1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22 /* 23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 * 26 * Define an Alist, a list maintained as a reallocable array, and a for() loop 27 * macro to generalize its traversal. Note that the array can be reallocated 28 * as it is being traversed, thus the offset of each element is recomputed from 29 * the start of the structure. 30 */ 31 32 #ifndef _ALIST_H 33 #define _ALIST_H 34 35 #pragma ident "%Z%%M% %I% %E% SMI" 36 37 #ifdef __cplusplus 38 extern "C" { 39 #endif 40 41 #include <sys/types.h> 42 #include <sys/machelf.h> 43 44 /* 45 * An Alist implements array lists. The functionality is similar to 46 * that of a linked list. However, an Alist is represented by a single 47 * contigious allocation of memory. The head of the memory is a header 48 * that contains control information for the list. Following the header 49 * is an array used to hold the user data. In the type definitions that 50 * follow, we define these as an array with a single element, but when 51 * we allocate the memory, we actually allocate the amount of memory needed. 52 * 53 * There are two "flavors" of array list: 54 * 55 * Alist - Contain arbitrary data, usually structs. 56 * APlist - Contain pointers to data allocated elsewhere. 57 * 58 * This differentiation is useful, because pointer lists are heavily 59 * used, and support a slightly different set of operations that are 60 * unique to their purpose. 61 * 62 * Array lists are initially represented by a NULL pointer. The memory 63 * for the list is only allocated if an item is inserted. This is very 64 * efficient for data structures that may or may not be needed for a 65 * given linker operation --- you only pay for what you use. In addition: 66 * 67 * - Array lists grow as needed (memory is reallocated as necessary) 68 * - Data is kept contiguously (no unused holes in between elements) 69 * at the beginning of the data area. This locality has 70 * good cache behavior, as access to adjacent items are 71 * highly likely to be in the same page of memory. 72 * - Insert/Delete operations at the end of the list are very 73 * efficient. However, insert/delete operations elsewhere 74 * will cause a relatively expensive overlapped memory 75 * copy of the data following the insert/delete location. 76 * - As with any generic memory alloctor (i.e. malloc()/free()), 77 * array lists are not type safe for the data they contain. 78 * Data is managed as (void *) pointers to data of a given 79 * length, so the Alist module cannot prevent the caller from 80 * inserting/extracting the wrong type of data. The caller 81 * must guard against this. 82 * - To free an array list, simply call the standard free() function 83 * on the list pointer. 84 */ 85 86 87 88 /* 89 * Aliste is used to represent list indexes, offsets, and sizes. 90 */ 91 typedef size_t Aliste; 92 93 94 95 /* 96 * Alist is used to hold non-pointer items --- usually structs: 97 * - There must be an even number of Aliste fields before the 98 * al_data field. This ensures that al_data will have 99 * an alignment of 8, no matter whether sizeof(Aliste) 100 * is 4 or 8. That means that al_data will have sufficient 101 * alignment for any use, just like memory allocated via 102 * malloc(). 103 * - al_nitems and al_next are redundant, in that they are 104 * directly related: 105 * al_next = al_nitems * al_size 106 * We do this to make ALIST_TRAVERSE_BYOFFSET maximally 107 * efficient. This doesn't waste space, because of the 108 * requirement to have an even # of Alist fields (above). 109 * 110 * Note that Alists allow the data to be referenced by 0 based array 111 * index, or by their byte offset from the start of the Alist memory 112 * allocation. The index form is preferred for most use, as it is simpler. 113 * However, by-offset access is used by rtld link maps, and this ability 114 * is convenient in that case. 115 */ 116 typedef struct { 117 Aliste al_arritems; /* # of items in al_data allocation */ 118 Aliste al_nitems; /* # items (index of next avail item) */ 119 Aliste al_next; /* offset of next available al_data[] */ 120 Aliste al_size; /* size of each al_data[] item */ 121 void *al_data[1]; /* data (can grow) */ 122 } Alist; 123 124 /* 125 * APlist is a variant of Alist that contains pointers. There are several 126 * benefits to this special type: 127 * - API is simpler 128 * - Pointers are used directly, instead of requiring a 129 * pointer-to-pointer double indirection. 130 * - The implementation is slightly more efficient. 131 * - Operations that make particular sense for pointers 132 * can be supported without confusing the API for the 133 * regular Alists. 