ns_list.h

00001 /*
00002  * Copyright (c) 2014-2015 ARM Limited. All rights reserved.
00003  * SPDX-License-Identifier: Apache-2.0
00004  * Licensed under the Apache License, Version 2.0 (the License); you may
00005  * not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  * http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00012  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 #ifndef NS_LIST_H_
00018 #define NS_LIST_H_
00019 
00020 #include "ns_types.h"
00021 
00022 #ifdef __cplusplus
00023 extern "C" {
00024 #endif
00025 
00026 /** \file
00027  * \brief Linked list support library
00028  *
00029  * The ns_list.h file provides a doubly-linked list/queue, providing O(1)
00030  * performance for all insertion/removal operations, and access to either
00031  * end of the list.
00032  *
00033  * Memory footprint is two pointers for the list head, and two pointers in each
00034  * list entry. It is similar in concept to BSD's TAILQ.
00035  *
00036  * Although the API is symmetrical and O(1) in both directions, due to internal
00037  * pointer design, it is *slightly* more efficient to insert at the end when
00038  * used as a queue, and to iterate forwards rather than backwards.
00039  *
00040  * Example of an entry type that can be stored to this list.
00041  * ~~~
00042  *     typedef struct example_entry
00043  *     {
00044  *         uint8_t        *data;
00045  *         uint32_t       data_count;
00046  *         ns_list_link_t link;
00047  *     }
00048  *     example_entry_t;
00049  *
00050  *     static NS_LIST_HEAD(example_entry_t, link) my_list;
00051  *     ns_list_init(&my_list);
00052  * ~~~
00053  * OR
00054  * ~~~
00055  *     NS_LIST_HEAD(example_entry_t, link) my_list = NS_LIST_INIT(my_list);
00056  * ~~~
00057  * OR
00058  * ~~~
00059  *     static NS_LIST_DEFINE(my_list, example_entry_t, link);
00060  * ~~~
00061  * OR
00062  * ~~~
00063  *     typedef NS_LIST_HEAD(example_entry_t, link) example_list_t;
00064  *     example_list_t NS_LIST_NAME_INIT(my_list);
00065  * ~~~
00066  * NOTE: the link field SHALL NOT be accessed by the user.
00067  *
00068  * An entry can exist on multiple lists by having multiple link fields.
00069  *
00070  * All the list operations are implemented as macros, most of which are backed
00071  * by optionally-inline functions. The macros do not evaluate any arguments more
00072  * than once, unless documented.
00073  *
00074  * In macro documentation, `list_t` refers to a list type defined using
00075  * NS_LIST_HEAD(), and `entry_t` to the entry type that was passed to it.
00076  */
00077 
00078 /** \brief Underlying generic linked list head.
00079  *
00080  * Users should not use this type directly, but use the NS_LIST_HEAD() macro.
00081  */
00082 typedef struct ns_list {
00083     void *first_entry;      ///< Pointer to first entry, or NULL if list is empty
00084     void **last_nextptr;    ///< Pointer to last entry's `next` pointer, or
00085                             ///< to head's `first_entry` pointer if list is empty
00086 } ns_list_t;
00087 
00088 /** \brief Declare a list head type
00089  *
00090  * This union stores the real list head, and also encodes as compile-time type
00091  * information the offset of the link pointer, and the type of the entry.
00092  *
00093  * Note that type information is compiler-dependent; this means
00094  * ns_list_get_first() could return either `void *`, or a pointer to the actual
00095  * entry type. So `ns_list_get_first()->data` is not a portable construct -
00096  * always assign returned entry pointers to a properly typed pointer variable.
00097  * This assignment will be then type-checked where the compiler supports it, and
00098  * will dereference correctly on compilers that don't support this extension.
