2 * This implementation is based on code from uClibc-0.9.30.3 but was
3 * modified and extended for use within U-Boot.
5 * Copyright (C) 2010 Wolfgang Denk <wd@denx.de>
7 * Original license header:
9 * Copyright (C) 1993, 1995, 1996, 1997, 2002 Free Software Foundation, Inc.
10 * This file is part of the GNU C Library.
11 * Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1993.
13 * The GNU C Library is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU Lesser General Public
15 * License as published by the Free Software Foundation; either
16 * version 2.1 of the License, or (at your option) any later version.
18 * The GNU C Library is distributed in the hope that it will be useful,
19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
21 * Lesser General Public License for more details.
23 * You should have received a copy of the GNU Lesser General Public
24 * License along with the GNU C Library; if not, write to the Free
25 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
32 #ifdef USE_HOSTCC /* HOST build */
38 # define debug(fmt,args...) printf(fmt ,##args)
40 # define debug(fmt,args...)
43 #else /* U-Boot build */
45 # include <linux/string.h>
51 * [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
52 * [Knuth] The Art of Computer Programming, part 3 (6.4)
56 * The non-reentrant version use a global space for storing the hash table.
58 static struct hsearch_data htab;
61 * The reentrant version has no static variables to maintain the state.
62 * Instead the interface of all functions is extended to take an argument
63 * which describes the current status.
65 typedef struct _ENTRY {
76 * For the used double hash method the table size has to be a prime. To
77 * correct the user given table size we need a prime test. This trivial
78 * algorithm is adequate because
79 * a) the code is (most probably) called a few times per program run and
80 * b) the number is small because the table must fit in the core
82 static int isprime(unsigned int number)
84 /* no even number will be passed */
87 while (div * div < number && number % div != 0)
90 return number % div != 0;
93 int hcreate(size_t nel)
95 return hcreate_r(nel, &htab);
99 * Before using the hash table we must allocate memory for it.
100 * Test for an existing table are done. We allocate one element
101 * more as the found prime number says. This is done for more effective
102 * indexing as explained in the comment for the hsearch function.
103 * The contents of the table is zeroed, especially the field used
106 int hcreate_r(size_t nel, struct hsearch_data *htab)
108 /* Test for correct arguments. */
114 /* There is still another table active. Return with error. */
115 if (htab->table != NULL)
118 /* Change nel to the first prime number not smaller as nel. */
119 nel |= 1; /* make odd */
120 while (!isprime(nel))
126 /* allocate memory and zero out */
127 htab->table = (_ENTRY *) calloc(htab->size + 1, sizeof(_ENTRY));
128 if (htab->table == NULL)
131 /* everything went alright */
145 * After using the hash table it has to be destroyed. The used memory can
146 * be freed and the local static variable can be marked as not used.
148 void hdestroy_r(struct hsearch_data *htab)
152 /* Test for correct arguments. */
158 /* free used memory */
159 for (i = 1; i <= htab->size; ++i) {
160 if (htab->table[i].used) {
161 ENTRY *ep = &htab->table[i].entry;
169 /* the sign for an existing table is an value != NULL in htable */
178 * This is the search function. It uses double hashing with open addressing.
179 * The argument item.key has to be a pointer to an zero terminated, most
180 * probably strings of chars. The function for generating a number of the
181 * strings is simple but fast. It can be replaced by a more complex function
182 * like ajw (see [Aho,Sethi,Ullman]) if the needs are shown.
184 * We use an trick to speed up the lookup. The table is created by hcreate
185 * with one more element available. This enables us to use the index zero
186 * special. This index will never be used because we store the first hash
187 * index in the field used where zero means not used. Every other value
188 * means used. The used field can be used as a first fast comparison for
189 * equality of the stored and the parameter value. This helps to prevent
190 * unnecessary expensive calls of strcmp.
192 * This implementation differs from the standard library version of
193 * this function in a number of ways:
195 * - While the standard version does not make any assumptions about
196 * the type of the stored data objects at all, this implementation
197 * works with NUL terminated strings only.
198 * - Instead of storing just pointers to the original objects, we
199 * create local copies so the caller does not need to care about the
201 * - The standard implementation does not provide a way to update an
202 * existing entry. This version will create a new entry or update an
203 * existing one when both "action == ENTER" and "item.data != NULL".
204 * - Instead of returning 1 on success, we return the index into the
205 * internal hash table, which is also guaranteed to be positive.
206 * This allows us direct access to the found hash table slot for
207 * example for functions like hdelete().
210 ENTRY *hsearch(ENTRY item, ACTION action)
214 (void) hsearch_r(item, action, &result, &htab);
219 int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
220 struct hsearch_data *htab)
224 unsigned int len = strlen(item.key);
227 /* Compute an value for the given string. Perhaps use a better method. */
230 while (count-- > 0) {
232 hval += item.key[count];
236 * First hash function:
237 * simply take the modul but prevent zero.
