source: MondoRescue/branches/2.2.9/mindi-busybox/miscutils/dc.c@ 2725

/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"
#include <math.h>

//usage:#define dc_trivial_usage
//usage:       "EXPRESSION..."
//usage:
//usage:#define dc_full_usage "\n\n"
//usage:       "Tiny RPN calculator. Operations:\n"
//usage:       "+, add, -, sub, *, mul, /, div, %, mod, **, exp, and, or, not, eor,\n"
//usage:       "p - print top of the stack (without popping),\n"
//usage:       "f - print entire stack,\n"
//usage:       "o - pop the value and set output radix (must be 10, 16, 8 or 2).\n"
//usage:       "Examples: 'dc 2 2 add' -> 4, 'dc 8 8 * 2 2 + /' -> 16"
//usage:
//usage:#define dc_example_usage
//usage:       "$ dc 2 2 + p\n"
//usage:       "4\n"
//usage:       "$ dc 8 8 \\* 2 2 + / p\n"
//usage:       "16\n"
//usage:       "$ dc 0 1 and p\n"
//usage:       "0\n"
//usage:       "$ dc 0 1 or p\n"
//usage:       "1\n"
//usage:       "$ echo 72 9 div 8 mul p | dc\n"
//usage:       "64\n"

#if 0
typedef unsigned data_t;
#define DATA_FMT ""
#elif 0
typedef unsigned long data_t;
#define DATA_FMT "l"
#else
typedef unsigned long long data_t;
#define DATA_FMT "ll"
#endif


struct globals {
    unsigned pointer;
    unsigned base;
    double stack[1];
} FIX_ALIASING;
enum { STACK_SIZE = (COMMON_BUFSIZE - offsetof(struct globals, stack)) / sizeof(double) };
#define G (*(struct globals*)&bb_common_bufsiz1)
#define pointer   (G.pointer   )
#define base      (G.base      )
#define stack     (G.stack     )
#define INIT_G() do { \
    base = 10; \
} while (0)


static void push(double a)
{
    if (pointer >= STACK_SIZE)
        bb_error_msg_and_die("stack overflow");
    stack[pointer++] = a;
}

static double pop(void)
{
    if (pointer == 0)
        bb_error_msg_and_die("stack underflow");
    return stack[--pointer];
}

static void add(void)
{
    push(pop() + pop());
}

static void sub(void)
{
    double subtrahend = pop();

    push(pop() - subtrahend);
}

static void mul(void)
{
    push(pop() * pop());
}

#if ENABLE_FEATURE_DC_LIBM
static void power(void)
{
    double topower = pop();

    push(pow(pop(), topower));
}
#endif

static void divide(void)
{
    double divisor = pop();

    push(pop() / divisor);
}

static void mod(void)
{
    data_t d = pop();

    push((data_t) pop() % d);
}

static void and(void)
{
    push((data_t) pop() & (data_t) pop());
}

static void or(void)
{
    push((data_t) pop() | (data_t) pop());
}

static void eor(void)
{
    push((data_t) pop() ^ (data_t) pop());
}

static void not(void)
{
    push(~(data_t) pop());
}

static void set_output_base(void)
{
    static const char bases[] ALIGN1 = { 2, 8, 10, 16, 0 };
    unsigned b = (unsigned)pop();

    base = *strchrnul(bases, b);
    if (base == 0) {
        bb_error_msg("error, base %u is not supported", b);
        base = 10;
    }
}

static void print_base(double print)
{
    data_t x, i;

    x = (data_t) print;
    if (base == 10) {
        if (x == print) /* exactly representable as unsigned integer */
            printf("%"DATA_FMT"u\n", x);
        else
            printf("%g\n", print);
        return;
    }

    switch (base) {
    case 16:
        printf("%"DATA_FMT"x\n", x);
        break;
    case 8:
        printf("%"DATA_FMT"o\n", x);
        break;
    default: /* base 2 */
        i = MAXINT(data_t) - (MAXINT(data_t) >> 1);
        /* i is 100000...00000 */
        do {
            if (x & i)
                break;
            i >>= 1;
        } while (i > 1);
        do {
            bb_putchar('1' - !(x & i));
            i >>= 1;
        } while (i);
        bb_putchar('\n');
    }
}

static void print_stack_no_pop(void)
{
    unsigned i = pointer;
    while (i)
        print_base(stack[--i]);
}

static void print_no_pop(void)
{
    print_base(stack[pointer-1]);
}

struct op {
    const char name[4];
    void (*function) (void);
};

static const struct op operators[] = {
    {"+",   add},
    {"add", add},
    {"-",   sub},
    {"sub", sub},
    {"*",   mul},
    {"mul", mul},
    {"/",   divide},
    {"div", divide},
#if ENABLE_FEATURE_DC_LIBM
    {"**",  power},
    {"exp", power},
    {"pow", power},
#endif
    {"%",   mod},
    {"mod", mod},
    {"and", and},
    {"or",  or},
    {"not", not},
    {"eor", eor},
    {"xor", eor},
    {"p", print_no_pop},
    {"f", print_stack_no_pop},
    {"o", set_output_base},
    { "", NULL }
};

static void stack_machine(const char *argument)
{
    char *endPointer;
    double d;
    const struct op *o = operators;

    d = strtod(argument, &endPointer);

    if (endPointer != argument && *endPointer == '\0') {
        push(d);
        return;
    }

    while (o->function) {
        if (strcmp(o->name, argument) == 0) {
            o->function();
            return;
        }
        o++;
    }
    bb_error_msg_and_die("syntax error at '%s'", 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 *current = skip_whitespace(*buffer);
    if (*current != '\0') {
        *buffer = skip_non_whitespace(current);
        return current;
    }
    return NULL;
}

int dc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int dc_main(int argc UNUSED_PARAM, char **argv)
{
    INIT_G();

    argv++;
    if (!argv[0]) {
        /* take stuff from stdin if no args are given */
        char *line;
        char *cursor;
        char *token;
        while ((line = xmalloc_fgetline(stdin)) != NULL) {
            cursor = line;
            while (1) {
                token = get_token(&cursor);
                if (!token)
                    break;
                *cursor++ = '\0';
                stack_machine(token);
            }
            free(line);
        }
    } else {
        // why? it breaks "dc -2 2 * p"
        //if (argv[0][0] == '-')
        //  bb_show_usage();
        do {
            stack_machine(*argv);
        } while (*++argv);
    }
    return EXIT_SUCCESS;
}