00099  * ~~~
00100  *     NS_LIST_HEAD(example_entry_t, link) my_list;
00101  *
00102  *     example_entry_t *entry = ns_list_get_first(&my_list);
00103  *     do_something(entry->data);
00104  * ~~~
00105  * Each use of this macro generates a new anonymous union, so these two lists
00106  * have different types:
00107  * ~~~
00108  *     NS_LIST_HEAD(example_entry_t, link) my_list1;
00109  *     NS_LIST_HEAD(example_entry_t, link) my_list2;
00110  * ~~~
00111  * If you need to use a list type in multiple places, eg as a function
00112  * parameter, use typedef:
00113  * ~~~
00114  *     typedef NS_LIST_HEAD(example_entry_t, link) example_list_t;
00115  *
00116  *     void example_function(example_list_t *);
00117  * ~~~
00118  */
00119 #define NS_LIST_HEAD(entry_type, field) \
00120     NS_LIST_HEAD_BY_OFFSET_(entry_type, offsetof(entry_type, field))
00121 
00122 /** \brief Declare a list head type for an incomplete entry type.
00123  *
00124  * This declares a list head, similarly to NS_LIST_HEAD(), but unlike that
00125  * this can be used in contexts where the entry type may be incomplete.
00126  *
00127  * To use this, the link pointer must be the first member in the
00128  * actual complete structure. This is NOT checked - the definition of the
00129  * element should probably test NS_STATIC_ASSERT(offsetof(type, link) == 0)
00130  * if outside users are known to be using NS_LIST_HEAD_INCOMPLETE().
00131  * ~~~
00132  *     struct opaque;
00133  *     NS_LIST_HEAD_INCOMPLETE(struct opaque) opaque_list;
00134  * ~~~
00135  */
00136 #define NS_LIST_HEAD_INCOMPLETE(entry_type) \
00137     NS_LIST_HEAD_BY_OFFSET_(entry_type, 0)
00138 
00139 /// \privatesection
00140 /** \brief Internal macro defining a list head, given the offset to the link pointer
00141  * The +1 allows for link_offset being 0 - we can't declare a 0-size array
00142  */
00143 #define NS_LIST_HEAD_BY_OFFSET_(entry_type, link_offset) \
00144 union \
00145 { \
00146     ns_list_t slist; \
00147     NS_FUNNY_COMPARE_OK \
00148     NS_STATIC_ASSERT(link_offset <= UINT_FAST8_MAX, "link offset too large") \
00149     NS_FUNNY_COMPARE_RESTORE \
00150     char (*offset)[link_offset + 1]; \
00151     entry_type *type; \
00152 }
00153 
00154 /** \brief Get offset of link field in entry.
00155  * \return `(ns_list_offset_t)` The offset of the link field for entries on the specified list
00156  */
00157 #define NS_LIST_OFFSET_(list) ((ns_list_offset_t) (sizeof *(list)->offset - 1))
00158 
00159 /** \brief Get the entry pointer type.
00160  * \def NS_LIST_PTR_TYPE_
00161  *
00162  * \return An unqualified pointer type to an entry on the specified list.
00163  *
00164  * Only available if the compiler provides a "typeof" operator.
00165  */
00166 #if defined __cplusplus && __cplusplus >= 201103L
00167 #define NS_LIST_PTR_TYPE_(list) decltype((list)->type)
00168 #elif defined __GNUC__
00169 #define NS_LIST_PTR_TYPE_(list) __typeof__((list)->type)
00170 #endif
00171 
00172 /** \brief Check for compatible pointer types
00173  *
00174  * This test will produce a diagnostic about a pointer mismatch on
00175  * the == inside the sizeof operator. For example ARM/Norcroft C gives the error:
00176  *
00177  *     operand types are incompatible ("entry_t *" and "other_t *")
00178  */
00179 #ifdef CPPCHECK
00180 #define NS_PTR_MATCH_(a, b, str) ((void) 0)
00181 #else
00182 #define NS_PTR_MATCH_(a, b, str) ((void) sizeof ((a) == (b)))
00183 #endif
00184 
00185 /** \brief Internal macro to cast returned entry pointers to correct type.
00186  *
00187  * Not portable in C, alas. With GCC or C++11, the "get entry" macros return
00188  * correctly-typed pointers. Otherwise, the macros return `void *`.
00189  *
00190  * The attempt at a portable version would work if the C `?:` operator wasn't
00191  * broken - `x ? (t *) : (void *)` should really have type `(t *)` in C, but
00192  * it has type `(void *)`, which only makes sense for C++. The `?:` is left in,
00193  * in case some day it works. Some compilers may still warn if this is
00194  * assigned to a different type.
