[empserver] / src / lib / common / xundump.c

/*
 *  Empire - A multi-player, client/server Internet based war game.
 *  Copyright (C) 1986-2011, Dave Pare, Jeff Bailey, Thomas Ruschak,
 *                Ken Stevens, Steve McClure, Markus Armbruster
 *
 *  Empire 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 *  ---
 *
 *  See files README, COPYING and CREDITS in the root of the source
 *  tree for related information and legal notices.  It is expected
 *  that future projects/authors will amend these files as needed.
 *
 *  ---
 *
 *  xundump.c: Load back xdump output
 *
 *  Known contributors to this file:
 *     Ron Koenderink, 2005
 *     Markus Armbruster, 2005-2011
 */

/*
 * See doc/xdump!  And keep it up-to-date.
 *
 * Parsing of machine-readable xdump is not precise: it recognizes
 * comments, accepts whitespace in place of single space, and accepts
 * the full human-readable field syntax instead of its machine-
 * readable subset.
 *
 * FIXME:
 * - Normalize terminology: table/rows/columns or file/records/fields
 * - Loading tables with NSC_STRING elements more than once leaks memory
 * TODO:
 * - Check EFF_CFG tables are dense
 * - Symbolic array indexes
 * - Option to treat missing and unknown fields as warning, not error
 * TODO, but hardly worth the effort:
 * - Permit reordering of array elements
 */

#include <config.h>

#include <ctype.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include "file.h"
#include "match.h"
#include "nsc.h"
#include "optlist.h"
#include "xdump.h"

static char *fname;             /* Name of file being read */
static int lineno;              /* Current line number */

static int cur_type;            /* Current table's file type */
static int partno;              /* Counts from 0..#parts-1 */
static void *cur_obj;           /* The object being read into */
static int cur_id;              /* and its index in the table */
static int cur_obj_is_blank;
static unsigned char *idgap;    /* idgap && idgap[ID] iff part#0 lacks ID */
static int idgap_max;           /* FIXME */

static int human;               /* Reading human-readable syntax? */
static int ellipsis;            /* Header ended with ...? */
static int nflds;               /* #fields in input records */
static struct castr **fldca;    /* Map field number to selector */
static int *fldidx;             /* Map field number to index */
static int *caflds;             /* Map selector number to #fields seen */
static int *cafldspp;           /* ditto, in previous parts */
static int may_omit_id;         /* Okay to omit IDs? */
static int may_trunc;           /* Okay to truncate? */

static int gripe(char *, ...) ATTRIBUTE((format (printf, 1, 2)));
static int deffld(int, char *, int);
static int defellipsis(void);
static int chkflds(void);
static int setnum(int, double);
static int setstr(int, char *);
static int xunsymbol(char *, struct castr *, int);
static int setsym(int, char *);
static int mtsymset(int, long *);
static int add2symset(int, long *, char *);
static int xubody(FILE *);
static int xutail(FILE *, struct castr *);

/*
 * Gripe about the current line to stderr, return -1.
 */
static int
gripe(char *fmt, ...)
{
    va_list ap;

    fprintf(stderr, "%s:%d: ", fname, lineno);
    va_start(ap, fmt);
    vfprintf(stderr, fmt, ap);
    va_end(ap);
    putc('\n', stderr);

    return -1;
}

/* Make TYPE the current table.  */
static void
tbl_start(int type)
{
    cur_type = type;
    partno = 0;
    cur_id = -1;
    cur_obj = NULL;
    idgap = NULL;
    idgap_max = 0;
}

/* End the current table.  */
static void
tbl_end(void)
{
    free(idgap);
    tbl_start(EF_BAD);
}

/*
 * Seek to current table's ID-th record.
 * ID must be acceptable.
 * Store it in cur_obj, and set cur_id and cur_obj_is_blank accordingly.
 * Return 0 on success, -1 on failure.
 */
static int
tbl_seek(int id)
{
    struct empfile *ep = &empfile[cur_type];

    cur_obj_is_blank = id >= ep->fids;

    if (id >= ef_nelem(cur_type)) {
        if (!ef_ensure_space(cur_type, id, 1))
            return gripe("Can't put ID %d into table %s", id, ep->name);
    }

    cur_obj = ef_ptr(cur_type, id);
    if (CANT_HAPPEN(!cur_obj))
        return -1;
    cur_id = id;
    return 0;
}

