apr_tables.c

来自「Apache 2.0.63 is the current stable vers」· C语言 代码 · 共 1,208 行 · 第 1/3 页

    apr_table_t *res;

#ifdef POOL_DEBUG
    /* we don't copy keys and values, so it's necessary that
     * overlay->a.pool and base->a.pool have a life span at least
     * as long as p
     */
    if (!apr_pool_is_ancestor(overlay->a.pool, p)) {
	fprintf(stderr,
		"overlay_tables: overlay's pool is not an ancestor of p\n");
	abort();
    }
    if (!apr_pool_is_ancestor(base->a.pool, p)) {
	fprintf(stderr,
		"overlay_tables: base's pool is not an ancestor of p\n");
	abort();
    }
#endif

    res = apr_palloc(p, sizeof(apr_table_t));
    /* behave like append_arrays */
    res->a.pool = p;
    copy_array_hdr_core(&res->a, &overlay->a);
    apr_array_cat(&res->a, &base->a);
    table_reindex(res);
    return res;
}

/* And now for something completely abstract ...

 * For each key value given as a vararg:
 *   run the function pointed to as
 *     int comp(void *r, char *key, char *value);
 *   on each valid key-value pair in the apr_table_t t that matches the vararg key,
 *   or once for every valid key-value pair if the vararg list is empty,
 *   until the function returns false (0) or we finish the table.
 *
 * Note that we restart the traversal for each vararg, which means that
 * duplicate varargs will result in multiple executions of the function
 * for each matching key.  Note also that if the vararg list is empty,
 * only one traversal will be made and will cut short if comp returns 0.
 *
 * Note that the table_get and table_merge functions assume that each key in
 * the apr_table_t is unique (i.e., no multiple entries with the same key).  This
 * function does not make that assumption, since it (unfortunately) isn't
 * true for some of Apache's tables.
 *
 * Note that rec is simply passed-on to the comp function, so that the
 * caller can pass additional info for the task.
 *
 * ADDENDUM for apr_table_vdo():
 * 
 * The caching api will allow a user to walk the header values:
 *
 * apr_status_t apr_cache_el_header_walk(apr_cache_el *el, 
 *    int (*comp)(void *, const char *, const char *), void *rec, ...);
 *
 * So it can be ..., however from there I use a  callback that use a va_list:
 *
 * apr_status_t (*cache_el_header_walk)(apr_cache_el *el, 
 *    int (*comp)(void *, const char *, const char *), void *rec, va_list);
 *
 * To pass those ...'s on down to the actual module that will handle walking
 * their headers, in the file case this is actually just an apr_table - and
 * rather than reimplementing apr_table_do (which IMHO would be bad) I just
 * called it with the va_list. For mod_shmem_cache I don't need it since I
 * can't use apr_table's, but mod_file_cache should (though a good hash would
 * be better, but that's a different issue :). 
 *
 * So to make mod_file_cache easier to maintain, it's a good thing
 */
APR_DECLARE_NONSTD(int) apr_table_do(apr_table_do_callback_fn_t *comp,
                                     void *rec, const apr_table_t *t, ...)
{
    int rv;

    va_list vp;
    va_start(vp, t);
    rv = apr_table_vdo(comp, rec, t, vp);
    va_end(vp);

    return rv;
} 

/* XXX: do the semantics of this routine make any sense?  Right now,
 * if the caller passed in a non-empty va_list of keys to search for,
 * the "early termination" facility only terminates on *that* key; other
 * keys will continue to process.  Note that this only has any effect
 * at all if there are multiple entries in the table with the same key,
 * otherwise the called function can never effectively early-terminate
 * this function, as the zero return value is effectively ignored.
 *
 * Note also that this behavior is at odds with the behavior seen if an
 * empty va_list is passed in -- in that case, a zero return value terminates
 * the entire apr_table_vdo (which is what I think should happen in
 * both cases).
 *
 * If nobody objects soon, I'm going to change the order of the nested
 * loops in this function so that any zero return value from the (*comp)
 * function will cause a full termination of apr_table_vdo.  I'm hesitant
 * at the moment because these (funky) semantics have been around for a
 * very long time, and although Apache doesn't seem to use them at all,
 * some third-party vendor might.  I can only think of one possible reason
 * the existing semantics would make any sense, and it's very Apache-centric,
 * which is this: if (*comp) is looking for matches of a particular
 * substring in request headers (let's say it's looking for a particular
 * cookie name in the Set-Cookie headers), then maybe it wants to be
 * able to stop searching early as soon as it finds that one and move
 * on to the next key.  That's only an optimization of course, but changing
 * the behavior of this function would mean that any code that tried
 * to do that would stop working right.
 *
 * Sigh.  --JCW, 06/28/02
 */
APR_DECLARE(int) apr_table_vdo(apr_table_do_callback_fn_t *comp,
                               void *rec, const apr_table_t *t, va_list vp)
{
    char *argp;
    apr_table_entry_t *elts = (apr_table_entry_t *) t->a.elts;
    int vdorv = 1;

