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/* vi: set sw=4 ts=4: */
#include "busybox.h"
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>
/* Tiny RPN calculator, because "expr" didn't give me bitwise operations. */
static double stack[100];
static unsigned int pointer;
static void push(double a)
{
if (pointer >= (sizeof(stack) / sizeof(*stack)))
error_msg_and_die("stack overflow");
stack[pointer++] = a;
}
static double pop()
{
if (pointer == 0)
error_msg_and_die("stack underflow");
return stack[--pointer];
}
static void add()
{
push(pop() + pop());
}
static void sub()
{
double subtrahend = pop();
push(pop() - subtrahend);
}
static void mul()
{
push(pop() * pop());
}
static void divide()
{
double divisor = pop();
push(pop() / divisor);
}
static void and()
{
push((unsigned int) pop() & (unsigned int) pop());
}
static void or()
{
push((unsigned int) pop() | (unsigned int) pop());
}
static void eor()
{
push((unsigned int) pop() ^ (unsigned int) pop());
}
static void not()
{
push(~(unsigned int) pop());
}
static void print()
{
printf("%g\n", pop());
}
struct op {
const char *name;
void (*function) ();
};
static const struct op operators[] = {
{"+", add},
{"add", add},
{"-", sub},
{"sub", sub},
{"*", mul},
{"mul", mul},
{"/", divide},
{"div", divide},
{"and", and},
{"or", or},
{"not", not},
{"eor", eor},
{0, 0}
};
static void stack_machine(const char *argument)
{
char *endPointer = 0;
double d;
const struct op *o = operators;
if (argument == 0) {
print();
return;
}
d = strtod(argument, &endPointer);
if (endPointer != argument) {
push(d);
return;
}
while (o->name != 0) {
if (strcmp(o->name, argument) == 0) {
(*(o->function)) ();
return;
}
o++;
}
error_msg_and_die("%s: syntax error.", argument);
}
/* return pointer to next token in buffer and set *buffer to one char
* past the end of the above mentioned token
*/
static char *get_token(char **buffer)
{
char *start = NULL;
char *current = *buffer;
while (isspace(*current)) { current++; }
if (*current != 0) {
start = current;
while (!isspace(*current) && current != 0) { current++; }
*buffer = current;
}
return start;
}
/* In Perl one might say, scalar m|\s*(\S+)\s*|g */
static int number_of_tokens(char *buffer)
{
int i = 0;
char *b = buffer;
while (get_token(&b)) { i++; }
return i;
}
int dc_main(int argc, char **argv)
{
/* take stuff from stdin if no args are given */
if (argc <= 1) {
int i, len;
char *line = NULL;
char *cursor = NULL;
char *token = NULL;
while ((line = get_line_from_file(stdin))) {
cursor = line;
len = number_of_tokens(line);
for (i = 0; i < len; i++) {
token = get_token(&cursor);
*cursor++ = 0;
stack_machine(token);
}
free(line);
}
} else {
if (*argv[1]=='-')
usage(dc_usage);
while (argc >= 2) {
stack_machine(argv[1]);
argv++;
argc--;
}
}
stack_machine(0);
return EXIT_SUCCESS;
}
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