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/* ISC license. */
#include <string.h>
#include <skalibs/allreadwrite.h>
#include <skalibs/types.h>
#include <skalibs/strerr.h>
#define USAGE "s6-expr arithmetic expression"
#define bail() strerr_dief1x(2, "invalid expression")
enum expr_opnum_e
{
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 expr_token_s
{
char const *string ;
enum expr_opnum_e op ;
unsigned int type ;
} ;
struct expr_node_s
{
enum expr_opnum_e op ;
unsigned int type ;
unsigned int arg1 ;
unsigned int arg2 ;
long data ;
} ;
static unsigned int expr_lex (struct expr_node_s *tree, char const *const *argv)
{
static struct expr_token_s 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 }
} ;
unsigned int pos = 0 ;
for (; argv[pos] ; pos++)
{
unsigned int i = 0 ;
for (i = 0 ; tokens[i].string ; i++)
if (!strcmp(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 (!long_scan(argv[pos], &tree[pos].data)) bail() ;
}
}
return pos ;
}
static void expr_reduce (struct expr_node_s *tree, unsigned int *stack, 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 expr_parse (struct expr_node_s *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' : bail() ;
case '!' : cont = 0 ; break ;
case 's' : stack[++sp] = pos++ ; break ;
case 'M' :
if (tree[stack[sp-2]].type != 7) bail() ;
stack[sp-2] = stack[sp-1] ;
sp -= 2 ;
case 'm' : expr_reduce(tree, stack, &sp, 2) ; break ;
case 'a' : expr_reduce(tree, stack, &sp, 3) ; break ;
case 'c' : expr_reduce(tree, stack, &sp, 4) ; break ;
case 'A' : expr_reduce(tree, stack, &sp, 5) ; break ;
case 'O' : expr_reduce(tree, stack, &sp, 6) ; break ;
case 'E' : tree[stack[sp]].type = 14 ; break ;
case 'z' :
default : strerr_dief1x(101, "internal error in parse, please submit a bug-report.") ; /* can't happen */
}
}
if (sp != 2) bail() ;
return stack[1] ;
}
static long expr_run (struct expr_node_s const *tree, unsigned int root)
{
switch (tree[root].op)
{
case T_DATA :
return tree[root].data ;
case T_OR :
{
long r = expr_run(tree, tree[root].arg1) ;
return r ? r : expr_run(tree, tree[root].arg2) ;
}
case T_AND :
{
long r = expr_run(tree, tree[root].arg1) ;
return r ? expr_run(tree, tree[root].arg2) ? r : 0 : 0 ;
}
case T_EQUAL :
return expr_run(tree, tree[root].arg1) == expr_run(tree, tree[root].arg2) ;
case T_NEQUAL :
return expr_run(tree, tree[root].arg1) != expr_run(tree, tree[root].arg2) ;
case T_GREATER :
return expr_run(tree, tree[root].arg1) > expr_run(tree, tree[root].arg2) ;
case T_GREATERE :
return expr_run(tree, tree[root].arg1) >= expr_run(tree, tree[root].arg2) ;
case T_LESSER :
return expr_run(tree, tree[root].arg1) < expr_run(tree, tree[root].arg2) ;
case T_LESSERE :
return expr_run(tree, tree[root].arg1) <= expr_run(tree, tree[root].arg2) ;
case T_PLUS :
return expr_run(tree, tree[root].arg1) + expr_run(tree, tree[root].arg2) ;
case T_MINUS :
return expr_run(tree, tree[root].arg1) - expr_run(tree, tree[root].arg2) ;
case T_TIMES :
return expr_run(tree, tree[root].arg1) * expr_run(tree, tree[root].arg2) ;
case T_DIV :
return expr_run(tree, tree[root].arg1) / expr_run(tree, tree[root].arg2) ;
case T_MOD :
return expr_run(tree, tree[root].arg1) % expr_run(tree, tree[root].arg2) ;
default : strerr_dief1x(101, "internal error in expr_run, please submit a bug-report") ;
}
}
int main (int argc, char const *const *argv)
{
char fmt[LONG_FMT] ;
long val ;
size_t len ;
PROG = "s6-expr" ;
if (argc <= 1) return 2 ;
{
struct expr_node_s tree[argc + 1] ;
val = expr_run(tree, expr_parse(tree, expr_lex(tree, argv+1))) ;
}
len = long_fmt(fmt, val) ;
fmt[len++] = '\n' ;
if (allwrite(1, fmt, len) < len)
strerr_diefu1sys(111, "write to stdout") ;
return !val ;
}
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