root/bin/ksh/var.c 
/*      $NetBSD: var.c,v 1.26 2024/09/08 17:28:36 rillig Exp $  */

#include <sys/cdefs.h>

#ifndef lint
__RCSID("$NetBSD: var.c,v 1.26 2024/09/08 17:28:36 rillig Exp $");
#endif

#include <sys/stat.h>
#include <sys/time.h>
#include <time.h>
#include <ctype.h>
#include <stdbool.h>

#include "sh.h"
#include "ksh_limval.h"

/*
 * Variables
 *
 * WARNING: unreadable code, needs a rewrite
 *
 * if (flag&INTEGER), val.i contains integer value, and type contains base.
 * otherwise, (val.s + type) contains string value.
 * if (flag&EXPORT), val.s contains "name=value" for E-Z exporting.
 */
static  struct tbl vtemp;
static  struct table specials;
static char     *formatstr      ARGS((struct tbl *vp, const char *s));
static void     export          ARGS((struct tbl *vp, const char *val));
static int      special         ARGS((const char *name));
static void     unspecial       ARGS((const char *name));
static void     getspec         ARGS((struct tbl *vp));
static void     setspec         ARGS((struct tbl *vp));
static void     unsetspec       ARGS((struct tbl *vp));
static struct tbl *arraysearch  ARGS((struct tbl *, int));

/*
 * create a new block for function calls and simple commands
 * assume caller has allocated and set up e->loc
 */
void
newblock()
{
        struct block *l;
        static char *const empty[] = {null};

        l = (struct block *) alloc(sizeof(struct block), ATEMP);
        l->flags = 0;
        ainit(&l->area); /* todo: could use e->area (l->area => l->areap) */
        if (!e->loc) {
                l->argc = 0;
                l->argv = (char **) __UNCONST(empty);
        } else {
                l->argc = e->loc->argc;
                l->argv = e->loc->argv;
        }
        l->exit = l->error = NULL;
        tinit(&l->vars, &l->area, 0);
        tinit(&l->funs, &l->area, 0);
        l->next = e->loc;
        e->loc = l;
}

/*
 * pop a block handling special variables
 */
void
popblock()
{
        struct block *l = e->loc;
        struct tbl *vp, **vpp = l->vars.tbls, *vq;
        int i;

        e->loc = l->next;       /* pop block */
        for (i = l->vars.size; --i >= 0; ) {
                if ((vp = *vpp++) != NULL && (vp->flag&SPECIAL)) {
                        if ((vq = global(vp->name))->flag & ISSET)
                                setspec(vq);
                        else
                                unsetspec(vq);
                }
        }
        if (l->flags & BF_DOGETOPTS)
                user_opt = l->getopts_state;
        afreeall(&l->area);
        afree(l, ATEMP);
}

/* called by main() to initialize variable data structures */
void
initvar()
{
        static const struct {
                const char *name;
                int v;
        } names[] = {
                        { "COLUMNS",            V_COLUMNS },
                        { "IFS",                V_IFS },
                        { "OPTIND",             V_OPTIND },
                        { "PATH",               V_PATH },
                        { "POSIXLY_CORRECT",    V_POSIXLY_CORRECT },
                        { "TMPDIR",             V_TMPDIR },
#ifdef HISTORY
                        { "HISTFILE",           V_HISTFILE },
                        { "HISTSIZE",           V_HISTSIZE },
#endif /* HISTORY */
#ifdef EDIT
                        { "EDITOR",             V_EDITOR },
                        { "VISUAL",             V_VISUAL },
#endif /* EDIT */
#ifdef KSH
                        { "MAIL",               V_MAIL },
                        { "MAILCHECK",          V_MAILCHECK },
                        { "MAILPATH",           V_MAILPATH },
                        { "RANDOM",             V_RANDOM },
                        { "SECONDS",            V_SECONDS },
                        { "TMOUT",              V_TMOUT },
#endif /* KSH */
                        { "LINENO",             V_LINENO },
                        { (char *) 0,   0 }
                };
        int i;
        struct tbl *tp;

        tinit(&specials, APERM, 32); /* must be 2^n (currently 17 specials) */
        for (i = 0; names[i].name; i++) {
                tp = tenter(&specials, names[i].name, hash(names[i].name));
                tp->flag = DEFINED|ISSET;
                tp->type = names[i].v;
        }
}

/* Used to calculate an array index for global()/local().  Sets *arrayp to
 * non-zero if this is an array, sets *valp to the array index, returns
 * the basename of the array.
 */
const char *array_index_calc(const char *n, bool *arrayp, int *valp);

const char *
array_index_calc(n, arrayp, valp)
        const char *n;
        bool *arrayp;
        int *valp;
{
        const char *p;
        int len;

