array.c

/*
 * array.c - functions to create, destroy, access, and manipulate arrays
 *	     of strings.
 *
 * Arrays are sparse doubly-linked lists.  An element's index is stored
 * with it.
 *
 * Chet Ramey
 * chet@ins.cwru.edu
 */

/* Copyright (C) 1997-2023 Free Software Foundation, Inc.

   This file is part of GNU Bash, the Bourne Again SHell.

   Bash 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.

   Bash 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 Bash.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "config.h"

#if defined (ARRAY_VARS)

#if defined (HAVE_UNISTD_H)
#  ifdef _MINIX
#    include <sys/types.h>
#  endif
#  include <unistd.h>
#endif

#include <stdio.h>
#include "bashansi.h"

#include "shell.h"
#include "array.h"
#include "builtins/common.h"

#define ADD_BEFORE(ae, new) \
	do { \
		ae->prev->next = new; \
		new->prev = ae->prev; \
		ae->prev = new; \
		new->next = ae; \
	} while(0)
	
#define ADD_AFTER(ae, new) \
	do { \
		ae->next->prev = new; \
		new->next = ae->next; \
		new->prev = ae; \
		ae->next = new; \
	} while (0)

static char *array_to_string_internal (ARRAY_ELEMENT *, ARRAY_ELEMENT *, char *, int);

static char *spacesep = " ";

#define IS_LASTREF(a)	(a->lastref)

#define LASTREF_START(a, i) \
	(IS_LASTREF(a) && i >= element_index(a->lastref)) ? a->lastref \
						          : element_forw(a->head)

#define LASTREF(a)	(a->lastref ? a->lastref : element_forw(a->head))

#define INVALIDATE_LASTREF(a)	a->lastref = 0
#define SET_LASTREF(a, e)	a->lastref = (e)
#define UNSET_LASTREF(a)	a->lastref = 0;

ARRAY *
array_create(void)
{
	ARRAY	*r;
	ARRAY_ELEMENT	*head;

	r = (ARRAY *)xmalloc(sizeof(ARRAY));
	r->max_index = -1;
	r->num_elements = 0;
	r->lastref = (ARRAY_ELEMENT *)0;
	head = array_create_element(-1, (char *)NULL);	/* dummy head */
	head->prev = head->next = head;
	r->head = head;
	return(r);
}

void
array_flush (ARRAY *a)
{
	register ARRAY_ELEMENT *r, *r1;

	if (a == 0)
		return;
	for (r = element_forw(a->head); r != a->head; ) {
		r1 = element_forw(r);
		array_dispose_element(r);
		r = r1;
	}
	a->head->next = a->head->prev = a->head;
	a->max_index = -1;
	a->num_elements = 0;
	INVALIDATE_LASTREF(a);
}

void
array_dispose(ARRAY *a)
{
	if (a == 0)
		return;
	array_flush (a);
	array_dispose_element(a->head);
	free(a);
}

ARRAY *
array_copy(ARRAY *a)
{
	ARRAY	*a1;
	ARRAY_ELEMENT	*ae, *new;

	if (a == 0)
		return((ARRAY *) NULL);
	a1 = array_create();
	a1->max_index = a->max_index;
	a1->num_elements = a->num_elements;
	for (ae = element_forw(a->head); ae != a->head; ae = element_forw(ae)) {
		new = array_create_element(element_index(ae), element_value(ae));
		ADD_BEFORE(a1->head, new);
		if (ae == LASTREF(a))
			SET_LASTREF(a1, new);
	}
	return(a1);
}

/*
 * Make and return a new array composed of the elements in array A from
 * S to E, inclusive.
 */
ARRAY *
array_slice(ARRAY *array, ARRAY_ELEMENT *s, ARRAY_ELEMENT *e)
{
	ARRAY	*a;
	ARRAY_ELEMENT *p, *n;
	int	i;
	arrayind_t mi;

	a = array_create ();

	for (mi = 0, p = s, i = 0; p != e; p = element_forw(p), i++) {
		n = array_create_element (element_index(p), element_value(p));
		ADD_BEFORE(a->head, n);
		mi = element_index(n);
	}
	a->num_elements = i;
	a->max_index = mi;
	return a;
}

/*
 * Walk the array, calling FUNC once for each element, with the array
 * element as the argument.
 */
void
array_walk(ARRAY *a, sh_ae_map_func_t *func, void *udata)
{
	register ARRAY_ELEMENT *ae;

	if (a == 0 || array_empty(a))
		return;
	for (ae = element_forw(a->head); ae != a->head; ae = element_forw(ae))
		if ((*func)(ae, udata) < 0)
			return;
}

