mod_negotiation.c

最新apache的源代码

                         * match variants of types en and en-GB, but at
                         * much lower priority than matches of en-US
                         * directly, or of any other language listed on
                         * the Accept-Language header. Note that this
                         * fiddle does not handle multi-level prefixes.
                         */
                        if ((p = strchr(accs[i].name, '-'))) {
                            int plen = p - accs[i].name;

                            if (!strncmp(lang, accs[i].name, plen)) {
                                fiddle_q = 0.001f;
                            }
                        }
                    }
                }
                /* Finished looking at Accept-Language headers, the best
                 * (longest) match is in bestthistag, or NULL if no match
                 */
                if (!best ||
                    (bestthistag && bestthistag->quality > best->quality)) {
                    best = bestthistag;
                }

                /* See if the tag matches on a * in the Accept-Language
                 * header. If so, record this fact for later use
                 */
                if (!bestthistag && star) {
                    any_match_on_star = 1;
                }
            }

            /* If one of the language tags of the variant matched on *, we
             * need to see if its q is better than that of any non-* match
             * on any other tag of the variant.  If so the * match takes
             * precedence and the overall match is not definite.
             */
            if ( any_match_on_star &&
                ((best && star->quality > best->quality) ||
                 (!best)) ) {
                best = star;
                variant->definite = 0;
            }

            variant->lang_quality = best ? best->quality : fiddle_q;
        }
    }

    /* Handle the ForceDefaultLanguage overrides, based on the best match
     * to LanguagePriority order.  The best match is the lowest index of
     * any LanguagePriority match.
     */
    if (((forcepriority & FLP_PREFER)
             && (variant->lang_index < 0))
     || ((forcepriority & FLP_FALLBACK)
             && !variant->lang_quality))
    {
        int bestidx = -1;
        int j;

        for (j = 0; j < variant->content_languages->nelts; ++j)
        {
            /* lang is the variant's language-tag, which is the one
             * we are allowed to use the prefix of in HTTP/1.1
             */
            char *lang = ((char **) (variant->content_languages->elts))[j];
            int idx = -1;

            /* If we wish to fallback or
             * we use our own LanguagePriority index.
             */
            idx = find_lang_index(neg->conf->language_priority, lang);
            if ((idx >= 0) && ((bestidx == -1) || (idx < bestidx))) {
                bestidx = idx;
            }
        }

        if (bestidx >= 0) {
            if (variant->lang_quality) {
                if (forcepriority & FLP_PREFER) {
                    variant->lang_index = bestidx;
                }
            }
            else {
                if (forcepriority & FLP_FALLBACK) {
                    variant->lang_index = bestidx;
                    variant->lang_quality = .0001f;
                    variant->definite = 0;
                }
            }
        }
    }
    return;
}

/* Determining the content length --- if the map didn't tell us,
 * we have to do a stat() and remember for next time.
 */

static apr_off_t find_content_length(negotiation_state *neg, var_rec *variant)
{
    apr_finfo_t statb;

    if (variant->bytes < 0) {
        if (   variant->sub_req
            && (variant->sub_req->finfo.valid & APR_FINFO_SIZE)) {
            variant->bytes = variant->sub_req->finfo.size;
        }
        else {
            char *fullname = ap_make_full_path(neg->pool, neg->dir_name,
                                               variant->file_name);

            if (apr_stat(&statb, fullname,
                         APR_FINFO_SIZE, neg->pool) == APR_SUCCESS) {
                variant->bytes = statb.size;
            }
        }
    }

    return variant->bytes;
}

/* For a given variant, find the best matching Accept: header
 * and assign the Accept: header's quality value to the
 * mime_type_quality field of the variant, for later use in
 * determining the best matching variant.
 */

static void set_accept_quality(negotiation_state *neg, var_rec *variant)
{
    int i;
    accept_rec *accept_recs;
    float q = 0.0f;
    int q_definite = 1;

