source: vendor/gawk/3.1.5/field.c

/*
 * field.c - routines for dealing with fields and record parsing
 */

/* 
 * Copyright (C) 1986, 1988, 1989, 1991-2005 the Free Software Foundation, Inc.
 * 
 * This file is part of GAWK, the GNU implementation of the
 * AWK Programming Language.
 * 
 * GAWK 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.
 * 
 * GAWK 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */

#include "awk.h"

/*
 * In case that the system doesn't have isblank().
 * Don't bother with autoconf ifdef junk, just force it.
 * See dfa.c and regex_internal.h and regcomp.c. Bleah.
 */
static int
is_blank(int c)
{
        return c == ' ' || c == '\t';
}

typedef void (* Setfunc) P((long, char *, long, NODE *));

static long (*parse_field) P((long, char **, int, NODE *,
                             Regexp *, Setfunc, NODE *));
static void rebuild_record P((void));
static long re_parse_field P((long, char **, int, NODE *,
                             Regexp *, Setfunc, NODE *));
static long def_parse_field P((long, char **, int, NODE *,
                              Regexp *, Setfunc, NODE *));
static long posix_def_parse_field P((long, char **, int, NODE *,
                              Regexp *, Setfunc, NODE *));
static long null_parse_field P((long, char **, int, NODE *,
                             Regexp *, Setfunc, NODE *));
static long sc_parse_field P((long, char **, int, NODE *,
                             Regexp *, Setfunc, NODE *));
static long fw_parse_field P((long, char **, int, NODE *,
                             Regexp *, Setfunc, NODE *));
static void set_element P((long num, char * str, long len, NODE *arr));
static void grow_fields_arr P((long num));
static void set_field P((long num, char *str, long len, NODE *dummy));
static void update_PROCINFO P((char *subscript, char *str));


static char *parse_extent;      /* marks where to restart parse of record */
static long parse_high_water = 0; /* field number that we have parsed so far */
static long nf_high_water = 0;  /* size of fields_arr */
static int resave_fs;
static NODE *save_FS;           /* save current value of FS when line is read,
                                 * to be used in deferred parsing
                                 */
static int *FIELDWIDTHS = NULL;

NODE **fields_arr;              /* array of pointers to the field nodes */
int field0_valid;               /* $(>0) has not been changed yet */
int default_FS;                 /* TRUE when FS == " " */
Regexp *FS_re_yes_case = NULL;
Regexp *FS_re_no_case = NULL;
Regexp *FS_regexp = NULL;
NODE *Null_field = NULL;

/* using_FIELDWIDTHS --- static function, macro to avoid overhead */
#define using_FIELDWIDTHS()     (parse_field == fw_parse_field)

/* init_fields --- set up the fields array to start with */

void
init_fields()
{
        emalloc(fields_arr, NODE **, sizeof(NODE *), "init_fields");
        fields_arr[0] = Nnull_string;
        parse_extent = fields_arr[0]->stptr;
        save_FS = dupnode(FS_node->var_value);
        getnode(Null_field);
        *Null_field = *Nnull_string;
        Null_field->flags |= FIELD;
        Null_field->flags &= ~(NUMCUR|NUMBER|MAYBE_NUM|PERM);
        field0_valid = TRUE;
}

/* grow_fields --- acquire new fields as needed */

static void
grow_fields_arr(long num)
{
        register int t;
        register NODE *n;

        erealloc(fields_arr, NODE **, (num + 1) * sizeof(NODE *), "grow_fields_arr");
        for (t = nf_high_water + 1; t <= num; t++) {
                getnode(n);
                *n = *Null_field;
                fields_arr[t] = n;
        }
        nf_high_water = num;
}

/* set_field --- set the value of a particular field */

/*ARGSUSED*/
static void
set_field(long num,
        char *str,
        long len,
        NODE *dummy ATTRIBUTE_UNUSED)   /* just to make interface same as set_element */
{
        register NODE *n;

        if (num > nf_high_water)
                grow_fields_arr(num);
        n = fields_arr[num];
        n->stptr = str;
        n->stlen = len;
        n->flags = (STRCUR|STRING|MAYBE_NUM|FIELD);
}

