hashtable.c 24.2 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977
/*
 * This implementation is based on code from uClibc-0.9.30.3 but was
 * modified and extended for use within U-Boot.
 *
 * Copyright (C) 2010-2013 Wolfgang Denk <wd@denx.de>
 *
 * Original license header:
 *
 * Copyright (C) 1993, 1995, 1996, 1997, 2002 Free Software Foundation, Inc.
 * This file is part of the GNU C Library.
 * Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1993.
 *
 * SPDX-License-Identifier:	LGPL-2.1+
 */

#include <errno.h>
#include <malloc.h>

#ifdef USE_HOSTCC		/* HOST build */
# include <string.h>
# include <assert.h>
# include <ctype.h>

# ifndef debug
#  ifdef DEBUG
#   define debug(fmt,args...)	printf(fmt ,##args)
#  else
#   define debug(fmt,args...)
#  endif
# endif
#else				/* U-Boot build */
# include <common.h>
# include <linux/string.h>
# include <linux/ctype.h>
#endif

#ifndef	CONFIG_ENV_MIN_ENTRIES	/* minimum number of entries */
#define	CONFIG_ENV_MIN_ENTRIES 64
#endif
#ifndef	CONFIG_ENV_MAX_ENTRIES	/* maximum number of entries */
#define	CONFIG_ENV_MAX_ENTRIES 512
#endif

#include <env_callback.h>
#include <env_flags.h>
#include <search.h>
#include <slre.h>

/*
 * [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
 * [Knuth]	      The Art of Computer Programming, part 3 (6.4)
 */

/*
 * The reentrant version has no static variables to maintain the state.
 * Instead the interface of all functions is extended to take an argument
 * which describes the current status.
 */

typedef struct _ENTRY {
	int used;
	ENTRY entry;
} _ENTRY;


static void _hdelete(const char *key, struct hsearch_data *htab, ENTRY *ep,
	int idx);

/*
 * hcreate()
 */

/*
 * For the used double hash method the table size has to be a prime. To
 * correct the user given table size we need a prime test.  This trivial
 * algorithm is adequate because
 * a)  the code is (most probably) called a few times per program run and
 * b)  the number is small because the table must fit in the core
 * */
static int isprime(unsigned int number)
{
	/* no even number will be passed */
	unsigned int div = 3;

	while (div * div < number && number % div != 0)
		div += 2;

	return number % div != 0;
}

/*
 * Before using the hash table we must allocate memory for it.
 * Test for an existing table are done. We allocate one element
 * more as the found prime number says. This is done for more effective
 * indexing as explained in the comment for the hsearch function.
 * The contents of the table is zeroed, especially the field used
 * becomes zero.
 */

int hcreate_r(size_t nel, struct hsearch_data *htab)
{
	/* Test for correct arguments.  */
	if (htab == NULL) {
		__set_errno(EINVAL);
		return 0;
	}

	/* There is still another table active. Return with error. */
	if (htab->table != NULL)
		return 0;

	/* Change nel to the first prime number not smaller as nel. */
	nel |= 1;		/* make odd */
	while (!isprime(nel))
		nel += 2;

	htab->size = nel;
	htab->filled = 0;

	/* allocate memory and zero out */
	htab->table = (_ENTRY *) calloc(htab->size + 1, sizeof(_ENTRY));
	if (htab->table == NULL)
		return 0;

	/* everything went alright */
	return 1;
}


/*
 * hdestroy()
 */

/*
 * After using the hash table it has to be destroyed. The used memory can
 * be freed and the local static variable can be marked as not used.
 */

void hdestroy_r(struct hsearch_data *htab)
{
	int i;

	/* Test for correct arguments.  */
	if (htab == NULL) {
		__set_errno(EINVAL);
		return;
	}

	/* free used memory */
	for (i = 1; i <= htab->size; ++i) {
		if (htab->table[i].used > 0) {
			ENTRY *ep = &htab->table[i].entry;

			free((void *)ep->key);
			free(ep->data);
		}
	}
	free(htab->table);