00195  */
00196 #ifdef NS_LIST_PTR_TYPE_
00197 #define NS_LIST_TYPECAST_(list, val) ((NS_LIST_PTR_TYPE_(list)) (val))
00198 #else
00199 #define NS_LIST_TYPECAST_(list, val) (0 ? (list)->type : (val))
00200 #endif
00201 
00202 /** \brief Internal macro to check types of input entry pointer. */
00203 #define NS_LIST_TYPECHECK_(list, entry) \
00204     (NS_PTR_MATCH_((list)->type, (entry), "incorrect entry type for list"), (entry))
00205 
00206 /** \brief Type used to pass link offset to underlying functions
00207  *
00208  * We could use size_t, but it would be unnecessarily large on 8-bit systems,
00209  * where we can be (pretty) confident we won't have next pointers more than
00210  * 256 bytes into a structure.
00211  */
00212 typedef uint_fast8_t ns_list_offset_t;
00213 
00214 /// \publicsection
00215 /** \brief The type for the link member in the user's entry structure.
00216  *
00217  * Users should not access this member directly - just pass its name to the
00218  * list head macros. The funny prev pointer simplifies common operations
00219  * (eg insertion, removal), at the expense of complicating rare reverse iteration.
00220  *
00221  * NB - the list implementation relies on next being the first member.
00222  */
00223 typedef struct ns_list_link {
00224     void *next;     ///< Pointer to next entry, or NULL if none
00225     void **prev;    ///< Pointer to previous entry's (or head's) next pointer
00226 } ns_list_link_t;
00227 
00228 /** \brief "Poison" value placed in unattached entries' link pointers.
00229  * \internal What are good values for this? Platform dependent, maybe just NULL
00230  */
00231 #define NS_LIST_POISON ((void *) 0xDEADBEEF)
00232 
00233 /** \brief Initialiser for an entry's link member
00234  *
00235  * This initialiser is not required by the library, but a user may want an
00236  * initialiser to include in their own entry initialiser. See
00237  * ns_list_link_init() for more discussion.
00238  */
00239 #define NS_LIST_LINK_INIT(name) \
00240     NS_FUNNY_INTPTR_OK \
00241     { NS_LIST_POISON, NS_LIST_POISON } \
00242     NS_FUNNY_INTPTR_RESTORE
00243 
00244 /** \hideinitializer \brief Initialise an entry's list link
00245  *
00246  * This "initialises" an unattached entry's link by filling the fields with
00247  * poison. This is optional, as unattached entries field pointers are not
00248  * meaningful, and it is not valid to call ns_list_get_next or similar on
00249  * an unattached entry.
00250  *
00251  * \param entry Pointer to an entry
00252  * \param field The name of the link member to initialise
00253  */
00254 #define ns_list_link_init(entry, field) ns_list_link_init_(&(entry)->field)
00255 
00256 /** \hideinitializer \brief Initialise a list
00257  *
00258  * Initialise a list head before use. A list head must be initialised using this
00259  * function or one of the NS_LIST_INIT()-type macros before use. A zero-initialised
00260  * list head is *not* valid.
00261  *
00262  * If used on a list containing existing entries, those entries will
00263  * become detached. (They are not modified, but their links are now effectively
00264  * undefined).
00265  *
00266  * \param list Pointer to a NS_LIST_HEAD() structure.
00267  */
00268 #define ns_list_init(list) ns_list_init_(&(list)->slist)
00269 
00270 /** \brief Initialiser for an empty list
00271  *
00272  * Usage in an enclosing initialiser:
00273  * ~~~
00274  *      static my_type_including_list_t x = {
00275  *          "Something",
00276  *          23,
00277  *          NS_LIST_INIT(x),
00278  *      };
00279  * ~~~
00280  * NS_LIST_DEFINE() or NS_LIST_NAME_INIT() may provide a shorter alternative
00281  * in simpler cases.
