On Thu, 13 Nov 2014 14:05:19 -0800
Evan Gates <evan.ga...@gmail.com> wrote:
>
Hey Evan,
attached you'll find a small refactorization of your code.
Please take a look at yylex() and try to comment the other
sections accordingly in a way people understand how it
works without having to go through each line.
There were small issues I found, for instance the lack of
VAL in the precs-table and exclusive if-clauses, but overall
the code was pretty clean.
A relatively complex program like expr really needs to be
explained better. Apart from that, I really like your
solution very much.
Cheers
FRIGN
--
FRIGN <d...@frign.de>
/* See LICENSE file for copyright and license details. */
#include <inttypes.h>
#include <limits.h>
#include <regex.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "util.h"
enum {
VAL = CHAR_MAX + 1, GE, LE, NE
};
typedef struct {
char *s;
intmax_t n;
} Val;
static void doop(int*, int**, Val*, Val**);
static Val match(Val, Val);
static void num(Val);
static int valcmp(Val, Val);
static char *valstr(Val, char*);
static int yylex(void);
static int yyparse(int);
static char **args;
static size_t intlen;
static Val yylval;
// otop points to one past last op
// vtop points to one past last val
// guaranteed otop != ops
// pop two vals, pop op, apply op, push val
static void
doop(int *ops, int **otop, Val *vals, Val **vtop)
{
Val ret, a, b;
int op;
if ((*otop)[-1] == '(')
enprintf(2, "syntax error: extra (\n");
if (*vtop - vals < 2)
enprintf(2, "syntax error: missing expression or extra operator\n");
a = (*vtop)[-2];
b = (*vtop)[-1];
op = (*otop)[-1];
switch (op) {
case '|':
if ( a.s && *a.s) ret = (Val){ a.s , 0 };
else if (!a.s && a.n) ret = (Val){ NULL, a.n };
else if ( b.s && *b.s) ret = (Val){ b.s , 0 };
else ret = (Val){ NULL, b.n };
break;
case '&':
if (((a.s && *a.s) || a.n) && ((b.s && *b.s) || b.n))
ret = a;
else
ret = (Val){ NULL, 0 };
break;
case '=': ret = (Val){ NULL, valcmp(a, b) == 0 }; break;
case '>': ret = (Val){ NULL, valcmp(a, b) > 0 }; break;
case GE : ret = (Val){ NULL, valcmp(a, b) >= 0 }; break;
case '<': ret = (Val){ NULL, valcmp(a, b) < 0 }; break;
case LE : ret = (Val){ NULL, valcmp(a, b) <= 0 }; break;
case NE : ret = (Val){ NULL, valcmp(a, b) != 0 }; break;
case '+': num(a); num(b); ret = (Val){ NULL, a.n + b.n }; break;
case '-': num(a); num(b); ret = (Val){ NULL, a.n - b.n }; break;
case '*': num(a); num(b); ret = (Val){ NULL, a.n * b.n }; break;
case '/': num(a); num(b); ret = (Val){ NULL, a.n / b.n }; break;
case '%': num(a); num(b); ret = (Val){ NULL, a.n % b.n }; break;
case ':': ret = match(a, b); break;
}
(*vtop)[-2] = ret;
(*otop)--;
(*vtop)--;
}
static Val
match(Val vstr, Val vregx)
{
char b1[intlen], *str = valstr(vstr , b1);
char b2[intlen], *regx = valstr(vregx, b2);
char anchreg[strlen(regx) + 2];
char *ret, *p;
intmax_t d;
regex_t re;
regmatch_t matches[2];
sprintf(anchreg, "^%s", regx);
if (regcomp(&re, anchreg, 0))
enprintf(3, "regcomp failed\n");
if (regexec(&re, str, 2, matches, 0))
return (Val){ (re.re_nsub ? "" : NULL), 0 };
if (re.re_nsub) {
regoff_t len = matches[1].rm_eo - matches[1].rm_so + 1;
if (!(ret = malloc(len))) // FIXME: free
enprintf(3, "malloc failed\n");
d = strtoimax(ret, &p, 10);
strlcpy(ret, str + matches[1].rm_so, len);
if (*ret && !*p)
return (Val){ NULL, d };
return (Val){ ret, 0 };
}
return (Val){ NULL, matches[0].rm_eo - matches[0].rm_so };
}
static void
num(Val v)
{
if (v.s)
enprintf(2, "syntax error: expected integer got '%s'\n", v.s);
}
static int
valcmp(Val a, Val b)
{
char b1[intlen], *p = valstr(a, b1);
char b2[intlen], *q = valstr(b, b2);
if (!a.s && !b.s)
return (a.n > b.n) - (a.n < b.n);
return strcmp(p, q);
}
static char *
valstr(Val val, char *buf)
{
char *p = val.s;
if (!p) {
sprintf(buf, "%"PRIdMAX, val.n);
p = buf;
}
return p;
}
static int
yylex(void)
{
intmax_t d;
char *q, *p, *ops = "|&=><+-*/%():";
/* Reached end of expression */
if (!(p = *args++))
return 0;
/* Check if p is a clean integer */
d = strtoimax(p, &q, 10);
if(*p && !*q) {
yylval = (Val){ NULL, d };
return VAL;
}
/* Single character operator */
if (*p && !*(p+1) && strchr(ops, *p))
return *p;
/* Double character operator */
if (*p && *(p+1) == '=' && !*(p+2)) {
switch (*p) {
case '>': return GE;
case '<': return LE;
case '!': return NE;
}
}
/* Nothing matches, return raw val */
yylval = (Val){ p, 0 };
return VAL;
}
static int
yyparse(int argc)
{
Val vals[argc], *vtop = vals;
int ops [argc], *otop = ops;
int type, last = 0;
char prec[] = {
[VAL] = 0,
['|'] = 1,
['&'] = 2,
['='] = 3, ['>'] = 3, [GE] = 3, ['<'] = 3, [LE] = 3, [NE] = 3,
['+'] = 4, ['-'] = 4,
['*'] = 5, ['/'] = 5, ['%'] = 5,
[':'] = 6,
};
while ((type = yylex())) {
switch (type) {
case VAL:
*vtop++ = yylval;
break;
case '(':
*otop++ = '(';
break;
case ')':
if (last == '(')
enprintf(2, "syntax error: empty ( )\n");
while(otop > ops && otop[-1] != '(')
doop(ops, &otop, vals, &vtop);
if (otop == ops)
enprintf(2, "syntax error: extra )\n");
otop--;
break;
default:
if (prec[last])
enprintf(2, "syntax error: extra operator\n");
while (otop > ops && prec[otop[-1]] >= prec[type])
doop(ops, &otop, vals, &vtop);
*otop++ = type;
break;
}
last = type;
}
while (otop > ops)
doop(ops, &otop, vals, &vtop);
if (vtop == vals) {
enprintf(2, "syntax error: missing expression\n");
} else if (vtop - vals > 1) {
enprintf(2, "syntax error: extra expression\n");
}
vtop--;
if (vtop->s) {
printf("%s\n" , vtop->s);
} else {
printf("%"PRIdMAX"\n", vtop->n);
}
return (vtop->s && *vtop->s) || vtop->n;
}
int
main(int argc, char **argv)
{
if (!(intlen = snprintf(NULL, 0, "%"PRIdMAX, INTMAX_MIN) + 1))
enprintf(3, "failed to get max digits\n");
args = argv + 1;
if (*args && !strcmp("--", *args))
++args;
return !yyparse(argc);
}
