mod_negotiation.c

Apache官方在今天放出产品系列2.2的最新版本2.2.11的源码包 最流行的HTTP服务器软件之一

            accept_rec *accs = (accept_rec *) neg->accept_langs->elts;
            accept_rec *best = NULL, *star = NULL;
            accept_rec *bestthistag;
            char *lang, *p;
            float fiddle_q = 0.0f;
            int any_match_on_star = 0;
            int i, j;
            apr_size_t alen, longest_lang_range_len;

            for (j = 0; j < variant->content_languages->nelts; ++j) {
                p = NULL;
                bestthistag = NULL;
                longest_lang_range_len = 0;
                alen = 0;

                /* 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];

                /* 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) {
                    if (!strcmp(accs[i].name, "*")) {
                        if (!star) {
                            star = &accs[i];
                        }
                        continue;
                    }
                    /* Find language. We match if either the variant
                     * language tag exactly matches the language range
                     * from the accept header, or a prefix of the variant
                     * language tag up to a '-' character matches the
                     * whole of the language range in the Accept-Language
                     * header.  Note that HTTP/1.x allows any number of
                     * '-' characters in a tag or range, currently only
                     * tags with zero or one '-' characters are defined
                     * for general use (see rfc1766).
                     *
                     * We only use language range in the Accept-Language
                     * header the best match for the variant language tag
                     * if it is longer than the previous best match.
                     */

                    alen = strlen(accs[i].name);

                    if ((strlen(lang) >= alen) &&
                        !strncmp(lang, accs[i].name, alen) &&
                        ((lang[alen] == 0) || (lang[alen] == '-')) ) {

                        if (alen > longest_lang_range_len) {
                            longest_lang_range_len = alen;
                            bestthistag = &accs[i];
                        }
                    }

                    if (!bestthistag && !neg->dont_fiddle_headers) {
                        /* The next bit is a fiddle. Some browsers might
                         * be configured to send more specific language
                         * ranges than desirable. For example, an
                         * Accept-Language of en-US should never match
                         * variants with languages en or en-GB. But US
                         * English speakers might pick en-US as their
                         * language choice.  So this fiddle checks if the
                         * language range has a prefix, and if so, it
                         * matches variants which match that prefix with a
                         * priority of 0.001. So a request for en-US would
                         * 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_quali