        *arrayp = false;
        p = skip_varname(n, false);
        if (p != n && *p == '[' && (len = array_ref_len(p))) {
                char *sub, *tmp;
                long rval;

                /* Calculate the value of the subscript */
                *arrayp = true;
                tmp = str_nsave(p+1, len-2, ATEMP);
                sub = substitute(tmp, 0);
                afree(tmp, ATEMP);
                n = str_nsave(n, p - n, ATEMP);
                evaluate(sub, &rval, KSH_UNWIND_ERROR);
                if (rval < 0 || rval > ARRAYMAX)
                        errorf("%s: subscript out of range", n);
                *valp = rval;
                afree(sub, ATEMP);
        }
        return n;
}

/*
 * Search for variable, if not found create globally.
 */
struct tbl *
global(n)
        const char *n;
{
        struct block *l = e->loc;
        struct tbl *vp;
        int c;
        unsigned h;
        bool     array;
        int      val;

        /* Check to see if this is an array */
        n = array_index_calc(n, &array, &val);
        h = hash(n);
        c = n[0];
        if (!letter(c)) {
                if (array)
                        errorf("bad substitution");
                vp = &vtemp;
                vp->flag = DEFINED;
                vp->type = 0;
                vp->areap = ATEMP;
                *vp->name = c;
                if (digit(c)) {
                        for (c = 0; digit(*n); n++)
                                c = c*10 + *n-'0';
                        if (c <= l->argc)
                                /* setstr can't fail here */
                                setstr(vp, l->argv[c], KSH_RETURN_ERROR);
                        vp->flag |= RDONLY;
                        return vp;
                }
                vp->flag |= RDONLY;
                if (n[1] != '\0')
                        return vp;
                vp->flag |= ISSET|INTEGER;
                switch (c) {
                  case '$':
                        vp->val.i = kshpid;
                        break;
                  case '!':
                        /* If no job, expand to nothing */
                        if ((vp->val.i = j_async()) == 0)
                                vp->flag &= ~(ISSET|INTEGER);
                        break;
                  case '?':
                        vp->val.i = exstat;
                        break;
                  case '#':
                        vp->val.i = l->argc;
                        break;
                  case '-':
                        vp->flag &= ~INTEGER;
                        vp->val.s = getoptions();
                        break;
                  default:
                        vp->flag &= ~(ISSET|INTEGER);
                }
                return vp;
        }
        for (l = e->loc; ; l = l->next) {
                vp = mytsearch(&l->vars, n, h);
                if (vp != NULL) {
                        if (array)
                                return arraysearch(vp, val);
                        else
                                return vp;
                }
                if (l->next == NULL)
                        break;
        }
        vp = tenter(&l->vars, n, h);
        if (array)
                vp = arraysearch(vp, val);
        vp->flag |= DEFINED;
        if (special(n))
                vp->flag |= SPECIAL;
        return vp;
}

/*
 * Search for local variable, if not found create locally.
 */
struct tbl *
local(const char *n, bool copy)
{
        struct block *l = e->loc;
        struct tbl *vp;
        unsigned h;
        bool     array;
        int      val;

        /* Check to see if this is an array */
        n = array_index_calc(n, &array, &val);
        h = hash(n);
        if (!letter(*n)) {
                vp = &vtemp;
                vp->flag = DEFINED|RDONLY;
                vp->type = 0;
                vp->areap = ATEMP;
                return vp;
        }
        vp = tenter(&l->vars, n, h);
        if (copy && !(vp->flag & DEFINED)) {
                struct block *ll = l;
                struct tbl *vq = (struct tbl *) 0;

                while ((ll = ll->next) && !(vq = mytsearch(&ll->vars, n, h)))
                        ;
                if (vq) {
                        vp->flag |= vq->flag & (EXPORT|INTEGER|RDONLY
                                                |LJUST|RJUST|ZEROFIL
                                                |LCASEV|UCASEV_AL|INT_U|INT_L);
                        if (vq->flag & INTEGER)
                                vp->type = vq->type;
                        vp->u2.field = vq->u2.field;
                }
        }
        if (array)
                vp = arraysearch(vp, val);
        vp->flag |= DEFINED;
        if (special(n))
                vp->flag |= SPECIAL;
        return vp;
}