00282  */
00283 #define NS_LIST_INIT(name) { { NULL, &(name).slist.first_entry } }
00284 
00285 /** \brief Name and initialiser for an empty list
00286  *
00287  * Usage:
00288  * ~~~
00289  *      list_t NS_LIST_NAME_INIT(foo);
00290  * ~~~
00291  * acts as
00292  * ~~~
00293  *      list_t foo = { empty list };
00294  * ~~~
00295  * Also useful with designated initialisers:
00296  * ~~~
00297  *      .NS_LIST_NAME_INIT(foo),
00298  * ~~~
00299  * acts as
00300  * ~~~
00301  *      .foo = { empty list },
00302  * ~~~
00303  */
00304 #define NS_LIST_NAME_INIT(name) name = NS_LIST_INIT(name)
00305 
00306 /** \brief Define a list, and initialise to empty.
00307  *
00308  * Usage:
00309  * ~~~
00310  *     static NS_LIST_DEFINE(my_list, entry_t, link);
00311  * ~~~
00312  * acts as
00313  * ~~~
00314  *     static list_type my_list = { empty list };
00315  * ~~~
00316  */
00317 #define NS_LIST_DEFINE(name, type, field) \
00318     NS_LIST_HEAD(type, field) NS_LIST_NAME_INIT(name)
00319 
00320 /** \hideinitializer \brief Add an entry to the start of the linked list.
00321  *
00322  * ns_list_add_to_end() is *slightly* more efficient than ns_list_add_to_start().
00323  *
00324  * \param list  `(list_t *)`           Pointer to list.
00325  * \param entry `(entry_t * restrict)` Pointer to new entry to add.
00326  */
00327 #define ns_list_add_to_start(list, entry) \
00328     ns_list_add_to_start_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, entry))
00329 
00330 /** \hideinitializer \brief Add an entry to the end of the linked list.
00331  *
00332  * \param list  `(list_t *)`           Pointer to list.
00333  * \param entry `(entry_t * restrict)` Pointer to new entry to add.
00334  */
00335 #define ns_list_add_to_end(list, entry) \
00336     ns_list_add_to_end_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, entry))
00337 
00338 /** \hideinitializer \brief Add an entry before a specified entry.
00339  *
00340  * \param list   `(list_t *)`           Pointer to list.
00341  * \param before `(entry_t *)`          Existing entry before which to place the new entry.
00342  * \param entry  `(entry_t * restrict)` Pointer to new entry to add.
00343  */
00344 #define ns_list_add_before(list, before, entry) \
00345     ns_list_add_before_(NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, before), NS_LIST_TYPECHECK_(list, entry))
00346 
00347 /** \hideinitializer \brief Add an entry after a specified entry.
00348  *
00349  * ns_list_add_before() is *slightly* more efficient than ns_list_add_after().
00350  *
00351  * \param list  `(list_t *)`           Pointer to list.
00352  * \param after `(entry_t *)`          Existing entry after which to place the new entry.
00353  * \param entry `(entry_t * restrict)` Pointer to new entry to add.
00354  */
00355 #define ns_list_add_after(list, after, entry) \
00356     ns_list_add_after_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, after), NS_LIST_TYPECHECK_(list, entry))
00357 
00358 /** \brief Check if a list is empty.
00359  *
00360  * \param list `(const list_t *)` Pointer to list.
00361  *
00362  * \return     `(bool)`           true if the list is empty.
00363  */
00364 #define ns_list_is_empty(list) ((bool) ((list)->slist.first_entry == NULL))
00365 
00366 /** \brief Get the first entry.
00367  *
00368  * \param list `(const list_t *)` Pointer to list.
00369  *
00370  * \return     `(entry_t *)`      Pointer to first entry.
00371  * \return                        NULL if list is empty.
00372  */
00373 #define ns_list_get_first(list) NS_LIST_TYPECAST_(list, (list)->slist.first_entry)
00374 
00375 /** \hideinitializer \brief Get the previous entry.
00376  *
00377  * \param list    `(const list_t *)`  Pointer to list.
00378  * \param current `(const entry_t *)` Pointer to current entry.
00379  *
00380  * \return        `(entry_t *)`       Pointer to previous entry.
00381  * \return                            NULL if current entry is first.