/*
 * Get the next object.
 * Must not have a record index.
 * Store it in cur_obj, and set cur_id and cur_obj_is_blank accordingly.
 * Return 0 on success, -1 on failure.
 */
static int
tbl_next_obj(void)
{
    int max_id = ef_id_limit(cur_type);

    if (cur_id >= max_id)
        return gripe("Too many rows");
    return tbl_seek(cur_id + 1);
}

/*
 * Omit ID1..ID2-1.
 */
static void
omit_ids(int id1, int id2)
{
    int i;

    if (id1 >= id2)
        return;

    idgap = realloc(idgap, (id2 + 1) * sizeof(*idgap));
    for (i = idgap_max; i < id1; i++)
        idgap[i] = 0;
    for (i = id1; i < id2; i++)
        idgap[i] = 1;
    idgap[id2] = 0;
    idgap_max = id2;
}

/*
 * Return the smallest non-omitted ID in ID1..ID2-1 if any, else -1.
 */
static int
expected_id(int id1, int id2)
{
    int i;

    for (i = id1; i < id2; i++) {
        if (i >= idgap_max || !idgap[i])
            return i;
    }
    return -1;
}

/*
 * Get the next object, it has record index ID.
 * Store it in cur_obj, and set cur_id and cur_obj_is_blank accordingly.
 * Ensure we're omitting the same objects as the previous parts.
 * Return 0 on success, -1 on failure.
 */
static int
tbl_skip_to_obj(int id)
{
    struct empfile *ep = &empfile[cur_type];
    int prev_id = cur_id;
    int max_id, exp_id;

    if (partno == 0) {
        if (!may_omit_id && id != cur_id + 1)
            return gripe("Expected %d in field %d", cur_id + 1, 1);
        if (id <= cur_id)
            return gripe("Field %d must be > %d", 1, cur_id);
        max_id = ef_id_limit(cur_type);
        if (id > max_id)
            return gripe("Field %d must be <= %d", 1, max_id);
    } else {
        exp_id = expected_id(cur_id + 1, ep->fids);
        if (exp_id < 0)
            return gripe("Table's first part doesn't have this row");
        else if (id != exp_id)
            return gripe("Expected %d in field %d,"
                         " like in table's first part",
                         exp_id, 1);
    }

    if (tbl_seek(id) < 0)
        return -1;

    if (partno == 0)
        omit_ids(prev_id + 1, id);
    return 0;
}

/*
 * Finish table part.
 * If the table has variable length, truncate it.
 * Else ensure we're omitting the same objects as the previous parts.
 * Return 0 on success, -1 on failure.
 */
static int
tbl_part_done(void)
{
    struct empfile *ep = &empfile[cur_type];
    int exp_id;

    if (cur_id + 1 < ep->fids) {
        if (partno == 0) {
            if (may_trunc) {
                if (!ef_truncate(cur_type, cur_id + 1))
                    return -1;
            } else {
                if (!may_omit_id)
                    return gripe("Expected %d more rows",
                                 ep->fids - (cur_id + 1));
                omit_ids(cur_id + 1, ep->fids);
            }
        } else {
            exp_id = expected_id(cur_id + 1, ep->fids);
            if (exp_id >= 0)
                return gripe("Expected row with %d in field %d,"
                             " like in table's first part",
                             exp_id, 1);
        }
    }

    partno++;
    cur_id = -1;
    cur_obj = NULL;
    return 0;
}

/*
 * Read and ignore field separators from FP.
 * Return first character that is not a field separator.
 */
static int
skipfs(FILE *fp)
{
    int ch;

    do {
        ch = getc(fp);
    } while (ch == ' ' || ch == '\t');

    if (ch == '#') {
        do {
            ch = getc(fp);
        } while (ch != EOF && ch != '\n');
    }

    return ch;
}

/*
 * Decode escape sequences in BUF.
 * Return BUF on success, null pointer on failure.
 */
static char *
xuesc(char *buf)
{
    char *src, *dst;
    int octal_chr, n;

    dst = buf;
    src = buf;
    while (*src) {
        if (*src == '\\') {
            if (sscanf(++src, "%3o%n", &octal_chr, &n) != 1 || n != 3)
                return NULL;
            *dst++ = (char)octal_chr;
            src += 3;
        } else
            *dst++ = *src++;
    }
    *dst = '\0';
    return buf;
}

