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_STATIC_ASSERT(link_offset <= UINT_FAST8_MAX, "link offset too large") \
00148     char (*offset)[link_offset + 1]; \
00149     entry_type *type; \
00150 }
00151 
00152 /** \brief Get offset of link field in entry.
00153  * \return `(ns_list_offset_t)` The offset of the link field for entries on the specified list
00154  */
00155 #define NS_LIST_OFFSET_(list) ((ns_list_offset_t) (sizeof *(list)->offset - 1))
00156 
00157 /** \brief Get the entry pointer type.
00158  * \def NS_LIST_PTR_TYPE_
00159  *
00160  * \return An unqualified pointer type to an entry on the specified list.
00161  *
00162  * Only available if the compiler provides a "typeof" operator.
00163  */
00164 #if defined __cplusplus && __cplusplus >= 201103L
00165 #define NS_LIST_PTR_TYPE_(list) decltype((list)->type)
00166 #elif defined __GNUC__
00167 #define NS_LIST_PTR_TYPE_(list) __typeof__((list)->type)
00168 #endif
00169 
00170 /** \brief Check for compatible pointer types
00171  *
00172  * This test will produce a diagnostic about a pointer mismatch on
00173  * the == inside the sizeof operator. For example ARM/Norcroft C gives the error:
00174  *
00175  *     operand types are incompatible ("entry_t *" and "other_t *")
00176  */
00177 #ifdef CPPCHECK
00178 #define NS_PTR_MATCH_(a, b, str) ((void) 0)
00179 #else
00180 #define NS_PTR_MATCH_(a, b, str) ((void) sizeof ((a) == (b)))
00181 #endif
00182 
00183 /** \brief Internal macro to cast returned entry pointers to correct type.
00184  *
00185  * Not portable in C, alas. With GCC or C++11, the "get entry" macros return
00186  * correctly-typed pointers. Otherwise, the macros return `void *`.
00187  *
00188  * The attempt at a portable version would work if the C `?:` operator wasn't
00189  * broken - `x ? (t *) : (void *)` should really have type `(t *)` in C, but
00190  * it has type `(void *)`, which only makes sense for C++. The `?:` is left in,
00191  * in case some day it works. Some compilers may still warn if this is
00192  * assigned to a different type.
00193  */
00194 #ifdef NS_LIST_PTR_TYPE_
00195 #define NS_LIST_TYPECAST_(list, val) ((NS_LIST_PTR_TYPE_(list)) (val))
00196 #else
00197 #define NS_LIST_TYPECAST_(list, val) (0 ? (list)->type : (val))
00198 #endif
00199 
00200 /** \brief Internal macro to check types of input entry pointer. */
00201 #define NS_LIST_TYPECHECK_(list, entry) \
00202     (NS_PTR_MATCH_((list)->type, (entry), "incorrect entry type for list"), (entry))
00203 
00204 /** \brief Type used to pass link offset to underlying functions
00205  *
00206  * We could use size_t, but it would be unnecessarily large on 8-bit systems,
00207  * where we can be (pretty) confident we won't have next pointers more than
00208  * 256 bytes into a structure.
00209  */
00210 typedef uint_fast8_t ns_list_offset_t;
00211 
00212 /// \publicsection
00213 /** \brief The type for the link member in the user's entry structure.
00214  *
00215  * Users should not access this member directly - just pass its name to the
00216  * list head macros. The funny prev pointer simplifies common operations
00217  * (eg insertion, removal), at the expense of complicating rare reverse iteration.
00218  *
00219  * NB - the list implementation relies on next being the first member.
00220  */
00221 typedef struct ns_list_link {
00222     void *next;     ///< Pointer to next entry, or NULL if none
00223     void **prev;    ///< Pointer to previous entry's (or head's) next pointer
00224 } ns_list_link_t;
00225 
00226 /** \brief "Poison" value placed in unattached entries' link pointers.