/* rebuild_record --- Someone assigned a value to $(something).
                        Fix up $0 to be right */

static void
rebuild_record()
{
        /*
         * use explicit unsigned longs for lengths, in case
         * a size_t isn't big enough.
         */
        register unsigned long tlen;
        register unsigned long ofslen;
        register NODE *tmp;
        NODE *ofs;
        char *ops;
        register char *cops;
        long i;

        assert(NF != -1);

        tlen = 0;
        ofs = force_string(OFS_node->var_value);
        ofslen = ofs->stlen;
        for (i = NF; i > 0; i--) {
                tmp = fields_arr[i];
                tmp = force_string(tmp);
                tlen += tmp->stlen;
        }
        tlen += (NF - 1) * ofslen;
        if ((long) tlen < 0)
                tlen = 0;
        emalloc(ops, char *, tlen + 2, "rebuild_record");
        cops = ops;
        ops[0] = '\0';
        for (i = 1;  i <= NF; i++) {
                tmp = fields_arr[i];
                /* copy field */
                if (tmp->stlen == 1)
                        *cops++ = tmp->stptr[0];
                else if (tmp->stlen != 0) {
                        memcpy(cops, tmp->stptr, tmp->stlen);
                        cops += tmp->stlen;
                }
                /* copy OFS */
                if (i != NF) {
                        if (ofslen == 1)
                                *cops++ = ofs->stptr[0];
                        else if (ofslen != 0) {
                                memcpy(cops, ofs->stptr, ofslen);
                                cops += ofslen;
                        }
                }
        }
        tmp = make_str_node(ops, tlen, ALREADY_MALLOCED);

        /*
         * Since we are about to unref fields_arr[0], we want to find
         * any fields that still point into it, and have them point
         * into the new field zero.  This has to be done intelligently,
         * so that unrefing a field doesn't try to unref into the old $0.
         */
        for (cops = ops, i = 1; i <= NF; i++) {
                if (fields_arr[i]->stlen > 0) {
                        NODE *n;
                        getnode(n);

                        if ((fields_arr[i]->flags & FIELD) == 0) {
                                *n = *Null_field;
                                n->stlen = fields_arr[i]->stlen;
                                if ((fields_arr[i]->flags & (NUMCUR|NUMBER)) != 0) {
                                        n->flags |= (fields_arr[i]->flags & (NUMCUR|NUMBER));
                                        n->numbr = fields_arr[i]->numbr;
                                }
                        } else {
                                *n = *(fields_arr[i]);
                                n->flags &= ~(MALLOC|TEMP|PERM|STRING);
                        }

                        n->stptr = cops;
                        unref(fields_arr[i]);
                        fields_arr[i] = n;
                }
                cops += fields_arr[i]->stlen + ofslen;
        }

        unref(fields_arr[0]);

        fields_arr[0] = tmp;
        field0_valid = TRUE;
}

/*
 * set_record:
 * setup $0, but defer parsing rest of line until reference is made to $(>0)
 * or to NF.  At that point, parse only as much as necessary.
 *
 * Manage a private buffer for the contents of $0.  Doing so keeps us safe
 * if `getline var' decides to rearrange the contents of the IOBUF that
 * $0 might have been pointing into.  The cost is the copying of the buffer;
 * but better correct than fast.
 */
void
set_record(const char *buf, int cnt)
{
        NODE *n;
        static char *databuf;
        static unsigned long databuf_size;
#define INITIAL_SIZE    512
#define MAX_SIZE        ((unsigned long) ~0)    /* maximally portable ... */

        reset_record();

        /* buffer management: */
        if (databuf_size == 0) {        /* first time */
                emalloc(databuf, char *, INITIAL_SIZE, "set_record");
                databuf_size = INITIAL_SIZE;
                memset(databuf, '\0', INITIAL_SIZE);

        }
        /*
         * Make sure there's enough room. Since we sometimes need
         * to place a sentinel at the end, we make sure
         * databuf_size is > cnt after allocation.
         */
        if (cnt >= databuf_size) {
                while (cnt >= databuf_size && databuf_size <= MAX_SIZE)
                        databuf_size *= 2;
                erealloc(databuf, char *, databuf_size, "set_record");
                memset(databuf, '\0', databuf_size);
        }
        /* copy the data */
        memcpy(databuf, buf, cnt);