/*
 * Read an identifier from FP into BUF.
 * BUF must have space for 1024 characters.
 * Return number of characters read on success, -1 on failure.
 */
static int
getid(FILE *fp, char *buf)
{
    int n;
    if (fscanf(fp, "%1023[^\"#()<>= \t\n]%n", buf, &n) != 1
        || !isalpha(buf[0]))
        return -1;
    xuesc(buf);
    return n;
}

/*
 * Try to read a field name from FP.
 * I is the field number, counting from zero.
 * If a name is read, set fldca[I] and fldidx[I] for it, and update
 * caflds[].
 * Return 1 if a name or ... was read, 0 on end of line, -1 on error.
 */
static int
xufldname(FILE *fp, int i)
{
    int ch, idx;
    char buf[1024];

    ch = skipfs(fp);
    switch (ch) {
    case EOF:
        return gripe("Unexpected EOF");
    case '\n':
        if (chkflds() < 0)
            return -1;
        lineno++;
        return 0;
    case '.':
        if (getc(fp) != '.' || getc(fp) != '.')
            return gripe("Junk in header field %d", i + 1);
        if (defellipsis() < 0)
            return -1;
        ch = skipfs(fp);
        if (ch != EOF && ch != '\n')
            return gripe("Junk after ...");
        ungetc(ch, fp);
        return 1;
    default:
        ungetc(ch, fp);
        if (getid(fp, buf) < 0)
            return gripe("Junk in header field %d", i + 1);
        ch = getc(fp);
        if (ch != '(') {
            ungetc(ch, fp);
            return deffld(i, buf, -1);
        }
        ch = getc(fp);
        ungetc(ch, fp);
        if (isdigit(ch) || ch == '-' || ch == '+') {
            if (fscanf(fp, "%d", &idx) != 1)
                return gripe("Malformed number in index of header field %d",
                             i + 1);
            if (idx < 0)
                return gripe("Index must not be negative in header field %d",
                             i + 1);
        } else {
            if (getid(fp, buf) < 0)
                return gripe("Malformed index in header field %d", i + 1);
            return gripe("Symbolic index in header field %d not yet implemented",
                         i + 1);
        }
        ch = getc(fp);
        if (ch != ')')
            return gripe("Malformed index in header field %d", i + 1);
        return deffld(i, buf, idx);
    }
}

/*
 * Try to read a field value from FP.
 * I is the field number, counting from zero.
 * Return 1 if a value was read, 0 on end of line, -1 on error.
 */
static int
xufld(FILE *fp, int i)
{
    int ch;
    char buf[1024];
    double dbl;
    long set;

    ch = skipfs(fp);
    switch (ch) {
    case EOF:
        return gripe("Unexpected EOF");
    case '\n':
        CANT_HAPPEN(i > nflds);
        if (i < nflds) {
            if (fldca[i]->ca_type != NSC_STRINGY && fldca[i]->ca_len)
                return gripe("Field %s(%d) missing",
                             fldca[i]->ca_name, fldidx[i]);
            return gripe("Field %s missing", fldca[i]->ca_name);
        }
        lineno++;
        return 0;
    case '+': case '-': case '.':
    case '0': case '1': case '2': case '3': case '4':
    case '5': case '6': case '7': case '8': case '9':
        ungetc(ch, fp);
        if (fscanf(fp, "%lg", &dbl) != 1)
            return gripe("Malformed number in field %d", i + 1);
        return setnum(i, dbl);
    case '"':
        ch = getc(fp);
        if (ch == '"')
            buf[0] = 0;
        else {
            ungetc(ch, fp);
            if (fscanf(fp, "%1023[^\"\n]", buf) != 1 || getc(fp) != '"')
                return gripe("Malformed string in field %d", i + 1);
            if (!xuesc(buf))
                return gripe("Invalid escape sequence in field %d",
                             i + 1);
        }
        return setstr(i, buf);
    case '(':
        if (mtsymset(i, &set) < 0)
            return -1;
        for (;;) {
            ch = skipfs(fp);
            if (ch == EOF || ch == '\n')
                return gripe("Unmatched '(' in field %d", i + 1);
            if (ch == ')')
                break;
            ungetc(ch, fp);
            if (getid(fp, buf) < 0)
                return gripe("Junk in field %d", i + 1);
            if (add2symset(i, &set, buf) < 0)
                return -1;
        }
        return setnum(i, set);
    default:
        ungetc(ch, fp);
        if (getid(fp, buf) < 0)
            return gripe("Junk in field %d", i + 1);
        if (!strcmp(buf, "nil"))
            return setstr(i, NULL);
        else
            return setsym(i, buf);
    }
}