	/* the sign for an existing table is an value != NULL in htable */
	htab->table = NULL;
}

/*
 * hsearch()
 */

/*
 * This is the search function. It uses double hashing with open addressing.
 * The argument item.key has to be a pointer to an zero terminated, most
 * probably strings of chars. The function for generating a number of the
 * strings is simple but fast. It can be replaced by a more complex function
 * like ajw (see [Aho,Sethi,Ullman]) if the needs are shown.
 *
 * We use an trick to speed up the lookup. The table is created by hcreate
 * with one more element available. This enables us to use the index zero
 * special. This index will never be used because we store the first hash
 * index in the field used where zero means not used. Every other value
 * means used. The used field can be used as a first fast comparison for
 * equality of the stored and the parameter value. This helps to prevent
 * unnecessary expensive calls of strcmp.
 *
 * This implementation differs from the standard library version of
 * this function in a number of ways:
 *
 * - While the standard version does not make any assumptions about
 *   the type of the stored data objects at all, this implementation
 *   works with NUL terminated strings only.
 * - Instead of storing just pointers to the original objects, we
 *   create local copies so the caller does not need to care about the
 *   data any more.
 * - The standard implementation does not provide a way to update an
 *   existing entry.  This version will create a new entry or update an
 *   existing one when both "action == ENTER" and "item.data != NULL".
 * - Instead of returning 1 on success, we return the index into the
 *   internal hash table, which is also guaranteed to be positive.
 *   This allows us direct access to the found hash table slot for
 *   example for functions like hdelete().
 */

int hmatch_r(const char *match, int last_idx, ENTRY ** retval,
	     struct hsearch_data *htab)
{
	unsigned int idx;
	size_t key_len = strlen(match);

	for (idx = last_idx + 1; idx < htab->size; ++idx) {
		if (htab->table[idx].used <= 0)
			continue;
		if (!strncmp(match, htab->table[idx].entry.key, key_len)) {
			*retval = &htab->table[idx].entry;
			return idx;
		}
	}

	__set_errno(ESRCH);
	*retval = NULL;
	return 0;
}

/*
 * Compare an existing entry with the desired key, and overwrite if the action
 * is ENTER.  This is simply a helper function for hsearch_r().
 */
static inline int _compare_and_overwrite_entry(ENTRY item, ACTION action,
	ENTRY **retval, struct hsearch_data *htab, int flag,
	unsigned int hval, unsigned int idx)
{
	if (htab->table[idx].used == hval
	    && strcmp(item.key, htab->table[idx].entry.key) == 0) {
		/* Overwrite existing value? */
		if ((action == ENTER) && (item.data != NULL)) {
			/* check for permission */
			if (htab->change_ok != NULL && htab->change_ok(
			    &htab->table[idx].entry, item.data,
			    env_op_overwrite, flag)) {
				debug("change_ok() rejected setting variable "
					"%s, skipping it!\n", item.key);
				__set_errno(EPERM);
				*retval = NULL;
				return 0;
			}

			/* If there is a callback, call it */
			if (htab->table[idx].entry.callback &&
			    htab->table[idx].entry.callback(item.key,
			    item.data, env_op_overwrite, flag)) {
				debug("callback() rejected setting variable "
					"%s, skipping it!\n", item.key);
				__set_errno(EINVAL);
				*retval = NULL;
				return 0;
			}

			free(htab->table[idx].entry.data);
			htab->table[idx].entry.data = strdup(item.data);
			if (!htab->table[idx].entry.data) {
				__set_errno(ENOMEM);
				*retval = NULL;
				return 0;
			}
		}
		/* return found entry */
		*retval = &htab->table[idx].entry;
		return idx;
	}
	/* keep searching */
	return -1;
}

int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
	      struct hsearch_data *htab, int flag)
{
	unsigned int hval;
	unsigned int count;
	unsigned int len = strlen(item.key);
	unsigned int idx;
	unsigned int first_deleted = 0;
	int ret;