/* get variable string value */
char *
str_val(vp)
        struct tbl *vp;
{
        char *s;

        if ((vp->flag&SPECIAL))
                getspec(vp);
        if (!(vp->flag&ISSET))
                s = null;               /* special to dollar() */
        else if (!(vp->flag&INTEGER))   /* string source */
                s = vp->val.s + vp->type;
        else {                          /* integer source */
                /* worst case number length is when base=2, so use BITS(long) */
                             /* minus base #     number    null */
                static char strbuf[1 + 2 + 1 + BITS(long) + 1];
                const char *digits = (vp->flag & UCASEV_AL) ?
                                  "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                : "0123456789abcdefghijklmnopqrstuvwxyz";
                unsigned long n;
                int base;

                s = strbuf + sizeof(strbuf);
                if (vp->flag & INT_U)
                        n = (unsigned long) vp->val.i;
                else
                        n = (vp->val.i < 0) ? -vp->val.i : vp->val.i;
                base = (vp->type == 0) ? 10 : vp->type;

                *--s = '\0';
                do {
                        *--s = digits[n % base];
                        n /= base;
                } while (n != 0);
                if (base != 10) {
                        *--s = '#';
                        *--s = digits[base % 10];
                        if (base >= 10)
                                *--s = digits[base / 10];
                }
                if (!(vp->flag & INT_U) && vp->val.i < 0)
                        *--s = '-';
                if (vp->flag & (RJUST|LJUST)) { /* case already dealt with */
                        s = formatstr(vp, s);
                        (void)strlcpy(strbuf, s, sizeof(strbuf));
                        afree(s, ATEMP);
                        s = strbuf;
                }
        }
        return s;
}

/* get variable integer value, with error checking */
long
intval(vp)
        struct tbl *vp;
{
        long num;
        int base;

        base = getint(vp, &num);
        if (base == -1)
                /* XXX check calls - is error here ok by POSIX? */
                errorf("%s: bad number", str_val(vp));
        return num;
}

/* set variable to string value */
int
setstr(vq, s, error_ok)
        struct tbl *vq;
        const char *s;
        int error_ok;
{
        char *fs = NULL;
        int no_ro_check = error_ok & 0x4;
        error_ok &= ~0x4;
        if ((vq->flag & RDONLY) && !no_ro_check) {
                warningf(true, "%s: is read only", vq->name);
                if (!error_ok)
                        errorf("%s", null);
                return 0;
        }
        if (!(vq->flag&INTEGER)) { /* string dest */
                if ((vq->flag&ALLOC)) {
                        /* debugging */
                        if (s >= vq->val.s
                            && s <= vq->val.s + strlen(vq->val.s))
                                internal_errorf(true,
                                    "setstr: %s=%s: assigning to self",
                                    vq->name, s);
                        afree((void*)vq->val.s, vq->areap);
                }
                vq->flag &= ~(ISSET|ALLOC);
                vq->type = 0;
                if (s && (vq->flag & (UCASEV_AL|LCASEV|LJUST|RJUST)))
                        s = fs = formatstr(vq, s);
                if ((vq->flag&EXPORT))
                        export(vq, s);
                else {
                        vq->val.s = str_save(s, vq->areap);
                        vq->flag |= ALLOC;
                }
        } else                  /* integer dest */
                if (!v_evaluate(vq, s, error_ok))
                        return 0;
        vq->flag |= ISSET;
        if ((vq->flag&SPECIAL))
                setspec(vq);
        if (fs)
                afree(fs, ATEMP);
        return 1;
}

/* set variable to integer */
void
setint(vq, n)
        struct tbl *vq;
        long n;
{
        if (!(vq->flag&INTEGER)) {
                struct tbl *vp = &vtemp;
                vp->flag = (ISSET|INTEGER);
                vp->type = 0;
                vp->areap = ATEMP;
                vp->val.i = n;
                /* setstr can't fail here */
                setstr(vq, str_val(vp), KSH_RETURN_ERROR);
        } else
                vq->val.i = n;
        vq->flag |= ISSET;
        if ((vq->flag&SPECIAL))
                setspec(vq);
}

int
getint(vp, nump)
        struct tbl *vp;
        long *nump;
{
        char *s;
        int c;
        int base, neg;
        int have_base = 0;
        long num;

        if (vp->flag&SPECIAL)
                getspec(vp);
        /* XXX is it possible for ISSET to be set and val.s to be 0? */
        if (!(vp->flag&ISSET) || (!(vp->flag&INTEGER) && vp->val.s == NULL))
                return -1;
        if (vp->flag&INTEGER) {
                *nump = vp->val.i;
                return vp->type;
        }
        s = vp->val.s + vp->type;
        if (s == NULL)  /* redundant given initial test */
                s = null;
        base = 10;
        num = 0;
        neg = 0;
        if (*s == '-') {
                neg = 1;
                s++;
        }
        if (s[0] == '0' && s[1] == 'x') {
                base = 16;
                have_base = 1;
                s += 2;
        }
        for (c = (unsigned char)*s++; c ; c = (unsigned char)*s++) {
                if (c == '#') {
                        base = (int) num;
                        if (have_base || base < 2 || base > 36)
                                return -1;
                        num = 0;
                        have_base = 1;
                } else if (letnum(c)) {
                        if (isdigit(c))
                                c -= '0';
                        else if (islower(c))
                                c -= 'a' - 10; /* todo: assumes ascii */
                        else if (isupper(c))
                                c -= 'A' - 10; /* todo: assumes ascii */
                        else
                                c = -1; /* _: force error */
                        if (c < 0 || c >= base)
                                return -1;
                        num = num * base + c;
                } else
                        return -1;
        }
        if (neg)
                num = -num;
        *nump = num;
        return base;
}