134 */ 135 typedef struct { 136 Aliste apl_arritems; /* # of items in apl_data allocation */ 137 Aliste apl_nitems; /* # items (index of next avail item) */ 138 void *apl_data[1]; /* data area: (arrcnt * size) bytes */ 139 } APlist; 140 141 142 /* 143 * The ALIST_OFF_DATA and APLIST_OFF_DATA macros give the byte offset 144 * from the start of an array list to the first byte of the data area 145 * used to hold user data. The same trick used by the standard offsetof() 146 * macro is used. 147 */ 148 #define ALIST_OFF_DATA ((size_t)(((Alist *)0)->al_data)) 149 #define APLIST_OFF_DATA ((size_t)(((APlist *)0)->apl_data)) 150 151 152 /* 153 * The TRAVERSE macros are intended to be used within a for(), and 154 * cause the resulting loop to iterate over each item in the loop, 155 * in order. 156 * ALIST_TRAVERSE: Traverse over the items in an Alist, 157 * using the zero based item array index to refer to 158 * each item. 159 * ALIST_TRAVERSE_BY_OFFSET: Traverse over the items in an 160 * Alist using the byte offset from the head of the 161 * Alist pointer to refer to each item. It should be noted 162 * that the first such offset is given by ALIST_OFF_DATA, 163 * and as such, there will never be a 0 offset. Some code 164 * uses this fact to treat 0 as a reserved value with 165 * special meaning. 166 * 167 * By-offset access is convenient for some parts of 168 * rtld, where a value of 0 is used to indicate an 169 * uninitialized link map control. 170 * 171 * APLIST_TRAVERSE: Traverse over the pointers in an APlist, using 172 * the zero based item array index to refer to each pointer. 173 */ 174 175 /* 176 * Within the loop: 177 * 178 * LIST - Pointer to Alist structure for list 179 * IDX - The current item index 180 * OFF - The current item offset 181 * DATA - Pointer to item 182 */ 183 #define ALIST_TRAVERSE(LIST, IDX, DATA) \ 184 (IDX) = 0, \ 185 ((LIST) != NULL) && ((DATA) = (void *)(LIST)->al_data); \ 186 \ 187 ((LIST) != NULL) && ((IDX) < (LIST)->al_nitems); \ 188 \ 189 (IDX)++, \ 190 (DATA) = (void *) (((LIST)->al_size * (IDX)) + (char *)(LIST)->al_data) 191 192 #define ALIST_TRAVERSE_BY_OFFSET(LIST, OFF, DATA) \ 193 (((LIST) != NULL) && ((OFF) = ALIST_OFF_DATA) && \ 194 (((DATA) = (void *)((char *)(LIST) + (OFF))))); \ 195 \ 196 (((LIST) != NULL) && ((OFF) < (LIST)->al_next)); \ 197 \ 198 (((OFF) += ((LIST)->al_size)), \ 199 ((DATA) = (void *)((char *)(LIST) + (OFF)))) 200 201 /* 202 * Within the loop: 203 * 204 * LIST - Pointer to APlist structure for list 205 * IDX - The current item index 206 * PTR - item value 207 * 208 * Note that this macro is designed to ensure that PTR retains the 209 * value of the final pointer in the list after exiting the for loop, 210 * and to avoid dereferencing an out of range address. This is done by 211 * doing the dereference in the middle expression, using the comma 212 * operator to ensure that a NULL pointer won't stop the loop. 213 */ 214 #define APLIST_TRAVERSE(LIST, IDX, PTR) \ 215 (IDX) = 0; \ 216 \ 217 ((LIST) != NULL) && ((IDX) < (LIST)->apl_nitems) && \ 218 (((PTR) = ((LIST)->apl_data)[IDX]), 1); \ 219 \ 220 (IDX)++ 221 222 223 /* 224 * Possible values returned by aplist_test() 225 */ 226 typedef enum { 227 ALE_ALLOCFAIL = 0, /* Memory allocation error */ 228 ALE_EXISTS = 1, /* alist entry already exists */ 229 ALE_NOTFND = 2, /* item not found and insert not required */ 230 ALE_CREATE = 3 /* alist entry created */ 231 } aplist_test_t; 232 233 234 /* 235 * Access to an Alist item by index or offset. This is needed because the 236 * size of an item in an Alist is not known by the C compiler, and we 237 * have to do the indexing arithmetic explicitly. 238 * 239 * For an APlist, index the apl_data field directly --- No macro is needed. 240 */ 241 #define alist_item(_lp, _idx) \ 242 ((void *)(ALIST_OFF_DATA + ((_idx) * (_lp)->al_size) + (char *)(_lp))) 243 #define alist_item_by_offset(_lp, _off) \ 244 ((void *)((_off) + (char *)(_lp))) 245 246 /* 247 * # of items currently found in a list. These macros handle the case 248 * where the list has not been allocated yet. 249 */ 250 #define alist_nitems(_lp) (((_lp) == NULL) ? 0 : (_lp)->al_nitems) 251 #define aplist_nitems(_lp) (((_lp) == NULL) ? 0 : (_lp)->apl_nitems) 252 253 254 extern void *alist_append(Alist **, const void *, size_t, Aliste); 255 extern void alist_delete(Alist *, Aliste *); 256 extern void alist_delete_by_offset(Alist *, Aliste *); 257 extern void *alist_insert(Alist **, const void *, size_t, 258 Aliste, Aliste); 259 extern void *alist_insert_by_offset(Alist **, const void *, size_t, 260 Aliste, Aliste); 261 extern void alist_reset(Alist *); 262 263 264 extern void *aplist_append(APlist **, const void *, Aliste); 265 extern void aplist_delete(APlist *, Aliste *); 266 extern int aplist_delete_value(APlist *, const void *); 267 extern void *aplist_insert(APlist **, const void *, 268 Aliste, Aliste idx); 269 extern void aplist_reset(APlist *); 270 extern aplist_test_t aplist_test(APlist **, const void *, Aliste); 271 272 #ifdef __cplusplus 273 } 274 #endif 275 276 #endif /* _ALIST_H */ 277