mod_negotiation.c

apache简化版

    ++filp;
    prefix_len = strlen(filp);

    dirp = ap_popendir(neg->pool, neg->dir_name);

    if (dirp == NULL) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, r,
                    "cannot read directory for multi: %s", neg->dir_name);
        return HTTP_FORBIDDEN;
    }

    while ((dir_entry = readdir(dirp))) {
        request_rec *sub_req;

        /* Do we have a match? */

        if (strncmp(dir_entry->d_name, filp, prefix_len)) {
            continue;
        }
        if (dir_entry->d_name[prefix_len] != '.') {
            continue;
        }

        /* Yep.  See if it's something which we have access to, and 
         * which has a known type and encoding (as opposed to something
         * which we'll be slapping default_type on later).
         */

        sub_req = ap_sub_req_lookup_file(dir_entry->d_name, r);

        /* If it has a handler, we'll pretend it's a CGI script,
         * since that's a good indication of the sort of thing it
         * might be doing.
         */
        if (sub_req->handler && !sub_req->content_type) {
            sub_req->content_type = CGI_MAGIC_TYPE;
        }

        if (sub_req->status != HTTP_OK || !sub_req->content_type) {
            ap_destroy_sub_req(sub_req);
            continue;
        }

        /* If it's a map file, we use that instead of the map
         * we're building...
         */

        if (((sub_req->content_type) &&
             !strcmp(sub_req->content_type, MAP_FILE_MAGIC_TYPE)) ||
            ((sub_req->handler) &&
             !strcmp(sub_req->handler, "type-map"))) {

            ap_pclosedir(neg->pool, dirp);
            neg->avail_vars->nelts = 0;
	    if (sub_req->status != HTTP_OK) {
		return sub_req->status;
	    }
            return read_type_map(neg, sub_req);
        }

        /* Have reasonable variant --- gather notes.
         */

        mime_info.sub_req = sub_req;
        mime_info.file_name = ap_pstrdup(neg->pool, dir_entry->d_name);
        if (sub_req->content_encoding) {
            mime_info.content_encoding = sub_req->content_encoding;
        }
        if (sub_req->content_languages) {
            mime_info.content_languages = sub_req->content_languages;
        }

        get_entry(neg->pool, &accept_info, sub_req->content_type);
        set_mime_fields(&mime_info, &accept_info);

        new_var = ap_push_array(neg->avail_vars);
        memcpy(new_var, (void *) &mime_info, sizeof(var_rec));

        neg->count_multiviews_variants++;

        clean_var_rec(&mime_info);
    }

    ap_pclosedir(neg->pool, dirp);
    return OK;
}


/*****************************************************************
 * And now for the code you've been waiting for... actually
 * finding a match to the client's requirements.
 */

/* Matching MIME types ... the star/star and foo/star commenting conventions
 * are implemented here.  (You know what I mean by star/star, but just
 * try mentioning those three characters in a C comment).  Using strcmp()
 * is legit, because everything has already been smashed to lowercase.
 *
 * Note also that if we get an exact match on the media type, we update
 * level_matched for use in level_cmp below...
 * 
 * We also give a value for mime_stars, which is used later. It should
 * be 1 for star/star, 2 for type/star and 3 for type/subtype.
 */

static int mime_match(accept_rec *accept_r, var_rec *avail)
{
    char *accept_type = accept_r->type_name;
    char *avail_type = avail->type_name;
    int len = strlen(accept_type);

    if (accept_type[0] == '*') {        /* Anything matches star/star */
        if (avail->mime_stars < 1) {
            avail->mime_stars = 1;
        }
        return 1;
    }
    else if ((accept_type[len - 1] == '*') &&
             !strncmp(accept_type, avail_type, len - 2)) {
        if (avail->mime_stars < 2) {
            avail->mime_stars = 2;
        }
        return 1;
    }
    else if (!strcmp(accept_type, avail_type)
             || (!strcmp(accept_type, "text/html")
                 && (!strcmp(avail_type, INCLUDES_MAGIC_TYPE)
                     || !strcmp(avail_type, INCLUDES_MAGIC_TYPE3)))) {
        if (accept_r->level >= avail->level) {
            avail->level_matched = avail->level;
            avail->mime_stars = 3;
            return 1;
        }
    }