/* convert variable vq to integer variable, setting its value from vp
 * (vq and vp may be the same)
 */
struct tbl *
setint_v(vq, vp)
        struct tbl *vq, *vp;
{
        int base;
        long num;

        if ((base = getint(vp, &num)) == -1)
                return NULL;
        if (!(vq->flag & INTEGER) && (vq->flag & ALLOC)) {
                vq->flag &= ~ALLOC;
                afree(vq->val.s, vq->areap);
        }
        vq->val.i = num;
        if (vq->type == 0) /* default base */
                vq->type = base;
        vq->flag |= ISSET|INTEGER;
        if (vq->flag&SPECIAL)
                setspec(vq);
        return vq;
}

static char *
formatstr(vp, s)
        struct tbl *vp;
        const char *s;
{
        int olen, nlen;
        char *p, *q;

        olen = strlen(s);

        if (vp->flag & (RJUST|LJUST)) {
                if (!vp->u2.field)      /* default field width */
                        vp->u2.field = olen;
                nlen = vp->u2.field;
        } else
                nlen = olen;

        p = (char *) alloc(nlen + 1, ATEMP);
        if (vp->flag & (RJUST|LJUST)) {
                int slen;

                if (vp->flag & RJUST) {
                        const char *r = s + olen;
                        /* strip trailing spaces (at&t ksh uses q[-1] == ' ') */
                        while (r > s && isspace((unsigned char)r[-1]))
                                --r;
                        slen = r - s;
                        if (slen > vp->u2.field) {
                                s += slen - vp->u2.field;
                                slen = vp->u2.field;
                        }
                        shf_snprintf(p, nlen + 1,
                                ((vp->flag & ZEROFIL) && digit(*s)) ?
                                          "%0*s%.*s" : "%*s%.*s",
                                vp->u2.field - slen, null, slen, s);
                } else {
                        /* strip leading spaces/zeros */
                        while (isspace((unsigned char)*s))
                                s++;
                        if (vp->flag & ZEROFIL)
                                while (*s == '0')
                                        s++;
                        shf_snprintf(p, nlen + 1, "%-*.*s",
                                vp->u2.field, vp->u2.field, s);
                }
        } else
                memcpy(p, s, olen + 1);

        if (vp->flag & UCASEV_AL) {
                for (q = p; *q; q++)
                        if (islower((unsigned char)*q))
                                *q = toupper((unsigned char)*q);
        } else if (vp->flag & LCASEV) {
                for (q = p; *q; q++)
                        if (isupper((unsigned char)*q))
                                *q = tolower((unsigned char)*q);
        }

        return p;
}

/*
 * make vp->val.s be "name=value" for quick exporting.
 */
static void
export(vp, val)
        struct tbl *vp;
        const char *val;
{
        char *xp;
        char *op = (vp->flag&ALLOC) ? vp->val.s : NULL;
        int namelen = strlen(vp->name);
        int vallen = strlen(val) + 1;

        vp->flag |= ALLOC;
        xp = (char*)alloc(namelen + 1 + vallen, vp->areap);
        memcpy(vp->val.s = xp, vp->name, namelen);
        xp += namelen;
        *xp++ = '=';
        vp->type = xp - vp->val.s; /* offset to value */
        memcpy(xp, val, vallen);
        if (op != NULL)
                afree((void*)op, vp->areap);
}

/*
 * lookup variable (according to (set&LOCAL)),
 * set its attributes (INTEGER, RDONLY, EXPORT, TRACE, LJUST, RJUST, ZEROFIL,
 * LCASEV, UCASEV_AL), and optionally set its value if an assignment.
 */
struct tbl *
typeset(var, set, clr, field, base)
        const char *var;
        Tflag clr, set;
        int field, base;
{
        struct tbl *vp;
        struct tbl *vpbase, *t;
        char *tvar;
        const char *val;

