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#include <u.h>
#include <libc.h>
#include <ctype.h>
#include "roman.h"
static int decimal[] = {
1000, 900,
500, 400,
100, 90,
50, 40,
10, 9,
5, 4,
1
};
static char *roman[] = {
"M", "CM",
"D", "CD",
"C", "XC",
"L", "XL",
"X", "IX",
"V", "IV",
"I"
};
static int alpha2roman[] = {
/* A, B, C, D, E, F, G, H, I, J, K, L, M */
0, 0, 100, 500, 0, 0, 0, 0, 1, 1, 0, 50, 1000,
/* N, O, P, Q, R, S, T, U, V, W, X, Y, Z */
0, 0, 0, 0, 0, 0, 0, 5, 5, 0, 10, 0, 0
};
static int
getroman(char c)
{
if(!isalpha(c))
return -1;
return alpha2roman[toupper(c) - 'A'];
}
int
dectoroman(int n, char *buf, ulong len)
{
char *p;
int i, o;
o = 0;
for(i = 0; i < nelem(decimal); i++){
while(n >= decimal[i] && o < len-1){
for(p = roman[i]; *p != 0 && o < len-1; )
buf[o++] = *p++;
n -= decimal[i];
}
}
buf[o] = 0;
return 0;
}
int
romantodec(char *buf)
{
char *ebuf, *larger;
int curno, largerno, dec;
ebuf = strchr(buf, '\0');
dec = 0;
while(buf < ebuf){
curno = getroman(*buf);
if(curno < 0)
return -1;
larger = buf;
do{
largerno = getroman(*larger);
if(largerno < 0)
return -1;
if(largerno > curno)
break;
}while(*++larger != 0);
if(*larger == 0)
dec += curno;
else{
dec += largerno;
while(buf < larger)
dec -= getroman(*buf++);
}
buf++;
}
return dec;
}
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