ref: 1018d7a7091fd5e0433f501a3474cdc3fec322cc
dir: /libmp/port/mpvecsub.c/
#include "os.h" #include <mp.h> #include "dat.h" // prereq: a >= b, alen >= blen, diff has at least alen digits void mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff) { int i, borrow; mpdigit x, y; borrow = 0; for(i = 0; i < blen; i++){ x = *a++; y = *b++; y += borrow; if(y < borrow) borrow = 1; else borrow = 0; if(x < y) borrow++; *diff++ = x - y; } for(; i < alen; i++){ x = *a++; y = x - borrow; if(y > x) borrow = 1; else borrow = 0; *diff++ = y; } }