        /* check for valid variable name, search for value */
        val = skip_varname(var, false);
        if (val == var)
                return NULL;
        if (*val == '[') {
                int len;

                len = array_ref_len(val);
                if (len == 0)
                        return NULL;
                /* IMPORT is only used when the shell starts up and is
                 * setting up its environment.  Allow only simple array
                 * references at this time since parameter/command substitution
                 * is performed on the [expression], which would be a major
                 * security hole.
                 */
                if (set & IMPORT) {
                        int i;
                        for (i = 1; i < len - 1; i++)
                                if (!digit(val[i]))
                                        return NULL;
                }
                val += len;
        }
        if (*val == '=')
                tvar = str_nsave(var, val++ - var, ATEMP);
        else {
                /* Importing from original environment: must have an = */
                if (set & IMPORT)
                        return NULL;
                tvar = (char *) __UNCONST(var);
                val = NULL;
        }

        /* Prevent typeset from creating a local PATH/ENV/SHELL */
        if (Flag(FRESTRICTED) && (strcmp(tvar, "PATH") == 0
                                  || strcmp(tvar, "ENV") == 0
                                  || strcmp(tvar, "SHELL") == 0))
                errorf("%s: restricted", tvar);

        vp = (set&LOCAL) ? local(tvar, (set & LOCAL_COPY) ? true : false)
                : global(tvar);
        set &= ~(LOCAL|LOCAL_COPY);

        vpbase = (vp->flag & ARRAY) ? global(arrayname(var)) : vp;

        /* only allow export flag to be set.  at&t ksh allows any attribute to
         * be changed, which means it can be truncated or modified
         * (-L/-R/-Z/-i).
         */
        if ((vpbase->flag&RDONLY)
            && (val || clr || (set & ~EXPORT)))
                /* XXX check calls - is error here ok by POSIX? */
                errorf("%s: is read only", tvar);
        if (val)
                afree(tvar, ATEMP);

        /* most calls are with set/clr == 0 */
        if (set | clr) {
                int ok = 1;
                /* XXX if x[0] isn't set, there will be problems: need to have
                 * one copy of attributes for arrays...
                 */
                for (t = vpbase; t; t = t->u.array) {
                        int fake_assign;
                        char UNINITIALIZED(*s);
                        char UNINITIALIZED(*free_me);

                        fake_assign = (t->flag & ISSET) && (!val || t != vp)
                                      && ((set & (UCASEV_AL|LCASEV|LJUST|RJUST|ZEROFIL))
                                          || ((t->flag & INTEGER) && (clr & INTEGER))
                                          || (!(t->flag & INTEGER) && (set & INTEGER)));
                        if (fake_assign) {
                                if (t->flag & INTEGER) {
                                        s = str_val(t);
                                        free_me = (char *) 0;
                                } else {
                                        s = t->val.s + t->type;
                                        free_me = (t->flag & ALLOC) ? t->val.s
                                                                  : (char *) 0;
                                }
                                t->flag &= ~ALLOC;
                        }
                        if (!(t->flag & INTEGER) && (set & INTEGER)) {
                                t->type = 0;
                                t->flag &= ~ALLOC;
                        }
                        t->flag = (t->flag | set) & ~clr;
                        /* Don't change base if assignment is to be done,
                         * in case assignment fails.
                         */
                        if ((set & INTEGER) && base > 0 && (!val || t != vp))
                                t->type = base;
                        if (set & (LJUST|RJUST|ZEROFIL))
                                t->u2.field = field;
                        if (fake_assign) {
                                if (!setstr(t, s, KSH_RETURN_ERROR)) {
                                        /* Somewhat arbitrary action here:
                                         * zap contents of variable, but keep
                                         * the flag settings.
                                         */
                                        ok = 0;
                                        if (t->flag & INTEGER)
                                                t->flag &= ~ISSET;
                                        else {
                                                if (t->flag & ALLOC)
                                                        afree((void*) t->val.s,
                                                              t->areap);
                                                t->flag &= ~(ISSET|ALLOC);
                                                t->type = 0;
                                        }
                                }
                                if (free_me)
                                        afree((void *) free_me, t->areap);
                        }
                }
                if (!ok)
                    errorf("%s", null);
        }

        if (val != NULL) {
                if (vp->flag&INTEGER) {
                        /* do not zero base before assignment */
                        setstr(vp, val, KSH_UNWIND_ERROR | 0x4);
                        /* Done after assignment to override default */
                        if (base > 0)
                                vp->type = base;
                } else
                        /* setstr can't fail (readonly check already done) */
                        setstr(vp, val, KSH_RETURN_ERROR | 0x4);
        }