00382  */
00383 #define ns_list_get_previous(list, current) \
00384     NS_LIST_TYPECAST_(list, ns_list_get_previous_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, current)))
00385 
00386 /** \hideinitializer \brief Get the next entry.
00387  *
00388  * \param list    `(const list_t *)`  Pointer to list.
00389  * \param current `(const entry_t *)` Pointer to current entry.
00390  *
00391  * \return        `(entry_t *)`       Pointer to next entry.
00392  * \return                            NULL if current entry is last.
00393  */
00394 #define ns_list_get_next(list, current) \
00395     NS_LIST_TYPECAST_(list, ns_list_get_next_(NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, current)))
00396 
00397 /** \hideinitializer \brief Get the last entry.
00398  *
00399  * \param list `(const list_t *)` Pointer to list.
00400  *
00401  * \return     `(entry_t *)`      Pointer to last entry.
00402  * \return                        NULL if list is empty.
00403  */
00404 #define ns_list_get_last(list) \
00405     NS_LIST_TYPECAST_(list, ns_list_get_last_(&(list)->slist, NS_LIST_OFFSET_(list)))
00406 
00407 /** \hideinitializer \brief Remove an entry.
00408  *
00409  * \param list  `(list_t *)`  Pointer to list.
00410  * \param entry `(entry_t *)` Entry on list to be removed.
00411  */
00412 #define ns_list_remove(list, entry) \
00413     ns_list_remove_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, entry))
00414 
00415 /** \hideinitializer \brief Replace an entry.
00416  *
00417  * \param list        `(list_t *)`           Pointer to list.
00418  * \param current     `(entry_t *)`          Existing entry on list to be replaced.
00419  * \param replacement `(entry_t * restrict)` New entry to be the replacement.
00420  */
00421 #define ns_list_replace(list, current, replacement) \
00422     ns_list_replace_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, current), NS_LIST_TYPECHECK_(list, replacement))
00423 
00424 /** \hideinitializer \brief Concatenate two lists.
00425  *
00426  * Attach the entries on the source list to the end of the destination
00427  * list, leaving the source list empty.
00428  *
00429  * \param dst `(list_t *)` Pointer to destination list.
00430  * \param src `(list_t *)` Pointer to source list.
00431  *
00432  */
00433 #define ns_list_concatenate(dst, src) \
00434         (NS_PTR_MATCH_(dst, src, "concatenating different list types"), \
00435         ns_list_concatenate_(&(dst)->slist, &(src)->slist, NS_LIST_OFFSET_(src)))
00436 
00437 /** \brief Iterate forwards over a list.
00438  *
00439  * Example:
00440  * ~~~
00441  *     ns_list_foreach(const my_entry_t, cur, &my_list)
00442  *     {
00443  *         printf("%s\n", cur->name);
00444  *     }
00445  * ~~~
00446  * Deletion of the current entry is not permitted as its next is checked after
00447  * running user code.
00448  *
00449  * The iteration pointer is declared inside the loop, using C99/C++, so it
00450  * is not accessible after the loop.  This encourages good code style, and
00451  * matches the semantics of C++11's "ranged for", which only provides the
00452  * declaration form:
00453  * ~~~
00454  *     for (const my_entry_t cur : my_list)
00455  * ~~~
00456  * If you need to see the value of the iteration pointer after a `break`,
00457  * you will need to assign it to a variable declared outside the loop before
00458  * breaking:
00459  * ~~~
00460  *      my_entry_t *match = NULL;
00461  *      ns_list_foreach(my_entry_t, cur, &my_list)
00462  *      {
00463  *          if (cur->id == id)
00464  *          {
00465  *              match = cur;
00466  *              break;
00467  *          }
00468  *      }
00469  * ~~~
00470  *
00471  * The user has to specify the entry type for the pointer definition, as type
00472  * extraction from the list argument isn't portable. On the other hand, this
00473  * also permits const qualifiers, as in the example above, and serves as
00474  * documentation. The entry type will be checked against the list type where the
00475  * compiler supports it.
00476  *
00477  * \param type                    Entry type `([const] entry_t)`.
00478  * \param e                       Name for iteration pointer to be defined
00479  *                                inside the loop.
