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/* ISC license. */
#include <unistd.h>
#include <skalibs/allreadwrite.h>
#include <skalibs/bytestr.h>
#include <skalibs/uint.h>
#include <skalibs/fmtscan.h>
#include <skalibs/strerr2.h>
#define USAGE "s6-expr arithmetic expression"
enum opnum
{
T_DATA,
T_AND,
T_OR,
T_LEFTP,
T_RIGHTP,
T_EQUAL,
T_NEQUAL,
T_GREATER,
T_GREATERE,
T_LESSER,
T_LESSERE,
T_PLUS,
T_MINUS,
T_TIMES,
T_DIV,
T_MOD
} ;
struct token
{
char const *string ;
enum opnum op ;
unsigned int type ;
} ;
struct node
{
enum opnum op ;
unsigned int type ;
unsigned int arg1 ;
unsigned int arg2 ;
int data ;
} ;
static unsigned int lex (struct node *tree, char const *const *argv)
{
static struct token const tokens[16] =
{
{ "+", T_PLUS, 3 },
{ "-", T_MINUS, 3 },
{ "*", T_TIMES, 2 },
{ "/", T_DIV, 2 },
{ "%", T_MOD, 2 },
{ "(", T_LEFTP, 7 },
{ ")", T_RIGHTP, 8 },
{ "=", T_EQUAL, 4 },
{ "!=", T_NEQUAL, 4 },
{ "<", T_LESSER, 4 },
{ "<=", T_LESSERE, 4 },
{ ">", T_GREATER, 4 },
{ ">=", T_GREATERE, 4 },
{ "|", T_OR, 6 },
{ "&", T_AND, 5 },
{ 0, 0, 0 }
} ;
register unsigned int pos = 0 ;
for (; argv[pos] ; pos++)
{
register unsigned int i = 0 ;
for (i = 0 ; tokens[i].string ; i++)
if (!str_diff(argv[pos], tokens[i].string))
{
tree[pos].op = tokens[i].op ;
tree[pos].type = tokens[i].type ;
break ;
}
if (!tokens[i].string)
{
tree[pos].op = T_DATA ;
tree[pos].type = 0 ;
if (!int_scan(argv[pos], &tree[pos].data))
strerr_dief1x(2, "invalid expression") ;
}
}
return pos ;
}
static void reduce (struct node *tree, register unsigned int *stack, register unsigned int *sp, unsigned int type)
{
if (tree[stack[*sp-1]].type == type)
{
tree[stack[*sp-1]].arg1 = stack[*sp-2] ;
tree[stack[*sp-1]].arg2 = stack[*sp] ;
stack[*sp-2] = stack[*sp-1] ;
*sp -= 2 ;
}
tree[stack[*sp]].type = type + 7 ;
}
static unsigned int parse (struct node *tree, unsigned int n)
{
static char const table[9][15] =
{
"xsssssssxzzzzzz",
"xxxxxxxx!zzzzzz",
"mxxxxxxxMszzzzz",
"mxxxxxxxMaszzzz",
"mxxxxxxxMacszzz",
"mxxxxxxxMacAszz",
"mxxxxxxxMacAOsz",
"xsssssssxzzzzzz",
"mxxxxxxxMacAOEs"
} ;
unsigned int stack[n] ;
unsigned int sp = 0, pos = 0 ;
char cont = 1 ;
stack[0] = n + 1 ;
tree[n].type = 8 ; /* add ) for the final reduce */
tree[n+1].type = 1 ; /* add EOF */
while (cont)
{
switch (table[tree[pos].type][tree[stack[sp]].type])
{
case 'x' : _exit(2) ;
case '!' : cont = 0 ; break ;
case 's' : stack[++sp] = pos++ ; break ;
case 'm' : reduce(tree, stack, &sp, 2) ; break ;
case 'a' : reduce(tree, stack, &sp, 3) ; break ;
case 'c' : reduce(tree, stack, &sp, 4) ; break ;
case 'A' : reduce(tree, stack, &sp, 5) ; break ;
case 'O' : reduce(tree, stack, &sp, 6) ; break ;
case 'E' : tree[stack[sp]].type = 14 ; break ;
case 'M' :
{
if (tree[stack[sp-2]].type != 7) _exit(2) ;
stack[sp-2] = stack[sp-1] ;
sp -= 2 ;
reduce(tree, stack, &sp, 2) ;
break ;
}
case 'z' :
default : strerr_dief1x(101, "internal error in parse, please submit a bug-report.") ; /* can't happen */
}
}
if (sp != 2) strerr_dief1x(2, "invalid expression") ;
return stack[1] ;
}
static int run (struct node const *tree, unsigned int root)
{
switch (tree[root].op)
{
case T_DATA :
return tree[root].data ;
case T_OR :
{
int r = run(tree, tree[root].arg1) ;
return r ? r : run(tree, tree[root].arg2) ;
}
case T_AND :
{
int r = run(tree, tree[root].arg1) ;
return r ? run(tree, tree[root].arg2) ? r : 0 : 0 ;
}
case T_EQUAL :
return run(tree, tree[root].arg1) == run(tree, tree[root].arg2) ;
case T_NEQUAL :
return run(tree, tree[root].arg1) != run(tree, tree[root].arg2) ;
case T_GREATER :
return run(tree, tree[root].arg1) > run(tree, tree[root].arg2) ;
case T_GREATERE :
return run(tree, tree[root].arg1) >= run(tree, tree[root].arg2) ;
case T_LESSER :
return run(tree, tree[root].arg1) < run(tree, tree[root].arg2) ;
case T_LESSERE :
return run(tree, tree[root].arg1) <= run(tree, tree[root].arg2) ;
case T_PLUS :
return run(tree, tree[root].arg1) + run(tree, tree[root].arg2) ;
case T_MINUS :
return run(tree, tree[root].arg1) - run(tree, tree[root].arg2) ;
case T_TIMES :
return run(tree, tree[root].arg1) * run(tree, tree[root].arg2) ;
case T_DIV :
return run(tree, tree[root].arg1) / run(tree, tree[root].arg2) ;
case T_MOD :
return run(tree, tree[root].arg1) % run(tree, tree[root].arg2) ;
default: strerr_dief1x(101, "internal error in run, please submit a bug-report") ;
}
}
int main (int argc, char const *const *argv)
{
char fmt[UINT_FMT+1] ;
int val ;
unsigned int len ;
PROG = "s6-expr" ;
if (argc <= 1) return 2 ;
{
struct node tree[argc + 1] ;
val = run(tree, parse(tree, lex(tree, argv+1))) ;
}
len = int_fmt(fmt, val) ;
fmt[len++] = '\n' ;
if (allwrite(1, fmt, len) < len)
strerr_diefu1sys(111, "write to stdout") ;
return !val ;
}
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