/*
 * Shift the array A N elements to the left.  Delete the first N elements
 * and subtract N from the indices of the remaining elements.  If FLAGS
 * does not include AS_DISPOSE, this returns a singly-linked null-terminated
 * list of elements so the caller can dispose of the chain.  If FLAGS
 * includes AS_DISPOSE, this function disposes of the shifted-out elements
 * and returns NULL.
 */
ARRAY_ELEMENT *
array_shift(ARRAY *a, int n, int flags)
{
	register ARRAY_ELEMENT *ae, *ret;
	register int i;

	if (a == 0 || array_empty(a) || n <= 0)
		return ((ARRAY_ELEMENT *)NULL);

	INVALIDATE_LASTREF(a);
	for (i = 0, ret = ae = element_forw(a->head); ae != a->head && i < n; ae = element_forw(ae), i++)
		;
	if (ae == a->head) {
		/* Easy case; shifting out all of the elements */
		if (flags & AS_DISPOSE) {
			array_flush (a);
			return ((ARRAY_ELEMENT *)NULL);
		}
		for (ae = ret; element_forw(ae) != a->head; ae = element_forw(ae))
			;
		element_forw(ae) = (ARRAY_ELEMENT *)NULL;
		a->head->next = a->head->prev = a->head;
		a->max_index = -1;
		a->num_elements = 0;
		return ret;
	}
	/*
	 * ae now points to the list of elements we want to retain.
	 * ret points to the list we want to either destroy or return.
	 */
	ae->prev->next = (ARRAY_ELEMENT *)NULL;		/* null-terminate RET */

	a->head->next = ae;		/* slice RET out of the array */
	ae->prev = a->head;

	for ( ; ae != a->head; ae = element_forw(ae))
		element_index(ae) -= n;	/* renumber retained indices */

	a->num_elements -= n;		/* modify bookkeeping information */
	a->max_index = element_index(a->head->prev);

	if (flags & AS_DISPOSE) {
		for (ae = ret; ae; ) {
			ret = element_forw(ae);
			array_dispose_element(ae);
			ae = ret;
		}
		return ((ARRAY_ELEMENT *)NULL);
	}

	return ret;
}

/*
 * Shift array A right N indices.  If S is non-null, it becomes the value of
 * the new element 0.  Returns the number of elements in the array after the
 * shift.
 */
int
array_rshift (ARRAY *a, int n, char *s)
{
	register ARRAY_ELEMENT	*ae, *new;

	if (a == 0 || (array_empty(a) && s == 0))
		return 0;
	else if (n <= 0)
		return (a->num_elements);

	ae = element_forw(a->head);
	if (s) {
		new = array_create_element(0, s);
		ADD_BEFORE(ae, new);
		a->num_elements++;
		if (array_num_elements(a) == 1)	{	/* array was empty */
			a->max_index = 0;
			return 1;
		}
	}

	/*
	 * Renumber all elements in the array except the one we just added.
	 */
	for ( ; ae != a->head; ae = element_forw(ae))
		element_index(ae) += n;

	a->max_index = element_index(a->head->prev);

	INVALIDATE_LASTREF(a);
	return (a->num_elements);
}

ARRAY_ELEMENT *
array_unshift_element(ARRAY *a)
{
	return (array_shift (a, 1, 0));
}

int
array_shift_element(ARRAY *a, char *v)
{
	return (array_rshift (a, 1, v));
}

ARRAY *
array_quote(ARRAY *array)
{
	ARRAY_ELEMENT	*a;
	char	*t;

	if (array == 0 || array_head(array) == 0 || array_empty(array))
		return (ARRAY *)NULL;
	for (a = element_forw(array->head); a != array->head; a = element_forw(a)) {
		t = quote_string (a->value);
		FREE(a->value);
		a->value = t;
	}
	return array;
}

ARRAY *
array_quote_escapes(ARRAY *array)
{
	ARRAY_ELEMENT	*a;
	char	*t;

	if (array == 0 || array_head(array) == 0 || array_empty(array))
		return (ARRAY *)NULL;
	for (a = element_forw(array->head); a != array->head; a = element_forw(a)) {
		t = quote_escapes (a->value);
		FREE(a->value);
		a->value = t;
	}
	return array;
}