        /* only x[0] is ever exported, so use vpbase */
        if ((vpbase->flag&EXPORT) && !(vpbase->flag&INTEGER)
            && vpbase->type == 0)
                export(vpbase, (vpbase->flag&ISSET) ? vpbase->val.s : null);

        return vp;
}

/* Unset a variable.  array_ref is set if there was an array reference in
 * the name lookup (eg, x[2]).
 */
void
unset(vp, array_ref)
        struct tbl *vp;
        int array_ref;
{
        if (vp->flag & ALLOC)
                afree((void*)vp->val.s, vp->areap);
        if ((vp->flag & ARRAY) && !array_ref) {
                struct tbl *a, *tmp;

                /* Free up entire array */
                for (a = vp->u.array; a; ) {
                        tmp = a;
                        a = a->u.array;
                        if (tmp->flag & ALLOC)
                                afree((void *) tmp->val.s, tmp->areap);
                        afree(tmp, tmp->areap);
                }
                vp->u.array = (struct tbl *) 0;
        }
        /* If foo[0] is being unset, the remainder of the array is kept... */
        vp->flag &= SPECIAL | (array_ref ? ARRAY|DEFINED : 0);
        if (vp->flag & SPECIAL)
                unsetspec(vp);  /* responsible for `unspecial'ing var */
}

/* return a pointer to the first char past a legal variable name (returns the
 * argument if there is no legal name, returns * a pointer to the terminating
 * null if whole string is legal).
 */
char *
skip_varname(s, aok)
        const char *s;
        int aok;
{
        int alen;

        if (s && letter(*s)) {
                while (*++s && letnum(*s))
                        ;
                if (aok && *s == '[' && (alen = array_ref_len(s)))
                        s += alen;
        }
        return (char *) __UNCONST(s);
}

/* Return a pointer to the first character past any legal variable name.  */
char *
skip_wdvarname(s, aok)
        const char *s;
        int aok;        /* skip array de-reference? */
{
        if (s[0] == CHAR && letter(s[1])) {
                do
                        s += 2;
                while (s[0] == CHAR && letnum(s[1]));
                if (aok && s[0] == CHAR && s[1] == '[') {
                        /* skip possible array de-reference */
                        const char *p = s;
                        char c;
                        int depth = 0;

                        while (1) {
                                if (p[0] != CHAR)
                                        break;
                                c = p[1];
                                p += 2;
                                if (c == '[')
                                        depth++;
                                else if (c == ']' && --depth == 0) {
                                        s = p;
                                        break;
                                }
                        }
                }
        }
        return (char *) __UNCONST(s);
}

/* Check if coded string s is a variable name */
int
is_wdvarname(s, aok)
        const char *s;
        int aok;
{
        char *p = skip_wdvarname(s, aok);

        return p != s && p[0] == EOS;
}

/* Check if coded string s is a variable assignment */
int
is_wdvarassign(s)
        const char *s;
{
        char *p = skip_wdvarname(s, true);

        return p != s && p[0] == CHAR && p[1] == '=';
}

/*
 * Make the exported environment from the exported names in the dictionary.
 */
char **
makenv()
{
        struct block *l = e->loc;
        XPtrV env;
        struct tbl *vp, **vpp;
        int i;

        XPinit(env, 64);
        for (l = e->loc; l != NULL; l = l->next)
                for (vpp = l->vars.tbls, i = l->vars.size; --i >= 0; )
                        if ((vp = *vpp++) != NULL
                            && (vp->flag&(ISSET|EXPORT)) == (ISSET|EXPORT)) {
                                struct block *l2;
                                struct tbl *vp2;
                                unsigned h = hash(vp->name);

                                /* unexport any redefined instances */
                                for (l2 = l->next; l2 != NULL; l2 = l2->next) {
                                        vp2 = mytsearch(&l2->vars, vp->name, h);
                                        if (vp2 != NULL)
                                                vp2->flag &= ~EXPORT;
                                }
                                if ((vp->flag&INTEGER)) {
                                        /* integer to string */
                                        char *val;
                                        val = str_val(vp);
                                        vp->flag &= ~(INTEGER|RDONLY);
                                        /* setstr can't fail here */
                                        setstr(vp, val, KSH_RETURN_ERROR);
                                }
                                XPput(env, vp->val.s);
                        }
        XPput(env, NULL);
        return (char **) XPclose(env);
}

/*
 * Called after a fork in parent to bump the random number generator.
 * Done to ensure children will not get the same random number sequence
 * if the parent doesn't use $RANDOM.
 */
void
change_random()
{
    rand();
}

/*
 * handle special variables with side effects - PATH, SECONDS.
 */

/* Test if name is a special parameter */
static int
special(name)
        const char * name;
{
        struct tbl *tp;

        tp = mytsearch(&specials, name, hash(name));
        return tp && (tp->flag & ISSET) ? tp->type : V_NONE;
}

