buckets/apr_buckets_pool.c

   1 /* Licensed to the Apache Software Foundation (ASF) under one or more
   2  * contributor license agreements.  See the NOTICE file distributed with
   3  * this work for additional information regarding copyright ownership.
   4  * The ASF licenses this file to You under the Apache License, Version 2.0
   5  * (the "License"); you may not use this file except in compliance with
   6  * the License.  You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include "apr_buckets.h"
  18 #define APR_WANT_MEMFUNC
  19 #include "apr_want.h"
  20
  21 static apr_status_t pool_bucket_cleanup(void *data)
  22 {
  23     apr_bucket_pool *p = data;
  24
  25     /*
  26      * If the pool gets cleaned up, we have to copy the data out
  27      * of the pool and onto the heap.  But the apr_buckets out there
  28      * that point to this pool bucket need to be notified such that
  29      * they can morph themselves into a regular heap bucket the next
  30      * time they try to read.  To avoid having to manipulate
  31      * reference counts and b->data pointers, the apr_bucket_pool
  32      * actually _contains_ an apr_bucket_heap as its first element,
  33      * so the two share their apr_bucket_refcount member, and you
  34      * can typecast a pool bucket struct to make it look like a
  35      * regular old heap bucket struct.
  36      */
  37     p->heap.base = apr_bucket_alloc(p->heap.alloc_len, p->list);
  38     memcpy(p->heap.base, p->base, p->heap.alloc_len);
  39     p->base = NULL;
  40     p->pool = NULL;
  41
  42     return APR_SUCCESS;
  43 }
  44
  45 static apr_status_t pool_bucket_read(apr_bucket *b, const char **str,
  46                                      apr_size_t *len, apr_read_type_e block)
  47 {
  48     apr_bucket_pool *p = b->data;
  49     const char *base = p->base;
  50
  51     if (p->pool == NULL) {
  52         /*
  53          * pool has been cleaned up... masquerade as a heap bucket from now
  54          * on. subsequent bucket operations will use the heap bucket code.
  55          */
  56         b->type = &apr_bucket_type_heap;
  57         base = p->heap.base;
  58     }
  59     *str = base + b->start;
  60     *len = b->length;
  61     return APR_SUCCESS;
  62 }
  63
  64 static void pool_bucket_destroy(void *data)
  65 {
  66     apr_bucket_pool *p = data;
  67
  68     /* If the pool is cleaned up before the last reference goes
  69      * away, the data is really now on the heap; heap_destroy() takes
  70      * over.  free() in heap_destroy() thinks it's freeing
  71      * an apr_bucket_heap, when in reality it's freeing the whole
  72      * apr_bucket_pool for us.
  73      */
  74     if (p->pool) {
  75         /* the shared resource is still in the pool
  76          * because the pool has not been cleaned up yet
  77          */
  78         if (apr_bucket_shared_destroy(p)) {
  79             apr_pool_cleanup_kill(p->pool, p, pool_bucket_cleanup);
  80             apr_bucket_free(p);
  81         }
  82     }
  83     else {
  84         /* the shared resource is no longer in the pool, it's
  85          * on the heap, but this reference still thinks it's a pool
  86          * bucket.  we should just go ahead and pass control to
  87          * heap_destroy() for it since it doesn't know any better.
  88          */
  89         apr_bucket_type_heap.destroy(p);
  90     }
  91 }
  92
  93 APU_DECLARE(apr_bucket *) apr_bucket_pool_make(apr_bucket *b,
  94                       const char *buf, apr_size_t length, apr_pool_t *pool)
  95 {
  96     apr_bucket_pool *p;
  97
  98     p = apr_bucket_alloc(sizeof(*p), b->list);
  99
 100     /* XXX: we lose the const qualifier here which indicates
 101      * there's something screwy with the API...
 102      */
 103     /* XXX: why is this?  buf is const, p->base is const... what's
 104      * the problem?  --jcw */
 105     p->base = (char *) buf;
 106     p->pool = pool;
 107     p->list = b->list;
 108
 109     b = apr_bucket_shared_make(b, p, 0, length);
 110     b->type = &apr_bucket_type_pool;
 111
 112     /* pre-initialize heap bucket member */
 113     p->heap.alloc_len = length;
 114     p->heap.base      = NULL;
 115     p->heap.free_func = apr_bucket_free;
 116
 117     apr_pool_cleanup_register(p->pool, p, pool_bucket_cleanup,
 118                               apr_pool_cleanup_null);
 119     return b;
 120 }
 121
 122 APU_DECLARE(apr_bucket *) apr_bucket_pool_create(const char *buf,
 123                                                  apr_size_t length,
 124                                                  apr_pool_t *pool,
 125                                                  apr_bucket_alloc_t *list)
 126 {
 127     apr_bucket *b = apr_bucket_alloc(sizeof(*b), list);
 128
 129     APR_BUCKET_INIT(b);
 130     b->free = apr_bucket_free;
 131     b->list = list;
 132     return apr_bucket_pool_make(b, buf, length, pool);
 133 }
 134
 135 APU_DECLARE_DATA const apr_bucket_type_t apr_bucket_type_pool = {
 136     "POOL", 5, APR_BUCKET_DATA,
 137     pool_bucket_destroy,
 138     pool_bucket_read,
 139     apr_bucket_setaside_noop, /* don't need to setaside thanks to the cleanup*/
 140     apr_bucket_shared_split,
 141     apr_bucket_shared_copy
 142 };