        /* manage field 0: */
        unref(fields_arr[0]);
        getnode(n);
        n->stptr = databuf;
        n->stlen = cnt;
        n->stref = 1;
        n->type = Node_val;
        n->stfmt = -1;
        n->flags = (STRING|STRCUR|MAYBE_NUM|FIELD);
        fields_arr[0] = n;

#undef INITIAL_SIZE
#undef MAX_SIZE
}

/* reset_record --- start over again with current $0 */

void
reset_record()
{
        register int i;
        NODE *n;

        (void) force_string(fields_arr[0]);

        NF = -1;
        for (i = 1; i <= parse_high_water; i++) {
                unref(fields_arr[i]);
                getnode(n);
                *n = *Null_field;
                fields_arr[i] = n;
        }

        parse_high_water = 0;
        /*
         * $0 = $0 should resplit using the current value of FS.
         */
        if (resave_fs) {
                resave_fs = FALSE;
                unref(save_FS);
                save_FS = dupnode(FS_node->var_value);
        }

        field0_valid = TRUE;
}

/* set_NF --- handle what happens to $0 and fields when NF is changed */

void
set_NF()
{
        register int i;
        NODE *n;

        assert(NF != -1);

        NF = (long) force_number(NF_node->var_value);

        if (NF < 0)
                fatal(_("NF set to negative value"));

        if (NF > nf_high_water)
                grow_fields_arr(NF);
        if (parse_high_water < NF) {
                for (i = parse_high_water + 1; i >= 0 && i <= NF; i++) {
                        unref(fields_arr[i]);
                        getnode(n);
                        *n = *Null_field;
                        fields_arr[i] = n;
                }
        } else if (parse_high_water > 0) {
                for (i = NF + 1; i >= 0 && i <= parse_high_water; i++) {
                        unref(fields_arr[i]);
                        getnode(n);
                        *n = *Null_field;
                        fields_arr[i] = n;
                }
                parse_high_water = NF;
        }
        field0_valid = FALSE;
}

/*
 * re_parse_field --- parse fields using a regexp.
 *
 * This is called both from get_field() and from do_split()
 * via (*parse_field)().  This variation is for when FS is a regular
 * expression -- either user-defined or because RS=="" and FS==" "
 */
static long
re_parse_field(long up_to,      /* parse only up to this field number */
        char **buf,     /* on input: string to parse; on output: point to start next */
        int len,
        NODE *fs ATTRIBUTE_UNUSED,
        Regexp *rp,
        Setfunc set,    /* routine to set the value of the parsed field */
        NODE *n)
{
        register char *scan = *buf;
        register long nf = parse_high_water;
        register char *field;
        register char *end = scan + len;
#ifdef MBS_SUPPORT
        size_t mbclen = 0;
        mbstate_t mbs;
        if (gawk_mb_cur_max > 1)
                memset(&mbs, 0, sizeof(mbstate_t));
#endif

        if (up_to == UNLIMITED)
                nf = 0;
        if (len == 0)
                return nf;

        if (RS_is_null && default_FS)
                while (scan < end && (*scan == ' ' || *scan == '\t' || *scan == '\n'))
                        scan++;
        field = scan;
        while (scan < end
               && research(rp, scan, 0, (end - scan), RE_NEED_START) != -1
               && nf < up_to) {
                if (REEND(rp, scan) == RESTART(rp, scan)) {   /* null match */
#ifdef MBS_SUPPORT
                        if (gawk_mb_cur_max > 1)        {
                                mbclen = mbrlen(scan, end-scan, &mbs);
                                if ((mbclen == 1) || (mbclen == (size_t) -1)
                                        || (mbclen == (size_t) -2) || (mbclen == 0)) {
                                        /* We treat it as a singlebyte character.  */
                                        mbclen = 1;
                                }
                                scan += mbclen;
                        } else
#endif
                        scan++;
                        if (scan == end) {
                                (*set)(++nf, field, (long)(scan - field), n);
                                up_to = nf;
                                break;
                        }
                        continue;
                }
                (*set)(++nf, field,
                       (long)(scan + RESTART(rp, scan) - field), n);
                scan += REEND(rp, scan);
                field = scan;
                if (scan == end)        /* FS at end of record */
                        (*set)(++nf, field, 0L, n);
        }
        if (nf != up_to && scan < end) {
                (*set)(++nf, scan, (long)(end - scan), n);
                scan = end;
        }
        *buf = scan;
        return nf;
}