    /* if no Accept: header, leave quality alone (will
     * remain at the default value of 1)
     *
     * XXX: This if is currently never true because of the effect of
     * maybe_add_default_accepts().
     */
    if (!neg->accepts) {
        if (variant->mime_type && *variant->mime_type)
            variant->definite = 0;
        return;
    }

    accept_recs = (accept_rec *) neg->accepts->elts;

    /*
     * Go through each of the ranges on the Accept: header,
     * looking for the 'best' match with this variant's
     * content-type. We use the best match's quality
     * value (from the Accept: header) for this variant's
     * mime_type_quality field.
     *
     * The best match is determined like this:
     *    type/type is better than type/ * is better than * / *
     *    if match is type/type, use the level mime param if available
     */
    for (i = 0; i < neg->accepts->nelts; ++i) {

        accept_rec *type = &accept_recs[i];
        int prev_mime_stars;

        prev_mime_stars = variant->mime_stars;

        if (!mime_match(type, variant)) {
            continue;           /* didn't match the content type at all */
        }
        else {
            /* did match - see if there were less or more stars than
             * in previous match
             */
            if (prev_mime_stars == variant->mime_stars) {
                continue;       /* more stars => not as good a match */
            }
        }

        /* If we are allowed to mess with the q-values
         * and have no explicit q= parameters in the accept header,
         * make wildcards very low, so we have a low chance
         * of ending up with them if there's something better.
         */

        if (!neg->dont_fiddle_headers && !neg->accept_q &&
            variant->mime_stars == 1) {
            q = 0.01f;
        }
        else if (!neg->dont_fiddle_headers && !neg->accept_q &&
                 variant->mime_stars == 2) {
            q = 0.02f;
        }
        else {
            q = type->quality;
        }

        q_definite = (variant->mime_stars == 3);
    }
    variant->mime_type_quality = q;
    variant->definite = variant->definite && q_definite;

}

/* For a given variant, find the 'q' value of the charset given
 * on the Accept-Charset line. If no charsets are listed,
 * assume value of '1'.
 */
static void set_charset_quality(negotiation_state *neg, var_rec *variant)
{
    int i;
    accept_rec *accept_recs;
    const char *charset = variant->content_charset;
    accept_rec *star = NULL;

    /* if no Accept-Charset: header, leave quality alone (will
     * remain at the default value of 1)
     */
    if (!neg->accept_charsets) {
        if (charset && *charset)
            variant->definite = 0;
        return;
    }

    accept_recs = (accept_rec *) neg->accept_charsets->elts;

    if (charset == NULL || !*charset) {
        /* Charset of variant not known */

        /* if not a text / * type, leave quality alone */
        if (!(!strncmp(variant->mime_type, "text/", 5)
              || !strcmp(variant->mime_type, INCLUDES_MAGIC_TYPE)
              || !strcmp(variant->mime_type, INCLUDES_MAGIC_TYPE3)
              ))
            return;

        /* Don't go guessing if we are in strict header mode,
         * e.g. when running the rvsa, as any guess won't be reflected
         * in the variant list or content-location headers.
         */
        if (neg->dont_fiddle_headers)
            return;

        charset = "iso-8859-1"; /* The default charset for HTTP text types */
    }

    /*
     * Go through each of the items on the Accept-Charset header,
     * looking for a match with this variant's charset. If none
     * match, charset is unacceptable, so set quality to 0.
     */
    for (i = 0; i < neg->accept_charsets->nelts; ++i) {

        accept_rec *type = &accept_recs[i];

        if (!strcmp(type->name, charset)) {
            variant->charset_quality = type->quality;
            return;
        }
        else if (strcmp(type->name, "*") == 0) {
            star = type;
        }
    }
    /* No explicit match */
    if (star) {
        variant->charset_quality = star->quality;
        variant->definite = 0;
        return;
    }
    /* If this variant is in charset iso-8859-1, the default is 1.0 */
    if (strcmp(charset, "iso-8859-1") == 0) {
        variant->charset_quality = 1.0f;
    }
    else {
        variant->charset_quality = 0.0f;
    }
}