    argp = va_arg(vp, char *);
    do {
        int rv = 1, i;
        if (argp) {
            /* Scan for entries that match the next key */
            int hash = TABLE_HASH(argp);
            if (TABLE_INDEX_IS_INITIALIZED(t, hash)) {
                apr_uint32_t checksum;
                COMPUTE_KEY_CHECKSUM(argp, checksum);
                for (i = t->index_first[hash];
                     rv && (i <= t->index_last[hash]); ++i) {
                    if (elts[i].key && (checksum == elts[i].key_checksum) &&
                                        !strcasecmp(elts[i].key, argp)) {
                        rv = (*comp) (rec, elts[i].key, elts[i].val);
                    }
                }
            }
        }
        else {
            /* Scan the entire table */
            for (i = 0; rv && (i < t->a.nelts); ++i) {
                if (elts[i].key) {
                    rv = (*comp) (rec, elts[i].key, elts[i].val);
                }
            }
        }
        if (rv == 0) {
            vdorv = 0;
        }
    } while (argp && ((argp = va_arg(vp, char *)) != NULL));

    return vdorv;
}

static apr_table_entry_t **table_mergesort(apr_pool_t *pool,
                                           apr_table_entry_t **values, int n)
{
    /* Bottom-up mergesort, based on design in Sedgewick's "Algorithms
     * in C," chapter 8
     */
    apr_table_entry_t **values_tmp =
        (apr_table_entry_t **)apr_palloc(pool, n * sizeof(apr_table_entry_t*));
    int i;
    int blocksize;

    /* First pass: sort pairs of elements (blocksize=1) */
    for (i = 0; i + 1 < n; i += 2) {
        if (strcasecmp(values[i]->key, values[i + 1]->key) > 0) {
            apr_table_entry_t *swap = values[i];
            values[i] = values[i + 1];
            values[i + 1] = swap;
        }
    }

    /* Merge successively larger blocks */
    blocksize = 2;
    while (blocksize < n) {
        apr_table_entry_t **dst = values_tmp;
        int next_start;
        apr_table_entry_t **swap;

        /* Merge consecutive pairs blocks of the next blocksize.
         * Within a block, elements are in sorted order due to
         * the previous iteration.
         */
        for (next_start = 0; next_start + blocksize < n;
             next_start += (blocksize + blocksize)) {

            int block1_start = next_start;
            int block2_start = block1_start + blocksize;
            int block1_end = block2_start;
            int block2_end = block2_start + blocksize;
            if (block2_end > n) {
                /* The last block may be smaller than blocksize */
                block2_end = n;
            }
            for (;;) {

                /* Merge the next two blocks:
                 * Pick the smaller of the next element from
                 * block 1 and the next element from block 2.
                 * Once either of the blocks is emptied, copy
                 * over all the remaining elements from the
                 * other block
                 */
                if (block1_start == block1_end) {
                    for (; block2_start < block2_end; block2_start++) {
                        *dst++ = values[block2_start];
                    }
                    break;
                }
                else if (block2_start == block2_end) {
                    for (; block1_start < block1_end; block1_start++) {
                        *dst++ = values[block1_start];
                    }
                    break;
                }
                if (strcasecmp(values[block1_start]->key,
                               values[block2_start]->key) > 0) {
                    *dst++ = values[block2_start++];
                }
                else {
                    *dst++ = values[block1_start++];
                }
            }
        }

        /* If n is not a multiple of 2*blocksize, some elements
         * will be left over at the end of the array.
         */
        for (i = dst - values_tmp; i < n; i++) {
            values_tmp[i] = values[i];
        }

        /* The output array of this pass becomes the input
         * array of the next pass, and vice versa
         */
        swap = values_tmp;
        values_tmp = values;
        values = swap;

        blocksize += blocksize;
    }

    return values;
}

APR_DECLARE(void) apr_table_compress(apr_table_t *t, unsigned flags)
{
    apr_table_entry_t **sort_array;
    apr_table_entry_t **sort_next;
    apr_table_entry_t **sort_end;
    apr_table_entry_t *table_next;
    apr_table_entry_t **last;
    int i;
    int dups_found;

    if (t->a.nelts <= 1) {
        return;
    }

    /* Copy pointers to all the table elements into an
     * array and sort to allow for easy detection of
     * duplicate keys
     */
    sort_array = (apr_table_entry_t **)
        apr_palloc(t->a.pool, t->a.nelts * sizeof(apr_table_entry_t*));
    sort_next = sort_array;
    table_next = (apr_table_entry_t *)t->a.elts;
    i = t->a.nelts;
    do {
        *sort_next++ = table_next++;
    } while (--i);