00480  * \param list `(const list_t *)` Pointer to list - evaluated multiple times.
00481  */
00482 #define ns_list_foreach(type, e, list) \
00483     for (type *e = ns_list_get_first(list); e; e = ns_list_get_next(list, e))
00484 
00485 /** \brief Iterate forwards over a list, where user may delete.
00486  *
00487  * As ns_list_foreach(), but deletion of current entry is permitted as its
00488  * next pointer is recorded before running user code.
00489  *
00490  * Example:
00491  * ~~~
00492  *     ns_list_foreach_safe(my_entry_t, cur, &my_list)
00493  *     {
00494  *         ns_list_remove(cur);
00495  *     }
00496  * ~~~
00497  * \param type               Entry type `(entry_t)`.
00498  * \param e                  Name for iteration pointer to be defined
00499  *                           inside the loop.
00500  * \param list `(list_t *)`  Pointer to list - evaluated multiple times.
00501  */
00502 #define ns_list_foreach_safe(type, e, list) \
00503     for (type *e = ns_list_get_first(list), *_next##e; \
00504         e && (_next##e = ns_list_get_next(list, e), true); e = _next##e)
00505 
00506 /** \brief Iterate backwards over a list.
00507  *
00508  * As ns_list_foreach(), but going backwards - see its documentation.
00509  * Iterating forwards is *slightly* more efficient.
00510  */
00511 #define ns_list_foreach_reverse(type, e, list) \
00512     for (type *e = ns_list_get_last(list); e; e = ns_list_get_previous(list, e))
00513 
00514 /** \brief Iterate backwards over a list, where user may delete.
00515  *
00516  * As ns_list_foreach_safe(), but going backwards - see its documentation.
00517  * Iterating forwards is *slightly* more efficient.
00518  */
00519 #define ns_list_foreach_reverse_safe(type, e, list) \
00520     for (type *e = ns_list_get_last(list), *_next##e; \
00521         e && (_next##e = ns_list_get_previous(list, e), true); e = _next##e)
00522 
00523 /** \hideinitializer \brief Count entries on a list
00524  *
00525  * Unlike other operations, this is O(n). Note: if list might contain over
00526  * 65535 entries, this function **must not** be used to get the entry count.
00527  *
00528  * \param list `(const list_t *)` Pointer to list.
00529 
00530  * \return     `(uint_fast16_t)`  Number of entries that are stored in list.
00531  */
00532 #define ns_list_count(list) ns_list_count_(&(list)->slist, NS_LIST_OFFSET_(list))
00533 
00534 /** \privatesection
00535  *  Internal functions - designed to be accessed using corresponding macros above
00536  */
00537 NS_INLINE void ns_list_init_(ns_list_t *list);
00538 NS_INLINE void ns_list_link_init_(ns_list_link_t *link);
00539 NS_INLINE void ns_list_add_to_start_(ns_list_t *list, ns_list_offset_t link_offset, void *restrict entry);
00540 NS_INLINE void ns_list_add_to_end_(ns_list_t *list, ns_list_offset_t link_offset, void *restrict entry);
00541 NS_INLINE void ns_list_add_before_(ns_list_offset_t link_offset, void *before, void *restrict entry);
00542 NS_INLINE void ns_list_add_after_(ns_list_t *list, ns_list_offset_t link_offset, void *after, void *restrict entry);
00543 NS_INLINE void *ns_list_get_next_(ns_list_offset_t link_offset, const void *current);
00544 NS_INLINE void *ns_list_get_previous_(const ns_list_t *list, ns_list_offset_t link_offset, const void *current);
00545 NS_INLINE void *ns_list_get_last_(const ns_list_t *list,  ns_list_offset_t offset);
00546 NS_INLINE void ns_list_remove_(ns_list_t *list, ns_list_offset_t link_offset, void *entry);
00547 NS_INLINE void ns_list_replace_(ns_list_t *list, ns_list_offset_t link_offset, void *current, void *restrict replacement);
00548 NS_INLINE void ns_list_concatenate_(ns_list_t *dst, ns_list_t *src, ns_list_offset_t offset);
00549 NS_INLINE uint_fast16_t ns_list_count_(const ns_list_t *list, ns_list_offset_t link_offset);
