/* vi: set sw=4 ts=4: */#include <ctype.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <math.h>#include "busybox.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]=='-')			show_usage();		while (argc >= 2) {			stack_machine(argv[1]);			argv++;			argc--;		}	}	stack_machine(0);	return EXIT_SUCCESS;}