00227  * \internal What are good values for this? Platform dependent, maybe just NULL
00228  */
00229 #define NS_LIST_POISON ((void *) 0xDEADBEEF)
00230 
00231 /** \brief Initialiser for an entry's link member
00232  *
00233  * This initialiser is not required by the library, but a user may want an
00234  * initialiser to include in their own entry initialiser. See
00235  * ns_list_link_init() for more discussion.
00236  */
00237 #define NS_LIST_LINK_INIT(name) \
00238     NS_FUNNY_INTPTR_OK \
00239     { NS_LIST_POISON, NS_LIST_POISON } \
00240     NS_FUNNY_INTPTR_RESTORE
00241 
00242 /** \hideinitializer \brief Initialise an entry's list link
00243  *
00244  * This "initialises" an unattached entry's link by filling the fields with
00245  * poison. This is optional, as unattached entries field pointers are not
00246  * meaningful, and it is not valid to call ns_list_get_next or similar on
00247  * an unattached entry.
00248  *
00249  * \param entry Pointer to an entry
00250  * \param field The name of the link member to initialise
00251  */
00252 #define ns_list_link_init(entry, field) ns_list_link_init_(&(entry)->field)
00253 
00254 /** \hideinitializer \brief Initialise a list
00255  *
00256  * Initialise a list head before use. A list head must be initialised using this
00257  * function or one of the NS_LIST_INIT()-type macros before use. A zero-initialised
00258  * list head is *not* valid.
00259  *
00260  * If used on a list containing existing entries, those entries will
00261  * become detached. (They are not modified, but their links are now effectively
00262  * undefined).
00263  *
00264  * \param list Pointer to a NS_LIST_HEAD() structure.
00265  */
00266 #define ns_list_init(list) ns_list_init_(&(list)->slist)
00267 
00268 /** \brief Initialiser for an empty list
00269  *
00270  * Usage in an enclosing initialiser:
00271  * ~~~
00272  *      static my_type_including_list_t x = {
00273  *          "Something",
00274  *          23,
00275  *          NS_LIST_INIT(x),
00276  *      };
00277  * ~~~
00278  * NS_LIST_DEFINE() or NS_LIST_NAME_INIT() may provide a shorter alternative
00279  * in simpler cases.
00280  */
00281 #define NS_LIST_INIT(name) { { NULL, &(name).slist.first_entry } }
00282 
00283 /** \brief Name and initialiser for an empty list
00284  *
00285  * Usage:
00286  * ~~~
00287  *      list_t NS_LIST_NAME_INIT(foo);
00288  * ~~~
00289  * acts as
00290  * ~~~
00291  *      list_t foo = { empty list };
00292  * ~~~
00293  * Also useful with designated initialisers:
00294  * ~~~
00295  *      .NS_LIST_NAME_INIT(foo),
00296  * ~~~
00297  * acts as
00298  * ~~~
00299  *      .foo = { empty list },
00300  * ~~~
00301  */
00302 #define NS_LIST_NAME_INIT(name) name = NS_LIST_INIT(name)
00303 
00304 /** \brief Define a list, and initialise to empty.
00305  *
00306  * Usage:
00307  * ~~~
00308  *     static NS_LIST_DEFINE(my_list, entry_t, link);
00309  * ~~~
00310  * acts as
00311  * ~~~
00312  *     static list_type my_list = { empty list };
00313  * ~~~
00314  */
00315 #define NS_LIST_DEFINE(name, type, field) \
00316     NS_LIST_HEAD(type, field) NS_LIST_NAME_INIT(name)
00317 
00318 /** \hideinitializer \brief Add an entry to the start of the linked list.
00319  *
00320  * ns_list_add_to_end() is *slightly* more efficient than ns_list_add_to_start().
00321  *
00322  * \param list  `(list_t *)`           Pointer to list.
