1 files changed, 290 insertions, 0 deletions
diff --git a/db2/common/db_salloc.c b/db2/common/db_salloc.c
new file mode 100644
index 0000000000..f0202ddb90
--- /dev/null
+++ b/db2/common/db_salloc.c
@@ -0,0 +1,290 @@
+/*-
+ * See the file LICENSE for redistribution information.
+ *
+ * Copyright (c) 1996, 1997
+ *	Sleepycat Software.  All rights reserved.
+ */
+
+#include "config.h"
+
+#ifndef lint
+static const char sccsid[] = "@(#)db_salloc.c	10.6 (Sleepycat) 7/5/97";
+#endif /* not lint */
+
+#ifndef NO_SYSTEM_INCLUDES
+#include <sys/types.h>
+
+#include <errno.h>
+#include <stdio.h>
+#endif
+
+#include "db_int.h"
+#include "shqueue.h"
+#include "common_ext.h"
+
+/*
+ * Implement shared memory region allocation, using simple first-fit algorithm.
+ * The model is that we take a "chunk" of shared memory store and begin carving
+ * it up into areas, similarly to how malloc works.  We do coalescing on free.
+ *
+ * The "len" field in the __data struct contains the length of the free region
+ * (less the size_t bytes that holds the length).  We use the address provided
+ * by the caller to find this length, which allows us to free a chunk without
+ * requiring that the caller pass in the length of the chunk they're freeing.
+ */
+SH_LIST_HEAD(__head);
+struct __data {
+	size_t len;
+	SH_LIST_ENTRY links;
+};
+
+/*
+ * __db_shalloc_init --
+ *	Initialize the area as one large chunk.
+ *
+ * PUBLIC: void __db_shalloc_init __P((void *, size_t));
+ */
+void
+__db_shalloc_init(area, size)
+	void *area;
+	size_t size;
+{
+	struct __data *elp;
+	struct __head *hp;
+
+	hp = area;
+	SH_LIST_INIT(hp);
+
+	elp = (struct __data *)(hp + 1);
+	elp->len = size - sizeof(struct __head) - sizeof(elp->len);
+	SH_LIST_INSERT_HEAD(hp, elp, links, __data);
+}
+
+/*
+ * __db_shalloc --
+ *	Allocate some space from the shared region.
+ *
+ * PUBLIC: int __db_shalloc __P((void *, size_t, size_t, void *));
+ */
+int
+__db_shalloc(p, len, align, retp)
+	void *p, *retp;
+	size_t len, align;
+{
+	struct __data *elp;
+	size_t *sp;
+	void *rp;
+
+	/*
+	 * We never allocate less than the size of a struct __data, align
+	 * to less than a size_t boundary, or align to something that's not
+	 * a multiple of a size_t.
+	 */
+	if (len < sizeof(struct __data))
+		len = sizeof(struct __data);
+	align = align <= sizeof(size_t) ?
+	    sizeof(size_t) : ALIGN(align, sizeof(size_t));
+
+	/* Walk the list, looking for a slot. */
+	for (elp = SH_LIST_FIRST((struct __head *)p, __data);
+	    elp != NULL;
+	    elp = SH_LIST_NEXT(elp, links, __data)) {
+		/*
+		 * Calculate the value of the returned pointer if we were to
+		 * use this chunk.
+		 *	+ Find the end of the chunk.
+		 *	+ Subtract the memory the user wants.
+		 *	+ Find the closest previous correctly-aligned address.
+		 */
+		rp = (u_int8_t *)elp + sizeof(size_t) + elp->len;
+		rp = (u_int8_t *)rp - len;
+		rp = (u_int8_t *)((ALIGNTYPE)rp & ~(align - 1));
+
+		/*
+		 * Rp may now point before elp->links, in which case the chunk
+		 * was too small, and we have to try again.
+		 */
+		if ((u_int8_t *)rp < (u_int8_t *)&elp->links)
+			continue;
+
+		*(void **)retp = rp;
+
+		/*
+		 * If there are at least 32 bytes of additional memory, divide
+		 * the chunk into two chunks.
+		 */
+		if ((u_int8_t *)rp >= (u_int8_t *)&elp->links + 32) {
+			sp = rp;
+			*--sp = elp->len -
+			    ((u_int8_t *)rp - (u_int8_t *)&elp->links);
+			elp->len -= *sp + sizeof(size_t);
+			return (0);
+		}
+
+		/*
+		 * Otherwise, we return the entire chunk, wasting some amount
+		 * of space to keep the list compact.  However, because the
+		 * address we're returning to the user may not be the address
+		 * of the start of the region for alignment reasons, set the
+		 * size_t length fields back to the "real" length field to a
+		 * flag value, so that we can find the real length during free.