/*
 * Read fields from FP.
 * Use PARSE() to read each field.
 * Return number of fields read on success, -1 on error.
 */
static int
xuflds(FILE *fp, int (*parse)(FILE *, int))
{
    int i, ch, res;

    for (i = 0; ; i++) {
        res = parse(fp, i);
        if (res < 0)
            return -1;
        if (res == 0)
            return i;
        ch = getc(fp);
        if (ch == '\n')
            ungetc(ch, fp);
        else if (ch != ' ' && ch != '\t')
            return gripe("Bad field separator after field %d", i + 1);
    }
}

/*
 * Define the FLDNO-th field.
 * If IDX is negative, define as selector NAME, else as NAME(IDX).
 * Set fldca[FLDNO] and fldidx[FLDNO] accordingly.
 * Update caflds[].
 * Return 1 on success, -1 on error.
 */
static int
deffld(int fldno, char *name, int idx)
{
    struct castr *ca = ef_cadef(cur_type);
    int res;

    res = stmtch(name, ca, offsetof(struct castr, ca_name),
                 sizeof(struct castr));
    if (res < 0)
        return gripe("Header %s of field %d is %s", name, fldno + 1,
                     res == M_NOTUNIQUE ? "ambiguous" : "unknown");
    if ((ca[res].ca_flags & NSC_EXTRA) || CANT_HAPPEN(ca[res].ca_get))
        return gripe("Extraneous header %s in field %d", name, fldno + 1);
    if (ca[res].ca_type != NSC_STRINGY && ca[res].ca_len != 0) {
        if (idx < 0)
            return gripe("Header %s requires an index in field %d",
                         ca[res].ca_name, fldno + 1);
        if (idx >= ca[res].ca_len)
            return gripe("Header %s(%d) index out of bounds in field %d",
                         ca[res].ca_name, idx, fldno + 1);
        if (idx < caflds[res])
            return gripe("Duplicate header %s(%d) in field %d",
                         ca[res].ca_name, idx, fldno + 1);
        if (idx > caflds[res])
            return gripe("Expected header %s(%d) in field %d",
                         ca[res].ca_name, caflds[res], fldno + 1);
    } else {
        if (idx >= 0)
            return gripe("Header %s doesn't take an index in field %d",
                         ca[res].ca_name, fldno + 1);
        idx = 0;
        if (caflds[res])
            return gripe("Duplicate header %s in field %d",
                         ca[res].ca_name, fldno + 1);
    }
    fldca[fldno] = &ca[res];
    fldidx[fldno] = idx;
    caflds[res]++;
    return 1;
}

/*
 * Record that header ends with ...
 * Set ellipsis and is_partial.
 * Return 0 on success, -1 on error.
 */
static int
defellipsis(void)
{
    struct castr *ca = ef_cadef(cur_type);

    if (ca[0].ca_table != cur_type || (ca[0].ca_flags & NSC_EXTRA))
        return gripe("Table %s doesn't support ...", ef_nameof(cur_type));
    ellipsis = 1;
    return 0;
}

/* Is table split into parts? */
static int
is_partial(void)
{
    return ellipsis || partno;
}

/*
 * Check fields in xdump are sane.
 * Return 0 on success, -1 on error.
 */
static int
chkflds(void)
{
    struct castr *ca = ef_cadef(cur_type);
    int i, len, cafldsmax, res = 0;