00323  * \param entry `(entry_t * restrict)` Pointer to new entry to add.
00324  */
00325 #define ns_list_add_to_start(list, entry) \
00326     ns_list_add_to_start_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, entry))
00327 
00328 /** \hideinitializer \brief Add an entry to the end of the linked list.
00329  *
00330  * \param list  `(list_t *)`           Pointer to list.
00331  * \param entry `(entry_t * restrict)` Pointer to new entry to add.
00332  */
00333 #define ns_list_add_to_end(list, entry) \
00334     ns_list_add_to_end_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, entry))
00335 
00336 /** \hideinitializer \brief Add an entry before a specified entry.
00337  *
00338  * \param list   `(list_t *)`           Pointer to list.
00339  * \param before `(entry_t *)`          Existing entry before which to place the new entry.
00340  * \param entry  `(entry_t * restrict)` Pointer to new entry to add.
00341  */
00342 #define ns_list_add_before(list, before, entry) \
00343     ns_list_add_before_(NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, before), NS_LIST_TYPECHECK_(list, entry))
00344 
00345 /** \hideinitializer \brief Add an entry after a specified entry.
00346  *
00347  * ns_list_add_before() is *slightly* more efficient than ns_list_add_after().
00348  *
00349  * \param list  `(list_t *)`           Pointer to list.
00350  * \param after `(entry_t *)`          Existing entry after which to place the new entry.
00351  * \param entry `(entry_t * restrict)` Pointer to new entry to add.
00352  */
00353 #define ns_list_add_after(list, after, entry) \
00354     ns_list_add_after_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, after), NS_LIST_TYPECHECK_(list, entry))
00355 
00356 /** \brief Check if a list is empty.
00357  *
00358  * \param list `(const list_t *)` Pointer to list.
00359  *
00360  * \return     `(bool)`           true if the list is empty.
00361  */
00362 #define ns_list_is_empty(list) ((bool) ((list)->slist.first_entry == NULL))
00363 
00364 /** \brief Get the first entry.
00365  *
00366  * \param list `(const list_t *)` Pointer to list.
00367  *
00368  * \return     `(entry_t *)`      Pointer to first entry.
00369  * \return                        NULL if list is empty.
00370  */
00371 #define ns_list_get_first(list) NS_LIST_TYPECAST_(list, (list)->slist.first_entry)
00372 
00373 /** \hideinitializer \brief Get the previous entry.
00374  *
00375  * \param list    `(const list_t *)`  Pointer to list.
00376  * \param current `(const entry_t *)` Pointer to current entry.
00377  *
00378  * \return        `(entry_t *)`       Pointer to previous entry.
00379  * \return                            NULL if current entry is first.
00380  */
00381 #define ns_list_get_previous(list, current) \
00382     NS_LIST_TYPECAST_(list, ns_list_get_previous_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, current)))
00383 
00384 /** \hideinitializer \brief Get the next entry.
00385  *
00386  * \param list    `(const list_t *)`  Pointer to list.
00387  * \param current `(const entry_t *)` Pointer to current entry.
00388  *
00389  * \return        `(entry_t *)`       Pointer to next entry.
00390  * \return                            NULL if current entry is last.
00391  */
00392 #define ns_list_get_next(list, current) \
00393     NS_LIST_TYPECAST_(list, ns_list_get_next_(NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, current)))
00394 
00395 /** \hideinitializer \brief Get the last entry.
00396  *
00397  * \param list `(const list_t *)` Pointer to list.
00398  *
00399  * \return     `(entry_t *)`      Pointer to last entry.
00400  * \return                        NULL if list is empty.
00401  */
00402 #define ns_list_get_last(list) \
00403     NS_LIST_TYPECAST_(list, ns_list_get_last_(&(list)->slist, NS_LIST_OFFSET_(list)))
00404 
00405 /** \hideinitializer \brief Remove an entry.
00406  *
00407  * \param list  `(list_t *)`  Pointer to list.