	/* Compute an value for the given string. Perhaps use a better method. */
	hval = len;
	count = len;
	while (count-- > 0) {
		hval <<= 4;
		hval += item.key[count];
	}

	/*
	 * First hash function:
	 * simply take the modul but prevent zero.
	 */
	hval %= htab->size;
	if (hval == 0)
		++hval;

	/* The first index tried. */
	idx = hval;

	if (htab->table[idx].used) {
		/*
		 * Further action might be required according to the
		 * action value.
		 */
		unsigned hval2;

		if (htab->table[idx].used == -1
		    && !first_deleted)
			first_deleted = idx;

		ret = _compare_and_overwrite_entry(item, action, retval, htab,
			flag, hval, idx);
		if (ret != -1)
			return ret;

		/*
		 * Second hash function:
		 * as suggested in [Knuth]
		 */
		hval2 = 1 + hval % (htab->size - 2);

		do {
			/*
			 * Because SIZE is prime this guarantees to
			 * step through all available indices.
			 */
			if (idx <= hval2)
				idx = htab->size + idx - hval2;
			else
				idx -= hval2;

			/*
			 * If we visited all entries leave the loop
			 * unsuccessfully.
			 */
			if (idx == hval)
				break;

			/* If entry is found use it. */
			ret = _compare_and_overwrite_entry(item, action, retval,
				htab, flag, hval, idx);
			if (ret != -1)
				return ret;
		}
		while (htab->table[idx].used);
	}

	/* An empty bucket has been found. */
	if (action == ENTER) {
		/*
		 * If table is full and another entry should be
		 * entered return with error.
		 */
		if (htab->filled == htab->size) {
			__set_errno(ENOMEM);
			*retval = NULL;
			return 0;
		}

		/*
		 * Create new entry;
		 * create copies of item.key and item.data
		 */
		if (first_deleted)
			idx = first_deleted;

		htab->table[idx].used = hval;
		htab->table[idx].entry.key = strdup(item.key);
		htab->table[idx].entry.data = strdup(item.data);
		if (!htab->table[idx].entry.key ||
		    !htab->table[idx].entry.data) {
			__set_errno(ENOMEM);
			*retval = NULL;
			return 0;
		}

		++htab->filled;

		/* This is a new entry, so look up a possible callback */
		env_callback_init(&htab->table[idx].entry);
		/* Also look for flags */
		env_flags_init(&htab->table[idx].entry);

		/* check for permission */
		if (htab->change_ok != NULL && htab->change_ok(
		    &htab->table[idx].entry, item.data, env_op_create, flag)) {
			debug("change_ok() rejected setting variable "
				"%s, skipping it!\n", item.key);
			_hdelete(item.key, htab, &htab->table[idx].entry, idx);
			__set_errno(EPERM);
			*retval = NULL;
			return 0;
		}

		/* If there is a callback, call it */
		if (htab->table[idx].entry.callback &&
		    htab->table[idx].entry.callback(item.key, item.data,
		    env_op_create, flag)) {
			debug("callback() rejected setting variable "
				"%s, skipping it!\n", item.key);
			_hdelete(item.key, htab, &htab->table[idx].entry, idx);
			__set_errno(EINVAL);
			*retval = NULL;
			return 0;
		}

		/* return new entry */
		*retval = &htab->table[idx].entry;
		return 1;
	}

	__set_errno(ESRCH);
	*retval = NULL;
	return 0;
}


/*
 * hdelete()
 */

/*
 * The standard implementation of hsearch(3) does not provide any way
 * to delete any entries from the hash table.  We extend the code to
 * do that.
 */

static void _hdelete(const char *key, struct hsearch_data *htab, ENTRY *ep,
	int idx)
{
	/* free used ENTRY */
	debug("hdelete: DELETING key \"%s\"\n", key);
	free((void *)ep->key);
	free(ep->data);
	ep->callback = NULL;
	ep->flags = 0;
	htab->table[idx].used = -1;