/*
 * def_parse_field --- default field parsing.
 *
 * This is called both from get_field() and from do_split()
 * via (*parse_field)().  This variation is for when FS is a single space
 * character.
 */

static long
def_parse_field(long up_to,     /* parse only up to this field number */
        char **buf,     /* on input: string to parse; on output: point to start next */
        int len,
        NODE *fs,
        Regexp *rp ATTRIBUTE_UNUSED,
        Setfunc set,    /* routine to set the value of the parsed field */
        NODE *n)
{
        register char *scan = *buf;
        register long nf = parse_high_water;
        register char *field;
        register char *end = scan + len;
        char sav;

        if (up_to == UNLIMITED)
                nf = 0;
        if (len == 0)
                return nf;

        /*
         * Nasty special case. If FS set to "", return whole record
         * as first field. This is not worth a separate function.
         */
        if (fs->stlen == 0) {
                (*set)(++nf, *buf, len, n);
                *buf += len;
                return nf;
        }

        /* before doing anything save the char at *end */
        sav = *end;
        /* because it will be destroyed now: */

        *end = ' ';     /* sentinel character */
        for (; nf < up_to; scan++) {
                /*
                 * special case:  fs is single space, strip leading whitespace 
                 */
                while (scan < end && (*scan == ' ' || *scan == '\t' || *scan == '\n'))
                        scan++;
                if (scan >= end)
                        break;
                field = scan;
                while (*scan != ' ' && *scan != '\t' && *scan != '\n')
                        scan++;
                (*set)(++nf, field, (long)(scan - field), n);
                if (scan == end)
                        break;
        }

        /* everything done, restore original char at *end */
        *end = sav;

        *buf = scan;
        return nf;
}

/*
 * posix_def_parse_field --- default field parsing.
 *
 * This is called both from get_field() and from do_split()
 * via (*parse_field)().  This variation is for when FS is a single space
 * character.  The only difference between this and def_parse_field()
 * is that this one does not allow newlines to separate fields.
 */

static long
posix_def_parse_field(long up_to,       /* parse only up to this field number */
        char **buf,     /* on input: string to parse; on output: point to start next */
        int len,
        NODE *fs,
        Regexp *rp ATTRIBUTE_UNUSED,
        Setfunc set,    /* routine to set the value of the parsed field */
        NODE *n)
{
        register char *scan = *buf;
        register long nf = parse_high_water;
        register char *field;
        register char *end = scan + len;
        char sav;

        if (up_to == UNLIMITED)
                nf = 0;
        if (len == 0)
                return nf;

        /*
         * Nasty special case. If FS set to "", return whole record
         * as first field. This is not worth a separate function.
         */
        if (fs->stlen == 0) {
                (*set)(++nf, *buf, len, n);
                *buf += len;
                return nf;
        }

        /* before doing anything save the char at *end */
        sav = *end;
        /* because it will be destroyed now: */

        *end = ' ';     /* sentinel character */
        for (; nf < up_to; scan++) {
                /*
                 * special case:  fs is single space, strip leading whitespace 
                 */
                while (scan < end && (*scan == ' ' || *scan == '\t'))
                        scan++;
                if (scan >= end)
                        break;
                field = scan;
                while (*scan != ' ' && *scan != '\t')
                        scan++;
                (*set)(++nf, field, (long)(scan - field), n);
                if (scan == end)
                        break;
        }

        /* everything done, restore original char at *end */
        *end = sav;

        *buf = scan;
        return nf;
}

/*
 * null_parse_field --- each character is a separate field
 *
 * This is called both from get_field() and from do_split()
 * via (*parse_field)().  This variation is for when FS is the null string.
 */
static long
null_parse_field(long up_to,    /* parse only up to this field number */
        char **buf,     /* on input: string to parse; on output: point to start next */
        int len,
        NODE *fs ATTRIBUTE_UNUSED,
        Regexp *rp ATTRIBUTE_UNUSED,
        Setfunc set,    /* routine to set the value of the parsed field */
        NODE *n)
{
        register char *scan = *buf;
        register long nf = parse_high_water;
        register char *end = scan + len;

        if (up_to == UNLIMITED)
                nf = 0;
        if (len == 0)
                return nf;

