source: MondoRescue/branches/stable/mindi-busybox/coreutils/expr.c@ 1247

/* vi: set sw=4 ts=4: */
/*
 * Mini expr implementation for busybox
 *
 * based on GNU expr Mike Parker.
 * Copyright (C) 86, 1991-1997, 1999 Free Software Foundation, Inc.
 *
 * Busybox modifications
 * Copyright (c) 2000  Edward Betts <edward@debian.org>.
 * Copyright (C) 2003-2005  Vladimir Oleynik <dzo@simtreas.ru>
 *  - reduced 464 bytes.
 *  - 64 math support
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

/* This program evaluates expressions.  Each token (operator, operand,
 * parenthesis) of the expression must be a separate argument.  The
 * parser used is a reasonably general one, though any incarnation of
 * it is language-specific.  It is especially nice for expressions.
 *
 * No parse tree is needed; a new node is evaluated immediately.
 * One function can handle multiple operators all of equal precedence,
 * provided they all associate ((x op x) op x). */

/* no getopt needed */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <regex.h>
#include <sys/types.h>
#include <errno.h>
#include "busybox.h"


/* The kinds of value we can have.  */
enum valtype {
    integer,
    string
};
typedef enum valtype TYPE;

#if ENABLE_EXPR_MATH_SUPPORT_64
typedef int64_t arith_t;
#define PF_REZ      "ll"
#define PF_REZ_TYPE (long long)
#define STRTOL(s, e, b) strtoll(s, e, b)
#else
typedef long arith_t;
#define PF_REZ      "l"
#define PF_REZ_TYPE (long)
#define STRTOL(s, e, b) strtol(s, e, b)
#endif

/* A value is.... */
struct valinfo {
    TYPE type;                      /* Which kind. */
    union {                         /* The value itself. */
        arith_t i;
        char *s;
    } u;
};
typedef struct valinfo VALUE;

/* The arguments given to the program, minus the program name.  */
static char **args;

static VALUE *docolon (VALUE *sv, VALUE *pv);
static VALUE *eval (void);
static VALUE *int_value (arith_t i);
static VALUE *str_value (char *s);
static int nextarg (char *str);
static int null (VALUE *v);
static int toarith (VALUE *v);
static void freev (VALUE *v);
static void tostring (VALUE *v);

int expr_main (int argc, char **argv)
{
    VALUE *v;

    if (argc == 1) {
        bb_error_msg_and_die("too few arguments");
    }

    args = argv + 1;

    v = eval ();
    if (*args)
        bb_error_msg_and_die ("syntax error");

    if (v->type == integer)
        printf ("%" PF_REZ "d\n", PF_REZ_TYPE v->u.i);
    else
        puts (v->u.s);

    exit (null (v));
}

/* Return a VALUE for I.  */

static VALUE *int_value (arith_t i)
{
    VALUE *v;

    v = xmalloc (sizeof(VALUE));
    v->type = integer;
    v->u.i = i;
    return v;
}

/* Return a VALUE for S.  */

static VALUE *str_value (char *s)
{
    VALUE *v;

    v = xmalloc (sizeof(VALUE));
    v->type = string;
    v->u.s = bb_xstrdup (s);
    return v;
}

/* Free VALUE V, including structure components.  */

static void freev (VALUE *v)
{
    if (v->type == string)
        free (v->u.s);
    free (v);
}

/* Return nonzero if V is a null-string or zero-number.  */

static int null (VALUE *v)
{
    switch (v->type) {
        case integer:
            return v->u.i == 0;
        default: /* string: */
            return v->u.s[0] == '\0' || strcmp (v->u.s, "0") == 0;
    }
}

/* Coerce V to a string value (can't fail).  */

static void tostring (VALUE *v)
{
    if (v->type == integer) {
        v->u.s = bb_xasprintf ("%" PF_REZ "d", PF_REZ_TYPE v->u.i);
        v->type = string;
    }
}

/* Coerce V to an integer value.  Return 1 on success, 0 on failure.  */

static int toarith (VALUE *v)
{
    if(v->type == string) {
        arith_t i;
        char *e;