	--htab->filled;
}

int hdelete_r(const char *key, struct hsearch_data *htab, int flag)
{
	ENTRY e, *ep;
	int idx;

	debug("hdelete: DELETE key \"%s\"\n", key);

	e.key = (char *)key;

	idx = hsearch_r(e, FIND, &ep, htab, 0);
	if (idx == 0) {
		__set_errno(ESRCH);
		return 0;	/* not found */
	}

	/* Check for permission */
	if (htab->change_ok != NULL &&
	    htab->change_ok(ep, NULL, env_op_delete, flag)) {
		debug("change_ok() rejected deleting variable "
			"%s, skipping it!\n", key);
		__set_errno(EPERM);
		return 0;
	}

	/* If there is a callback, call it */
	if (htab->table[idx].entry.callback &&
	    htab->table[idx].entry.callback(key, NULL, env_op_delete, flag)) {
		debug("callback() rejected deleting variable "
			"%s, skipping it!\n", key);
		__set_errno(EINVAL);
		return 0;
	}

	_hdelete(key, htab, ep, idx);

	return 1;
}

/*
 * hexport()
 */

#ifndef CONFIG_SPL_BUILD
/*
 * Export the data stored in the hash table in linearized form.
 *
 * Entries are exported as "name=value" strings, separated by an
 * arbitrary (non-NUL, of course) separator character. This allows to
 * use this function both when formatting the U-Boot environment for
 * external storage (using '\0' as separator), but also when using it
 * for the "printenv" command to print all variables, simply by using
 * as '\n" as separator. This can also be used for new features like
 * exporting the environment data as text file, including the option
 * for later re-import.
 *
 * The entries in the result list will be sorted by ascending key
 * values.
 *
 * If the separator character is different from NUL, then any
 * separator characters and backslash characters in the values will
 * be escaped by a preceeding backslash in output. This is needed for
 * example to enable multi-line values, especially when the output
 * shall later be parsed (for example, for re-import).
 *
 * There are several options how the result buffer is handled:
 *
 * *resp  size
 * -----------
 *  NULL    0	A string of sufficient length will be allocated.
 *  NULL   >0	A string of the size given will be
 *		allocated. An error will be returned if the size is
 *		not sufficient.  Any unused bytes in the string will
 *		be '\0'-padded.
 * !NULL    0	The user-supplied buffer will be used. No length
 *		checking will be performed, i. e. it is assumed that
 *		the buffer size will always be big enough. DANGEROUS.
 * !NULL   >0	The user-supplied buffer will be used. An error will
 *		be returned if the size is not sufficient.  Any unused
 *		bytes in the string will be '\0'-padded.
 */

static int cmpkey(const void *p1, const void *p2)
{
	ENTRY *e1 = *(ENTRY **) p1;
	ENTRY *e2 = *(ENTRY **) p2;

	return (strcmp(e1->key, e2->key));
}

static int match_string(int flag, const char *str, const char *pat, void *priv)
{
	switch (flag & H_MATCH_METHOD) {
	case H_MATCH_IDENT:
		if (strcmp(str, pat) == 0)
			return 1;
		break;
	case H_MATCH_SUBSTR:
		if (strstr(str, pat))
			return 1;
		break;
#ifdef CONFIG_REGEX
	case H_MATCH_REGEX:
		{
			struct slre *slrep = (struct slre *)priv;
			struct cap caps[slrep->num_caps + 2];

			if (slre_match(slrep, str, strlen(str), caps))
				return 1;
		}
		break;
#endif
	default:
		printf("## ERROR: unsupported match method: 0x%02x\n",
			flag & H_MATCH_METHOD);
		break;
	}
	return 0;
}

static int match_entry(ENTRY *ep, int flag,
		 int argc, char * const argv[])
{
	int arg;
	void *priv = NULL;

	for (arg = 0; arg < argc; ++arg) {
#ifdef CONFIG_REGEX
		struct slre slre;