/* is_identity_encoding is included for back-compat, but does anyone
 * use 7bit, 8bin or binary in their var files??
 */

static int is_identity_encoding(const char *enc)
{
    return (!enc || !enc[0] || !strcmp(enc, "7bit") || !strcmp(enc, "8bit")
            || !strcmp(enc, "binary"));
}

/*
 * set_encoding_quality determines whether the encoding for a particular
 * variant is acceptable for the user-agent.
 *
 * The rules for encoding are that if the user-agent does not supply
 * any Accept-Encoding header, then all encodings are allowed but a
 * variant with no encoding should be preferred.
 * If there is an empty Accept-Encoding header, then no encodings are
 * acceptable. If there is a non-empty Accept-Encoding header, then
 * any of the listed encodings are acceptable, as well as no encoding
 * unless the "identity" encoding is specifically excluded.
 */
static void set_encoding_quality(negotiation_state *neg, var_rec *variant)
{
    accept_rec *accept_recs;
    const char *enc = variant->content_encoding;
    accept_rec *star = NULL;
    float value_if_not_found = 0.0f;
    int i;

    if (!neg->accept_encodings) {
        /* We had no Accept-Encoding header, assume that all
         * encodings are acceptable with a low quality,
         * but we prefer no encoding if available.
         */
        if (!enc || is_identity_encoding(enc))
            variant->encoding_quality = 1.0f;
        else
            variant->encoding_quality = 0.5f;

        return;
    }

    if (!enc || is_identity_encoding(enc)) {
        enc = "identity";
        value_if_not_found = 0.0001f;
    }

    accept_recs = (accept_rec *) neg->accept_encodings->elts;

    /* Go through each of the encodings on the Accept-Encoding: header,
     * looking for a match with our encoding. x- prefixes are ignored.
     */
    if (enc[0] == 'x' && enc[1] == '-') {
        enc += 2;
    }
    for (i = 0; i < neg->accept_encodings->nelts; ++i) {

        char *name = accept_recs[i].name;

        if (name[0] == 'x' && name[1] == '-') {
            name += 2;
        }

        if (!strcmp(name, enc)) {
            variant->encoding_quality = accept_recs[i].quality;
            return;
        }

        if (strcmp(name, "*") == 0) {
            star = &accept_recs[i];
        }

    }
    /* No explicit match */
    if (star) {
        variant->encoding_quality = star->quality;
        return;
    }

    /* Encoding not found on Accept-Encoding: header, so it is
     * _not_ acceptable unless it is the identity (no encoding)
     */
    variant->encoding_quality = value_if_not_found;
}

/*************************************************************
 * Possible results of the variant selection algorithm
 */
enum algorithm_results {
    alg_choice = 1,              /* choose variant */
    alg_list                     /* list variants */
};

/* Below is the 'best_match' function. It returns an int, which has
 * one of the two values alg_choice or alg_list, which give the result
 * of the variant selection algorithm.  alg_list means that no best
 * variant was found by the algorithm, alg_choice means that a best
 * variant was found and should be returned.  The list/choice
 * terminology comes from TCN (rfc2295), but is used in a more generic
 * way here.  The best variant is returned in *pbest. best_match has
 * two possible algorithms for determining the best variant: the
 * RVSA/1.0 algorithm (from RFC2296), and the standard Apache
 * algorithm. These are split out into separate functions
 * (is_variant_better_rvsa() and is_variant_better()).  Selection of
 * one is through the neg->use_rvsa flag.
 *
 * The call to best_match also creates full information, including
 * language, charset, etc quality for _every_ variant. This is needed
 * for generating a correct Vary header, and can be used for the
 * Alte