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

/* 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
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/* 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 "libbb.h"
#include "xregex.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

/* TODO: use bb_strtol[l]? It's easier to check for errors... */

/* 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.  */
struct globals {
    char **args;
};
#define G (*(struct globals*)&bb_common_bufsiz1)

/* forward declarations */
static VALUE *eval(void);


/* 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(const char *s)
{
    VALUE *v;

    v = xmalloc(sizeof(VALUE));
    v->type = string;
    v->u.s = 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)
{
    if (v->type == integer)
        return v->u.i == 0;
    /* string: */
    return v->u.s[0] == '\0' || LONE_CHAR(v->u.s, '0');
}

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

static void tostring(VALUE * v)
{
    if (v->type == integer) {
        v->u.s = 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 bool 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 bool nextarg(const char *str)
{
    if (*G.args == NULL)
        return 0;
    return strcmp(*G.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;
    if (op == '<')
        return cmpval < 0;
    if (op == ('L' + 'E'))
        return cmpval <= 0;
    if (op == '=')
        return cmpval == 0;
    if (op == '!')
        return cmpval != 0;
    if (op == '>')
        return cmpval > 0;
    /* >= */
    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");
    if (op == '+')
        return li + ri;
    else if (op == '-')
        return li - ri;
    else if (op == '*')
        return li * ri;
    else if (op == '/')
        return li / ri;
    else
        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] == '^') {
        bb_error_msg("\
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));
    xregcomp(&re_buffer, pv->u.s, 0);

    /* 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);
    }
//FIXME: sounds like here is a bit missing: regfree(&re_buffer);
    return v;
}

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

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

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

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

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

    return str_value(*G.args++);
}

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

static VALUE *eval6(void)
{
    static const char keywords[] ALIGN1 =
        "quote\0""length\0""match\0""index\0""substr\0";

    VALUE *r, *i1, *i2;
    VALUE *l = l; /* silence gcc */
    VALUE *v = v; /* silence gcc */
    int key = *G.args ? index_in_strings(keywords, *G.args) + 1 : 0;

    if (key == 0) /* not a keyword */
        return eval7();
    G.args++; /* We have a valid token, so get the next argument.  */
    if (key == 1) { /* quote */
        if (!*G.args)
            bb_error_msg_and_die("syntax error");
        return str_value(*G.args++);
    }
    if (key == 2) { /* length */
        r = eval6();
        tostring(r);
        v = int_value(strlen(r->u.s));
        freev(r);
    } else
        l = eval6();

    if (key == 3) { /* match */
        r = eval6();
        v = docolon(l, r);
        freev(l);
        freev(r);
    }
    if (key == 4) { /* index */
        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);
    }
    if (key == 5) { /* substr */
        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 = xstrndup(l->u.s + i1->u.i - 1, i2->u.i);
        }
        freev(l);
        freev(i1);
        freev(i2);
    }
    return v;

}

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

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

    l = eval6();
    while (nextarg(":")) {
        G.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;
        G.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;
        G.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;
        G.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("&")) {
        G.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("|")) {
        G.args++;
        r = eval1();
        if (null(l)) {
            freev(l);
            l = r;
        } else
            freev(r);
    }
    return l;
}

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

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

    G.args = argv + 1;

    v = eval();
    if (*G.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);

    fflush_stdout_and_exit(null(v));
}