/* Make a variable non-special */
static void
unspecial(name)
        const char * name;
{
        struct tbl *tp;

        tp = mytsearch(&specials, name, hash(name));
        if (tp)
                mytdelete(tp);
}

#ifdef KSH
static  time_t  seconds;                /* time SECONDS last set */
#endif /* KSH */
static  int     user_lineno;            /* what user set $LINENO to */

static void
getspec(vp)
        struct tbl *vp;
{
        switch (special(vp->name)) {
#ifdef KSH
          case V_SECONDS:
                vp->flag &= ~SPECIAL;
                /* On start up the value of SECONDS is used before seconds
                 * has been set - don't do anything in this case
                 * (see initcoms[] in main.c).
                 */
                if (vp->flag & ISSET)
                        setint(vp, (long) (time((time_t *)0) - seconds));
                vp->flag |= SPECIAL;
                break;
          case V_RANDOM:
                vp->flag &= ~SPECIAL;
                setint(vp, (long) (rand() & 0x7fff));
                vp->flag |= SPECIAL;
                break;
#endif /* KSH */
#ifdef HISTORY
          case V_HISTSIZE:
                vp->flag &= ~SPECIAL;
                setint(vp, (long) histsize);
                vp->flag |= SPECIAL;
                break;
#endif /* HISTORY */
          case V_OPTIND:
                vp->flag &= ~SPECIAL;
                setint(vp, (long) user_opt.uoptind);
                vp->flag |= SPECIAL;
                break;
          case V_LINENO:
                vp->flag &= ~SPECIAL;
                setint(vp, (long) current_lineno + user_lineno);
                vp->flag |= SPECIAL;
                break;
        }
}

static void
setspec(vp)
        struct tbl *vp;
{
        char *s;

        switch (special(vp->name)) {
          case V_PATH:
                if (path)
                        afree(path, APERM);
                path = str_save(str_val(vp), APERM);
                flushcom(1);    /* clear tracked aliases */
                break;
          case V_IFS:
                setctypes(s = str_val(vp), C_IFS);
                ifs0 = *s;
                break;
          case V_OPTIND:
                vp->flag &= ~SPECIAL;
                getopts_reset((int) intval(vp));
                vp->flag |= SPECIAL;
                break;
          case V_POSIXLY_CORRECT:
                change_flag(FPOSIX, OF_SPECIAL, 1);
                break;
          case V_TMPDIR:
                if (tmpdir) {
                        afree(tmpdir, APERM);
                        tmpdir = (char *) 0;
                }
                /* Use tmpdir iff it is an absolute path, is writable and
                 * searchable and is a directory...
                 */
                {
                        struct stat statb;
                        s = str_val(vp);
                        if (ISABSPATH(s) && eaccess(s, W_OK|X_OK) == 0
                            && stat(s, &statb) == 0 && S_ISDIR(statb.st_mode))
                                tmpdir = str_save(s, APERM);
                }
                break;
#ifdef HISTORY
          case V_HISTSIZE:
                vp->flag &= ~SPECIAL;
                sethistsize((int) intval(vp));
                vp->flag |= SPECIAL;
                break;
          case V_HISTFILE:
                sethistfile(str_val(vp));
                break;
#endif /* HISTORY */
#ifdef EDIT
          case V_VISUAL:
                set_editmode(str_val(vp));
                break;
          case V_EDITOR:
                if (!(global("VISUAL")->flag & ISSET))
                        set_editmode(str_val(vp));
                break;
          case V_COLUMNS:
                if ((x_cols = intval(vp)) <= MIN_COLS)
                        x_cols = MIN_COLS;
                break;
#endif /* EDIT */
#ifdef KSH
          case V_MAIL:
                mbset(str_val(vp));
                break;
          case V_MAILPATH:
                mpset(str_val(vp));
                break;
          case V_MAILCHECK:
                vp->flag &= ~SPECIAL;
                mcset(intval(vp));
                vp->flag |= SPECIAL;
                break;
          case V_RANDOM:
                vp->flag &= ~SPECIAL;
                srand((unsigned int)intval(vp));
                vp->flag |= SPECIAL;
                break;
          case V_SECONDS:
                vp->flag &= ~SPECIAL;
                seconds = time((time_t*) 0) - intval(vp);
                vp->flag |= SPECIAL;
                break;
          case V_TMOUT:
                /* at&t ksh seems to do this (only listen if integer) */
                if (vp->flag & INTEGER)
                        ksh_tmout = vp->val.i >= 0 ? vp->val.i : 0;
                break;
#endif /* KSH */
          case V_LINENO:
                vp->flag &= ~SPECIAL;
                /* The -1 is because line numbering starts at 1. */
                user_lineno = (unsigned int) intval(vp) - current_lineno - 1;
                vp->flag |= SPECIAL;
                break;
        }
}