ARRAY *
array_dequote(ARRAY *array)
{
	ARRAY_ELEMENT	*a;
	char	*t;

	if (array == 0 || array_head(array) == 0 || array_empty(array))
		return (ARRAY *)NULL;
	for (a = element_forw(array->head); a != array->head; a = element_forw(a)) {
		t = dequote_string (a->value);
		FREE(a->value);
		a->value = t;
	}
	return array;
}

ARRAY *
array_dequote_escapes(ARRAY *array)
{
	ARRAY_ELEMENT	*a;
	char	*t;

	if (array == 0 || array_head(array) == 0 || array_empty(array))
		return (ARRAY *)NULL;
	for (a = element_forw(array->head); a != array->head; a = element_forw(a)) {
		t = dequote_escapes (a->value);
		FREE(a->value);
		a->value = t;
	}
	return array;
}

ARRAY *
array_remove_quoted_nulls(ARRAY *array)
{
	ARRAY_ELEMENT	*a;

	if (array == 0 || array_head(array) == 0 || array_empty(array))
		return (ARRAY *)NULL;
	for (a = element_forw(array->head); a != array->head; a = element_forw(a))
		a->value = remove_quoted_nulls (a->value);
	return array;
}

/*
 * Return a string whose elements are the members of array A beginning at
 * index START and spanning NELEM members.  Null elements are counted.
 * Since arrays are sparse, unset array elements are not counted.
 */
char *
array_subrange (ARRAY *a, arrayind_t start, arrayind_t nelem, int starsub, int quoted, int pflags)
{
	ARRAY		*a2;
	ARRAY_ELEMENT	*h, *p;
	arrayind_t	i;
	char		*t;
	WORD_LIST	*wl;

	p = a ? array_head (a) : 0;
	if (p == 0 || array_empty (a) || start > array_max_index(a))
		return ((char *)NULL);

	/*
	 * Find element with index START.  If START corresponds to an unset
	 * element (arrays can be sparse), use the first element whose index
	 * is >= START.  If START is < 0, we count START indices back from
	 * the end of A (not elements, even with sparse arrays -- START is an
	 * index).
	 */
	for (p = element_forw(p); p != array_head(a) && start > element_index(p); p = element_forw(p))
		;

	if (p == a->head)
		return ((char *)NULL);

	/* Starting at P, take NELEM elements, inclusive. */
	for (i = 0, h = p; p != a->head && i < nelem; i++, p = element_forw(p))
		;

	a2 = array_slice(a, h, p);

	wl = array_to_word_list(a2);
	array_dispose(a2);
	if (wl == 0)
		return (char *)NULL;
	t = string_list_pos_params(starsub ? '*' : '@', wl, quoted, pflags);	/* XXX */
	dispose_words(wl);

	return t;
}

char *
array_patsub (ARRAY *a, char *pat, char *rep, int mflags)
{
	char	*t;
	int	pchar, qflags, pflags;
	WORD_LIST	*wl, *save;

	if (a == 0 || array_head(a) == 0 || array_empty(a))
		return ((char *)NULL);

	wl = array_to_word_list(a);
	if (wl == 0)
		return (char *)NULL;

	for (save = wl; wl; wl = wl->next) {
		t = pat_subst (wl->word->word, pat, rep, mflags);
		FREE (wl->word->word);
		wl->word->word = t;
	}

	pchar = (mflags & MATCH_STARSUB) == MATCH_STARSUB ? '*' : '@';
	qflags = (mflags & MATCH_QUOTED) == MATCH_QUOTED ? Q_DOUBLE_QUOTES : 0;
	pflags = (mflags & MATCH_ASSIGNRHS) ? PF_ASSIGNRHS : 0;

	t = string_list_pos_params (pchar, save, qflags, pflags);
	dispose_words(save);

	return t;
}

char *
array_modcase (ARRAY *a, char *pat, int modop, int mflags)
{
	char	*t;
	int	pchar, qflags, pflags;
	WORD_LIST	*wl, *save;

	if (a == 0 || array_head(a) == 0 || array_empty(a))
		return ((char *)NULL);

	wl = array_to_word_list(a);
	if (wl == 0)
		return ((char *)NULL);

	for (save = wl; wl; wl = wl->next) {
		t = sh_modcase(wl->word->word, pat, modop);
		FREE(wl->word->word);
		wl->word->word = t;
	}

	pchar = (mflags & MATCH_STARSUB) == MATCH_STARSUB ? '*' : '@';
	qflags = (mflags & MATCH_QUOTED) == MATCH_QUOTED ? Q_DOUBLE_QUOTES : 0;
	pflags = (mflags & MATCH_ASSIGNRHS) ? PF_ASSIGNRHS : 0;