#ifdef MBS_SUPPORT
        if (gawk_mb_cur_max > 1) {
                mbstate_t mbs;
                memset(&mbs, 0, sizeof(mbstate_t));
                for (; nf < up_to && scan < end;) {
                        size_t mbclen = mbrlen(scan, end-scan, &mbs);
                        if ((mbclen == 1) || (mbclen == (size_t) -1)
                                || (mbclen == (size_t) -2) || (mbclen == 0)) {
                                /* We treat it as a singlebyte character.  */
                                mbclen = 1;
                        }
                        (*set)(++nf, scan, mbclen, n);
                        scan += mbclen;
                }
        } else
#endif
        for (; nf < up_to && scan < end; scan++)
                (*set)(++nf, scan, 1L, n);

        *buf = scan;
        return nf;
}

/*
 * sc_parse_field --- single character field separator
 *
 * This is called both from get_field() and from do_split()
 * via (*parse_field)().  This variation is for when FS is a single character
 * other than space.
 */
static long
sc_parse_field(long up_to,      /* parse only up to this field number */
        char **buf,     /* on input: string to parse; on output: point to start next */
        int len,
        NODE *fs,
        Regexp *rp ATTRIBUTE_UNUSED,
        Setfunc set,    /* routine to set the value of the parsed field */
        NODE *n)
{
        register char *scan = *buf;
        register char fschar;
        register long nf = parse_high_water;
        register char *field;
        register char *end = scan + len;
        char sav;
#ifdef MBS_SUPPORT
        size_t mbclen = 0;
        mbstate_t mbs;
        if (gawk_mb_cur_max > 1)
                memset(&mbs, 0, sizeof(mbstate_t));
#endif

        if (up_to == UNLIMITED)
                nf = 0;
        if (len == 0)
                return nf;

        if (RS_is_null && fs->stlen == 0)
                fschar = '\n';
        else
                fschar = fs->stptr[0];

        /* before doing anything save the char at *end */
        sav = *end;
        /* because it will be destroyed now: */
        *end = fschar;  /* sentinel character */

        for (; nf < up_to;) {
                field = scan;
#ifdef MBS_SUPPORT
                if (gawk_mb_cur_max > 1) {
                        while (*scan != fschar) {
                                mbclen = mbrlen(scan, end-scan, &mbs);
                                if ((mbclen == 1) || (mbclen == (size_t) -1)
                                        || (mbclen == (size_t) -2) || (mbclen == 0)) {
                                        /* We treat it as a singlebyte character.  */
                                        mbclen = 1;
                                }
                                scan += mbclen;
                        }
                } else
#endif
                while (*scan != fschar)
                        scan++;
                (*set)(++nf, field, (long)(scan - field), n);
                if (scan == end)
                        break;
                scan++;
                if (scan == end) {      /* FS at end of record */
                        (*set)(++nf, field, 0L, n);
                        break;
                }
        }

        /* everything done, restore original char at *end */
        *end = sav;

        *buf = scan;
        return nf;
}

/*
 * fw_parse_field --- field parsing using FIELDWIDTHS spec
 *
 * This is called from get_field() via (*parse_field)().
 * This variation is for fields are fixed widths.
 */
static long
fw_parse_field(long up_to,      /* parse only up to this field number */
        char **buf,     /* on input: string to parse; on output: point to start next */
        int len,
        NODE *fs ATTRIBUTE_UNUSED,
        Regexp *rp ATTRIBUTE_UNUSED,
        Setfunc set,    /* routine to set the value of the parsed field */
        NODE *n)
{
        register char *scan = *buf;
        register long nf = parse_high_water;
        register char *end = scan + len;

        if (up_to == UNLIMITED)
                nf = 0;
        if (len == 0)
                return nf;
        for (; nf < up_to && (len = FIELDWIDTHS[nf+1]) != -1; ) {
                if (len > end - scan)
                        len = end - scan;
                (*set)(++nf, scan, (long) len, n);
                scan += len;
        }
        if (len == -1)
                *buf = end;
        else
                *buf = scan;
        return nf;
}

