mod_substitute.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

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * mod_substitute.c: Perform content rewriting on the fly
 */

#include "httpd.h"
#include "http_config.h"
#include "http_core.h"
#include "apr_general.h"
#include "apr_strings.h"
#include "apr_strmatch.h"
#include "apr_lib.h"
#include "util_filter.h"
#include "apr_buckets.h"
#include "http_request.h"
#define APR_WANT_STRFUNC
#include "apr_want.h"

static const char substitute_filter_name[] = "SUBSTITUTE";

module AP_MODULE_DECLARE_DATA substitute_module;

typedef struct subst_pattern_t {
    const apr_strmatch_pattern *pattern;
    const ap_regex_t *regexp;
    const char *replacement;
    apr_size_t replen;
    apr_size_t patlen;
    int flatten;
} subst_pattern_t;

typedef struct {
    apr_array_header_t *patterns;
} subst_dir_conf;

typedef struct {
    apr_bucket_brigade *linebb;
    apr_bucket_brigade *linesbb;
    apr_bucket_brigade *passbb;
    apr_bucket_brigade *pattbb;
    apr_pool_t *tpool;
} substitute_module_ctx;

static void *create_substitute_dcfg(apr_pool_t *p, char *d)
{
    subst_dir_conf *dcfg =
    (subst_dir_conf *) apr_pcalloc(p, sizeof(subst_dir_conf));

    dcfg->patterns = apr_array_make(p, 10, sizeof(subst_pattern_t));
    return dcfg;
}

static void *merge_substitute_dcfg(apr_pool_t *p, void *basev, void *overv)
{
    subst_dir_conf *a =
    (subst_dir_conf *) apr_pcalloc(p, sizeof(subst_dir_conf));
    subst_dir_conf *base = (subst_dir_conf *) basev;
    subst_dir_conf *over = (subst_dir_conf *) overv;

    a->patterns = apr_array_append(p, over->patterns,
                                                  base->patterns);
    return a;
}

#define AP_MAX_BUCKETS 1000

#define SEDSCAT(s1, s2, pool, buff, blen, repl) do { \
    if (!s1) {                                       \
        s1 = apr_pstrmemdup(pool, buff, blen);       \
    }                                                \
    else {                                           \
        s2 = apr_pstrmemdup(pool, buff, blen);       \
        s1 = apr_pstrcat(pool, s1, s2, NULL);        \
    }                                                \
    s1 = apr_pstrcat(pool, s1, repl, NULL);          \
} while (0)

#define SEDRMPATBCKT(b, offset, tmp_b, patlen) do {  \
    apr_bucket_split(b, offset);                     \
    tmp_b = APR_BUCKET_NEXT(b);                      \
    apr_bucket_split(tmp_b, patlen);                 \
    b = APR_BUCKET_NEXT(tmp_b);                      \
    apr_bucket_delete(tmp_b);                        \
} while (0)

static void do_pattmatch(ap_filter_t *f, apr_bucket *inb,
                         apr_bucket_brigade *mybb,
                         apr_pool_t *tmp_pool)
{
    int i;
    int force_quick = 0;
    ap_regmatch_t regm[AP_MAX_REG_MATCH];
    apr_size_t bytes;
    apr_size_t len;
    apr_size_t fbytes;
    const char *buff;
    const char *repl;
    char *scratch;
    char *p;
    char *s1;
    char *s2;
    apr_bucket *b;
    apr_bucket *tmp_b;
    apr_pool_t *tpool;

    subst_dir_conf *cfg =
    (subst_dir_conf *) ap_get_module_config(f->r->per_dir_config,
                                             &substitute_module);
    subst_pattern_t *script;

    APR_BRIGADE_INSERT_TAIL(mybb, inb);
    