	t = string_list_pos_params (pchar, save, qflags, pflags);
	dispose_words(save);

	return t;
}

/*
 * Allocate and return a new array element with index INDEX and value
 * VALUE.
 */
ARRAY_ELEMENT *
array_create_element(arrayind_t indx, char *value)
{
	ARRAY_ELEMENT *r;

	r = (ARRAY_ELEMENT *)xmalloc(sizeof(ARRAY_ELEMENT));
	r->ind = indx;
	r->value = value ? savestring(value) : (char *)NULL;
	r->next = r->prev = (ARRAY_ELEMENT *) NULL;
	return(r);
}

#ifdef INCLUDE_UNUSED
ARRAY_ELEMENT *
array_copy_element(ARRAY_ELEMENT *ae)
{
	return(ae ? array_create_element(element_index(ae), element_value(ae))
		  : (ARRAY_ELEMENT *) NULL);
}
#endif

void
array_dispose_element(ARRAY_ELEMENT *ae)
{
	if (ae) {
		FREE(ae->value);
		free(ae);
	}
}

/*
 * Add a new element with index I and value V to array A (a[i] = v).
 */
int
array_insert(ARRAY *a, arrayind_t i, char *v)
{
	register ARRAY_ELEMENT *new, *ae, *start;
	arrayind_t startind;
	int direction;

	if (a == 0)
		return(-1);
	new = array_create_element(i, v);
	if (i > array_max_index(a)) {
		/*
		 * Hook onto the end.  This also works for an empty array.
		 * Fast path for the common case of allocating arrays
		 * sequentially.
		 */
		ADD_BEFORE(a->head, new);
		a->max_index = i;
		a->num_elements++;
		SET_LASTREF(a, new);
		return(0);
	} else if (i < array_first_index(a)) {
		/* Hook at the beginning */
		ADD_AFTER(a->head, new);
		a->num_elements++;
		SET_LASTREF(a, new);
		return(0);
	}
#if OPTIMIZE_SEQUENTIAL_ARRAY_ASSIGNMENT
	/*
	 * Otherwise we search for the spot to insert it.  The lastref
	 * handle optimizes the case of sequential or almost-sequential
	 * assignments that are not at the end of the array.
	 */
	start = LASTREF(a);
	/* Use same strategy as array_reference to avoid paying large penalty
	   for semi-random assignment pattern. */
	startind = element_index(start);
	if (i < startind/2) {
		start = element_forw(a->head);
		startind = element_index(start);
		direction = 1;
	} else if (i >= startind) {
		direction = 1;
	} else {
		direction = -1;
	}
#else
	start = element_forw(ae->head);
	startind = element_index(start);
	direction = 1;
#endif
	for (ae = start; ae != a->head; ) {
		if (element_index(ae) == i) {
			/*
			 * Replacing an existing element.
			 */
			free(element_value(ae));
			/* Just swap in the new value */
			ae->value = new->value;
			new->value = 0;
			array_dispose_element(new);
			SET_LASTREF(a, ae);
			return(0);
		} else if (direction == 1 && element_index(ae) > i) {
			ADD_BEFORE(ae, new);
			a->num_elements++;
			SET_LASTREF(a, new);
			return(0);
		} else if (direction == -1 && element_index(ae) < i) {
			ADD_AFTER(ae, new);
			a->num_elements++;
			SET_LASTREF(a, new);
			return(0);
		}
		ae = direction == 1 ? element_forw(ae) : element_back(ae);
	}
	array_dispose_element(new);
	INVALIDATE_LASTREF(a);
	return (-1);		/* problem */
}

/*
 * Delete the element with index I from array A and return it so the
 * caller can dispose of it.
 */
ARRAY_ELEMENT *
array_remove(ARRAY *a, arrayind_t i)
{
	register ARRAY_ELEMENT *ae, *start;
	arrayind_t startind;
	int direction;