    return OK;
}

/* This code implements a piece of the tie-breaking algorithm between
 * variants of equal quality.  This piece is the treatment of variants
 * of the same base media type, but different levels.  What we want to
 * return is the variant at the highest level that the client explicitly
 * claimed to accept.
 *
 * If all the variants available are at a higher level than that, or if
 * the client didn't say anything specific about this media type at all
 * and these variants just got in on a wildcard, we prefer the lowest
 * level, on grounds that that's the one that the client is least likely
 * to choke on.
 *
 * (This is all motivated by treatment of levels in HTML --- we only
 * want to give level 3 to browsers that explicitly ask for it; browsers
 * that don't, including HTTP/0.9 browsers that only get the implicit
 * "Accept: * / *" [space added to avoid confusing cpp --- no, that
 * syntax doesn't really work] should get HTML2 if available).
 *
 * (Note that this code only comes into play when we are choosing among
 * variants of equal quality, where the draft standard gives us a fair
 * bit of leeway about what to do.  It ain't specified by the standard;
 * rather, it is a choice made by this server about what to do in cases
 * where the standard does not specify a unique course of action).
 */

static int level_cmp(var_rec *var1, var_rec *var2)
{
    /* Levels are only comparable between matching media types */

    if (var1->is_pseudo_html && !var2->is_pseudo_html) {
        return 0;
    }

    if (!var1->is_pseudo_html && strcmp(var1->type_name, var2->type_name)) {
        return 0;
    }

    /* Take highest level that matched, if either did match. */

    if (var1->level_matched > var2->level_matched) {
        return 1;
    }
    if (var1->level_matched < var2->level_matched) {
        return -1;
    }

    /* Neither matched.  Take lowest level, if there's a difference. */

    if (var1->level < var2->level) {
        return 1;
    }
    if (var1->level > var2->level) {
        return -1;
    }

    /* Tied */

    return 0;
}

/* Finding languages.  The main entry point is set_language_quality()
 * which is called for each variant. It sets two elements in the
 * variant record:
 *    language_quality  - the 'q' value of the 'best' matching language
 *                        from Accept-Language: header (HTTP/1.1)
 *    lang_index    -     Pre HTTP/1.1 language priority, using
 *                        position of language on the Accept-Language:
 *                        header, if present, else LanguagePriority
 *                        directive order.
 *
 * When we do the variant checking for best variant, we use language
 * quality first, and if a tie, language_index next (this only
 * applies when _not_ using the network algorithm). If using
 * network algorithm, lang_index is never used.
 *
 * set_language_quality() calls find_lang_index() and find_default_index()
 * to set lang_index.
 */

static int find_lang_index(array_header *accept_langs, char *lang)
{
    accept_rec *accs;
    int i;

    if (!lang) {
        return -1;
    }

    accs = (accept_rec *) accept_langs->elts;

    for (i = 0; i < accept_langs->nelts; ++i) {
        if (!strncmp(lang, accs[i].type_name, strlen(accs[i].type_name))) {
            return i;
        }
    }

    return -1;
}

/* This function returns the priority of a given language
 * according to LanguagePriority.  It is used in case of a tie
 * between several languages.
 */

static int find_default_index(neg_dir_config *conf, char *lang)
{
    array_header *arr;
    int nelts;
    char **elts;
    int i;

    if (!lang) {
        return -1;
    }

    arr = conf->language_priority;
    nelts = arr->nelts;
    elts = (char **) arr->elts;

    for (i = 0; i < nelts; ++i) {
        if (!strcasecmp(elts[i], lang)) {
            return i;
        }
    }

    return -1;
}

/* set_default_lang_quality() sets the quality we apply to variants
 * which have no language assigned to them. If none of the variants
 * have a language, we are not negotiating on language, so all are
 * acceptable, and we set the default q value to 1.0. However if
 * some of the variants have languages, we set this default to 0.001.
 * The value of this default will be applied to all variants with
 * no explicit language -- which will have the effect of making them
 * acceptable, but only if no variants with an explicit language
 * are acceptable. The default q value set here is assigned to variants
 * with no language type in set_language_quality().
 *
 * Note that if using the transparent negotiation network algorythm,
 * we don't use this fiddle.
 */