static void
unsetspec(vp)
        struct tbl *vp;
{
        switch (special(vp->name)) {
          case V_PATH:
                if (path)
                        afree(path, APERM);
                path = str_save(def_path, APERM);
                flushcom(1);    /* clear tracked aliases */
                break;
          case V_IFS:
                setctypes(" \t\n", C_IFS);
                ifs0 = ' ';
                break;
          case V_TMPDIR:
                /* should not become unspecial */
                if (tmpdir) {
                        afree(tmpdir, APERM);
                        tmpdir = (char *) 0;
                }
                break;
#ifdef KSH
          case V_MAIL:
                mbset((char *) 0);
                break;
          case V_MAILPATH:
                mpset((char *) 0);
                break;
#endif /* KSH */

          case V_LINENO:
#ifdef KSH
          case V_MAILCHECK:     /* at&t ksh leaves previous value in place */
          case V_RANDOM:
          case V_SECONDS:
          case V_TMOUT:         /* at&t ksh leaves previous value in place */
#endif /* KSH */
                unspecial(vp->name);
                break;

          /* at&t ksh man page says OPTIND, OPTARG and _ lose special meaning,
           * but OPTARG does not (still set by getopts) and _ is also still
           * set in various places.
           * Don't know what at&t does for:
           *            MAIL, MAILPATH, HISTSIZE, HISTFILE,
           * Unsetting these in at&t ksh does not lose the `specialness':
           *    no effect: IFS, COLUMNS, PATH, TMPDIR,
           *            VISUAL, EDITOR,
           * pdkshisms: no effect:
           *            POSIXLY_CORRECT (use set +o posix instead)
           */
        }
}

/*
 * Search for (and possibly create) a table entry starting with
 * vp, indexed by val.
 */
static struct tbl *
arraysearch(vp, val)
        struct tbl *vp;
        int val;
{
        struct tbl *prev, *curr, *new;
        size_t namelen = strlen(vp->name) + 1;

        vp->flag |= ARRAY|DEFINED;

        /* The table entry is always [0] */
        if (val == 0) {
                vp->index = 0;
                return vp;
        }
        prev = vp;
        curr = vp->u.array;
        while (curr && curr->index < val) {
                prev = curr;
                curr = curr->u.array;
        }
        if (curr && curr->index == val) {
                if (curr->flag&ISSET)
                        return curr;
                else
                        new = curr;
        } else
                new = (struct tbl *)alloc(sizeof(struct tbl) + namelen,
                    vp->areap);
        strlcpy(new->name, vp->name, namelen);
        new->flag = vp->flag & ~(ALLOC|DEFINED|ISSET|SPECIAL);
        new->type = vp->type;
        new->areap = vp->areap;
        new->u2.field = vp->u2.field;
        new->index = val;
        if (curr != new) {              /* not reusing old array entry */
                prev->u.array = new;
                new->u.array = curr;
        }
        return new;
}

/* Return the length of an array reference (eg, [1+2]) - cp is assumed
 * to point to the open bracket.  Returns 0 if there is no matching closing
 * bracket.
 */
int
array_ref_len(cp)
        const char *cp;
{
        const char *s = cp;
        int c;
        int depth = 0;

        while ((c = *s++) && (c != ']' || --depth))
                if (c == '[')
                        depth++;
        if (!c)
                return 0;
        return s - cp;
}

/*
 * Make a copy of the base of an array name
 */
char *
arrayname(str)
        const char *str;
{
        const char *p;

        if ((p = strchr(str, '[')) == 0)
                /* Shouldn't happen, but why worry? */
                return (char *) __UNCONST(str);

        return str_nsave(str, p - str, ATEMP);
}

/* Set (or overwrite, if !reset) the array variable var to the values in vals.
 */
void
set_array(var, reset, vals)
        const char *var;
        int reset;
        char **vals;
{
        struct tbl *vp, *vq;
        int i;

        /* to get local array, use "typeset foo; set -A foo" */
        vp = global(var);

        /* Note: at&t ksh allows set -A but not set +A of a read-only var */
        if ((vp->flag&RDONLY))
                errorf("%s: is read only", var);
        /* This code is quite non-optimal */
        if (reset > 0)
                /* trash existing values and attributes */
                unset(vp, 0);
        /* todo: would be nice for assignment to completely succeed or
         * completely fail.  Only really affects integer arrays:
         * evaluation of some of vals[] may fail...
         */
        for (i = 0; vals[i]; i++) {
                vq = arraysearch(vp, i);
                /* would be nice to deal with errors here... (see above) */
                setstr(vq, vals[i], KSH_RETURN_ERROR);
        }
}