243 /* The first index tried. */
246 if (htab->table[idx].used) {
248 * Further action might be required according to the
253 if (htab->table[idx].used == hval
254 && strcmp(item.key, htab->table[idx].entry.key) == 0) {
255 /* Overwrite existing value? */
256 if ((action == ENTER) && (item.data != NULL)) {
257 free(htab->table[idx].entry.data);
258 htab->table[idx].entry.data =
260 if (!htab->table[idx].entry.data) {
266 /* return found entry */
267 *retval = &htab->table[idx].entry;
272 * Second hash function:
273 * as suggested in [Knuth]
275 hval2 = 1 + hval % (htab->size - 2);
279 * Because SIZE is prime this guarantees to
280 * step through all available indices.
283 idx = htab->size + idx - hval2;
288 * If we visited all entries leave the loop
294 /* If entry is found use it. */
295 if ((htab->table[idx].used == hval)
296 && strcmp(item.key, htab->table[idx].entry.key) == 0) {
297 /* Overwrite existing value? */
298 if ((action == ENTER) && (item.data != NULL)) {
299 free(htab->table[idx].entry.data);
300 htab->table[idx].entry.data =
302 if (!htab->table[idx].entry.data) {
308 /* return found entry */
309 *retval = &htab->table[idx].entry;
313 while (htab->table[idx].used);
316 /* An empty bucket has been found. */
317 if (action == ENTER) {
319 * If table is full and another entry should be
320 * entered return with error.
322 if (htab->filled == htab->size) {
330 * create copies of item.key and item.data
332 htab->table[idx].used = hval;
333 htab->table[idx].entry.key = strdup(item.key);
334 htab->table[idx].entry.data = strdup(item.data);
335 if (!htab->table[idx].entry.key ||
336 !htab->table[idx].entry.data) {
344 /* return new entry */
345 *retval = &htab->table[idx].entry;
360 * The standard implementation of hsearch(3) does not provide any way
361 * to delete any entries from the hash table. We extend the code to
365 int hdelete(const char *key)
367 return hdelete_r(key, &htab);
370 int hdelete_r(const char *key, struct hsearch_data *htab)
375 debug("hdelete: DELETE key \"%s\"\n", key);
379 if ((idx = hsearch_r(e, FIND, &ep, htab)) == 0) {
381 return 0; /* not found */
384 /* free used ENTRY */
385 debug("hdelete: DELETING key \"%s\"\n", key);
389 htab->table[idx].used = 0;
401 * Export the data stored in the hash table in linearized form.
403 * Entries are exported as "name=value" strings, separated by an
404 * arbitrary (non-NUL, of course) separator character. This allows to
405 * use this function both when formatting the U-Boot environment for
406 * external storage (using '\0' as separator), but also when using it
407 * for the "printenv" command to print all variables, simply by using
408 * as '\n" as separator. This can also be used for new features like
409 * exporting the environment data as text file, including the option
410 * for later re-import.
412 * The entries in the result list will be sorted by ascending key
415 * If the separator character is different from NUL, then any
416 * separator characters and backslash characters in the values will
417 * be escaped by a preceeding backslash in output. This is needed for
418 * example to enable multi-line values, especially when the output
419 * shall later be parsed (for example, for re-import).
421 * There are several options how the result buffer is handled:
425 * NULL 0 A string of sufficient length will be allocated.
426 * NULL >0 A string of the size given will be
427 * allocated. An error will be returned if the size is
428 * not sufficient. Any unused bytes in the string will
430 * !NULL 0 The user-supplied buffer will be used. No length
431 * checking will be performed, i. e. it is assumed that
432 * the buffer size will always be big enough. DANGEROUS.
433 * !NULL >0 The user-supplied buffer will be used. An error will
434 * be returned if the size is not sufficient. Any unused
435 * bytes in the string will be '\0'-padded.
438 ssize_t hexport(const char sep, char **resp, size_t size)
440 return hexport_r(&htab, sep, resp, size);
443 static int cmpkey(const void *p1, const void *p2)
445 ENTRY *e1 = *(ENTRY **) p1;
446 ENTRY *e2 = *(ENTRY **) p2;
448 return (strcmp(e1->key, e2->key));
451 ssize_t hexport_r(struct hsearch_data *htab, const char sep,
452 char **resp, size_t size)
454 ENTRY *list[htab->size];
459 /* Test for correct arguments. */
460 if ((resp == NULL) || (htab == NULL)) {
465 debug("EXPORT table = %p, htab.size = %d, htab.filled = %d, size = %d\n",
466 htab, htab->size, htab->filled, size);
469 * search used entries,
470 * save addresses and compute total length
472 for (i = 1, n = 0, totlen = 0; i <= htab->size; ++i) {
474 if (htab->table[i].used) {
475 ENTRY *ep = &htab->table[i].entry;
479 totlen += strlen(ep->key) + 2;
482 totlen += strlen(ep->data);
483 } else { /* check if escapes are needed */
488 /* add room for needed escape chars */
489 if ((*s == sep) || (*s == '\\'))
494 totlen += 2; /* for '=' and 'sep' char */
499 /* Pass 1a: print unsorted list */
500 printf("Unsorted: n=%d\n", n);
501 for (i = 0; i < n; ++i) {
502 printf("\t%3d: %p ==> %-10s => %s\n",
503 i, list[i], list[i]->key, list[i]->data);
507 /* Sort list by keys */
508 qsort(list, n, sizeof(ENTRY *), cmpkey);
510 /* Check if the user supplied buffer size is sufficient */
512 if (size < totlen + 1) { /* provided buffer too small */
513 debug("### buffer too small: %d, but need %d\n",
522 /* Check if the user provided a buffer */
526 memset(res, '\0', size);
528 /* no, allocate and clear one */
529 *resp = res = calloc(1, size);
537 * export sorted list of result data
539 for (i = 0, p = res; i < n; ++i) {
550 if ((*s == sep) || (*s == '\\'))
551 *p++ = '\\'; /* escape */
556 *p = '\0'; /* terminate result */
567 * Import linearized data into hash table.
