Name

Per-Directory Merger

Synopsis

void *module_dir_merge(pool *pPool, void *base_conf, void *new_conf)

Like the per-server merger, this is called once for each virtual host (not for each directory). It is handed the per-server document root per-directory Config (that is, the one that was created with a NULL directory name).

Whenever a request is processed, this function merges all relevant <Directory> sections and then merges .htacess files (interleaved, starting at the root and working downward), then <File> and <Location> sections, in that order.

Unlike the per-server merger, per-directory merger is called as the server runs, possibly with different combinations of directory, location, and file configurations for each request, so it is important that it copies the configuration (in new_conf) if it is going to change it.

Now the reason we chose mod_rewrite.c for the per-directory creator becomes apparent, as it is a little more interesting than most. See Example 21-5.

Example

Example 21-5. mod_rewrite.c

static void *config_perdir_merge(pool *p, void *basev, void *overridesv)
{
    rewrite_perdir_conf *a, *base, *overrides;
    a     = (rewrite_perdir_conf *)pcalloc(p, sizeof(rewrite_perdir_conf));
    base  = (rewrite_perdir_conf *)basev;
    overrides = (rewrite_perdir_conf *)overridesv;

    a->state           = overrides->state;
    a->options         = overrides->options;
    a->directory       = overrides->directory;
    a->baseurl         = overrides->baseurl;
    if (a->options & OPTION_INHERIT) {
        a->rewriteconds = append_arrays(p, overrides->rewriteconds, 
             base->rewriteconds);
        a->rewriterules = append_arrays(p, overrides->rewriterules, 
             base->rewriterules);
    }
    else {
        a->rewriteconds = overrides->rewriteconds;
        a->rewriterules = overrides->rewriterules;
    }
    return (void *)a;
}

As you can see, this merges the configuration from the base conditionally, depending on whether the new configuration specified an INHERIT option.

Once more, the only change in 2.0 is that pool has become apr_pool_t. See Example 21-6 for an excerpt from mod_env.c.

Example 21-6. mod_env.c

static void *merge_env_dir_configs(pool *p, void *basev, void *addv)
{
    env_dir_config_rec *base = (env_dir_config_rec *) basev;
    env_dir_config_rec *add = (env_dir_config_rec *) addv;
    env_dir_config_rec *new =
    (env_dir_config_rec *) ap_palloc(p, sizeof(env_dir_config_rec));
    table *new_table;
    table_entry *elts;
    array_header *arr;
    int i;
    const char *uenv, *unset;

    new_table = ap_copy_table(p, base->vars);

    arr = ap_table_elts(add->vars);
    elts = (table_entry *)arr->elts;

    for (i = 0; i < arr->nelts; ++i) {
        ap_table_setn(new_table, elts[i].key, elts[i].val);
    }

    unset = add->unsetenv;
    uenv = ap_getword_conf(p, &unset);
    while (uenv[0] != '\0') {
        ap_table_unset(new_table, uenv);
        uenv = ap_getword_conf(p, &unset);
    }

    new->vars = new_table;

    new->vars_present = base->vars_present || add->vars_present;

    return new;
}

This function creates a new configuration into which it then copies the base vars table (a table of environment variable names and values). It then runs through the individual entries of the addv vars table, setting them in the new table. It does this rather than use overlay_tables() because overlay_tables() does not deal with duplicated keys. Then the addv configuration’s unsetenv (which is a space-separated list of environment variables to unset) unsets any variables specified to be unset for addv ’s server.

The 2.0 version of this function has a number of alterations, but on close inspection is actually very much the same, allowing for differences in function names and some rather radical restructuring:

static void *merge_env_dir_configs(apr_pool_t *p, void *basev, void *addv)
{
    env_dir_config_rec *base = basev;
    env_dir_config_rec *add = addv;
    env_dir_config_rec *res = apr_palloc(p, sizeof(*res));
    const apr_table_entry_t *elts;
    const apr_array_header_t *arr;
    int i;

    res->vars = apr_table_copy(p, base->vars);
    res->unsetenv = NULL;

    arr = apr_table_elts(add->unsetenv);
    elts = (const apr_table_entry_t *)arr->elts;

    for (i = 0; i < arr->nelts; ++i) {
        apr_table_unset(res->vars, elts[i].key);
    }

    arr = apr_table_elts(add->vars);
    elts = (const apr_table_entry_t *)arr->elts;

    for (i = 0; i < arr->nelts; ++i) {
        apr_table_setn(res->vars, elts[i].key, elts[i].val);
    }

    return res;
}