00408  * \param entry `(entry_t *)` Entry on list to be removed.
00409  */
00410 #define ns_list_remove(list, entry) \
00411     ns_list_remove_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, entry))
00412 
00413 /** \hideinitializer \brief Replace an entry.
00414  *
00415  * \param list        `(list_t *)`           Pointer to list.
00416  * \param current     `(entry_t *)`          Existing entry on list to be replaced.
00417  * \param replacement `(entry_t * restrict)` New entry to be the replacement.
00418  */
00419 #define ns_list_replace(list, current, replacement) \
00420     ns_list_replace_(&(list)->slist, NS_LIST_OFFSET_(list), NS_LIST_TYPECHECK_(list, current), NS_LIST_TYPECHECK_(list, replacement))
00421 
00422 /** \hideinitializer \brief Concatenate two lists.
00423  *
00424  * Attach the entries on the source list to the end of the destination
00425  * list, leaving the source list empty.
00426  *
00427  * \param dst `(list_t *)` Pointer to destination list.
00428  * \param src `(list_t *)` Pointer to source list.
00429  *
00430  */
00431 #define ns_list_concatenate(dst, src) \
00432         (NS_PTR_MATCH_(dst, src, "concatenating different list types"), \
00433         ns_list_concatenate_(&(dst)->slist, &(src)->slist, NS_LIST_OFFSET_(src)))
00434 
00435 /** \brief Iterate forwards over a list.
00436  *
00437  * Example:
00438  * ~~~
00439  *     ns_list_foreach(const my_entry_t, cur, &my_list)
00440  *     {
00441  *         printf("%s\n", cur->name);
00442  *     }
00443  * ~~~
00444  * Deletion of the current entry is not permitted as its next is checked after
00445  * running user code.
00446  *
00447  * The iteration pointer is declared inside the loop, using C99/C++, so it
00448  * is not accessible after the loop.  This encourages good code style, and
00449  * matches the semantics of C++11's "ranged for", which only provides the
00450  * declaration form:
00451  * ~~~
00452  *     for (const my_entry_t cur : my_list)
00453  * ~~~
00454  * If you need to see the value of the iteration pointer after a `break`,
00455  * you will need to assign it to a variable declared outside the loop before
00456  * breaking:
00457  * ~~~
00458  *      my_entry_t *match = NULL;
00459  *      ns_list_foreach(my_entry_t, cur, &my_list)
00460  *      {
00461  *          if (cur->id == id)
00462  *          {
00463  *              match = cur;
00464  *              break;
00465  *          }
00466  *      }
00467  * ~~~
00468  *
00469  * The user has to specify the entry type for the pointer definition, as type
00470  * extraction from the list argument isn't portable. On the other hand, this
00471  * also permits const qualifiers, as in the example above, and serves as
00472  * documentation. The entry type will be checked against the list type where the
00473  * compiler supports it.
00474  *
00475  * \param type                    Entry type `([const] entry_t)`.
00476  * \param e                       Name for iteration pointer to be defined
00477  *                                inside the loop.
00478  * \param list `(const list_t *)` Pointer to list - evaluated multiple times.
00479  */
00480 #define ns_list_foreach(type, e, list) \
00481     for (type *e = ns_list_get_first(list); e; e = ns_list_get_next(list, e))
00482 
00483 /** \brief Iterate forwards over a list, where user may delete.
00484  *
00485  * As ns_list_foreach(), but deletion of current entry is permitted as its
00486  * next pointer is recorded before running user code.
00487  *
00488  * Example:
00489  * ~~~
00490  *     ns_list_foreach_safe(my_entry_t, cur, &my_list)
00491  *     {
00492  *         ns_list_remove(cur);
00493  *     }
00494  * ~~~
00495  * \param type               Entry type `(entry_t)`.
00496  * \param e                  Name for iteration pointer to be defined
00497  *                           inside the loop.