    /* Record index must come first, to make cur_id work, see setnum() */
    if (ca[0].ca_table == cur_type && caflds[0] && fldca[0] != &ca[0])
        res = gripe("Header field %s must come first", ca[0].ca_name);

    if (is_partial()) {
        /* Need a join field, use 0-th selector */
        if (!caflds[0])
            res = gripe("Header field %s required in each table part",
                        ca[0].ca_name);
    }

    if (ellipsis)
        return res;             /* table is split, another part expected */

    /* Check for missing fields */
    for (i = 0; ca[i].ca_name; i++) {
        cafldsmax = MAX(caflds[i], cafldspp[i]);
        if (ca[i].ca_flags & NSC_EXTRA)
            continue;
        len = ca[i].ca_type != NSC_STRINGY ? ca[i].ca_len : 0;
        if (!len && !cafldsmax)
            res = gripe("Header field %s missing", ca[i].ca_name);
        else if (len && cafldsmax == len - 1)
            res = gripe("Header field %s(%d) missing",
                        ca[i].ca_name, len - 1);
        else if (len && cafldsmax < len - 1)
            res = gripe("Header fields %s(%d) ... %s(%d) missing",
                        ca[i].ca_name, cafldsmax, ca[i].ca_name, len - 1);
    }

    return res;
}

/*
 * Get selector for field FLDNO.
 * Assign the field's selector index to *IDX, unless it is null.
 * Return the selector on success, null pointer on error.
 */
static struct castr *
getfld(int fldno, int *idx)
{
    if (fldno >= nflds) {
        gripe("Too many fields, expected only %d", nflds);
        return NULL;
    }
    if (CANT_HAPPEN(fldno < 0))
        return NULL;
    if (idx)
        *idx = fldidx[fldno];
    return fldca[fldno];
}

/*
 * Is a new value for field FLDNO required to match the old one?
 */
static int
fldval_must_match(int fldno)
{
    struct castr *ca = ef_cadef(cur_type);
    int i = fldca[fldno] - ca;

    /*
     * Value must match if:
     * it's for a const selector, unless the object is still blank, or
     * it was already given in a previous part of a split table.
     */
    return (!cur_obj_is_blank && (fldca[fldno]->ca_flags & NSC_CONST))
        || fldidx[fldno] < cafldspp[i];
}

/*
 * Set value of field FLDNO in current object to DBL.
 * Return 1 on success, -1 on error.
 */
static int
setnum(int fldno, double dbl)
{
    struct castr *ca;
    int next_id, idx;
    char *memb_ptr;
    double old, new;

    ca = getfld(fldno, &idx);
    if (!ca)
        return -1;

    if (fldno == 0) {
        if (ca->ca_table == cur_type) {
            /* Got record index */
            next_id = (int)dbl;
            if (next_id != dbl)
                return gripe("Field %d can't hold this value", fldno + 1);
            if (tbl_skip_to_obj(next_id) < 0)
                return -1;
        } else {
            if (tbl_next_obj() < 0)
                return -1;
        }
    }
    memb_ptr = cur_obj;
    memb_ptr += ca->ca_off;