00550 
00551 /* Provide definitions, either for inlining, or for ns_list.c */
00552 #if defined NS_ALLOW_INLINING || defined NS_LIST_FN
00553 #ifndef NS_LIST_FN
00554 #define NS_LIST_FN NS_INLINE
00555 #endif
00556 
00557 /* Pointer to the link member in entry e */
00558 #define NS_LIST_LINK_(e, offset) ((ns_list_link_t *)((char *)(e) + offset))
00559 
00560 /* Lvalue of the next link pointer in entry e */
00561 #define NS_LIST_NEXT_(e, offset) (NS_LIST_LINK_(e, offset)->next)
00562 
00563 /* Lvalue of the prev link pointer in entry e */
00564 #define NS_LIST_PREV_(e, offset) (NS_LIST_LINK_(e, offset)->prev)
00565 
00566 /* Convert a pointer to a link member back to the entry;
00567  * works for linkptr either being a ns_list_link_t pointer, or its next pointer,
00568  * as the next pointer is first in the ns_list_link_t */
00569 #define NS_LIST_ENTRY_(linkptr, offset) ((void *)((char *)(linkptr) - offset))
00570 
00571 NS_LIST_FN void ns_list_init_(ns_list_t *list)
00572 {
00573     list->first_entry = NULL;
00574     list->last_nextptr = &list->first_entry;
00575 }
00576 
00577 NS_LIST_FN void ns_list_link_init_(ns_list_link_t *link)
00578 {
00579     NS_FUNNY_INTPTR_OK
00580     link->next = NS_LIST_POISON;
00581     link->prev = NS_LIST_POISON;
00582     NS_FUNNY_INTPTR_RESTORE
00583 }
00584 
00585 NS_LIST_FN void ns_list_add_to_start_(ns_list_t *list, ns_list_offset_t offset, void *restrict entry)
00586 {
00587     void *next;
00588 
00589     NS_LIST_PREV_(entry, offset) = &list->first_entry;
00590     NS_LIST_NEXT_(entry, offset) = next = list->first_entry;
00591 
00592     if (next) {
00593         NS_LIST_PREV_(next, offset) = &NS_LIST_NEXT_(entry, offset);
00594     } else {
00595         list->last_nextptr = &NS_LIST_NEXT_(entry, offset);
00596     }
00597 
00598     list->first_entry = entry;
00599 }
00600 
00601 NS_LIST_FN void ns_list_add_after_(ns_list_t *list, ns_list_offset_t offset, void *current, void *restrict entry)
00602 {
00603     void *next;
00604 
00605     NS_LIST_PREV_(entry, offset) = &NS_LIST_NEXT_(current, offset);
00606     NS_LIST_NEXT_(entry, offset) = next = NS_LIST_NEXT_(current, offset);
00607 
00608     if (next) {
00609         NS_LIST_PREV_(next, offset) = &NS_LIST_NEXT_(entry, offset);
00610     } else {
00611         list->last_nextptr = &NS_LIST_NEXT_(entry, offset);
00612     }
00613 
00614     NS_LIST_NEXT_(current, offset) = entry;
00615 }
00616 
00617 NS_LIST_FN void ns_list_add_before_(ns_list_offset_t offset, void *current, void *restrict entry)
00618 {
00619     void **prev_nextptr;
00620 
00621     NS_LIST_NEXT_(entry, offset) = current;
00622     NS_LIST_PREV_(entry, offset) = prev_nextptr = NS_LIST_PREV_(current, offset);
00623     *prev_nextptr = entry;
00624     NS_LIST_PREV_(current, offset) = &NS_LIST_NEXT_(entry, offset);
00625 }
00626 
00627 NS_LIST_FN void ns_list_add_to_end_(ns_list_t *list, ns_list_offset_t offset, void *restrict entry)
00628 {
00629     void **prev_nextptr;
00630 
00631     NS_LIST_NEXT_(entry, offset) = NULL;
00632     NS_LIST_PREV_(entry, offset) = prev_nextptr = list->last_nextptr;
00633     *prev_nextptr = entry;
00634     list->last_nextptr = &NS_LIST_NEXT_(entry, offset);
00635 }
00636 
00637 NS_LIST_FN void *ns_list_get_next_(ns_list_offset_t offset, const void *current)
00638 {
00639     return NS_LIST_NEXT_(current, offset);
00640 }
00641 
00642 NS_LIST_FN void *ns_list_get_previous_(const ns_list_t *list, ns_list_offset_t offset, const void *current)
00643 {
00644     if (current == list->first_entry) {
00645         return NULL;
00646     }
00647 
00648     // Tricky. We don't have a direct previous pointer, but a pointer to the
00649     // pointer that points to us - ie &head->first_entry OR &{prev}->next.
