X-Git-Url: https://git.ozlabs.org/?a=blobdiff_plain;f=ccan%2Fintmap%2Fintmap.c;fp=ccan%2Fintmap%2Fintmap.c;h=d27b645695c43d4c52d66ab37358f92f624c5d06;hb=d9e93014a999102aa1cc9979e041cd58e6aca724;hp=0000000000000000000000000000000000000000;hpb=3f642347378afc9e1db1768d88c9f5b2baffe9ba;p=ccan

diff --git a/ccan/intmap/intmap.c b/ccan/intmap/intmap.c
new file mode 100644
index 00000000..d27b6456
--- /dev/null
+++ b/ccan/intmap/intmap.c
@@ -0,0 +1,212 @@
+/* CC0 license (public domain) - see LICENSE file for details */
+/* This code is based on ccan/strmap.c. */
+#include <ccan/intmap/intmap.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/str/str.h>
+#include <ccan/ilog/ilog.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <errno.h>
+
+struct node {
+	/* These point to strings or nodes. */
+	struct intmap child[2];
+	/* The bit where these children differ (0 == lsb) */
+	u8 bit_num;
+};
+
+/* Closest member to this in a non-empty map. */
+static struct intmap *closest(struct intmap *n, intmap_index_t index)
+{
+	/* Anything with NULL value is a node. */
+	while (!n->v) {
+		u8 direction = (index >> n->u.n->bit_num) & 1;
+		n = &n->u.n->child[direction];
+	}
+	return n;
+}
+
+void *intmap_get_(const struct intmap *map, intmap_index_t index)
+{
+	struct intmap *n;
+
+	/* Not empty map? */
+	if (!intmap_empty_(map)) {
+		n = closest((struct intmap *)map, index);
+		if (index == n->u.i)
+			return n->v;
+	}
+	errno = ENOENT;
+	return NULL;
+}
+
+bool intmap_add_(struct intmap *map, intmap_index_t index, const void *value)
+{
+	struct intmap *n;
+	struct node *newn;
+	u8 bit_num, new_dir;
+
+	assert(value);
+
+	/* Empty map? */
+	if (intmap_empty_(map)) {
+		map->u.i = index;
+		map->v = (void *)value;
+		return true;
+	}
+
+	/* Find closest existing member. */
+	n = closest(map, index);
+
+	/* Find highest bit where they differ. */
+	bit_num = ilog64(n->u.i ^ index);
+	if (bit_num == 0) {
+		errno = EEXIST;
+		return false;
+	}
+	bit_num--;
+
+	assert(bit_num < CHAR_BIT*sizeof(index));
+
+	/* Which direction do we go at this bit? */
+	new_dir = (index >> bit_num) & 1;
+
+	/* Allocate new node. */
+	newn = malloc(sizeof(*newn));
+	if (!newn) {
+		errno = ENOMEM;
+		return false;
+	}
+	newn->bit_num = bit_num;
+	newn->child[new_dir].v = (void *)value;
+	newn->child[new_dir].u.i = index;
+
+	/* Find where to insert: not closest, but first which differs! */
+	n = map;
+	while (!n->v) {
+		u8 direction;
+
+		/* Subtle: bit numbers are "backwards" for comparison */
+		if (n->u.n->bit_num < bit_num)
+			break;
+
+		direction = (index >> n->u.n->bit_num) & 1;
+		n = &n->u.n->child[direction];
+	}
+
+	newn->child[!new_dir] = *n;
+	n->u.n = newn;
+	n->v = NULL;
+	return true;
+}
+
+void *intmap_del_(struct intmap *map, intmap_index_t index)
+{
+	struct intmap *parent = NULL, *n;
+	u8 direction;
+	void *value;
+
+	/* Empty map? */
+	if (intmap_empty_(map)) {
+		errno = ENOENT;
+		return NULL;
+	}
+
+	/* Find closest, but keep track of parent. */
+	n = map;
+	/* Anything with NULL value is a node. */
+	while (!n->v) {
+		parent = n;
+		direction = (index >> n->u.n->bit_num) & 1;
+		n = &n->u.n->child[direction];
+	}
+
+	/* Did we find it? */
+	if (index != n->u.i) {
+		errno = ENOENT;
+		return NULL;
+	}
+
+	value = n->v;
+
+	if (!parent) {
+		/* We deleted last node. */
+		intmap_init_(map);
+	} else {
+		struct node *old = parent->u.n;
+		/* Raise other node to parent. */
+		*parent = old->child[!direction];
+		free(old);
+	}
+	errno = 0;
+	return value;
+}
+
+intmap_index_t intmap_first_(const struct intmap *map)
+{
+	const struct intmap *n;
+
+	if (intmap_empty_(map)) {
+		errno = ENOENT;
+		return UINTMAP_NONE;
+	}
+	
+	n = map;
+	/* Anything with NULL value is a node. */
+	while (!n->v)
+		n = &n->u.n->child[0];
+	errno = 0;
+	return n->u.i;
+}
+		
+intmap_index_t intmap_after_(const struct intmap *map, intmap_index_t index)
+{
+	const struct intmap *n, *prev = NULL;
+
+	/* Special case of unincrementable value, or empty map */
+	if (index == UINTMAP_NONE || intmap_empty_(map)) {
+		errno = ENOENT;
+		return UINTMAP_NONE;
+	}
+
+	/* Follow down, track the last place where we could have set a bit
+	 * instead of clearing it: this is the higher alternative tree. */
+	n = map;
+	while (!n->v) {
+		u8 direction = (index >> n->u.n->bit_num) & 1;
+		if (!direction)
+			prev = n;
+		n = &n->u.n->child[direction];
+	}
+
+	/* Found a successor? */
+	if (n->u.i > index) {
+		errno = 0;
+		return n->u.i;
+	}
+
+	/* Nowhere to go back up to? */
+	if (!prev) {
+		errno = ENOENT;
+		return UINTMAP_NONE;
+	}
+
+	/* Get first one from that other branch. */
+	return intmap_first_(&prev->u.n->child[1]);
+}
+
+static void clear(struct intmap n)
+{
+	if (!n.v) {
+		clear(n.u.n->child[0]);
+		clear(n.u.n->child[1]);
+		free(n.u.n);
+	}
+}
+
+void intmap_clear_(struct intmap *map)
+{
+	if (!intmap_empty_(map))
+		clear(*map);
+	intmap_init_(map);
+}