    switch (ca->ca_type) {
    case NSC_CHAR:
        old = ((signed char *)memb_ptr)[idx];
        new = ((signed char *)memb_ptr)[idx] = (signed char)dbl;
        break;
    case NSC_UCHAR:
    case NSC_HIDDEN:
        old = ((unsigned char *)memb_ptr)[idx];
        new = ((unsigned char *)memb_ptr)[idx] = (unsigned char)dbl;
        break;
    case NSC_SHORT:
        old = ((short *)memb_ptr)[idx];
        new = ((short *)memb_ptr)[idx] = (short)dbl;
        break;
    case NSC_USHORT:
        old = ((unsigned short *)memb_ptr)[idx];
        new = ((unsigned short *)memb_ptr)[idx] = (unsigned short)dbl;
        break;
    case NSC_INT:
        old = ((int *)memb_ptr)[idx];
        new = ((int *)memb_ptr)[idx] = (int)dbl;
        break;
    case NSC_LONG:
        old = ((long *)memb_ptr)[idx];
        new = ((long *)memb_ptr)[idx] = (long)dbl;
        break;
    case NSC_XCOORD:
        old = ((coord *)memb_ptr)[idx];
        /* FIXME use variant of xrel() that takes orig instead of nation */
        if (old >= WORLD_X / 2)
            old -= WORLD_X;
        new = ((coord *)memb_ptr)[idx] = XNORM((coord)dbl);
        if (new >= WORLD_X / 2)
            new -= WORLD_X;
        break;
    case NSC_YCOORD:
        old = ((coord *)memb_ptr)[idx];
        /* FIXME use variant of yrel() that takes orig instead of nation */
        if (old >= WORLD_Y / 2)
            old -= WORLD_Y;
        new = ((coord *)memb_ptr)[idx] = YNORM((coord)dbl);
        if (new >= WORLD_Y / 2)
            new -= WORLD_Y;
        break;
    case NSC_FLOAT:
        old = ((float *)memb_ptr)[idx];
        ((float *)memb_ptr)[idx] = (float)dbl;
        new = dbl;              /* suppress new != dbl check */
        break;
    case NSC_DOUBLE:
        old = ((double *)memb_ptr)[idx];
        ((double *)memb_ptr)[idx] = dbl;
        new = dbl;              /* suppress new != dbl check */
        break;
    case NSC_TIME:
        old = ((time_t *)memb_ptr)[idx];
        new = ((time_t *)memb_ptr)[idx] = (time_t)dbl;
        break;
    default:
        return gripe("Field %d doesn't take numbers", fldno + 1);
    }

    if (fldval_must_match(fldno) && old != dbl)
        return gripe("Value for field %d must be %g", fldno + 1, old);
    if (new != dbl)
        return gripe("Field %d can't hold this value", fldno + 1);

    return 1;
}

/*
 * Set value of field FLDNO in current object to STR.
 * Return 1 on success, -1 on error.
 */
static int
setstr(int fldno, char *str)
{
    struct castr *ca;
    int must_match, idx;
    size_t len;
    char *memb_ptr, *old;

    ca = getfld(fldno, &idx);
    if (!ca)
        return -1;

    if (fldno == 0) {
        if (tbl_next_obj() < 0)
            return -1;
    }
    memb_ptr = cur_obj;
    memb_ptr += ca->ca_off;
    must_match = fldval_must_match(fldno);

    switch (ca->ca_type) {
    case NSC_STRING:
        old = ((char **)memb_ptr)[idx];
        if (!must_match)
            /* FIXME may leak old value */
            ((char **)memb_ptr)[idx] = str ? strdup(str) : NULL;
        len = 65535;            /* really SIZE_MAX, but that's C99 */
        break;
    case NSC_STRINGY:
        if (CANT_HAPPEN(idx))
            return -1;
        if (!str)
            return gripe("Field %d doesn't take nil", fldno + 1);
        len = ca->ca_len;
        if (strlen(str) > len)
            return gripe("Field %d takes at most %d characters",
                         fldno + 1, (int)len);
        old = memb_ptr;
        if (!must_match)
            strncpy(memb_ptr, str, len);
        break;
    default:
        return gripe("Field %d doesn't take strings", fldno + 1);
    }

    if (must_match) {
        if (old && (!str || strncmp(old, str, len)))
            return gripe("Value for field %d must be \"%.*s\"",
                         fldno + 1, (int)len, old);
        if (!old && str)
            return gripe("Value for field %d must be nil", fldno + 1);
    }

    return 1;
}

/*
 * Resolve symbol name ID in table referred to by CA.
 * Use field number N for error messages.
 * Return index in referred table on success, -1 on failure.
 */
static int
xunsymbol(char *id, struct castr *ca, int n)
{
    int i = ef_elt_byname(ca->ca_table, id);
    if (i < 0)
        return gripe("%s %s symbol `%s' in field %d",
                     i == M_NOTUNIQUE ? "Ambiguous" : "Unknown",
                     ca->ca_name, id, n + 1);
    return i;
}

/*
 * Map symbol index to symbol value.
 * CA is the table, and I is the index in it.
 */
static int
symval(struct castr *ca, int i)
{
    int type = ca->ca_table;

    if (type != EF_BAD && ef_cadef(type) == symbol_ca)
        /* symbol table, value is in the table */
        return ((struct symbol *)ef_ptr(type, i))->value;
    /* value is the table index */
    return i;
}