00650     // This makes life easier on insertion and removal, but this is where we
00651     // pay the price.
00652 
00653     // We have to check manually for being the first entry above, so we know it's
00654     // a real link's next pointer. Then next is the first field of
00655     // ns_list_link_t, so we can use the normal offset value.
00656 
00657     return NS_LIST_ENTRY_(NS_LIST_PREV_(current, offset), offset);
00658 }
00659 
00660 NS_LIST_FN void *ns_list_get_last_(const ns_list_t *list, ns_list_offset_t offset)
00661 {
00662     if (!list->first_entry) {
00663         return NULL;
00664     }
00665 
00666     // See comments in ns_list_get_previous_()
00667     return NS_LIST_ENTRY_(list->last_nextptr, offset);
00668 }
00669 
00670 NS_LIST_FN void ns_list_remove_(ns_list_t *list, ns_list_offset_t offset, void *removed)
00671 {
00672     void *next;
00673     void **prev_nextptr;
00674 
00675     next = NS_LIST_NEXT_(removed, offset);
00676     prev_nextptr = NS_LIST_PREV_(removed, offset);
00677     if (next) {
00678         NS_LIST_PREV_(next, offset) = prev_nextptr;
00679     } else {
00680         list->last_nextptr = prev_nextptr;
00681     }
00682     *prev_nextptr = next;
00683 
00684     ns_list_link_init_(NS_LIST_LINK_(removed, offset));
00685 }
00686 
00687 NS_LIST_FN void ns_list_replace_(ns_list_t *list, ns_list_offset_t offset, void *current, void *restrict replacement)
00688 {
00689     void *next;
00690     void **prev_nextptr;
00691 
00692     NS_LIST_PREV_(replacement, offset) = prev_nextptr = NS_LIST_PREV_(current, offset);
00693     NS_LIST_NEXT_(replacement, offset) = next = NS_LIST_NEXT_(current, offset);
00694 
00695     if (next) {
00696         NS_LIST_PREV_(next, offset) = &NS_LIST_NEXT_(replacement, offset);
00697     } else {
00698         list->last_nextptr = &NS_LIST_NEXT_(replacement, offset);
00699     }
00700     *prev_nextptr = replacement;
00701 
00702     ns_list_link_init_(NS_LIST_LINK_(current, offset));
00703 }
00704 
00705 NS_LIST_FN void ns_list_concatenate_(ns_list_t *dst, ns_list_t *src, ns_list_offset_t offset)
00706 {
00707     ns_list_link_t *src_first;
00708 
00709     src_first = src->first_entry;
00710     if (!src_first) {
00711         return;
00712     }
00713 
00714     *dst->last_nextptr = src_first;
00715     NS_LIST_PREV_(src_first, offset) = dst->last_nextptr;
00716     dst->last_nextptr = src->last_nextptr;
00717 
00718     ns_list_init_(src);
00719 }
00720 
00721 NS_LIST_FN uint_fast16_t ns_list_count_(const ns_list_t *list, ns_list_offset_t offset)
00722 {
00723     uint_fast16_t count = 0;
00724 
00725     for (void *p = list->first_entry; p; p = NS_LIST_NEXT_(p, offset)) {
00726         count++;
00727     }
00728 
00729     return count;
00730 }
00731 #endif /* defined NS_ALLOW_INLINING || defined NS_LIST_FN */
00732 
00733 #ifdef __cplusplus
00734 }
00735 #endif
00736 
00737 #endif /* NS_LIST_H_ */
00738