	if (a == 0 || array_empty(a))
		return((ARRAY_ELEMENT *) NULL);
	if (i > array_max_index(a) || i < array_first_index(a))
		return((ARRAY_ELEMENT *)NULL);	/* Keep roving pointer into array to optimize sequential access */
	start = LASTREF(a);
	/* Use same strategy as array_reference to avoid paying large penalty
	   for semi-random assignment pattern. */
	startind = element_index(start);
	if (i < startind/2) {
		start = element_forw(a->head);
		startind = element_index(start);
		direction = 1;
	} else if (i >= startind) {
		direction = 1;
	} else {
		direction = -1;
	}
	for (ae = start; ae != a->head; ) {
		if (element_index(ae) == i) {
			ae->next->prev = ae->prev;
			ae->prev->next = ae->next;
			a->num_elements--;
			if (i == array_max_index(a))
				a->max_index = element_index(ae->prev);
#if 0
			INVALIDATE_LASTREF(a);
#else
			if (ae->next != a->head)
				SET_LASTREF(a, ae->next);
			else if (ae->prev != a->head)
				SET_LASTREF(a, ae->prev);
			else
				INVALIDATE_LASTREF(a);
#endif
			return(ae);
		}
		ae = (direction == 1) ? element_forw(ae) : element_back(ae);
		if (direction == 1 && element_index(ae) > i)
			break;
		else if (direction == -1 && element_index(ae) < i)
			break;
	}
	return((ARRAY_ELEMENT *) NULL);
}

/*
 * Return the value of a[i].
 */
char *
array_reference(ARRAY *a, arrayind_t i)
{
	register ARRAY_ELEMENT *ae, *start;
	arrayind_t startind;
	int direction;

	if (a == 0 || array_empty(a))
		return((char *) NULL);
	if (i > array_max_index(a) || i < array_first_index(a))
		return((char *)NULL);	/* Keep roving pointer into array to optimize sequential access */
	start = LASTREF(a);	/* lastref pointer */
	startind = element_index(start);
	if (i < startind/2) {	/* XXX - guess */
		start = element_forw(a->head);
		startind = element_index(start);
		direction = 1;
	} else if (i >= startind) {
		direction = 1;
	} else {
		direction = -1;
	}
	for (ae = start; ae != a->head; ) {
		if (element_index(ae) == i) {
			SET_LASTREF(a, ae);
			return(element_value(ae));
		}
		ae = (direction == 1) ? element_forw(ae) : element_back(ae);
		/* Take advantage of index ordering to short-circuit */
		/* If we don't find it, set the lastref pointer to the element
		   that's `closest', assuming that the unsuccessful reference
		   will quickly be followed by an assignment.  No worse than
		   not changing it from the previous value or resetting it. */
		if (direction == 1 && element_index(ae) > i) {
			start = ae;	/* use for SET_LASTREF below */
			break;
		} else if (direction == -1 && element_index(ae) < i) {
			start = ae;	/* use for SET_LASTREF below */
			break;
		}
	}
#if 0
	UNSET_LASTREF(a);
#else
	SET_LASTREF(a, start);
#endif
	return((char *) NULL);
}

/* Convenience routines for the shell to translate to and from the form used
   by the rest of the code. */

WORD_LIST *
array_to_word_list(ARRAY *a)
{
	WORD_LIST	*list;
	ARRAY_ELEMENT	*ae;

	if (a == 0 || array_empty(a))
		return((WORD_LIST *)NULL);
	list = (WORD_LIST *)NULL;
	for (ae = element_forw(a->head); ae != a->head; ae = element_forw(ae))
		list = make_word_list (make_bare_word(element_value(ae)), list);
	return (REVERSE_LIST(list, WORD_LIST *));
}

ARRAY *
array_from_word_list (WORD_LIST *list)
{
	ARRAY	*a;

	if (list == 0)
		return((ARRAY *)NULL);
	a = array_create();
	return (array_assign_list (a, list));
}

WORD_LIST *
array_keys_to_word_list(ARRAY *a)
{
	WORD_LIST	*list;
	ARRAY_ELEMENT	*ae;
	char		*t;

	if (a == 0 || array_empty(a))
		return((WORD_LIST *)NULL);
	list = (WORD_LIST *)NULL;
	for (ae = element_forw(a->head); ae != a->head; ae = element_forw(ae)) {
		t = itos(element_index(ae));
		list = make_word_list (make_bare_word(t), list);
		free(t);
	}
	return (REVERSE_LIST(list, WORD_LIST *));
}

WORD_LIST *
array_to_kvpair_list(ARRAY *a)
{
	WORD_LIST	*list;
	ARRAY_ELEMENT	*ae;
	char		*k, *v;

	if (a == 0 || array_empty(a))
		return((WORD_LIST *)NULL);
	list = (WORD_LIST *)NULL;
	for (ae = element_forw(a->head); ae != a->head; ae = element_forw(ae)) {
		k = itos(element_index(ae));
		v = element_value(ae);
		list = make_word_list (make_bare_word(k), list);
		list = make_word_list (make_bare_word(v), list);
		free(k);
	}
	return (REVERSE_LIST(list, WORD_LIST *));
}

