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