/*
 * Set value of field FLDNO in current object to value of symbol SYM.
 * Return 1 on success, -1 on error.
 */
static int
setsym(int fldno, char *sym)
{
    struct castr *ca;
    int i;

    ca = getfld(fldno, NULL);
    if (!ca)
        return -1;

    if (ca->ca_table == EF_BAD || (ca->ca_flags & NSC_BITS))
        return gripe("Field %d doesn't take symbols", fldno + 1);

    i = xunsymbol(sym, ca, fldno);
    if (i < 0)
        return -1;
    return setnum(fldno, symval(ca, i));
}

/*
 * Create an empty symbol set for field FLDNO in *SET.
 * Return 1 on success, -1 on error.
 */
static int
mtsymset(int fldno, long *set)
{
    struct castr *ca;

    ca = getfld(fldno, NULL);
    if (!ca)
        return -1;

    if (ca->ca_table == EF_BAD || ef_cadef(ca->ca_table) != symbol_ca
        || !(ca->ca_flags & NSC_BITS))
        return gripe("Field %d doesn't take symbol sets", fldno + 1);
    *set = 0;
    return 0;
}

/*
 * Add a symbol to a symbol set for field FLDNO in *SET.
 * SYM is the name of the symbol to add.
 * Return 1 on success, -1 on error.
 */
static int
add2symset(int fldno, long *set, char *sym)
{
    struct castr *ca;
    int i;

    ca = getfld(fldno, NULL);
    if (!ca)
        return -1;

    i = xunsymbol(sym, ca, fldno);
    if (i < 0)
        return -1;
    *set |= symval(ca, i);
    return 0;
}

/*
 * Read an xdump table header line from FP.
 * Expect header for EXPECTED_TABLE, unless it is EF_BAD.
 * Recognize header for machine- and human-readable syntax, and set
 * human accordingly.
 * Return table type on success, -2 on EOF before header, -1 on failure.
 */
static int
xuheader(FILE *fp, int expected_table)
{
    char name[64];
    int res, ch;
    int type;

    while ((ch = skipfs(fp)) == '\n')
        lineno++;
    if (ch == EOF && expected_table == EF_BAD)
        return -2;
    ungetc(ch, fp);

    human = ch == 'c';
    res = -1;
    if ((human
         ? fscanf(fp, "config%*[ \t]%63[^ \t#\n]%n", name, &res) != 1
         : fscanf(fp, "XDUMP%*[ \t]%63[^ \t#\n]%*[ \t]%*[^ \t#\n]%n",
                  name, &res) != 1) || res < 0)
        return gripe("Expected xdump header");

    type = ef_byname(name);
    if (type < 0)
        return gripe("Unknown table `%s'", name);
    if (expected_table != EF_BAD && expected_table != type)
        return gripe("Expected table `%s', not `%s'",
                     ef_nameof(expected_table), name);

    if (!empfile[type].file
        || !ef_cadef(type) || !(ef_flags(type) & EFF_MEM)) {
        CANT_HAPPEN(expected_table != EF_BAD);
        return gripe("Table `%s' is not permitted here", name);
    }

    if (skipfs(fp) != '\n')
        return gripe("Junk after xdump header");
    lineno++;

    return type;
}

/*
 * Find fields in this xdump.
 * If reading human-readable syntax, read a field header line from FP.
 * Else take fields from the table's selectors in CA[].
 * Set ellipsis, nflds, fldca[], fldidx[] and caflds[] accordingly.
 * Return 0 on success, -1 on failure.
 */
static int
xufldhdr(FILE *fp, struct castr ca[])
{
    struct castr **fca;
    int *fidx;
    int ch, i, j, n;

    for (i = 0; ca[i].ca_name; i++)
        caflds[i] = 0;
    ellipsis = 0;

    if (human) {
        while ((ch = skipfs(fp)) == '\n')
            lineno++;
        ungetc(ch, fp);
        nflds = xuflds(fp, xufldname);
        if (nflds < 0)
            return -1;
        nflds -= ellipsis != 0;
    } else {
        fca = fldca;
        fidx = fldidx;