ARRAY *
array_assign_list (ARRAY *array, WORD_LIST *list)
{
	register WORD_LIST *l;
	register arrayind_t i;

	for (l = list, i = 0; l; l = l->next, i++)
		array_insert(array, i, l->word->word);
	return array;
}

char **
array_to_argv (ARRAY *a, int *countp)
{
	char		**ret, *t;
	int		i;
	ARRAY_ELEMENT	*ae;

	if (a == 0 || array_empty(a)) {
		if (countp)
			*countp = 0;
		return ((char **)NULL);
	}
	ret = strvec_create (array_num_elements (a) + 1);
	i = 0;
	for (ae = element_forw(a->head); ae != a->head; ae = element_forw(ae)) {
		t = element_value (ae);
		if (t)
			ret[i++] = savestring (t);
	}
	ret[i] = (char *)NULL;
	if (countp)
		*countp = i;
	return (ret);
}

ARRAY *
array_from_argv(ARRAY *a, char **vec, int count)
{
  arrayind_t	i;
  ARRAY_ELEMENT	*ae;
  char	*t;

  if (a == 0 || array_num_elements (a) == 0)
    {
      for (i = 0; i < count; i++)
	array_insert (a, i, vec[i]);
      return a;
    }

  /* Fast case */
  if (array_num_elements (a) == count && count == 1)
    {
      ae = element_forw (a->head);
      t = vec[0] ? savestring (vec[0]) : 0;
      ARRAY_ELEMENT_REPLACE (ae, t);
    }
  else if (array_num_elements (a) <= count)
    {
      /* modify in array_num_elements members in place, then add */
      ae = a->head;
      for (i = 0; i < array_num_elements (a); i++)
	{
	  ae = element_forw (ae);
	  t = vec[0] ? savestring (vec[0]) : 0;
	  ARRAY_ELEMENT_REPLACE (ae, t);
	}
      /* add any more */
      for ( ; i < count; i++)
	array_insert (a, i, vec[i]);
    }
  else
    {
      /* deleting elements.  it's faster to rebuild the array. */	  
      array_flush (a);
      for (i = 0; i < count; i++)
	array_insert (a, i, vec[i]);
    }

  return a;
}
	
/*
 * Return a string that is the concatenation of the elements in A from START
 * to END, separated by SEP.
 */
static char *
array_to_string_internal (ARRAY_ELEMENT *start, ARRAY_ELEMENT *end, char *sep, int quoted)
{
	char	*result, *t;
	ARRAY_ELEMENT *ae;
	int	slen, rsize, rlen, reg;

	if (start == end)	/* XXX - should not happen */
		return ((char *)NULL);

	slen = strlen(sep);
	result = NULL;
	for (rsize = rlen = 0, ae = start; ae != end; ae = element_forw(ae)) {
		if (rsize == 0)
			result = (char *)xmalloc (rsize = 64);
		if (element_value(ae)) {
			t = quoted ? quote_string(element_value(ae)) : element_value(ae);
			reg = strlen(t);
			RESIZE_MALLOCED_BUFFER (result, rlen, (reg + slen + 2),
						rsize, rsize);
			strcpy(result + rlen, t);
			rlen += reg;
			if (quoted)
				free(t);
			/*
			 * Add a separator only after non-null elements.
			 */
			if (element_forw(ae) != end) {
				strcpy(result + rlen, sep);
				rlen += slen;
			}
		}
	}
	if (result)
	  result[rlen] = '\0';	/* XXX */
	return(result);
}

char *
array_to_kvpair (ARRAY *a, int quoted)
{
	char	*result, *valstr, *is;
	char	indstr[INT_STRLEN_BOUND(intmax_t) + 1];
	ARRAY_ELEMENT *ae;
	int	rsize, rlen, elen;

	if (a == 0 || array_empty (a))
		return((char *)NULL);

	result = (char *)xmalloc (rsize = 128);
	result[rlen = 0] = '\0';

	for (ae = element_forw(a->head); ae != a->head; ae = element_forw(ae)) {
		is = inttostr (element_index(ae), indstr, sizeof(indstr));
		valstr = element_value (ae) ?
				(ansic_shouldquote (element_value (ae)) ?
				   ansic_quote (element_value(ae), 0, (int *)0) :
				   sh_double_quote (element_value (ae)))
					    : (char *)NULL;
		elen = STRLEN (is) + 8 + STRLEN (valstr);
		RESIZE_MALLOCED_BUFFER (result, rlen, (elen + 1), rsize, rsize);

		strcpy (result + rlen, is);
		rlen += STRLEN (is);
		result[rlen++] = ' ';
		if (valstr) {
			strcpy (result + rlen, valstr);
			rlen += STRLEN (valstr);
		} else {
			strcpy (result + rlen, "\"\"");
			rlen += 2;
		}

		if (element_forw(ae) != a->head)
		  result[rlen++] = ' ';

