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| -rw-r--r-- | include/apr_ring.h | 517 |
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diff --git a/include/apr_ring.h b/include/apr_ring.h new file mode 100644 index 0000000..7280245 --- /dev/null +++ b/include/apr_ring.h @@ -0,0 +1,517 @@ +/* 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. + */ + +/* + * This code draws heavily from the 4.4BSD <sys/queue.h> macros + * and Dean Gaudet's "splim/ring.h". + * <http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/sys/queue.h> + * <http://www.arctic.org/~dean/splim/> + * + * We'd use Dean's code directly if we could guarantee the + * availability of inline functions. + */ + +#ifndef APR_RING_H +#define APR_RING_H + +/** + * @file apr_ring.h + * @brief APR Rings + */ + +/* + * for offsetof() + */ +#include "apr_general.h" + +/** + * @defgroup apr_ring Ring Macro Implementations + * @ingroup APR + * A ring is a kind of doubly-linked list that can be manipulated + * without knowing where its head is. + * @{ + */ + +/** + * The Ring Element + * + * A ring element struct is linked to the other elements in the ring + * through its ring entry field, e.g. + * <pre> + * struct my_element_t { + * APR_RING_ENTRY(my_element_t) link; + * int foo; + * char *bar; + * }; + * </pre> + * + * An element struct may be put on more than one ring if it has more + * than one APR_RING_ENTRY field. Each APR_RING_ENTRY has a corresponding + * APR_RING_HEAD declaration. + * + * @warning For strict C standards compliance you should put the APR_RING_ENTRY + * first in the element struct unless the head is always part of a larger + * object with enough earlier fields to accommodate the offsetof() used + * to compute the ring sentinel below. You can usually ignore this caveat. + */ +#define APR_RING_ENTRY(elem) \ + struct { \ + struct elem * volatile next; \ + struct elem * volatile prev; \ + } + +/** + * The Ring Head + * + * Each ring is managed via its head, which is a struct declared like this: + * <pre> + * APR_RING_HEAD(my_ring_t, my_element_t); + * struct my_ring_t ring, *ringp; + * </pre> + * + * This struct looks just like the element link struct so that we can + * be sure that the typecasting games will work as expected. + * + * The first element in the ring is next after the head, and the last + * element is just before the head. + */ +#define APR_RING_HEAD(head, elem) \ + struct head { \ + struct elem * volatile next; \ + struct elem * volatile prev; \ + } + +/** + * The Ring Sentinel + * + * This is the magic pointer value that occurs before the first and + * after the last elements in the ring, computed from the address of + * the ring's head. The head itself isn't an element, but in order to + * get rid of all the special cases when dealing with the ends of the + * ring, we play typecasting games to make it look like one. + * + * Here is a diagram to illustrate the arrangements of the next and + * prev pointers of each element in a single ring. Note that they point + * to the start of each element, not to the APR_RING_ENTRY structure. + * + * <pre> + * +->+------+<-+ +->+------+<-+ +->+------+<-+ + * | |struct| | | |struct| | | |struct| | + * / | elem | \/ | elem | \/ | elem | \ + * ... | | /\ | | /\ | | ... + * +------+ | | +------+ | | +------+ + * ...--|prev | | +--|ring | | +--|prev | + * | next|--+ | entry|--+ | next|--... + * +------+ +------+ +------+ + * | etc. | | etc. | | etc. | + * : : : : : : + * </pre> + * + * The APR_RING_HEAD is nothing but a bare APR_RING_ENTRY. The prev + * and next pointers in the first and last elements don't actually + * point to the head, they point to a phantom place called the + * sentinel. Its value is such that last->next->next == first because + * the offset from the sentinel to the head's next pointer is the same + * as the offset from the start of an element to its next pointer. + * This also works in the opposite direction. + * + * <pre> + * last first + * +->+------+<-+ +->sentinel<-+ +->+------+<-+ + * | |struct| | | | | |struct| | + * / | elem | \/ \/ | elem | \ + * ... | | /\ /\ | | ... + * +------+ | | +------+ | | +------+ + * ...