) break;
+
+ b += 4;
+ r += 4;
+ }
+ }
+ else
+ {
+ int save_dl = dl;
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_sub_part_words %d + %d (dl > 0, c = %d)\n", cl, dl, c);
+#endif
+ while(c)
+ {
+ t = a[0];
+ r[0] = (t-c)&BN_MASK2;
+ if (t != 0) c=0;
+ if (--dl <= 0) break;
+
+ t = a[1];
+ r[1] = (t-c)&BN_MASK2;
+ if (t != 0) c=0;
+ if (--dl <= 0) break;
+
+ t = a[2];
+ r[2] = (t-c)&BN_MASK2;
+ if (t != 0) c=0;
+ if (--dl <= 0) break;
+
+ t = a[3];
+ r[3] = (t-c)&BN_MASK2;
+ if (t != 0) c=0;
+ if (--dl <= 0) break;
+
+ save_dl = dl;
+ a += 4;
+ r += 4;
+ }
+ if (dl > 0)
+ {
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_sub_part_words %d + %d (dl > 0, c == 0)\n", cl, dl);
+#endif
+ if (save_dl > dl)
+ {
+ switch (save_dl - dl)
+ {
+ case 1:
+ r[1] = a[1];
+ if (--dl <= 0) break;
+ case 2:
+ r[2] = a[2];
+ if (--dl <= 0) break;
+ case 3:
+ r[3] = a[3];
+ if (--dl <= 0) break;
+ }
+ a += 4;
+ r += 4;
+ }
+ }
+ if (dl > 0)
+ {
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_sub_part_words %d + %d (dl > 0, copy)\n", cl, dl);
+#endif
+ for(;;)
+ {
+ r[0] = a[0];
+ if (--dl <= 0) break;
+ r[1] = a[1];
+ if (--dl <= 0) break;
+ r[2] = a[2];
+ if (--dl <= 0) break;
+ r[3] = a[3];
+ if (--dl <= 0) break;
+
+ a += 4;
+ r += 4;
+ }
+ }
+ }
+ return c;
+ }
+
+BN_ULONG bn_add_part_words(BN_ULONG *r,
+ const BN_ULONG *a, const BN_ULONG *b,
+ int cl, int dl)
+ {
+ BN_ULONG c, l, t;
+
+ assert(cl >= 0);
+ c = bn_add_words(r, a, b, cl);
+
+ if (dl == 0)
+ return c;
+
+ r += cl;
+ a += cl;
+ b += cl;
+
+ if (dl < 0)
+ {
+ int save_dl = dl;
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_add_part_words %d + %d (dl < 0, c = %d)\n", cl, dl, c);
+#endif
+ while (c)
+ {
+ l=(c+b[0])&BN_MASK2;
+ c=(l < c);
+ r[0]=l;
+ if (++dl >= 0) break;
+
+ l=(c+b[1])&BN_MASK2;
+ c=(l < c);
+ r[1]=l;
+ if (++dl >= 0) break;
+
+ l=(c+b[2])&BN_MASK2;
+ c=(l < c);
+ r[2]=l;
+ if (++dl >= 0) break;
+
+ l=(c+b[3])&BN_MASK2;
+ c=(l < c);
+ r[3]=l;
+ if (++dl >= 0) break;
+
+ save_dl = dl;
+ b+=4;
+ r+=4;
+ }
+ if (dl < 0)
+ {
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_add_part_words %d + %d (dl < 0, c == 0)\n", cl, dl);
+#endif
+ if (save_dl < dl)
+ {
+ switch (dl - save_dl)
+ {
+ case 1:
+ r[1] = b[1];
+ if (++dl >= 0) break;
+ case 2:
+ r[2] = b[2];
+ if (++dl >= 0) break;
+ case 3:
+ r[3] = b[3];
+ if (++dl >= 0) break;
+ }
+ b += 4;
+ r += 4;
+ }
+ }
+ if (dl < 0)
+ {
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_add_part_words %d + %d (dl < 0, copy)\n", cl, dl);
+#endif
+ for(;;)
+ {
+ r[0] = b[0];
+ if (++dl >= 0) break;
+ r[1] = b[1];
+ if (++dl >= 0) break;
+ r[2] = b[2];
+ if (++dl >= 0) break;
+ r[3] = b[3];
+ if (++dl >= 0) break;
+
+ b += 4;
+ r += 4;
+ }
+ }
+ }
+ else
+ {
+ int save_dl = dl;
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_add_part_words %d + %d (dl > 0)\n", cl, dl);
+#endif
+ while (c)
+ {
+ t=(a[0]+c)&BN_MASK2;
+ c=(t < c);
+ r[0]=t;
+ if (--dl <= 0) break;
+
+ t=(a[1]+c)&BN_MASK2;
+ c=(t < c);
+ r[1]=t;
+ if (--dl <= 0) break;
+
+ t=(a[2]+c)&BN_MASK2;
+ c=(t < c);
+ r[2]=t;
+ if (--dl <= 0) break;
+
+ t=(a[3]+c)&BN_MASK2;
+ c=(t < c);
+ r[3]=t;
+ if (--dl <= 0) break;
+
+ save_dl = dl;
+ a+=4;
+ r+=4;
+ }
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_add_part_words %d + %d (dl > 0, c == 0)\n", cl, dl);
+#endif
+ if (dl > 0)
+ {
+ if (save_dl > dl)
+ {
+ switch (save_dl - dl)
+ {
+ case 1:
+ r[1] = a[1];
+ if (--dl <= 0) break;
+ case 2:
+ r[2] = a[2];
+ if (--dl <= 0) break;
+ case 3:
+ r[3] = a[3];
+ if (--dl <= 0) break;
+ }
+ a += 4;
+ r += 4;
+ }
+ }
+ if (dl > 0)
+ {
+#ifdef BN_COUNT
+ fprintf(stderr, " bn_add_part_words %d + %d (dl > 0, copy)\n", cl, dl);
+#endif
+ for(;;)
+ {
+ r[0] = a[0];
+ if (--dl <= 0) break;
+ r[1] = a[1];
+ if (--dl <= 0) break;
+ r[2] = a[2];
+ if (--dl <= 0) break;
+ r[3] = a[3];
+ if (--dl <= 0) break;
+
+ a += 4;
+ r += 4;
+ }
+ }
+ }
+ return c;
+ }
+