		FREE (valstr);
	}
	RESIZE_MALLOCED_BUFFER (result, rlen, 1, rsize, 8);
	result[rlen] = '\0';

	if (quoted) {
		/* This is not as efficient as it could be... */
		valstr = sh_single_quote (result);
		free (result);
		result = valstr;
	}
	return(result);
}

char *
array_to_assign (ARRAY *a, int quoted)
{
	char	*result, *valstr, *is;
	char	indstr[INT_STRLEN_BOUND(intmax_t) + 1];
	ARRAY_ELEMENT *ae;
	int	rsize, rlen, elen;

	if (a == 0 || array_empty (a))
		return((char *)NULL);

	result = (char *)xmalloc (rsize = 128);
	result[0] = '(';
	rlen = 1;

	for (ae = element_forw(a->head); ae != a->head; ae = element_forw(ae)) {
		is = inttostr (element_index(ae), indstr, sizeof(indstr));
		valstr = element_value (ae) ?
				(ansic_shouldquote (element_value (ae)) ?
				   ansic_quote (element_value(ae), 0, (int *)0) :
				   sh_double_quote (element_value (ae)))
					    : (char *)NULL;
		elen = STRLEN (is) + 8 + STRLEN (valstr);
		RESIZE_MALLOCED_BUFFER (result, rlen, (elen + 1), rsize, rsize);

		result[rlen++] = '[';
		strcpy (result + rlen, is);
		rlen += STRLEN (is);
		result[rlen++] = ']';
		result[rlen++] = '=';
		if (valstr) {
			strcpy (result + rlen, valstr);
			rlen += STRLEN (valstr);
		}

		if (element_forw(ae) != a->head)
		  result[rlen++] = ' ';

		FREE (valstr);
	}
	RESIZE_MALLOCED_BUFFER (result, rlen, 1, rsize, 8);
	result[rlen++] = ')';
	result[rlen] = '\0';
	if (quoted) {
		/* This is not as efficient as it could be... */
		valstr = sh_single_quote (result);
		free (result);
		result = valstr;
	}
	return(result);
}

char *
array_to_string (ARRAY *a, char *sep, int quoted)
{
	if (a == 0)
		return((char *)NULL);
	if (array_empty(a))
		return(savestring(""));
	return (array_to_string_internal (element_forw(a->head), a->head, sep, quoted));
}

#if defined (INCLUDE_UNUSED) || defined (TEST_ARRAY)
/*
 * Return an array consisting of elements in S, separated by SEP
 */
ARRAY *
array_from_string(char *s, char *sep)
{
	ARRAY	*a;
	WORD_LIST *w;

	if (s == 0)
		return((ARRAY *)NULL);
	w = list_string (s, sep, 0);
	if (w == 0)
		return((ARRAY *)NULL);
	a = array_from_word_list (w);
	return (a);
}
#endif

#if defined (TEST_ARRAY)
/*
 * To make a running version, compile -DTEST_ARRAY and link with:
 * 	xmalloc.o syntax.o lib/malloc/libmalloc.a lib/sh/libsh.a
 */
int interrupt_immediately = 0;

int
signal_is_trapped(int s)
{
	return 0;
}

void
fatal_error(const char *s, ...)
{
	fprintf(stderr, "array_test: fatal memory error\n");
	abort();
}

void
programming_error(const char *s, ...)
{
	fprintf(stderr, "array_test: fatal programming error\n");
	abort();
}

WORD_DESC *
make_bare_word (const char *s)
{
	WORD_DESC *w;

	w = (WORD_DESC *)xmalloc(sizeof(WORD_DESC));
	w->word = s ? savestring(s) : savestring ("");
	w->flags = 0;
	return w;
}

WORD_LIST *
make_word_list(WORD_DESC *x, WORD_LIST *l)
{
	WORD_LIST *w;

	w = (WORD_LIST *)xmalloc(sizeof(WORD_LIST));
	w->word = x;
	w->next = l;
	return w;
}