		if (slre_compile(&slre, argv[arg]) == 0) {
			printf("Error compiling regex: %s\n", slre.err_str);
			return 0;
		}

		priv = (void *)&slre;
#endif
		if (flag & H_MATCH_KEY) {
			if (match_string(flag, ep->key, argv[arg], priv))
				return 1;
		}
		if (flag & H_MATCH_DATA) {
			if (match_string(flag, ep->data, argv[arg], priv))
				return 1;
		}
	}
	return 0;
}

ssize_t hexport_r(struct hsearch_data *htab, const char sep, int flag,
		 char **resp, size_t size,
		 int argc, char * const argv[])
{
	ENTRY *list[htab->size];
	char *res, *p;
	size_t totlen;
	int i, n;

	/* Test for correct arguments.  */
	if ((resp == NULL) || (htab == NULL)) {
		__set_errno(EINVAL);
		return (-1);
	}

	debug("EXPORT  table = %p, htab.size = %d, htab.filled = %d, "
		"size = %zu\n", htab, htab->size, htab->filled, size);
	/*
	 * Pass 1:
	 * search used entries,
	 * save addresses and compute total length
	 */
	for (i = 1, n = 0, totlen = 0; i <= htab->size; ++i) {

		if (htab->table[i].used > 0) {
			ENTRY *ep = &htab->table[i].entry;
			int found = match_entry(ep, flag, argc, argv);

			if ((argc > 0) && (found == 0))
				continue;

			if ((flag & H_HIDE_DOT) && ep->key[0] == '.')
				continue;

			list[n++] = ep;

			totlen += strlen(ep->key) + 2;

			if (sep == '\0') {
				totlen += strlen(ep->data);
			} else {	/* check if escapes are needed */
				char *s = ep->data;

				while (*s) {
					++totlen;
					/* add room for needed escape chars */
					if ((*s == sep) || (*s == '\\'))
						++totlen;
					++s;
				}
			}
			totlen += 2;	/* for '=' and 'sep' char */
		}
	}

#ifdef DEBUG
	/* Pass 1a: print unsorted list */
	printf("Unsorted: n=%d\n", n);
	for (i = 0; i < n; ++i) {
		printf("\t%3d: %p ==> %-10s => %s\n",
		       i, list[i], list[i]->key, list[i]->data);
	}
#endif

	/* Sort list by keys */
	qsort(list, n, sizeof(ENTRY *), cmpkey);

	/* Check if the user supplied buffer size is sufficient */
	if (size) {
		if (size < totlen + 1) {	/* provided buffer too small */
			printf("Env export buffer too small: %zu, "
				"but need %zu\n", size, totlen + 1);
			__set_errno(ENOMEM);
			return (-1);
		}
	} else {
		size = totlen + 1;
	}

	/* Check if the user provided a buffer */
	if (*resp) {
		/* yes; clear it */
		res = *resp;
		memset(res, '\0', size);
	} else {
		/* no, allocate and clear one */
		*resp = res = calloc(1, size);
		if (res == NULL) {
			__set_errno(ENOMEM);
			return (-1);
		}
	}
	/*
	 * Pass 2:
	 * export sorted list of result data
	 */
	for (i = 0, p = res; i < n; ++i) {
		const char *s;

		s = list[i]->key;
		while (*s)
			*p++ = *s++;
		*p++ = '=';

		s = list[i]->data;

		while (*s) {
			if ((*s == sep) || (*s == '\\'))
				*p++ = '\\';	/* escape */
			*p++ = *s++;
		}
		*p++ = sep;
	}
	*p = '\0';		/* terminate result */

	return size;
}
#endif


/*
 * himport()
 */

/*
 * Check whether variable 'name' is amongst vars[],
 * and remove all instances by setting the pointer to NULL
 */
static int drop_var_from_set(const char *name, int nvars, char * vars[])
{
	int i = 0;
	int res = 0;