/* get_field --- return a particular $n */

/* assign is not NULL if this field is on the LHS of an assign */

NODE **
get_field(register long requested, Func_ptr *assign)
{
        /*
         * if requesting whole line but some other field has been altered,
         * then the whole line must be rebuilt
         */
        if (requested == 0) {
                if (! field0_valid) {
                        /* first, parse remainder of input record */
                        if (NF == -1) {
                                NF = (*parse_field)(UNLIMITED-1, &parse_extent,
                                        fields_arr[0]->stlen -
                                        (parse_extent - fields_arr[0]->stptr),
                                        save_FS, FS_regexp, set_field,
                                        (NODE *) NULL);
                                parse_high_water = NF;
                        }
                        rebuild_record();
                }
                if (assign != NULL)
                        *assign = reset_record;
                return &fields_arr[0];
        }

        /* assert(requested > 0); */

        if (assign != NULL)
                field0_valid = FALSE;           /* $0 needs reconstruction */

        if (requested <= parse_high_water)      /* already parsed this field */
                return &fields_arr[requested];

        if (NF == -1) { /* have not yet parsed to end of record */
                /*
                 * parse up to requested fields, calling set_field() for each,
                 * saving in parse_extent the point where the parse left off
                 */
                if (parse_high_water == 0)      /* starting at the beginning */
                        parse_extent = fields_arr[0]->stptr;
                parse_high_water = (*parse_field)(requested, &parse_extent,
                     fields_arr[0]->stlen - (parse_extent - fields_arr[0]->stptr),
                     save_FS, FS_regexp, set_field, (NODE *) NULL);

                /*
                 * if we reached the end of the record, set NF to the number of
                 * fields so far.  Note that requested might actually refer to
                 * a field that is beyond the end of the record, but we won't
                 * set NF to that value at this point, since this is only a
                 * reference to the field and NF only gets set if the field
                 * is assigned to -- this case is handled below
                 */
                if (parse_extent == fields_arr[0]->stptr + fields_arr[0]->stlen)
                        NF = parse_high_water;
                if (requested == UNLIMITED-1)   /* UNLIMITED-1 means set NF */
                        requested = parse_high_water;
        }
        if (parse_high_water < requested) { /* requested beyond end of record */
                if (assign != NULL) {   /* expand record */
                        if (requested > nf_high_water)
                                grow_fields_arr(requested);

                        NF = requested;
                        parse_high_water = requested;
                } else
                        return &Null_field;
        }

        return &fields_arr[requested];
}

/* set_element --- set an array element, used by do_split() */

static void
set_element(long num, char *s, long len, NODE *n)
{
        register NODE *it;

        it = make_string(s, len);
        it->flags |= MAYBE_NUM;
        *assoc_lookup(n, tmp_number((AWKNUM) (num)), FALSE) = it;
}

/* do_split --- implement split(), semantics are same as for field splitting */

NODE *
do_split(NODE *tree)
{
        NODE *src, *arr, *sep, *fs, *src2, *fs2, *tmp;
        char *s;
        long (*parseit) P((long, char **, int, NODE *,
                         Regexp *, Setfunc, NODE *));
        Regexp *rp = NULL;

        src = force_string(tree_eval(tree->lnode));

        arr = get_param(tree->rnode->lnode);
        if (arr->type != Node_var_array)
                fatal(_("split: second argument is not an array"));

        sep = tree->rnode->rnode->lnode;

        if (src->stlen == 0) {
                /*
                 * Skip the work if first arg is the null string.
                 */
                free_temp(src);
                /*
                 * Evaluate sep if it may have side effects.
                 */
                if ((sep->re_flags & (FS_DFLT|CONST)) == 0)
                        free_temp(tree_eval(sep->re_exp));
                /*
                 * And now we can safely turn off the array.
                 */
                assoc_clear(arr);
                return tmp_number((AWKNUM) 0);
        }

        if ((sep->re_flags & FS_DFLT) != 0 && ! using_FIELDWIDTHS() && ! RS_is_null) {
                parseit = parse_field;
                fs = force_string(FS_node->var_value);
                rp = FS_regexp;
        } else {
                fs = force_string(tree_eval(sep->re_exp));
                if (fs->stlen == 0) {
                        static short warned = FALSE;

                        parseit = null_parse_field;