WORD_LIST *
list_string(char *s, char *t, int i)
{
	char	*r, *a;
	WORD_LIST	*wl;

	if (s == 0)
		return (WORD_LIST *)NULL;
	r = savestring(s);
	wl = (WORD_LIST *)NULL;
	a = strtok(r, t);
	while (a) {
		wl = make_word_list (make_bare_word(a), wl);
		a = strtok((char *)NULL, t);
	}
	return (REVERSE_LIST (wl, WORD_LIST *));
}

GENERIC_LIST *
list_reverse (GENERIC_LIST *list)
{
	register GENERIC_LIST *next, *prev;

	for (prev = 0; list; ) {
		next = list->next;
		list->next = prev;
		prev = list;
		list = next;
	}
	return prev;
}

char *
pat_subst(char *s, char *t, char *u, int i)
{
	return ((char *)NULL);
}

char *
quote_string(char *s)
{
	return savestring(s);
}

void
print_element(ARRAY_ELEMENT *ae)
{
	char	lbuf[INT_STRLEN_BOUND (intmax_t) + 1];

	printf("array[%s] = %s\n",
		inttostr (element_index(ae), lbuf, sizeof (lbuf)),
		element_value(ae));
}

void
print_array(ARRAY *a)
{
	printf("\n");
	array_walk(a, print_element, (void *)NULL);
}

int
main(int c, char **v)
{
	ARRAY	*a, *new_a, *copy_of_a;
	ARRAY_ELEMENT	*ae, *aew;
	char	*s;

	a = array_create();
	array_insert(a, 1, "one");
	array_insert(a, 7, "seven");
	array_insert(a, 4, "four");
	array_insert(a, 1029, "one thousand twenty-nine");
	array_insert(a, 12, "twelve");
	array_insert(a, 42, "forty-two");
	print_array(a);
	s = array_to_string (a, " ", 0);
	printf("s = %s\n", s);
	copy_of_a = array_from_string(s, " ");
	printf("copy_of_a:");
	print_array(copy_of_a);
	array_dispose(copy_of_a);
	printf("\n");
	free(s);
	ae = array_remove(a, 4);
	array_dispose_element(ae);
	ae = array_remove(a, 1029);
	array_dispose_element(ae);
	array_insert(a, 16, "sixteen");
	print_array(a);
	s = array_to_string (a, " ", 0);
	printf("s = %s\n", s);
	copy_of_a = array_from_string(s, " ");
	printf("copy_of_a:");
	print_array(copy_of_a);
	array_dispose(copy_of_a);
	printf("\n");
	free(s);
	array_insert(a, 2, "two");
	array_insert(a, 1029, "new one thousand twenty-nine");
	array_insert(a, 0, "zero");
	array_insert(a, 134, "");
	print_array(a);
	s = array_to_string (a, ":", 0);
	printf("s = %s\n", s);
	copy_of_a = array_from_string(s, ":");
	printf("copy_of_a:");
	print_array(copy_of_a);
	array_dispose(copy_of_a);
	printf("\n");
	free(s);
	new_a = array_copy(a);
	print_array(new_a);
	s = array_to_string (new_a, ":", 0);
	printf("s = %s\n", s);
	copy_of_a = array_from_string(s, ":");
	free(s);
	printf("copy_of_a:");
	print_array(copy_of_a);
	array_shift(copy_of_a, 2, AS_DISPOSE);
	printf("copy_of_a shifted by two:");
	print_array(copy_of_a);
	ae = array_shift(copy_of_a, 2, 0);
	printf("copy_of_a shifted by two:");
	print_array(copy_of_a);
	for ( ; ae; ) {
		aew = element_forw(ae);
		array_dispose_element(ae);
		ae = aew;
	}
	array_rshift(copy_of_a, 1, (char *)0);
	printf("copy_of_a rshift by 1:");
	print_array(copy_of_a);
	array_rshift(copy_of_a, 2, "new element zero");
	printf("copy_of_a rshift again by 2 with new element zero:");
	print_array(copy_of_a);
	s = array_to_assign(copy_of_a, 0);
	printf("copy_of_a=%s\n", s);
	free(s);
	ae = array_shift(copy_of_a, array_num_elements(copy_of_a), 0);
	for ( ; ae; ) {
		aew = element_forw(ae);
		array_dispose_element(ae);
		ae = aew;
	}
	array_dispose(copy_of_a);
	printf("\n");
	array_dispose(a);
	array_dispose(new_a);
}

#endif /* TEST_ARRAY */
#endif /* ARRAY_VARS */