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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ *
+ * Define an Alist, a list maintained as a reallocable array, and a for() loop
+ * macro to generalize its traversal.  Note that the array can be reallocated
+ * as it is being traversed, thus the offset of each element is recomputed from
+ * the start of the structure.
+ */
+
+#ifndef	_ALIST_H
+#define	_ALIST_H
+
+#pragma ident	"%Z%%M%	%I%	%E% SMI"
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+#include <sys/types.h>
+#if defined(sun)
+#include <sys/machelf.h>
+#else
+#include <sys/elf.h>
+#endif
+
+/*
+ * An Alist implements array lists. The functionality is similar to
+ * that of a linked list. However, an Alist is represented by a single
+ * contigious allocation of memory. The head of the memory is a header
+ * that contains control information for the list. Following the header
+ * is an array used to hold the user data. In the type definitions that
+ * follow, we define these as an array with a single element, but when
+ * we allocate the memory, we actually allocate the amount of memory needed.
+ *
+ * There are two "flavors" of array list:
+ *
+ *	Alist - Contain arbitrary data, usually structs.
+ *	APlist - Contain pointers to data allocated elsewhere.
+ *
+ * This differentiation is useful, because pointer lists are heavily
+ * used, and support a slightly different set of operations that are
+ * unique to their purpose.
+ *
+ * Array lists are initially represented by a NULL pointer. The memory
+ * for the list is only allocated if an item is inserted. This is very
+ * efficient for data structures that may or may not be needed for a
+ * given linker operation --- you only pay for what you use. In addition:
+ *
+ *	- Array lists grow as needed (memory is reallocated as necessary)
+ *	- Data is kept contiguously (no unused holes in between elements)
+ *		at the beginning of the data area. This locality has
+ *		good cache behavior, as access to adjacent items are
+ *		highly likely to be in the same page of memory.
+ *	- Insert/Delete operations at the end of the list are very
+ *		efficient. However, insert/delete operations elsewhere
+ *		will cause a relatively expensive overlapped memory
+ *		copy of the data following the insert/delete location.
+ *	- As with any generic memory alloctor (i.e. malloc()/free()),
+ *		array lists are not type safe for the data they contain.
+ *		Data is managed as (void *) pointers to data of a given
+ *		length, so the Alist module cannot prevent the caller from
+ *		inserting/extracting the wrong type of data. The caller
+ *		must guard against this.
+ *	- To free an array list, simply call the standard free() function
+ *		on the list pointer.
+ */
+
+
+
+/*
+ * Aliste is used to represent list indexes, offsets, and sizes.
+ */
+typedef	size_t	Aliste;
+
+
+
+/*
+ * Alist is used to hold non-pointer items --- usually structs:
+ *	- There must be an even number of Aliste fields before the
+ *		al_data field. This ensures that al_data will have
+ *		an alignment of 8, no matter whether sizeof(Aliste)
+ *		is 4 or 8. That means that al_data will have sufficient
+ *		alignment for any use, just like memory allocated via
+ *		malloc().
+ *	- al_nitems and al_next are redundant, in that they are
+ *		directly related:
+ *			al_next = al_nitems * al_size
+ *		We do this to make ALIST_TRAVERSE_BYOFFSET maximally
+ *		efficient. This doesn't waste space, because of the
+ *		requirement to have an even # of Alist fields (above).
+ *
+ * Note that Alists allow the data to be referenced by 0 based array
+ * index, or by their byte offset from the start of the Alist memory
+ * allocation. The index form is preferred for most use, as it is simpler.
+ * However, by-offset access is used by rtld link maps, and this ability
+ * is convenient in that case.
+ */
+typedef struct {
+	Aliste 		al_arritems;	/* # of items in al_data allocation */
+	Aliste 		al_nitems;	/* # items (index of next avail item) */
+	Aliste 		al_next;	/* offset of next available al_data[] */
+	Aliste		al_size;	/* size of each al_data[] item */
+	void 		*al_data[1];	/* data (can grow) */
+} Alist;
+
+/*
+ * APlist is a variant of Alist that contains pointers. There are several
+ * benefits to this special type:
+ *	- API is simpler
+ *	- Pointers are used directly, instead of requiring a
+ *		pointer-to-pointer double indirection.
+ *	- The implementation is slightly more efficient.
+ *	- Operations that make particular sense for pointers
+ *		can be supported without confusing the API for the
+ *		regular Alists.
+ */
+typedef struct {
+	Aliste		apl_arritems;	/* # of items in apl_data allocation */
+	Aliste 		apl_nitems;	/* # items (index of next avail item) */
+	void		*apl_data[1];	/* data area: (arrcnt * size) bytes */
+} APlist;
+
+
+/*
+ * The ALIST_OFF_DATA and APLIST_OFF_DATA macros give the byte offset
+ * from the start of an array list to the first byte of the data area
+ * used to hold user data. The same trick used by the standard offsetof()
+ * macro is used.
+ */
+#define	ALIST_OFF_DATA	((size_t)(((Alist *)0)->al_data))
+#define	APLIST_OFF_DATA	((size_t)(((APlist *)0)->apl_data))
+
+
+/*
+ * The TRAVERSE macros are intended to be used within a for(), and
+ * cause the resulting loop to iterate over each item in the loop,
+ * in order.