                        if (do_lint && ! warned) {
                                warned = TRUE;
                                lintwarn(_("split: null string for third arg is a gawk extension"));
                        }
                } else if (fs->stlen == 1 && (sep->re_flags & CONST) == 0) {
                        if (fs->stptr[0] == ' ') {
                                if (do_posix)
                                        parseit = posix_def_parse_field;
                                else
                                        parseit = def_parse_field;
                        } else
                                parseit = sc_parse_field;
                } else {
                        parseit = re_parse_field;
                        rp = re_update(sep);
                }
        }

        /*
         * do dupnode(), to avoid problems like
         *      x = split(a["LINE"], a, a["FS"])
         * since we assoc_clear the array. gack.
         * this also gives us complete call by value semantics.
         */
        src2 = dupnode(src);
        free_temp(src);

        fs2 = dupnode(fs);
        free_temp(fs);

        assoc_clear(arr);

        s = src2->stptr;
        tmp = tmp_number((AWKNUM) (*parseit)(UNLIMITED, &s, (int) src2->stlen,
                                             fs2, rp, set_element, arr));
        unref(src2);
        unref(fs2);
        return tmp;
}

/* set_FIELDWIDTHS --- handle an assignment to FIELDWIDTHS */

void
set_FIELDWIDTHS()
{
        register char *scan;
        char *end;
        register int i;
        static int fw_alloc = 4;
        static int warned = FALSE;
        extern unsigned long strtoul P((const char *, char **endptr, int base));

        if (do_lint && ! warned) {
                warned = TRUE;
                lintwarn(_("`FIELDWIDTHS' is a gawk extension"));
        }
        if (do_traditional)     /* quick and dirty, does the trick */
                return;

        /*
         * If changing the way fields are split, obey least-suprise
         * semantics, and force $0 to be split totally.
         */
        if (fields_arr != NULL)
                (void) get_field(UNLIMITED - 1, 0);

        parse_field = fw_parse_field;
        scan = force_string(FIELDWIDTHS_node->var_value)->stptr;
        end = scan + 1;
        if (FIELDWIDTHS == NULL)
                emalloc(FIELDWIDTHS, int *, fw_alloc * sizeof(int), "set_FIELDWIDTHS");
        FIELDWIDTHS[0] = 0;
        for (i = 1; ; i++) {
                unsigned long int tmp;
                if (i >= fw_alloc) {
                        fw_alloc *= 2;
                        erealloc(FIELDWIDTHS, int *, fw_alloc * sizeof(int), "set_FIELDWIDTHS");
                }
                /* Ensure that there is no leading `-' sign.  Otherwise,
                   strtoul would accept it and return a bogus result.  */
                while (is_blank(*scan)) {
                        ++scan;
                }
                if (*scan == '-')
                        fatal(_("invalid FIELDWIDTHS value, near `%s'"),
                              scan);

                /* Detect an invalid base-10 integer, a valid value that
                   is followed by something other than a blank or '\0',
                   or a value that is not in the range [1..INT_MAX].  */
                errno = 0;
                tmp = strtoul(scan, &end, 10);
                if (errno != 0
                    || !(*end == '\0' || is_blank(*end))
                    || !(0 < tmp && tmp <= INT_MAX))
                        fatal(_("invalid FIELDWIDTHS value, near `%s'"),
                              scan);
                FIELDWIDTHS[i] = tmp;
                scan = end;
                /* Skip past any trailing blanks.  */
                while (is_blank(*scan)) {
                        ++scan;
                }
                if (*scan == '\0')
                        break;
        }
        FIELDWIDTHS[i] = -1;

        update_PROCINFO("FS", "FIELDWIDTHS");
}

/* set_FS --- handle things when FS is assigned to */

void
set_FS()
{
        char buf[10];
        NODE *fs;
        static NODE *save_fs = NULL;
        static NODE *save_rs = NULL;
        int remake_re = TRUE;

        /*
         * If changing the way fields are split, obey least-suprise
         * semantics, and force $0 to be split totally.
         */
        if (fields_arr != NULL)
                (void) get_field(UNLIMITED - 1, 0);

        /* It's possible that only IGNORECASE changed, or FS = FS */
        /*
         * This comparison can't use cmp_nodes(), which pays attention
         * to IGNORECASE, and that's not what we want.
         */
        if (save_fs
                && FS_node->var_value->stlen == save_fs->stlen
                && memcmp(FS_node->var_value->stptr, save_fs->stptr, save_fs->stlen) == 0
                && save_rs
                && RS_node->var_value->stlen == save_rs->stlen
                && memcmp(RS_node->var_value->stptr, save_rs->stptr, save_rs->stlen) == 0) {
                if (FS_regexp != NULL)
                        FS_regexp = (IGNORECASE ? FS_re_no_case : FS_re_yes_case);