--|prev | | +--|ring | | +--|prev | + * | next|--+ | head|--+ | next|--... + * +------+ +------+ +------+ + * | etc. | | etc. | + * : : : : + * </pre> + * + * Note that the offset mentioned above is different for each kind of + * ring that the element may be on, and each kind of ring has a unique + * name for its APR_RING_ENTRY in each element, and has its own type + * for its APR_RING_HEAD. + * + * Note also that if the offset is non-zero (which is required if an + * element has more than one APR_RING_ENTRY), the unreality of the + * sentinel may have bad implications on very perverse implementations + * of C -- see the warning in APR_RING_ENTRY. + * + * @param hp The head of the ring + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_SENTINEL(hp, elem, link) \ + (struct elem *)((char *)(&(hp)->next) - APR_OFFSETOF(struct elem, link)) + +/** + * The first element of the ring + * @param hp The head of the ring + */ +#define APR_RING_FIRST(hp) (hp)->next +/** + * The last element of the ring + * @param hp The head of the ring + */ +#define APR_RING_LAST(hp) (hp)->prev +/** + * The next element in the ring + * @param ep The current element + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_NEXT(ep, link) (ep)->link.next +/** + * The previous element in the ring + * @param ep The current element + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_PREV(ep, link) (ep)->link.prev + + +/** + * Initialize a ring + * @param hp The head of the ring + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_INIT(hp, elem, link) do { \ + APR_RING_FIRST((hp)) = APR_RING_SENTINEL((hp), elem, link); \ + APR_RING_LAST((hp)) = APR_RING_SENTINEL((hp), elem, link); \ + } while (0) + +/** + * Determine if a ring is empty + * @param hp The head of the ring + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + * @return true or false + */ +#define APR_RING_EMPTY(hp, elem, link) \ + (APR_RING_FIRST((hp)) == APR_RING_SENTINEL((hp), elem, link)) + +/** + * Initialize a singleton element + * @param ep The element + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_ELEM_INIT(ep, link) do { \ + APR_RING_NEXT((ep), link) = (ep); \ + APR_RING_PREV((ep), link) = (ep); \ + } while (0) + + +/** + * Splice the sequence ep1..epN into the ring before element lep + * (..lep.. becomes ..ep1..epN..lep..) + * @warning This doesn't work for splicing before the first element or on + * empty rings... see APR_RING_SPLICE_HEAD for one that does + * @param lep Element in the ring to splice before + * @param ep1 First element in the sequence to splice in + * @param epN Last element in the sequence to splice in + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_SPLICE_BEFORE(lep, ep1, epN, link) do { \ + APR_RING_NEXT((epN), link) = (lep); \ + APR_RING_PREV((ep1), link) = APR_RING_PREV((lep), link); \ + APR_RING_NEXT(APR_RING_PREV((lep), link), link) = (ep1); \ + APR_RING_PREV((lep), link) = (epN); \ + } while (0) + +/** + * Splice the sequence ep1..epN into the ring after element lep + * (..lep.. becomes ..lep..ep1..epN..) + * @warning This doesn't work for splicing after the last element or on + * empty rings... see APR_RING_SPLICE_TAIL for one that does + * @param lep Element in the ring to splice after + * @param ep1 First element in the sequence to splice in + * @param epN Last element in the sequence to splice in + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_SPLICE_AFTER(lep, ep1, epN, link) do { \ + APR_RING_PREV((ep1), link) = (lep); \ + APR_RING_NEXT((epN), link) = APR_RING_NEXT((lep), link); \ + APR_RING_PREV(APR_RING_NEXT((lep), link), link) = (epN); \ + APR_RING_NEXT((lep), link) = (ep1); \ + } while (0) + +/** + * Insert the element nep into the ring before element lep + * (..lep.. becomes ..nep..lep..) + * @warning This doesn't work for inserting before the first element or on + * empty rings... see APR_RING_INSERT_HEAD for one that does + * @param lep Element in the ring to insert before + * @param nep Element to insert + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_INSERT_BEFORE(lep, nep, link) \ + APR_RING_SPLICE_BEFORE((lep), (nep), (nep), link) + +/** + * Insert the element nep into the ring after element lep + * (..lep.. becomes ..lep..nep..) + * @warning This doesn't work for inserting after the last element or on + * empty rings... see APR_RING_INSERT_TAIL for one that does + * @param lep Element in the ring to insert after + * @param nep Element to insert + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_INSERT_AFTER(lep, nep, link) \ + APR_RING_SPLICE_AFTER((lep), (nep), (nep), link) + + +/** + * Splice the sequence ep1..epN into the ring before the first element + * (..hp.. becomes ..hp..ep1..epN..) + * @param hp Head of the ring + * @param ep1 First element in the sequence to splice in + * @param epN Last element in the sequence to splice in + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_SPLICE_HEAD(hp, ep1, epN, elem, link) do { \ + APR_RING_PREV((ep1), link) = APR_RING_SENTINEL((hp), elem, link);\ + APR_RING_NEXT((epN), link) = APR_RING_FIRST((hp)); \ + APR_RING_PREV(APR_RING_FIRST((hp)), link) = (epN); \ + APR_RING_FIRST((hp)) = (ep1); \ + } while (0) + +/** + * Splice the sequence ep1..epN into the ring after the last element + * (..hp.. becomes ..ep1..epN..hp..) + * @param hp Head of the ring + * @param ep1 First element in the sequence to splice in + * @param epN Last element in the sequence to splice in + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_SPLICE_TAIL(hp, ep1, epN, elem, link) do { \ + APR_RING_NEXT((epN), link) = APR_RING_SENTINEL((hp), elem, link);\ + APR_RING_PREV((ep1), link) = APR_RING_LAST((hp)); \ + APR_RING_NEXT(APR_RING_LAST((hp)), link) = (ep1); \ + APR_RING_LAST((hp)) = (epN); \ + } while (0) + +/** + * Insert the element nep into the ring before the first element + * (..hp.. becomes ..hp..nep..) + * @param hp Head of the ring + * @param nep Element to insert + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_INSERT_HEAD(hp, nep, elem, link) \ + APR_RING_SPLICE_HEAD((hp), (nep), (nep), elem, link) + +/** + * Insert the element nep into the ring after the last element + * (..hp.. becomes ..nep..hp..) + * @param hp Head of the ring + * @param nep Element to insert + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_INSERT_TAIL(hp, nep, elem, link) \ + APR_RING_SPLICE_TAIL((hp), (nep), (nep), elem, link) + +/** + * Concatenate ring h2 onto the end of ring h1, leaving h2 empty. + * @param h1 Head of the ring to concatenate onto + * @param h2 Head of the ring to concatenate + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_CONCAT(h1, h2, elem, link) do { \ + if (!APR_RING_EMPTY((h2), elem, link)) { \ + APR_RING_SPLICE_TAIL((h1), APR_RING_FIRST((h2)), \ + APR_RING_LAST((h2)), elem, link); \ + APR_RING_INIT((h2), elem, link); \ + } \ + } while (0) + +/** + * Prepend ring h2 onto the beginning of ring h1, leaving h2 empty. + * @param h1 Head of the ring to prepend onto + * @param h2 Head of the ring to prepend + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_PREPEND(h1, h2, elem, link) do { \ + if (!APR_RING_EMPTY((h2), elem, link)) { \ + APR_RING_SPLICE_HEAD((h1), APR_RING_FIRST((h2)), \ + APR_RING_LAST((h2)), elem, link); \ + APR_RING_INIT((h2), elem, link); \ + } \ + } while (0) + +/** + * Unsplice a sequence of elements from a ring + * @warning The unspliced sequence is left with dangling pointers at either end + * @param ep1 First element in the sequence to unsplice + * @param epN Last element in the sequence to unsplice + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_UNSPLICE(ep1, epN, link) do { \ + APR_RING_NEXT(APR_RING_PREV((ep1), link), link) = \ + APR_RING_NEXT((epN), link); \ + APR_RING_PREV(APR_RING_NEXT((epN), link), link) = \ + APR_RING_PREV((ep1), link); \ + } while (0) + +/** + * Remove a single element from a ring + * @warning The unspliced element is left with dangling pointers at either end + * @param ep Element to remove + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_REMOVE(ep, link) \ + APR_RING_UNSPLICE((ep), (ep), link) + +/** + * Iterate over a ring + * @param ep The current element + * @param head The head of the ring + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_FOREACH(ep, head, elem, link) \ + for (ep = APR_RING_FIRST(head); \ + ep != APR_RING_SENTINEL(head, elem, link); \ + ep = APR_RING_NEXT(ep, link)) + +/** + * Iterate