1 /* 2 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. 3 * Copyright (c) 1988, 1989 by Adam de Boor 4 * Copyright (c) 1989 by Berkeley Softworks 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Adam de Boor. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)list.h 5.3 (Berkeley) 6/1/90 39 */ 40 41 /* 42 * list.h -- 43 * 44 * Structures, macros, and routines exported by the List module. 45 */ 46 47 #ifndef _LIST 48 #define _LIST 49 50 #ifndef _SPRITE 51 #include "sprite.h" 52 #endif _SPRITE 53 54 /* 55 * This module defines the list abstraction, which enables one to link 56 * together arbitrary data structures. Lists are doubly-linked and 57 * circular. A list contains a header followed by its real members, if 58 * any. (An empty list therefore consists of a single element, the 59 * header, whose nextPtr and prevPtr fields point to itself). To refer 60 * to a list as a whole, the user keeps a pointer to the header; that 61 * header is initialized by a call to List_Init(), which creates an empty 62 * list given a pointer to a List_Links structure (described below). 63 * 64 * The links are contained in a two-element structure called List_Links. 65 * A list joins List_Links records (that is, each List_Links structure 66 * points to other List_Links structures), but if the List_Links is the 67 * first field within a larger structure, then the larger structures are 68 * effectively linked together as follows: 69 * 70 * header 71 * (List_Links) first elt. second elt. 72 * ----------------- ----------------- ----------------- 73 * ..-> | nextPtr | ----> | List_Links | ----> | List_Links |----.. 74 * | - - - - - - - | | | | | 75 * ..-- | prevPtr | <---- | | <---- | |<---.. 76 * ----------------- - --- --- --- - - --- --- --- - 77 * | rest of | | rest of | 78 * | structure | | structure | 79 * | | | | 80 * | ... | | ... | 81 * ----------------- ----------------- 82 * 83 * It is possible to link structures through List_Links fields that are 84 * not at the beginning of the larger structure, but it is then necessary 85 * to perform pointer arithmetic to find the beginning of the larger 86 * structure, given a pointer to some point within it. 87 * 88 * A typical structure might be something like: 89 * 90 * typedef struct { 91 * List_Links links; 92 * char ch; 93 * integer flags; 94 * } EditChar; 95 * 96 * Before an element is inserted in a list for the first time, it must 97 * be initialized by calling the macro List_InitElement(). 98 */ 99 100 101 /* 102 * data structure for lists 103 */ 104 105 typedef struct List_Links { 106 struct List_Links *prevPtr; 107 struct List_Links *nextPtr; 108 } List_Links; 109 110 /* 111 * procedures 112 */ 113 114 void List_Init(); /* initialize a header to a list */ 115 void List_Insert(); /* insert an element into a list */ 116 void List_Remove(); /* remove an element from a list */ 117 void List_Move(); /* move an element elsewhere in a list */ 118 119 /* 120 * ---------------------------------------------------------------------------- 121 * 122 * List_InitElement -- 123 * 124 * Initialize a list element. Must be called before an element is first 125 * inserted into a list. 126 * 127 * ---------------------------------------------------------------------------- 128 */ 129 #define List_InitElement(elementPtr) \ 130 (elementPtr)->prevPtr = (List_Links *) NIL; \ 131 (elementPtr)->nextPtr = (List_Links *) NIL; 132 133 /* 134 * Macros for stepping through or selecting parts of lists 135 */ 136 137 /* 138 * ---------------------------------------------------------------------------- 139 * 140 * LIST_FORALL -- 141 * 142 * Macro to loop through a list and perform an operation on each member. 143 * 144 * Usage: LIST_FORALL(headerPtr, itemPtr) { 145 * / * 146 * * operation on itemPtr, which points to successive members 147 * * of the list 148 * * 149 * * It may be appropriate to first assign 150 * * foobarPtr = (Foobar *) itemPtr; 151 * * to refer to the entire Foobar structure. 152 * * / 153 * } 154 * 155 * Note: itemPtr must be a List_Links pointer variable, and headerPtr 156 * must evaluate to a pointer to a List_Links structure. 