    script = (subst_pattern_t *) cfg->patterns->elts;
    apr_pool_create(&tpool, tmp_pool);
    scratch = NULL;
    fbytes = 0;
    /*
     * Simple optimization. If we only have one pattern, then
     * we can safely avoid the overhead of flattening
     */
    if (cfg->patterns->nelts == 1) {
       force_quick = 1;
    }
    for (i = 0; i < cfg->patterns->nelts; i++) {
        for (b = APR_BRIGADE_FIRST(mybb);
             b != APR_BRIGADE_SENTINEL(mybb);
             b = APR_BUCKET_NEXT(b)) {
            if (APR_BUCKET_IS_METADATA(b)) {
                /*
                 * we should NEVER see this, because we should never
                 * be passed any, but "handle" it just in case.
                 */
                continue;
            }
            if (apr_bucket_read(b, &buff, &bytes, APR_BLOCK_READ)
                    == APR_SUCCESS) {
                s1 = NULL;
                if (script->pattern) {
                    while ((repl = apr_strmatch(script->pattern, buff, bytes)))
                    {
                        /* get offset into buff for pattern */
                        len = (apr_size_t) (repl - buff);
                        if (script->flatten && !force_quick) {
                            /*
                             * We are flattening the buckets here, meaning
                             * that we don't do the fast bucket splits.
                             * Instead we copy over what the buckets would
                             * contain and use them. This is slow, since we
                             * are constanting allocing space and copying
                             * strings.
                             */
                            SEDSCAT(s1, s2, tmp_pool, buff, len,
                                    script->replacement);
                        }
                        else {
                            /*
                             * We now split off the stuff before the regex
                             * as its own bucket, then isolate the pattern
                             * and delete it.
                             */
                            SEDRMPATBCKT(b, len, tmp_b, script->patlen);
                            /*
                             * Finally, we create a bucket that contains the
                             * replacement...
                             */
                            tmp_b = apr_bucket_transient_create(script->replacement,
                                      script->replen,
                                      f->r->connection->bucket_alloc);
                            /* ... and insert it */
                            APR_BUCKET_INSERT_BEFORE(b, tmp_b);
                        }
                        /* now we need to adjust buff for all these changes */
                        len += script->patlen;
                        bytes -= len;
                        buff += len;
                    }
                    if (script->flatten && s1 && !force_quick) {
                        /*
                         * we've finished looking at the bucket, so remove the
                         * old one and add in our new one
                         */
                        s2 = apr_pstrmemdup(tmp_pool, buff, bytes);
                        s1 = apr_pstrcat(tmp_pool, s1, s2, NULL);
                        tmp_b = apr_bucket_transient_create(s1, strlen(s1),
                                            f->r->connection->bucket_alloc);
                        APR_BUCKET_INSERT_BEFORE(b, tmp_b);
                        tmp_b = APR_BUCKET_NEXT(b);
                        apr_bucket_delete(b);
                        b = tmp_b;
                    }

                }
                else if (script->regexp) {
                    /*
                     * we need a null terminated string here :(. To hopefully
                     * save time and memory, we don't alloc for each run
                     * through, but only if we need to have a larger chunk
                     * to save the string to. So we keep track of how much
                     * we've allocated and only re-alloc when we need it.
                     * NOTE: this screams for a macro.
                     */
                    if (!scratch || (bytes > (fbytes + 1))) {
                        fbytes = bytes + 1;
                        scratch = apr_palloc(tpool, fbytes);
                    }
                    /* reset pointer to the scratch space */
                    p = scratch;
                    memcpy(p, buff, bytes);
                    p[bytes] = '\0';
                    while (!ap_regexec(script->regexp, p,
                                       AP_MAX_REG_MATCH, regm, 0)) {
                        /* first, grab the replacement string */
                        repl = ap_pregsub(tmp_pool, script->replacement, p,
                                          AP_MAX_REG_MATCH, regm);
                        if (script->flatten && !force_quick) {
                            SEDSCAT(s1, s2, tmp_pool, p, regm[0].rm_so, repl);
                        }
                        else {
                            len = (apr_size_t) (regm[0].rm_eo - regm[0].rm_so);
                            SEDRMPATBCKT(b, regm[0].rm_so, tmp_b, len);
                            tmp_b = apr_bucket_transient_create(repl,
                                                                strlen(repl),
                                             f->r->connection->bucket_alloc);
                            APR_BUCKET_INSERT_BEFORE(b, tmp_b);
                        }
                        /*
                         * reset to past what we just did. buff now maps to b
                         * again
                         */
                        p += regm[0].rm_eo;
                    }
                    if (script->flatten && s1 && !force_quick) {
                        s1 = apr_pstrcat(tmp_pool, s1, p, NULL);
                        tmp_b = apr_bucket_transient_create(s1, strlen(s1),
                                            f->r->connection->bucket_alloc);
                        APR_BUCKET_INSERT_BEFORE(b, tmp_b);
                        tmp_b = APR_BUCKET_NEXT(b);
                        apr_bucket_delete(b);
                        b = tmp_b;
                    }

                }
                else {
                    /* huh? */
                    continue;
                }
            }
        }
        script++;
    }

    apr_pool_destroy(tpool);

    return;
}

static apr_status_t substitute_filter(ap_filter_t *f, apr_bucket_brigade *bb)
{
    apr_size_t bytes;
    apr_size_t len;
    apr_size_t fbytes;
    const char *buff;
    const char *nl = NULL;
    char *bflat;
    apr_bucket *b;
    apr_bucket *tmp_b;
    apr_bucket_brigade *tmp_bb = NULL;
    apr_status_t rv;

    substitute_module_ctx *ctx = f->ctx;
    
    /*
     * First time around? Create the saved bb that we used for each pass
     * through. Note that we can also get here when we explicitly clear ctx,
     * for error handling
     */
    if (!ctx) {
        f->ctx = ctx = apr_pcalloc(f->r->pool, sizeof(*ctx));
        /*
         * Create all the temporary brigades we need and reuse them to avoid
         * creating them over and over again from r->pool which would cost a
         * lot of memory in some cases.
         */
        ctx->linebb = apr_brigade_create(f->r->pool, f->c->bucket_alloc);
        ctx->linesbb = apr_brigade_create(f->r->pool, f->c->bucket_alloc);
        ctx->pattbb = apr_brigade_create(f->r->pool, f->c->bucket_alloc);