over a ring safe against removal of the current element + * @param ep1 The current element + * @param ep2 Iteration cursor + * @param head The head of the ring + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_FOREACH_SAFE(ep1, ep2, head, elem, link) \ + for (ep1 = APR_RING_FIRST(head), ep2 = APR_RING_NEXT(ep1, link); \ + ep1 != APR_RING_SENTINEL(head, elem, link); \ + ep1 = ep2, ep2 = APR_RING_NEXT(ep1, link)) + +/* Debugging tools: */ + +#ifdef APR_RING_DEBUG +#include <stdio.h> +#include <assert.h> + +#define APR_RING_CHECK_ONE(msg, ptr) \ + fprintf(stderr, "*** %s %p\n", msg, ptr) + +#define APR_RING_CHECK(hp, elem, link, msg) \ + APR_RING_CHECK_ELEM(APR_RING_SENTINEL(hp, elem, link), elem, link, msg) + +#define APR_RING_CHECK_ELEM(ep, elem, link, msg) do { \ + struct elem *start = (ep); \ + struct elem *here = start; \ + fprintf(stderr, "*** ring check start -- %s\n", msg); \ + do { \ + fprintf(stderr, "\telem %p\n", here); \ + fprintf(stderr, "\telem->next %p\n", \ + APR_RING_NEXT(here, link)); \ + fprintf(stderr, "\telem->prev %p\n", \ + APR_RING_PREV(here, link)); \ + fprintf(stderr, "\telem->next->prev %p\n", \ + APR_RING_PREV(APR_RING_NEXT(here, link), link)); \ + fprintf(stderr, "\telem->prev->next %p\n", \ + APR_RING_NEXT(APR_RING_PREV(here, link), link)); \ + if (APR_RING_PREV(APR_RING_NEXT(here, link), link) != here) { \ + fprintf(stderr, "\t*** elem->next->prev != elem\n"); \ + break; \ + } \ + if (APR_RING_NEXT(APR_RING_PREV(here, link), link) != here) { \ + fprintf(stderr, "\t*** elem->prev->next != elem\n"); \ + break; \ + } \ + here = APR_RING_NEXT(here, link); \ + } while (here != start); \ + fprintf(stderr, "*** ring check end\n"); \ + } while (0) + +#define APR_RING_CHECK_CONSISTENCY(hp, elem, link) \ + APR_RING_CHECK_ELEM_CONSISTENCY(APR_RING_SENTINEL(hp, elem, link),\ + elem, link) + +#define APR_RING_CHECK_ELEM_CONSISTENCY(ep, elem, link) do { \ + struct elem *start = (ep); \ + struct elem *here = start; \ + do { \ + assert(APR_RING_PREV(APR_RING_NEXT(here, link), link) == here); \ + assert(APR_RING_NEXT(APR_RING_PREV(here, link), link) == here); \ + here = APR_RING_NEXT(here, link); \ + } while (here != start); \ + } while (0) + +#else +/** + * Print a single pointer value to STDERR + * (This is a no-op unless APR_RING_DEBUG is defined.) + * @param msg Descriptive message + * @param ptr Pointer value to print + */ +#define APR_RING_CHECK_ONE(msg, ptr) +/** + * Dump all ring pointers to STDERR, starting with the head and looping all + * the way around the ring back to the head. Aborts if an inconsistency + * is found. + * (This is a no-op unless APR_RING_DEBUG is defined.) + * @param hp Head of the ring + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + * @param msg Descriptive message + */ +#define APR_RING_CHECK(hp, elem, link, msg) +/** + * Loops around a ring and checks all the pointers for consistency. Pops + * an assertion if any inconsistency is found. Same idea as APR_RING_CHECK() + * except that it's silent if all is well. + * (This is a no-op unless APR_RING_DEBUG is defined.) + * @param hp Head of the ring + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_CHECK_CONSISTENCY(hp, elem, link) +/** + * Dump all ring pointers to STDERR, starting with the given element and + * looping all the way around the ring back to that element. Aborts if + * an inconsistency is found. + * (This is a no-op unless APR_RING_DEBUG is defined.) + * @param ep The element + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + * @param msg Descriptive message + */ +#define APR_RING_CHECK_ELEM(ep, elem, link, msg) +/** + * Loops around a ring, starting with the given element, and checks all + * the pointers for consistency. Pops an assertion if any inconsistency + * is found. Same idea as APR_RING_CHECK_ELEM() except that it's silent + * if all is well. + * (This is a no-op unless APR_RING_DEBUG is defined.) + * @param ep The element + * @param elem The name of the element struct + * @param link The name of the APR_RING_ENTRY in the element struct + */ +#define APR_RING_CHECK_ELEM_CONSISTENCY(ep, elem, link) +#endif + +/** @} */ + +#endif /* !APR_RING_H */ |