        /* Don't interpret the empty string as an integer.  */
        /* Currently does not worry about overflow or int/long differences. */
        i = STRTOL(v->u.s, &e, 10);
        if ((v->u.s == e) || *e)
            return 0;
        free (v->u.s);
        v->u.i = i;
        v->type = integer;
    }
    return 1;
}

/* Return nonzero if the next token matches STR exactly.
   STR must not be NULL.  */

static int
nextarg (char *str)
{
    if (*args == NULL)
        return 0;
    return strcmp (*args, str) == 0;
}

/* The comparison operator handling functions.  */

static int cmp_common (VALUE *l, VALUE *r, int op)
{
    int cmpval;

    if (l->type == string || r->type == string) {
        tostring (l);
        tostring (r);
        cmpval = strcmp (l->u.s, r->u.s);
    }
    else
        cmpval = l->u.i - r->u.i;
    switch(op) {
        case '<':
            return cmpval < 0;
        case ('L'+'E'):
            return cmpval <= 0;
        case '=':
            return cmpval == 0;
        case '!':
            return cmpval != 0;
        case '>':
            return cmpval > 0;
        default: /* >= */
            return cmpval >= 0;
    }
}

/* The arithmetic operator handling functions.  */

static arith_t arithmetic_common (VALUE *l, VALUE *r, int op)
{
  arith_t li, ri;

  if (!toarith (l) || !toarith (r))
    bb_error_msg_and_die ("non-numeric argument");
  li = l->u.i;
  ri = r->u.i;
  if((op == '/' || op == '%') && ri == 0)
    bb_error_msg_and_die ( "division by zero");
  switch(op) {
    case '+':
        return li + ri;
    case '-':
        return li - ri;
    case '*':
        return li * ri;
    case '/':
        return li / ri;
    default:
        return li % ri;
  }
}

/* Do the : operator.
   SV is the VALUE for the lhs (the string),
   PV is the VALUE for the rhs (the pattern).  */

static VALUE *docolon (VALUE *sv, VALUE *pv)
{
    VALUE *v;
    regex_t re_buffer;
    const int NMATCH = 2;
    regmatch_t re_regs[NMATCH];

    tostring (sv);
    tostring (pv);

    if (pv->u.s[0] == '^') {
        fprintf (stderr, "\
warning: unportable BRE: `%s': using `^' as the first character\n\
of a basic regular expression is not portable; it is being ignored",
        pv->u.s);
    }

    memset (&re_buffer, 0, sizeof (re_buffer));
    memset (re_regs, 0, sizeof (*re_regs));
    if( regcomp (&re_buffer, pv->u.s, 0) != 0 )
        bb_error_msg_and_die("Invalid regular expression");

    /* expr uses an anchored pattern match, so check that there was a
     * match and that the match starts at offset 0. */
    if (regexec (&re_buffer, sv->u.s, NMATCH, re_regs, 0) != REG_NOMATCH &&
            re_regs[0].rm_so == 0) {
        /* Were \(...\) used? */
        if (re_buffer.re_nsub > 0) {
            sv->u.s[re_regs[1].rm_eo] = '\0';
            v = str_value (sv->u.s + re_regs[1].rm_so);
        }
        else
            v = int_value (re_regs[0].rm_eo);
    }
    else {
        /* Match failed -- return the right kind of null.  */
        if (re_buffer.re_nsub > 0)
            v = str_value ("");
        else
            v = int_value (0);
    }
    return v;
}

/* Handle bare operands and ( expr ) syntax.  */

static VALUE *eval7 (void)
{
    VALUE *v;

    if (!*args)
        bb_error_msg_and_die ( "syntax error");

    if (nextarg ("(")) {
        args++;
        v = eval ();
        if (!nextarg (")"))
            bb_error_msg_and_die ( "syntax error");
            args++;
            return v;
        }

    if (nextarg (")"))
        bb_error_msg_and_die ( "syntax error");

    return str_value (*args++);
}

/* Handle match, substr, index, length, and quote keywords.  */

static VALUE *eval6 (void)
{
    VALUE *l, *r, *v, *i1, *i2;

