[people/ms/u-boot.git] / lib / hashtable.c

/*
 * 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 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.
 *
 * The GNU C Library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * The GNU C Library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with the GNU C Library; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
 * 02111-1307 USA.
 */

#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 "search.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;


/*
 * 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 do_apply)
{
        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;
                        if (do_apply && htab->apply != NULL) {
                                /* deletion is always forced */
                                htab->apply(ep->key, ep->data, NULL, H_FORCE);
                        }
                        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().
 */

/*
 * hstrstr_r - return index to entry whose key and/or data contains match
 */
int hstrstr_r(const char *match, int last_idx, ENTRY ** retval,
              struct hsearch_data *htab)
{
        unsigned int idx;

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

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

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;
}

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

        /* 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;

                if (htab->table[idx].used == hval
                    && strcmp(item.key, htab->table[idx].entry.key) == 0) {
                        /* Overwrite existing value? */
                        if ((action == ENTER) && (item.data != NULL)) {
                                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;
                }

                /*
                 * 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. */
                        if ((htab->table[idx].used == hval)
                            && strcmp(item.key, htab->table[idx].entry.key) == 0) {
                                /* Overwrite existing value? */
                                if ((action == ENTER) && (item.data != NULL)) {
                                        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;
                        }
                }
                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;

                /* 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.
 */

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

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

        e.key = (char *)key;

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

        /* free used ENTRY */
        debug("hdelete: DELETING key \"%s\"\n", key);
        if (do_apply && htab->apply != NULL)
                htab->apply(ep->key, ep->data, NULL, H_FORCE);
        free((void *)ep->key);
        free(ep->data);
        htab->table[idx].used = -1;

        --htab->filled;

        return 1;
}

/*
 * hexport()
 */

/*
 * 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));
}

ssize_t hexport_r(struct hsearch_data *htab, const char sep,
                 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 arg, found = 0;

                        for (arg = 0; arg < argc; ++arg) {
                                if (strcmp(argv[arg], ep->key) == 0) {
                                        found = 1;
                                        break;
                                }
                        }
                        if ((argc > 0) && (found == 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;
}


/*
 * himport()
 */

/* Check whether variable name is amongst vars[] */
static int is_var_in_set(const char *name, int nvars, char * const vars[])
{
        int i = 0;

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

        for (i = 0; i < nvars; i++) {
                if (!strcmp(name, vars[i]))
                        return 1;
        }
        debug("Skipping non-listed variable %s\n", name);

        return 0;
}

/*
 * 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 nvars, char * const vars[], int do_apply)
{
        char *data, *sp, *dp, *name, *value;

        /* 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;

        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, do_apply);
        }

        /*
         * 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 enviroment 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;
                }
        }

        /* 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 (!is_var_in_set(name, nvars, vars))
                                continue;

                        if (hdelete_r(name, htab, do_apply) == 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;

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

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

                /* if there is an apply function, check what it has to say */
                if (do_apply && htab->apply != NULL) {
                        debug("searching before calling cb function"
                                " for  %s\n", name);
                        /*
                         * Search for variable in existing env, so to pass
                         * its previous value to the apply callback
                         */
                        hsearch_r(e, FIND, &rv, htab);
                        debug("previous value was %s\n", rv ? rv->data : "");
                        if (htab->apply(name, rv ? rv->data : NULL,
                                value, flag)) {
                                debug("callback function refused to set"
                                        " variable %s, skipping it!\n", name);
                                continue;
                        }
                }

                hsearch_r(e, ENTER, &rv, htab);
                if (rv == NULL) {
                        printf("himport_r: can't insert \"%s=%s\" into hash table\n",
                                name, value);
                        return 0;
                }

                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);

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