    /* Note: the merge is done with mergesort instead of quicksort
     * because mergesort is a stable sort and runs in n*log(n)
     * time regardless of its inputs (quicksort is quadratic in
     * the worst case)
     */
    sort_array = table_mergesort(t->a.pool, sort_array, t->a.nelts);

    /* Process any duplicate keys */
    dups_found = 0;
    sort_next = sort_array;
    sort_end = sort_array + t->a.nelts;
    last = sort_next++;
    while (sort_next < sort_end) {
        if (((*sort_next)->key_checksum == (*last)->key_checksum) &&
            !strcasecmp((*sort_next)->key, (*last)->key)) {
            apr_table_entry_t **dup_last = sort_next + 1;
            dups_found = 1;
            while ((dup_last < sort_end) &&
                   ((*dup_last)->key_checksum == (*last)->key_checksum) &&
                   !strcasecmp((*dup_last)->key, (*last)->key)) {
                dup_last++;
            }
            dup_last--; /* Elements from last through dup_last, inclusive,
                         * all have the same key
                         */
            if (flags == APR_OVERLAP_TABLES_MERGE) {
                apr_size_t len = 0;
                apr_table_entry_t **next = last;
                char *new_val;
                char *val_dst;
                do {
                    len += strlen((*next)->val);
                    len += 2; /* for ", " or trailing null */
                } while (++next <= dup_last);
                new_val = (char *)apr_palloc(t->a.pool, len);
                val_dst = new_val;
                next = last;
                for (;;) {
                    strcpy(val_dst, (*next)->val);
                    val_dst += strlen((*next)->val);
                    next++;
                    if (next > dup_last) {
                        *val_dst = 0;
                        break;
                    }
                    else {
                        *val_dst++ = ',';
                        *val_dst++ = ' ';
                    }
                }
                (*last)->val = new_val;
            }
            else { /* overwrite */
                (*last)->val = (*dup_last)->val;
            }
            do {
                (*sort_next)->key = NULL;
            } while (++sort_next <= dup_last);
        }
        else {
            last = sort_next++;
        }
    }

    /* Shift elements to the left to fill holes left by removing duplicates */
    if (dups_found) {
        apr_table_entry_t *src = (apr_table_entry_t *)t->a.elts;
        apr_table_entry_t *dst = (apr_table_entry_t *)t->a.elts;
        apr_table_entry_t *last_elt = src + t->a.nelts;
        do {
            if (src->key) {
                *dst++ = *src;
            }
        } while (++src < last_elt);
        t->a.nelts -= (last_elt - dst);
    }

    table_reindex(t);
}

static void apr_table_cat(apr_table_t *t, const apr_table_t *s)
{
    const int n = t->a.nelts;
    register int idx;

    apr_array_cat(&t->a,&s->a);

    if (n == 0) {
        memcpy(t->index_first,s->index_first,sizeof(int) * TABLE_HASH_SIZE);
        memcpy(t->index_last, s->index_last, sizeof(int) * TABLE_HASH_SIZE);
        t->index_initialized = s->index_initialized;
        return;
    }

    for (idx = 0; idx < TABLE_HASH_SIZE; ++idx) {
        if (TABLE_INDEX_IS_INITIALIZED(s, idx)) {
            t->index_last[idx] = s->index_last[idx] + n;
            if (!TABLE_INDEX_IS_INITIALIZED(t, idx)) {
                t->index_first[idx] = s->index_first[idx] + n;
            }
        }
    }

    t->index_initialized |= s->index_initialized;
}

APR_DECLARE(void) apr_table_overlap(apr_table_t *a, const apr_table_t *b,
				    unsigned flags)
{
    const int m = a->a.nelts;
    const int n = b->a.nelts;
    apr_pool_t *p = b->a.pool;

    if (m + n == 0) {
        return;
    }

    /* copy (extend) a using b's pool */
    if (a->a.pool != p) {
        make_array_core(&a->a, p, m+n, sizeof(apr_table_entry_t), 0);
    }

    apr_table_cat(a, b);

    apr_table_compress(a, flags);
}