157 * 158 * ---------------------------------------------------------------------------- 159 */ 160 161 #define LIST_FORALL(headerPtr, itemPtr) \ 162 for (itemPtr = List_First(headerPtr); \ 163 !List_IsAtEnd((headerPtr),itemPtr); \ 164 itemPtr = List_Next(itemPtr)) 165 166 /* 167 * ---------------------------------------------------------------------------- 168 * 169 * List_IsEmpty -- 170 * 171 * Macro: Boolean value, TRUE if the given list does not contain any 172 * members. 173 * 174 * Usage: if (List_IsEmpty(headerPtr)) ... 175 * 176 * ---------------------------------------------------------------------------- 177 */ 178 179 #define List_IsEmpty(headerPtr) \ 180 ((headerPtr) == (headerPtr)->nextPtr) 181 182 /* 183 * ---------------------------------------------------------------------------- 184 * 185 * List_IsAtEnd -- 186 * 187 * Macro: Boolean value, TRUE if itemPtr is after the end of headerPtr 188 * (i.e., itemPtr is the header of the list). 189 * 190 * Usage: if (List_IsAtEnd(headerPtr, itemPtr)) ... 191 * 192 * ---------------------------------------------------------------------------- 193 */ 194 195 196 #define List_IsAtEnd(headerPtr, itemPtr) \ 197 ((itemPtr) == (headerPtr)) 198 199 200 /* 201 * ---------------------------------------------------------------------------- 202 * 203 * List_First -- 204 * 205 * Macro to return the first member in a list, which is the header if 206 * the list is empty. 207 * 208 * Usage: firstPtr = List_First(headerPtr); 209 * 210 * ---------------------------------------------------------------------------- 211 */ 212 213 #define List_First(headerPtr) ((headerPtr)->nextPtr) 214 215 /* 216 * ---------------------------------------------------------------------------- 217 * 218 * List_Last -- 219 * 220 * Macro to return the last member in a list, which is the header if 221 * the list is empty. 222 * 223 * Usage: lastPtr = List_Last(headerPtr); 224 * 225 * ---------------------------------------------------------------------------- 226 */ 227 228 #define List_Last(headerPtr) ((headerPtr)->prevPtr) 229 230 /* 231 * ---------------------------------------------------------------------------- 232 * 233 * List_Prev -- 234 * 235 * Macro to return the member preceding the given member in its list. 236 * If the given list member is the first element in the list, List_Prev 237 * returns the list header. 238 * 239 * Usage: prevPtr = List_Prev(itemPtr); 240 * 241 * ---------------------------------------------------------------------------- 242 */ 243 244 #define List_Prev(itemPtr) ((itemPtr)->prevPtr) 245 246 /* 247 * ---------------------------------------------------------------------------- 248 * 249 * List_Next -- 250 * 251 * Macro to return the member following the given member in its list. 252 * If the given list member is the last element in the list, List_Next 253 * returns the list header. 254 * 255 * Usage: nextPtr = List_Next(itemPtr); 256 * 257 * ---------------------------------------------------------------------------- 258 */ 259 260 #define List_Next(itemPtr) ((itemPtr)->nextPtr) 261 262 263 /* 264 * ---------------------------------------------------------------------------- 265 * The List_Insert procedure takes two arguments. The first argument 266 * is a pointer to the structure to be inserted into a list, and 267 * the second argument is a pointer to the list member after which 268 * the new element is to be inserted. Macros are used to determine 269 * which existing member will precede the new one. 270 * 271 * The List_Move procedure takes a destination argument with the same 272 * semantics as List_Insert. 273 * 274 * The following macros define where to insert the new element 275 * in the list: 276 * 277 * LIST_AFTER(itemPtr) -- insert after itemPtr 278 * LIST_BEFORE(itemPtr) -- insert before itemPtr 279 * LIST_ATFRONT(headerPtr) -- insert at front of list 280 * LIST_ATREAR(headerPtr) -- insert at end of list 281 * 282 * For example, 283 * 284 * List_Insert(itemPtr, LIST_AFTER(otherPtr)); 285 * 286 * will insert itemPtr following otherPtr in the list containing otherPtr. 287 * ---------------------------------------------------------------------------- 288 */ 289 290 #define LIST_AFTER(itemPtr) ((List_Links *) itemPtr) 291 292 #define LIST_BEFORE(itemPtr) (((List_Links *) itemPtr)->prevPtr) 293 294 #define LIST_ATFRONT(headerPtr) ((List_Links *) headerPtr) 295 296 #define LIST_ATREAR(headerPtr) (((List_Links *) headerPtr)->prevPtr) 297 298 #endif _LIST 299