+		 */
+#define	ILLEGAL_SIZE	1
+		SH_LIST_REMOVE(elp, links, __data);
+		for (sp = rp; (u_int8_t *)--sp >= (u_int8_t *)&elp->links;)
+			*sp = ILLEGAL_SIZE;
+		return (0);
+	}
+
+	/* Nothing found large enough; need to figure out how to grow region. */
+	return (ENOMEM);
+}
+
+/*
+ * __db_shalloc_free --
+ *	Free a shared memory allocation.
+ *
+ * PUBLIC: void __db_shalloc_free __P((void *, void *));
+ */
+void
+__db_shalloc_free(regionp, ptr)
+	void *regionp, *ptr;
+{
+	struct __data *elp, *lastp, *newp;
+	struct __head *hp;
+	size_t free_size, *sp;
+	int merged;
+
+	/*
+	 * Step back over flagged length fields to find the beginning of
+	 * the object and its real size.
+	 */
+	for (sp = (size_t *)ptr; sp[-1] == ILLEGAL_SIZE; --sp);
+	ptr = sp;
+
+	newp = (struct __data *)((u_int8_t *)ptr - sizeof(size_t));
+	free_size = newp->len;
+
+	/*
+	 * Walk the list, looking for where this entry goes.
+	 *
+	 * We keep the free list sorted by address so that coalescing is
+	 * trivial.
+	 *
+	 * XXX
+	 * Probably worth profiling this to see how expensive it is.
+	 */
+	hp = (struct __head *)regionp;
+	for (elp = SH_LIST_FIRST(hp, __data), lastp = NULL;
+	    elp != NULL && (void *)elp < (void *)ptr;
+	    lastp = elp, elp = SH_LIST_NEXT(elp, links, __data));
+
+	/*
+	 * Elp is either NULL (we reached the end of the list), or the slot
+	 * after the one that's being returned.  Lastp is either NULL (we're
+	 * returning the first element of the list) or the element before the
+	 * one being returned.
+	 *
+	 * Check for coalescing with the next element.
+	 */
+	merged = 0;
+	if ((u_int8_t *)ptr + free_size == (u_int8_t *)elp) {
+		newp->len += elp->len + sizeof(size_t);
+		SH_LIST_REMOVE(elp, links, __data);
+		if (lastp != NULL)
+			SH_LIST_INSERT_AFTER(lastp, newp, links, __data);
+		else
+			SH_LIST_INSERT_HEAD(hp, newp, links, __data);
+		merged = 1;
+	}
+
+	/* Check for coalescing with the previous element. */
+	if (lastp != NULL && (u_int8_t *)lastp +
+	    lastp->len + sizeof(size_t) == (u_int8_t *)newp) {
+		lastp->len += newp->len + sizeof(size_t);
+
+		/*
+		 * If we have already put the new element into the list take
+		 * it back off again because it's just been merged with the
+		 * previous element.
+		 */
+		if (merged)
+			SH_LIST_REMOVE(newp, links, __data);
+		merged = 1;
+	}
+
+	if (!merged)
+		if (lastp == NULL)
+			SH_LIST_INSERT_HEAD(hp, newp, links, __data);
+		else
+			SH_LIST_INSERT_AFTER(lastp, newp, links, __data);
+}
+
+/*
+ * __db_shalloc_count --
+ *	Return the amount of memory on the free list.
+ *
+ * PUBLIC: size_t __db_shalloc_count __P((void *));
+ */
+size_t
+__db_shalloc_count(addr)
+	void *addr;
+{
+	struct __data *elp;
+	size_t count;
+
+	count = 0;
+	for (elp = SH_LIST_FIRST((struct __head *)addr, __data);
+	    elp != NULL;
+	    elp = SH_LIST_NEXT(elp, links, __data))
+		count += elp->len;
+
+	return (count);
+}
+
+/*
+ * __db_shsizeof --
+ *	Return the size of a shalloc'd piece of memory.
+ *
+ * PUBLIC: size_t __db_shsizeof __P((void *));
+ */
+size_t
+__db_shsizeof(ptr)
+	void *ptr;
+{
+	struct __data *elp;
+	size_t *sp;
+
+	/*
+	 * Step back over flagged length fields to find the beginning of
+	 * the object and its real size.
+	 */
+	for (sp = (size_t *)ptr; sp[-1] == ILLEGAL_SIZE; --sp);
+
+	elp = (struct __data *)((u_int8_t *)sp - sizeof(size_t));
+	return (elp->len);
+}
+
+#ifdef DEBUG
+/*
+ * __db_shalloc_dump --
+ *
+ * PUBLIC: void __db_shalloc_dump __P((FILE *, void *));
+ */
+void
+__db_shalloc_dump(fp, addr)
+	FILE *fp;
+	void *addr;
+{
+	struct __data *elp;
+
+	if (fp == NULL)
+		fp = stderr;
+
+	for (elp = SH_LIST_FIRST((struct __head *)addr, __data);
+	    elp != NULL;
+	    elp = SH_LIST_NEXT(elp, links, __data))
+		fprintf(fp, "%#lx: %lu\t", (u_long)elp, (u_long)elp->len);
+	fprintf(fp, "\n");
+}
+#endif