        for (i = 0; ca[i].ca_name; i++) {
            if ((ca[i].ca_flags & NSC_EXTRA))
                continue;
            n = ca[i].ca_type != NSC_STRINGY ? ca[i].ca_len : 0;
            j = 0;
            do {
                *fca++ = &ca[i];
                *fidx++ = j;
            } while (++j < n);
        }

        nflds = fidx - fldidx;
    }

    return 0;
}

/*
 * Read xdump footer from FP.
 * CA[] contains the table's selectors.
 * The body had RECS records.
 * Update cafldspp[] from caflds[].
 * Return 0 on success, -1 on failure.
 */
static int
xufooter(FILE *fp, struct castr ca[], int recs)
{
    int res, n, i;

    res = -1;
    if (human) {
        if (fscanf(fp, "config%n", &res) != 0 || res < 0)
            return gripe("Malformed table footer");
    } else {
        if (fscanf(fp, "%d", &n) != 1)
            return gripe("Malformed table footer");
        if (recs != n)
            return gripe("Read %d rows, which doesn't match footer "
                         "%d rows", recs, n);
    }
    if (skipfs(fp) != '\n')
        return gripe("Junk after table footer");
    if (tbl_part_done() < 0)
        return -1;
    lineno++;

    for (i = 0; ca[i].ca_name; i++) {
        if (cafldspp[i] < caflds[i])
            cafldspp[i] = caflds[i];
    }

    return 0;
}

/*
 * Read an xdump table from FP.
 * Both machine- and human-readable xdump syntax are recognized.
 * Expect table EXPECTED_TABLE, unless it is EF_BAD.
 * Report errors to stderr.
 * Messages assume FP starts in the file FILE at line *PLNO.
 * Update *PLNO to reflect lines read from FP.
 * Return table type on success, -2 on EOF before header, -1 on failure.
 */
int
xundump(FILE *fp, char *file, int *plno, int expected_table)
{
    struct castr *ca;
    int type, nca, nf, i, ch;

    fname = file;
    lineno = *plno;

    if ((type = xuheader(fp, expected_table)) < 0)
        return type;

    ca = ef_cadef(type);
    if (CANT_HAPPEN(!ca))
        return -1;

    nca = nf = 0;
    may_omit_id = 1;
    may_trunc = empfile[type].nent < 0;
    for (i = 0; ca[i].ca_name; i++) {
        nca++;
        if (!(ca[i].ca_flags & NSC_EXTRA)) {
            nf += MAX(1, ca[i].ca_type != NSC_STRINGY ? ca[i].ca_len : 0);
            if (ca[i].ca_flags & NSC_CONST)
                may_omit_id = may_trunc = 0;
        }
    }
    fldca = malloc(nf * sizeof(*fldca));
    fldidx = malloc(nf * sizeof(*fldidx));
    caflds = malloc(nca * sizeof(*caflds));
    cafldspp = calloc(nca, sizeof(*cafldspp));

    tbl_start(type);
    if (xutail(fp, ca) < 0)
        type = EF_BAD;
    tbl_end();

    free(cafldspp);
    free(caflds);
    free(fldidx);
    free(fldca);

    /* Skip empty lines so that callers can easily check for EOF */
    while ((ch = skipfs(fp)) == '\n')
        lineno++;
    ungetc(ch, fp);

    *plno = lineno;
    return type;
}

/*
 * Read the remainder of an xdump after the table header line from FP.
 * CA[] contains the table's selectors.
 * Return 0 on success, -1 on failure.
 */
static int
xutail(FILE *fp, struct castr *ca)
{
    int recs;

    for (;;) {
        if (xufldhdr(fp, ca) < 0)
            return -1;
        if ((recs = xubody(fp)) < 0)
            return -1;
        if (xufooter(fp, ca, recs) < 0)
            return -1;
        if (!ellipsis)
            return 0;
        if (xuheader(fp, cur_type) < 0)
            return -1;
    }
}

/*
 * Read the body of an xdump table from FP.
 * Return number of rows read on success, -1 on failure.
 */
static int
xubody(FILE *fp)
{
    int i, ch;

    for (i = 0;; ++i) {
        while ((ch = skipfs(fp)) == '\n')
            lineno++;
        if (ch == '/')
            break;
        ungetc(ch, fp);
        if (xuflds(fp, xufld) < 0)
            return -1;
    }
    return i;
}