+ *	ALIST_TRAVERSE: Traverse over the items in an Alist,
+ *		using the zero based item array index to refer to
+ *		each item.
+ *	ALIST_TRAVERSE_BY_OFFSET: Traverse over the items in an
+ *		Alist using the byte offset from the head of the
+ *		Alist pointer to refer to each item. It should be noted
+ *		that the first such offset is given by ALIST_OFF_DATA,
+ *		and as such, there will never be a 0 offset. Some code
+ *		uses this fact to treat 0 as a reserved value with
+ *		special meaning.
+ *
+ *		By-offset access is convenient for some parts of
+ *		rtld, where a value of 0 is used to indicate an
+ *		uninitialized link map control.
+ *
+ *	APLIST_TRAVERSE: Traverse over the pointers in an APlist, using
+ *		the zero based item array index to refer to each pointer.
+ */
+
+/*
+ * Within the loop:
+ *
+ *	LIST - Pointer to Alist structure for list
+ *	IDX - The current item index
+ *	OFF - The current item offset
+ *	DATA - Pointer to item
+ */
+#define	ALIST_TRAVERSE(LIST, IDX, DATA) \
+	(IDX) = 0, \
+	((LIST) != NULL) && ((DATA) = (void *)(LIST)->al_data); \
+	\
+	((LIST) != NULL) && ((IDX) < (LIST)->al_nitems); \
+	\
+	(IDX)++, \
+	(DATA) = (void *) (((LIST)->al_size * (IDX)) + (char *)(LIST)->al_data)
+
+#define	ALIST_TRAVERSE_BY_OFFSET(LIST, OFF, DATA) \
+	(((LIST) != NULL) && ((OFF) = ALIST_OFF_DATA) && \
+	(((DATA) = (void *)((char *)(LIST) + (OFF))))); \
+	\
+	(((LIST) != NULL) && ((OFF) < (LIST)->al_next)); \
+	\
+	(((OFF) += ((LIST)->al_size)), \
+	((DATA) = (void *)((char *)(LIST) + (OFF))))
+
+/*
+ * Within the loop:
+ *
+ *	LIST - Pointer to APlist structure for list
+ *	IDX - The current item index
+ *	PTR - item value
+ *
+ * Note that this macro is designed to ensure that PTR retains the
+ * value of the final pointer in the list after exiting the for loop,
+ * and to avoid dereferencing an out of range address. This is done by
+ * doing the dereference in the middle expression, using the comma
+ * operator to ensure that a NULL pointer won't stop the loop.
+ */
+#define	APLIST_TRAVERSE(LIST, IDX, PTR) \
+	(IDX) = 0; \
+	\
+	((LIST) != NULL) && ((IDX) < (LIST)->apl_nitems) && \
+	(((PTR) = ((LIST)->apl_data)[IDX]), 1); \
+	\
+	(IDX)++
+
+
+/*
+ * Possible values returned by aplist_test()
+ */
+typedef enum {
+	ALE_ALLOCFAIL = 0,	/* Memory allocation error */
+	ALE_EXISTS =	1,	/* alist entry already exists */
+	ALE_NOTFND =	2,	/* item not found and insert not required */
+	ALE_CREATE =	3	/* alist entry created */
+} aplist_test_t;
+
+
+/*
+ * Access to an Alist item by index or offset. This is needed because the
+ * size of an item in an Alist is not known by the C compiler, and we
+ * have to do the indexing arithmetic explicitly.
+ *
+ * For an APlist, index the apl_data field directly --- No macro is needed.
+ */
+#define	alist_item(_lp, _idx) \
+	((void *)(ALIST_OFF_DATA + ((_idx) * (_lp)->al_size) + (char *)(_lp)))
+#define	alist_item_by_offset(_lp, _off) \
+	((void *)((_off) + (char *)(_lp)))
+
+/*
+ * # of items currently found in a list. These macros handle the case
+ * where the list has not been allocated yet.
+ */
+#define	alist_nitems(_lp) (((_lp) == NULL) ? 0 : (_lp)->al_nitems)
+#define	aplist_nitems(_lp) (((_lp) == NULL) ? 0 : (_lp)->apl_nitems)
+
+
+extern void		*alist_append(Alist **, const void *, size_t, Aliste);
+extern void		alist_delete(Alist *, Aliste *);
+extern void		alist_delete_by_offset(Alist *, Aliste *);
+extern void		*alist_insert(Alist **, const void *, size_t,
+			    Aliste, Aliste);
+extern void		*alist_insert_by_offset(Alist **, const void *, size_t,
+			    Aliste, Aliste);
+extern void		alist_reset(Alist *);
+
+
+extern void		*aplist_append(APlist **, const void *, Aliste);
+extern void		aplist_delete(APlist *, Aliste *);
+extern int		aplist_delete_value(APlist *, const void *);
+extern void		*aplist_insert(APlist **, const void *,
+			    Aliste, Aliste idx);
+extern void		aplist_reset(APlist *);
+extern aplist_test_t	aplist_test(APlist **, const void *, Aliste);
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif /* _ALIST_H */