static void set_default_lang_quality(negotiation_state *neg)
{
    var_rec *avail_recs = (var_rec *) neg->avail_vars->elts;
    int j;

    if (!neg->use_transparent_neg) {
        for (j = 0; j < neg->avail_vars->nelts; ++j) {
            var_rec *variant = &avail_recs[j];
            if (variant->content_languages &&
                variant->content_languages->nelts) {
                neg->default_lang_quality = 0.001f;
                return;
            }
        }
    }

    neg->default_lang_quality = 1.0f;
}

/* Set the language_quality value in the variant record. Also
 * assigns lang_index for back-compat. 
 *
 * To find the language_quality value, we look for the 'q' value
 * of the 'best' matching language on the Accept-Language:
 * header. The'best' match is the language on Accept-Language:
 * header which matches the language of this variant either fully,
 * or as far as the prefix marker (-). If two or more languages
 * match, use the longest string from the Accept-Language: header
 * (see HTTP/1.1 [14.4])
 *
 * When a variant has multiple languages, we find the 'best'
 * match for each variant language tag as above, then select the
 * one with the highest q value. Because both the accept-header
 * and variant can have multiple languages, we now have a hairy
 * loop-within-a-loop here.
 *
 * If the variant has no language and we have no Accept-Language
 * items, leave the quality at 1.0 and return.
 *
 * If the variant has no language, we use the default as set by
 * set_default_lang_quality() (1.0 if we are not negotiating on
 * language, 0.001 if we are).
 *
 * Following the setting of the language quality, we drop through to
 * set the old 'lang_index'. This is set based on either the order
 * of the languages on the Accept-Language header, or the
 * order on the LanguagePriority directive. This is only used
 * in the negotiation if the language qualities tie.
 */

static void set_language_quality(negotiation_state *neg, var_rec *variant)
{
    int i;
    int naccept = neg->accept_langs->nelts;
    int idx;
    neg_dir_config *conf = NULL;
    char *firstlang;

    if (naccept == 0) {
        conf = (neg_dir_config *) ap_get_module_config(neg->r->per_dir_config,
                                                    &negotiation_module);
    }

    if (naccept == 0 && (!variant->content_languages ||
                         !variant->content_languages->nelts)) {
        return;                 /* no accept-language and no variant lang */
    }

    if (!variant->content_languages || !variant->content_languages->nelts) {
        /* This variant has no content-language, so use the default
         * quality factor for variants with no content-language
         * (previously set by set_default_lang_quality()). */
        variant->lang_quality = neg->default_lang_quality;

        if (naccept == 0) {
            return;             /* no accept-language items */
        }

    }
    else if (naccept) {
        /* Variant has one (or more) languages, and we have one (or more)
         * language ranges on the Accept-Language header. Look for
         * the best match. We do this by going through each language
         * on the variant description looking for a match on the
         * Accept-Language header. The best match is the longest matching
         * language on the header. The final result is the best q value
         * from all the languages on the variant description.
         */
        int j;
        float fiddle_q = 0.0f;
        accept_rec *accs = (accept_rec *) neg->accept_langs->elts;
        accept_rec *best = NULL, *star = NULL;
        char *p;

        for (j = 0; j < variant->content_languages->nelts; ++j) {
            char *lang;         /* language from variant description */
            accept_rec *bestthistag = NULL;
            int prefixlen = 0;
            int longest_lang_range_len = 0;
            int len;

            /* lang is the variant's language-tag, which is the one
             * we are allowed to use the prefix of in HTTP/1.1
             */
            lang = ((char **) (variant->content_languages->elts))[j];
            p = strchr(lang, '-');      /* find prefix part (if any) */
            if (p) {
                prefixlen = p - lang;
            }

            /* now find the best (i.e. longest) matching Accept-Language
             * header language. We put the best match for this tag in 
             * bestthistag. We cannot update the overall best (based on
             * q value) because the best match for this tag is the longest
             * language item on the accept header, not necessarily the
             * highest q.
             */
            for (i = 0; i < neg->accept_langs->nelts; ++i) {