    if (nextarg ("quote")) {
        args++;
        if (!*args)
            bb_error_msg_and_die ( "syntax error");
        return str_value (*args++);
    }
    else if (nextarg ("length")) {
        args++;
        r = eval6 ();
        tostring (r);
        v = int_value (strlen (r->u.s));
        freev (r);
        return v;
    }
    else if (nextarg ("match")) {
        args++;
        l = eval6 ();
        r = eval6 ();
        v = docolon (l, r);
        freev (l);
        freev (r);
        return v;
    }
    else if (nextarg ("index")) {
        args++;
        l = eval6 ();
        r = eval6 ();
        tostring (l);
        tostring (r);
        v = int_value (strcspn (l->u.s, r->u.s) + 1);
        if (v->u.i == (arith_t) strlen (l->u.s) + 1)
            v->u.i = 0;
        freev (l);
        freev (r);
        return v;
    }
    else if (nextarg ("substr")) {
        args++;
        l = eval6 ();
        i1 = eval6 ();
        i2 = eval6 ();
        tostring (l);
        if (!toarith (i1) || !toarith (i2)
            || i1->u.i > (arith_t) strlen (l->u.s)
            || i1->u.i <= 0 || i2->u.i <= 0)
        v = str_value ("");
        else {
            v = xmalloc (sizeof(VALUE));
            v->type = string;
            v->u.s = bb_xstrndup(l->u.s + i1->u.i - 1, i2->u.i);
        }
        freev (l);
        freev (i1);
        freev (i2);
        return v;
    }
    else
        return eval7 ();
}

/* Handle : operator (pattern matching).
   Calls docolon to do the real work.  */

static VALUE *eval5 (void)
{
    VALUE *l, *r, *v;

    l = eval6 ();
    while (nextarg (":")) {
        args++;
        r = eval6 ();
        v = docolon (l, r);
        freev (l);
        freev (r);
        l = v;
    }
    return l;
}

/* Handle *, /, % operators.  */

static VALUE *eval4 (void)
{
    VALUE *l, *r;
    int op;
    arith_t val;

    l = eval5 ();
    while (1) {
        if (nextarg ("*"))
            op = '*';
        else if (nextarg ("/"))
            op = '/';
        else if (nextarg ("%"))
            op = '%';
        else
            return l;
        args++;
        r = eval5 ();
        val = arithmetic_common (l, r, op);
        freev (l);
        freev (r);
        l = int_value (val);
    }
}

/* Handle +, - operators.  */

static VALUE *eval3 (void)
{
    VALUE *l, *r;
    int op;
    arith_t val;

    l = eval4 ();
    while (1) {
        if (nextarg ("+"))
            op = '+';
        else if (nextarg ("-"))
            op = '-';
        else
            return l;
        args++;
        r = eval4 ();
        val = arithmetic_common (l, r, op);
        freev (l);
        freev (r);
        l = int_value (val);
    }
}

/* Handle comparisons.  */

static VALUE *eval2 (void)
{
    VALUE *l, *r;
    int op;
    arith_t val;

    l = eval3 ();
    while (1) {
        if (nextarg ("<"))
            op = '<';
        else if (nextarg ("<="))
            op = 'L'+'E';
        else if (nextarg ("=") || nextarg ("=="))
            op = '=';
        else if (nextarg ("!="))
            op = '!';
        else if (nextarg (">="))
            op = 'G'+'E';
        else if (nextarg (">"))
            op = '>';
        else
            return l;
        args++;
        r = eval3 ();
        toarith (l);
        toarith (r);
        val = cmp_common (l, r, op);
        freev (l);
        freev (r);
        l = int_value (val);
    }
}

/* Handle &.  */

static VALUE *eval1 (void)
{
    VALUE *l, *r;

    l = eval2 ();
    while (nextarg ("&")) {
        args++;
        r = eval2 ();
        if (null (l) || null (r)) {
            freev (l);
            freev (r);
            l = int_value (0);
        }
        else
            freev (r);
    }
    return l;
}

/* Handle |.  */

static VALUE *eval (void)
{
    VALUE *l, *r;

    l = eval1 ();
    while (nextarg ("|")) {
        args++;
        r = eval1 ();
        if (null (l)) {
            freev (l);
            l = r;
        }
        else
            freev (r);
    }
    return l;
}