                /* FS = FS */
                if (! using_FIELDWIDTHS()) {
                        return;
                } else {
                        remake_re = FALSE;
                        goto choose_fs_function;
                }
        }

        unref(save_fs);
        save_fs = dupnode(FS_node->var_value);
        unref(save_rs);
        save_rs = dupnode(RS_node->var_value);
        resave_fs = TRUE;
        if (FS_regexp != NULL) {
                refree(FS_re_yes_case);
                refree(FS_re_no_case);
                FS_re_yes_case = FS_re_no_case = FS_regexp = NULL;
        }


choose_fs_function:
        buf[0] = '\0';
        default_FS = FALSE;
        fs = force_string(FS_node->var_value);

        if (! do_traditional && fs->stlen == 0) {
                static short warned = FALSE;

                parse_field = null_parse_field;

                if (do_lint && ! warned) {
                        warned = TRUE;
                        lintwarn(_("null string for `FS' is a gawk extension"));
                }
        } else if (fs->stlen > 1) {
                parse_field = re_parse_field;
        } else if (RS_is_null) {
                /* we know that fs->stlen <= 1 */
                parse_field = sc_parse_field;
                if (fs->stlen == 1) {
                        if (fs->stptr[0] == ' ') {
                                default_FS = TRUE;
                                strcpy(buf, "[ \t\n]+");
                        } else if (fs->stptr[0] == '\\') {
                                /* yet another special case */
                                strcpy(buf, "[\\\\\n]");
                        } else if (fs->stptr[0] != '\n')
                                sprintf(buf, "[%c\n]", fs->stptr[0]);
                }
        } else {
                if (do_posix)
                        parse_field = posix_def_parse_field;
                else
                        parse_field = def_parse_field;

                if (fs->stlen == 1) {
                        if (fs->stptr[0] == ' ')
                                default_FS = TRUE;
                        else if (fs->stptr[0] == '\\')
                                /* same special case */
                                strcpy(buf, "[\\\\]");
                        else
                                parse_field = sc_parse_field;
                }
        }
        if (remake_re) {
                if (FS_regexp != NULL) {
                        refree(FS_re_yes_case);
                        refree(FS_re_no_case);
                        FS_re_yes_case = FS_re_no_case = FS_regexp = NULL;
                }

                if (buf[0] != '\0') {
                        FS_re_yes_case = make_regexp(buf, strlen(buf), FALSE, TRUE);
                        FS_re_no_case = make_regexp(buf, strlen(buf), TRUE, TRUE);
                        FS_regexp = (IGNORECASE ? FS_re_no_case : FS_re_yes_case);
                        parse_field = re_parse_field;
                } else if (parse_field == re_parse_field) {
                        FS_re_yes_case = make_regexp(fs->stptr, fs->stlen, FALSE, TRUE);
                        FS_re_no_case = make_regexp(fs->stptr, fs->stlen, TRUE, TRUE);
                        FS_regexp = (IGNORECASE ? FS_re_no_case : FS_re_yes_case);
                } else
                        FS_re_yes_case = FS_re_no_case = FS_regexp = NULL;
        }

        /*
         * For FS = "c", we don't use IGNORECASE. But we must use
         * re_parse_field to get the character and the newline as
         * field separators.
         */
        if (fs->stlen == 1 && parse_field == re_parse_field)
                FS_regexp = FS_re_yes_case;

        update_PROCINFO("FS", "FS");
}

/* using_fieldwidths --- is FS or FIELDWIDTHS in use? */

int
using_fieldwidths()
{
        return using_FIELDWIDTHS();
}

/* update_PROCINFO --- update PROCINFO[sub] when FS or FIELDWIDTHS set */

static void
update_PROCINFO(char *subscript, char *str)
{
        NODE **aptr;

        if (PROCINFO_node == NULL)
                return;

        aptr = assoc_lookup(PROCINFO_node, tmp_string(subscript, strlen(subscript)), FALSE);
        assign_val(aptr, tmp_string(str, strlen(str)));
}