00498  * \param list `(list_t *)`  Pointer to list - evaluated multiple times.
00499  */
00500 #define ns_list_foreach_safe(type, e, list) \
00501     for (type *e = ns_list_get_first(list), *_next; \
00502         e && (_next = ns_list_get_next(list, e), true); e = _next)
00503 
00504 /** \brief Iterate backwards over a list.
00505  *
00506  * As ns_list_foreach(), but going backwards - see its documentation.
00507  * Iterating forwards is *slightly* more efficient.
00508  */
00509 #define ns_list_foreach_reverse(type, e, list) \
00510     for (type *e = ns_list_get_last(list); e; e = ns_list_get_previous(list, e))
00511 
00512 /** \brief Iterate backwards over a list, where user may delete.
00513  *
00514  * As ns_list_foreach_safe(), but going backwards - see its documentation.
00515  * Iterating forwards is *slightly* more efficient.
00516  */
00517 #define ns_list_foreach_reverse_safe(type, e, list) \
00518     for (type *e = ns_list_get_last(list), *_next; \
00519         e && (_next = ns_list_get_previous(list, e), true); e = _next)
00520 
00521 /** \hideinitializer \brief Count entries on a list
00522  *
00523  * Unlike other operations, this is O(n). Note: if list might contain over
00524  * 65535 entries, this function **must not** be used to get the entry count.
00525  *
00526  * \param list `(const list_t *)` Pointer to list.
00527 
00528  * \return     `(uint_fast16_t)`  Number of entries that are stored in list.
00529  */
00530 #define ns_list_count(list) ns_list_count_(&(list)->slist, NS_LIST_OFFSET_(list))
00531 
00532 /** \privatesection
00533  *  Internal functions - designed to be accessed using corresponding macros above
00534  */
00535 NS_INLINE void ns_list_init_(ns_list_t *list);
00536 NS_INLINE void ns_list_link_init_(ns_list_link_t *link);
00537 NS_INLINE void ns_list_add_to_start_(ns_list_t *list, ns_list_offset_t link_offset, void *restrict entry);
00538 NS_INLINE void ns_list_add_to_end_(ns_list_t *list, ns_list_offset_t link_offset, void *restrict entry);
00539 NS_INLINE void ns_list_add_before_(ns_list_offset_t link_offset, void *before, void *restrict entry);
00540 NS_INLINE void ns_list_add_after_(ns_list_t *list, ns_list_offset_t link_offset, void *after, void *restrict entry);
00541 NS_INLINE void *ns_list_get_next_(ns_list_offset_t link_offset, const void *current);
00542 NS_INLINE void *ns_list_get_previous_(const ns_list_t *list, ns_list_offset_t link_offset, const void *current);
00543 NS_INLINE void *ns_list_get_last_(const ns_list_t *list,  ns_list_offset_t offset);
00544 NS_INLINE void ns_list_remove_(ns_list_t *list, ns_list_offset_t link_offset, void *entry);
00545 NS_INLINE void ns_list_replace_(ns_list_t *list, ns_list_offset_t link_offset, void *current, void *restrict replacement);
00546 NS_INLINE void ns_list_concatenate_(ns_list_t *dst, ns_list_t *src, ns_list_offset_t offset);
00547 NS_INLINE uint_fast16_t ns_list_count_(const ns_list_t *list, ns_list_offset_t link_offset);
00548 
00549 /* Provide definitions, either for inlining, or for ns_list.c */
00550 #if defined NS_ALLOW_INLINING || defined NS_LIST_FN
00551 #ifndef NS_LIST_FN
00552 #define NS_LIST_FN NS_INLINE
00553 #endif
00554 
00555 /* Pointer to the link member in entry e */
00556 #define NS_LIST_LINK_(e, offset) ((ns_list_link_t *)((char *)(e) + offset))
00557 
00558 /* Lvalue of the next link pointer in entry e */