569 * This is the inverse function to hexport(): it takes a linear list
570 * of "name=value" pairs and creates hash table entries from it.
572 * Entries without "value", i. e. consisting of only "name" or
573 * "name=", will cause this entry to be deleted from the hash table.
575 * The "flag" argument can be used to control the behaviour: when the
576 * H_NOCLEAR bit is set, then an existing hash table will kept, i. e.
577 * new data will be added to an existing hash table; otherwise, old
578 * data will be discarded and a new hash table will be created.
580 * The separator character for the "name=value" pairs can be selected,
581 * so we both support importing from externally stored environment
582 * data (separated by NUL characters) and from plain text files
583 * (entries separated by newline characters).
585 * To allow for nicely formatted text input, leading white space
586 * (sequences of SPACE and TAB chars) is ignored, and entries starting
587 * (after removal of any leading white space) with a '#' character are
588 * considered comments and ignored.
590 * [NOTE: this means that a variable name cannot start with a '#'
593 * When using a non-NUL separator character, backslash is used as
594 * escape character in the value part, allowing for example for
597 * In theory, arbitrary separator characters can be used, but only
598 * '\0' and '\n' have really been tested.
601 int himport(const char *env, size_t size, const char sep, int flag)
603 return himport_r(&htab, env, size, sep, flag);
606 int himport_r(struct hsearch_data *htab,
607 const char *env, size_t size, const char sep, int flag)
609 char *data, *sp, *dp, *name, *value;
611 /* Test for correct arguments. */
617 /* we allocate new space to make sure we can write to the array */
618 if ((data = malloc(size)) == NULL) {
619 debug("himport_r: can't malloc %d bytes\n", size);
623 memcpy(data, env, size);
626 if ((flag & H_NOCLEAR) == 0) {
627 /* Destroy old hash table if one exists */
628 debug("Destroy Hash Table: %p table = %p\n", htab,
635 * Create new hash table (if needed). The computation of the hash
636 * table size is based on heuristics: in a sample of some 70+
637 * existing systems we found an average size of 39+ bytes per entry
638 * in the environment (for the whole key=value pair). Assuming a
639 * size of 7 per entry (= safety factor of >5) should provide enough
640 * safety margin for any existing environment definitons and still
641 * allow for more than enough dynamic additions. Note that the
642 * "size" argument is supposed to give the maximum enviroment size
649 debug("Create Hash Table: N=%d\n", nent);
651 if (hcreate_r(nent, htab) == 0) {
657 /* Parse environment; allow for '\0' and 'sep' as separators */
661 /* skip leading white space */
662 while ((*dp == ' ') || (*dp == '\t'))
665 /* skip comment lines */
667 while (*dp && (*dp != sep))
674 for (name = dp; *dp != '=' && *dp && *dp != sep; ++dp)
677 /* deal with "name" and "name=" entries (delete var) */
678 if (*dp == '\0' || *(dp + 1) == '\0' ||
679 *dp == sep || *(dp + 1) == sep) {
682 *dp++ = '\0'; /* terminate name */
684 debug("DELETE CANDIDATE: \"%s\"\n", name);
686 if (hdelete_r(name, htab) == 0)
687 debug("DELETE ERROR ##############################\n");
691 *dp++ = '\0'; /* terminate name */
693 /* parse value; deal with escapes */
694 for (value = sp = dp; *dp && (*dp != sep); ++dp) {
695 if ((*dp == '\\') && *(dp + 1))
699 *sp++ = '\0'; /* terminate value */
702 /* enter into hash table */
706 hsearch_r(e, ENTER, &rv, htab);
708 printf("himport_r: can't insert \"%s=%s\" into hash table\n", name, value);
712 debug("INSERT: %p ==> name=\"%s\" value=\"%s\"\n", rv, name,
714 debug(" table = %p, size = %d, filled = %d\n", htab,
715 htab->size, htab->filled);
716 } while ((dp < data + size) && *dp); /* size check needed for text */
717 /* without '\0' termination */
720 return 1; /* everything OK */