	/* No variables specified means process all of them */
	if (nvars == 0)
		return 1;

	for (i = 0; i < nvars; i++) {
		if (vars[i] == NULL)
			continue;
		/* If we found it, delete all of them */
		if (!strcmp(name, vars[i])) {
			vars[i] = NULL;
			res = 1;
		}
	}
	if (!res)
		debug("Skipping non-listed variable %s\n", name);

	return res;
}

/*
 * Import linearized data into hash table.
 *
 * This is the inverse function to hexport(): it takes a linear list
 * of "name=value" pairs and creates hash table entries from it.
 *
 * Entries without "value", i. e. consisting of only "name" or
 * "name=", will cause this entry to be deleted from the hash table.
 *
 * The "flag" argument can be used to control the behaviour: when the
 * H_NOCLEAR bit is set, then an existing hash table will kept, i. e.
 * new data will be added to an existing hash table; otherwise, old
 * data will be discarded and a new hash table will be created.
 *
 * The separator character for the "name=value" pairs can be selected,
 * so we both support importing from externally stored environment
 * data (separated by NUL characters) and from plain text files
 * (entries separated by newline characters).
 *
 * To allow for nicely formatted text input, leading white space
 * (sequences of SPACE and TAB chars) is ignored, and entries starting
 * (after removal of any leading white space) with a '#' character are
 * considered comments and ignored.
 *
 * [NOTE: this means that a variable name cannot start with a '#'
 * character.]
 *
 * When using a non-NUL separator character, backslash is used as
 * escape character in the value part, allowing for example for
 * multi-line values.
 *
 * In theory, arbitrary separator characters can be used, but only
 * '\0' and '\n' have really been tested.
 */

int himport_r(struct hsearch_data *htab,
		const char *env, size_t size, const char sep, int flag,
		int crlf_is_lf, int nvars, char * const vars[])
{
	char *data, *sp, *dp, *name, *value;
	char *localvars[nvars];
	int i;

	/* Test for correct arguments.  */
	if (htab == NULL) {
		__set_errno(EINVAL);
		return 0;
	}

	/* we allocate new space to make sure we can write to the array */
	if ((data = malloc(size)) == NULL) {
		debug("himport_r: can't malloc %zu bytes\n", size);
		__set_errno(ENOMEM);
		return 0;
	}
	memcpy(data, env, size);
	dp = data;

	/* make a local copy of the list of variables */
	if (nvars)
		memcpy(localvars, vars, sizeof(vars[0]) * nvars);

	if ((flag & H_NOCLEAR) == 0) {
		/* Destroy old hash table if one exists */
		debug("Destroy Hash Table: %p table = %p\n", htab,
		       htab->table);
		if (htab->table)
			hdestroy_r(htab);
	}

	/*
	 * Create new hash table (if needed).  The computation of the hash
	 * table size is based on heuristics: in a sample of some 70+
	 * existing systems we found an average size of 39+ bytes per entry
	 * in the environment (for the whole key=value pair). Assuming a
	 * size of 8 per entry (= safety factor of ~5) should provide enough
	 * safety margin for any existing environment definitions and still
	 * allow for more than enough dynamic additions. Note that the
	 * "size" argument is supposed to give the maximum environment size
	 * (CONFIG_ENV_SIZE).  This heuristics will result in
	 * unreasonably large numbers (and thus memory footprint) for
	 * big flash environments (>8,000 entries for 64 KB
	 * envrionment size), so we clip it to a reasonable value.
	 * On the other hand we need to add some more entries for free
	 * space when importing very small buffers. Both boundaries can
	 * be overwritten in the board config file if needed.
	 */

	if (!htab->table) {
		int nent = CONFIG_ENV_MIN_ENTRIES + size / 8;

		if (nent > CONFIG_ENV_MAX_ENTRIES)
			nent = CONFIG_ENV_MAX_ENTRIES;

		debug("Create Hash Table: N=%d\n", nent);