00559 #define NS_LIST_NEXT_(e, offset) (NS_LIST_LINK_(e, offset)->next)
00560 
00561 /* Lvalue of the prev link pointer in entry e */
00562 #define NS_LIST_PREV_(e, offset) (NS_LIST_LINK_(e, offset)->prev)
00563 
00564 /* Convert a pointer to a link member back to the entry;
00565  * works for linkptr either being a ns_list_link_t pointer, or its next pointer,
00566  * as the next pointer is first in the ns_list_link_t */
00567 #define NS_LIST_ENTRY_(linkptr, offset) ((void *)((char *)(linkptr) - offset))
00568 
00569 NS_LIST_FN void ns_list_init_(ns_list_t *list)
00570 {
00571     list->first_entry = NULL;
00572     list->last_nextptr = &list->first_entry;
00573 }
00574 
00575 NS_LIST_FN void ns_list_link_init_(ns_list_link_t *link)
00576 {
00577     NS_FUNNY_INTPTR_OK
00578     link->next = NS_LIST_POISON;
00579     link->prev = NS_LIST_POISON;
00580     NS_FUNNY_INTPTR_RESTORE
00581 }
00582 
00583 NS_LIST_FN void ns_list_add_to_start_(ns_list_t *list, ns_list_offset_t offset, void *restrict entry)
00584 {
00585     void *next;
00586 
00587     NS_LIST_PREV_(entry, offset) = &list->first_entry;
00588     NS_LIST_NEXT_(entry, offset) = next = list->first_entry;
00589 
00590     if (next) {
00591         NS_LIST_PREV_(next, offset) = &NS_LIST_NEXT_(entry, offset);
00592     } else {
00593         list->last_nextptr = &NS_LIST_NEXT_(entry, offset);
00594     }
00595 
00596     list->first_entry = entry;
00597 }
00598 
00599 NS_LIST_FN void ns_list_add_after_(ns_list_t *list, ns_list_offset_t offset, void *current, void *restrict entry)
00600 {
00601     void *next;
00602 
00603     NS_LIST_PREV_(entry, offset) = &NS_LIST_NEXT_(current, offset);
00604     NS_LIST_NEXT_(entry, offset) = next = NS_LIST_NEXT_(current, offset);
00605 
00606     if (next) {
00607         NS_LIST_PREV_(next, offset) = &NS_LIST_NEXT_(entry, offset);
00608     } else {
00609         list->last_nextptr = &NS_LIST_NEXT_(entry, offset);
00610     }
00611 
00612     NS_LIST_NEXT_(current, offset) = entry;
00613 }
00614 
00615 NS_LIST_FN void ns_list_add_before_(ns_list_offset_t offset, void *current, void *restrict entry)
00616 {
00617     void **prev_nextptr;
00618 
00619     NS_LIST_NEXT_(entry, offset) = current;
00620     NS_LIST_PREV_(entry, offset) = prev_nextptr = NS_LIST_PREV_(current, offset);
00621     *prev_nextptr = entry;
00622     NS_LIST_PREV_(current, offset) = &NS_LIST_NEXT_(entry, offset);
00623 }
00624 
00625 NS_LIST_FN void ns_list_add_to_end_(ns_list_t *list, ns_list_offset_t offset, void *restrict entry)
00626 {
00627     void **prev_nextptr;
00628 
00629     NS_LIST_NEXT_(entry, offset) = NULL;
00630     NS_LIST_PREV_(entry, offset) = prev_nextptr = list->last_nextptr;
00631     *prev_nextptr = entry;
00632     list->last_nextptr = &NS_LIST_NEXT_(entry, offset);
00633 }
00634 
00635 NS_LIST_FN void *ns_list_get_next_(ns_list_offset_t offset, const void *current)
00636 {
00637     return NS_LIST_NEXT_(current, offset);
00638 }
00639 
00640 NS_LIST_FN void *ns_list_get_previous_(const ns_list_t *list, ns_list_offset_t offset, const void *current)
00641 {
00642     if (current == list->first_entry) {
00643         return NULL;
00644     }
00645 
00646     // Tricky. We don't have a direct previous pointer, but a pointer to the
00647     // pointer that points to us - ie &head->first_entry OR &{prev}->next.
00648     // This makes life easier on insertion and removal, but this is where we
00649     // pay the price.
00650 
00651     // We have to check manually for being the first entry above, so we know it's
00652     // a real link's next pointer. Then next is the first field of
00653     // ns_list_link_t, so we can use the normal offset value.
00654 
00655     return NS_LIST_ENTRY_(NS_LIST_PREV_(current, offset), offset);
00656 }
00657 
00658 NS_LIST_FN void *ns_list_get_last_(const ns_list_t *list, ns_list_offset_t offset)
00659 {
00660     if (!list->first_entry) {
00661         return NULL;
00662     }
00663 
00664     // See comments in ns_list_get_previous_()
00665     return NS_LIST_ENTRY_(list->last_nextptr, offset);
00666 }
00667 
00668 NS_LIST_FN void ns_list_remove_(ns_list_t *list, ns_list_offset_t offset, void *removed)
00669 {
00670     void *next;
00671     void **prev_nextptr;
00672 
00673     next = NS_LIST_NEXT_(removed, offset);
00674     prev_nextptr = NS_LIST_PREV_(removed, offset);
00675     if (next) {
00676         NS_LIST_PREV_(next, offset) = prev_nextptr;
00677     } else {
00678         list->last_nextptr = prev_nextptr;
00679     }
00680     *prev_nextptr = next;
00681 
00682     ns_list_link_init_(NS_LIST_LINK_(removed, offset));
00683 }
00684 
00685 NS_LIST_FN void ns_list_replace_(ns_list_t *list, ns_list_offset_t offset, void *current, void *restrict replacement)
00686 {
00687     void *next;
00688     void **prev_nextptr;
00689 
00690     NS_LIST_PREV_(replacement, offset) = prev_nextptr = NS_LIST_PREV_(current, offset);
00691     NS_LIST_NEXT_(replacement, offset) = next = NS_LIST_NEXT_(current, offset);
00692 
00693     if (next) {
00694         NS_LIST_PREV_(next, offset) = &NS_LIST_NEXT_(replacement, offset);
00695     } else {
00696         list->last_nextptr = &NS_LIST_NEXT_(replacement, offset);
00697     }
00698     *prev_nextptr = replacement;
00699 
00700     ns_list_link_init_(NS_LIST_LINK_(current, offset));
00701 }
00702 
00703 NS_LIST_FN void ns_list_concatenate_(ns_list_t *dst, ns_list_t *src, ns_list_offset_t offset)
00704 {
00705     ns_list_link_t *src_first;
00706 
00707     src_first = src->first_entry;
00708     if (!src_first) {
00709         return;
00710     }
00711 
00712     *dst->last_nextptr = src_first;
00713     NS_LIST_PREV_(src_first, offset) = dst->last_nextptr;
00714     dst->last_nextptr = src->last_nextptr;
00715 
00716     ns_list_init_(src);
00717 }
00718 
00719 NS_LIST_FN uint_fast16_t ns_list_count_(const ns_list_t *list, ns_list_offset_t offset)
00720 {
00721     uint_fast16_t count = 0;
00722 
00723     for (void *p = list->first_entry; p; p = NS_LIST_NEXT_(p, offset)) {
00724         count++;
00725     }
00726 
00727     return count;
00728 }
00729 #endif /* defined NS_ALLOW_INLINING || defined NS_LIST_FN */
00730 
00731 #ifdef __cplusplus
00732 }
00733 #endif
00734 
00735 #endif /* NS_LIST_H_ */
00736