		if (hcreate_r(nent, htab) == 0) {
			free(data);
			return 0;
		}
	}

	if(!size)
		return 1;		/* everything OK */
	if(crlf_is_lf) {
		/* Remove Carriage Returns in front of Line Feeds */
		unsigned ignored_crs = 0;
		for(;dp < data + size && *dp; ++dp) {
			if(*dp == '\r' &&
			   dp < data + size - 1 && *(dp+1) == '\n')
				++ignored_crs;
			else
				*(dp-ignored_crs) = *dp;
		}
		size -= ignored_crs;
		dp = data;
	}
	/* Parse environment; allow for '\0' and 'sep' as separators */
	do {
		ENTRY e, *rv;

		/* skip leading white space */
		while (isblank(*dp))
			++dp;

		/* skip comment lines */
		if (*dp == '#') {
			while (*dp && (*dp != sep))
				++dp;
			++dp;
			continue;
		}

		/* parse name */
		for (name = dp; *dp != '=' && *dp && *dp != sep; ++dp)
			;

		/* deal with "name" and "name=" entries (delete var) */
		if (*dp == '\0' || *(dp + 1) == '\0' ||
		    *dp == sep || *(dp + 1) == sep) {
			if (*dp == '=')
				*dp++ = '\0';
			*dp++ = '\0';	/* terminate name */

			debug("DELETE CANDIDATE: \"%s\"\n", name);
			if (!drop_var_from_set(name, nvars, localvars))
				continue;

			if (hdelete_r(name, htab, flag) == 0)
				debug("DELETE ERROR ##############################\n");

			continue;
		}
		*dp++ = '\0';	/* terminate name */

		/* parse value; deal with escapes */
		for (value = sp = dp; *dp && (*dp != sep); ++dp) {
			if ((*dp == '\\') && *(dp + 1))
				++dp;
			*sp++ = *dp;
		}
		*sp++ = '\0';	/* terminate value */
		++dp;

		if (*name == 0) {
			debug("INSERT: unable to use an empty key\n");
			__set_errno(EINVAL);
			return 0;
		}

		/* Skip variables which are not supposed to be processed */
		if (!drop_var_from_set(name, nvars, localvars))
			continue;

		/* enter into hash table */
		e.key = name;
		e.data = value;

		hsearch_r(e, ENTER, &rv, htab, flag);
		if (rv == NULL)
			printf("himport_r: can't insert \"%s=%s\" into hash table\n",
				name, value);

		debug("INSERT: table %p, filled %d/%d rv %p ==> name=\"%s\" value=\"%s\"\n",
			htab, htab->filled, htab->size,
			rv, name, value);
	} while ((dp < data + size) && *dp);	/* size check needed for text */
						/* without '\0' termination */
	debug("INSERT: free(data = %p)\n", data);
	free(data);

	/* process variables which were not considered */
	for (i = 0; i < nvars; i++) {
		if (localvars[i] == NULL)
			continue;
		/*
		 * All variables which were not deleted from the variable list
		 * were not present in the imported env
		 * This could mean two things:
		 * a) if the variable was present in current env, we delete it
		 * b) if the variable was not present in current env, we notify
		 *    it might be a typo
		 */
		if (hdelete_r(localvars[i], htab, flag) == 0)
			printf("WARNING: '%s' neither in running nor in imported env!\n", localvars[i]);
		else
			printf("WARNING: '%s' not in imported env, deleting it!\n", localvars[i]);
	}

	debug("INSERT: done\n");
	return 1;		/* everything OK */
}

/*
 * hwalk_r()
 */

/*
 * Walk all of the entries in the hash, calling the callback for each one.
 * this allows some generic operation to be performed on each element.
 */
int hwalk_r(struct hsearch_data *htab, int (*callback)(ENTRY *))
{
	int i;
	int retval;

	for (i = 1; i <= htab->size; ++i) {
		if (htab->table[i].used > 0) {
			retval = callback(&htab->table[i].entry);
			if (retval)
				return retval;
		}
	}

	return 0;
}