X-Git-Url: https://git.ozlabs.org/?a=blobdiff_plain;ds=sidebyside;f=ccan%2Fstrset%2Fstrset.c;fp=ccan%2Fstrset%2Fstrset.c;h=8088db47e808e3adb40f5bf583a6a8e6babeec59;hb=ab83de953730f5e5e571dbf69ffb3cc685a102dc;hp=0000000000000000000000000000000000000000;hpb=0845e79650c9257aa0ddef8ff99fd815b5edffac;p=ccan

diff --git a/ccan/strset/strset.c b/ccan/strset/strset.c
new file mode 100644
index 00000000..8088db47
--- /dev/null
+++ b/ccan/strset/strset.c
@@ -0,0 +1,298 @@
+/* This code is based on the public domain code at
+ * http://github.com/agl/critbit writtem by Adam Langley
+ * <agl@imperialviolet.org>.
+ *
+ * Here are the main implementation differences:
+ * (1) We don't strdup the string on insert; we use the pointer we're given.
+ * (2) We use a straight bit number rather than a mask; it's simpler.
+ * (3) We don't use the bottom bit of the pointer, but instead use a leading
+ *     zero to distinguish nodes from strings.
+ * (4) The empty string (which would look like a node) is handled
+ *     using a special "empty node".
+ * (5) Delete returns the string, so you can free it if you want to.
+ * (6) Unions instead of void *, bool instead of int.
+ */
+#include <ccan/strset/strset.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/likely/likely.h>
+#include <ccan/str/str.h>
+#include <ccan/ilog/ilog.h>
+#include <assert.h>
+#include <stdlib.h>
+
+struct node {
+	/* To differentiate us from strings. */
+	char nul_byte;
+	/* The bit where these children differ. */
+	u8 bit_num;
+	/* The byte number where first bit differs (-1 == empty string node). */
+	size_t byte_num;
+	/* These point to strings or nodes. */
+	struct strset child[2];
+};
+
+/* Closest member to this in a non-empty set. */
+static const char *closest(struct strset n, const char *member)
+{
+	size_t len = strlen(member);
+	const u8 *bytes = (const u8 *)member;
+
+	/* Anything with first byte 0 is a node. */
+	while (!n.u.s[0]) {
+		u8 direction = 0;
+
+		/* Special node which represents the empty string. */
+		if (unlikely(n.u.n->byte_num == (size_t)-1)) {
+			n = n.u.n->child[0];
+			break;
+		}
+
+		if (n.u.n->byte_num < len) {
+			u8 c = bytes[n.u.n->byte_num];
+			direction = (c >> n.u.n->bit_num) & 1;
+		}
+		n = n.u.n->child[direction];
+	}
+	return n.u.s;
+}
+
+char *strset_test(const struct strset *set, const char *member)
+{
+	const char *str;
+
+	/* Empty set? */
+	if (!set->u.n)
+		return NULL;
+	str = closest(*set, member);
+	if (streq(member, str))
+		return (char *)str;
+	return NULL;
+}
+
+static bool set_string(struct strset *set,
+		       struct strset *n, const char *member)
+{
+	/* Substitute magic empty node if this is the empty string */
+	if (unlikely(!member[0])) {
+		n->u.n = malloc(sizeof(*n->u.n));
+		if (unlikely(!n->u.n))
+			return false;
+		n->u.n->nul_byte = '\0';
+		n->u.n->byte_num = (size_t)-1;
+		/* Attach the string to child[0] */
+		n = &n->u.n->child[0];
+	}
+	n->u.s = member;
+	return true;
+}
+
+bool strset_set(struct strset *set, const char *member)
+{
+	size_t len = strlen(member);
+	const u8 *bytes = (const u8 *)member;
+	struct strset *np;
+	const char *str;
+	struct node *newn;
+	size_t byte_num;
+	u8 bit_num, new_dir;
+
+	/* Empty set? */
+	if (!set->u.n) {
+		return set_string(set, set, member);
+	}
+
+	/* Find closest existing member. */
+	str = closest(*set, member);
+
+	/* Find where they differ. */
+	for (byte_num = 0; str[byte_num] == member[byte_num]; byte_num++) {
+		if (member[byte_num] == '\0') {
+			/* All identical! */
+			return false;
+		}
+	}
+
+	/* Find which bit differs (if we had ilog8, we'd use it) */
+	bit_num = ilog32_nz((u8)str[byte_num] ^ bytes[byte_num]) - 1;
+	assert(bit_num < CHAR_BIT);
+
+	/* Which direction do we go at this bit? */
+	new_dir = ((bytes[byte_num]) >> bit_num) & 1;
+
+	/* Allocate new node. */
+	newn = malloc(sizeof(*newn));
+	if (!newn) {
+		/* FIXME */
+		return false;
+	}
+	newn->nul_byte = '\0';
+	newn->byte_num = byte_num;
+	newn->bit_num = bit_num;
+	if (unlikely(!set_string(set, &newn->child[new_dir], member))) {
+		free(newn);
+		return false;
+	}
+
+	/* Find where to insert: not closest, but first which differs! */
+	np = set;
+	while (!np->u.s[0]) {
+		u8 direction = 0;
+
+		/* Special node which represents the empty string will
+		 * break here too! */
+		if (np->u.n->byte_num > byte_num)
+			break;
+		/* Subtle: bit numbers are "backwards" for comparison */
+		if (np->u.n->byte_num == byte_num && np->u.n->bit_num < bit_num)
+			break;
+
+		if (np->u.n->byte_num < len) {
+			u8 c = bytes[np->u.n->byte_num];
+			direction = (c >> np->u.n->bit_num) & 1;
+		}
+		np = &np->u.n->child[direction];
+	}
+
+	newn->child[!new_dir]= *np;
+	np->u.n = newn;
+	return true;
+}
+
+char *strset_clear(struct strset *set, const char *member)
+{
+	size_t len = strlen(member);
+	const u8 *bytes = (const u8 *)member;
+	struct strset *parent = NULL, *n;
+	const char *ret = NULL;
+	u8 direction = 0; /* prevent bogus gcc warning. */
+
+	/* Empty set? */
+	if (!set->u.n)
+		return NULL;
+
+	/* Find closest, but keep track of parent. */
+	n = set;
+	/* Anything with first byte 0 is a node. */
+	while (!n->u.s[0]) {
+		u8 c = 0;
+
+		/* Special node which represents the empty string. */
+		if (unlikely(n->u.n->byte_num == (size_t)-1)) {
+			const char *empty_str = n->u.n->child[0].u.s;
+
+			if (member[0])
+				return NULL;
+
+			/* Sew empty string back so remaining logic works */
+			free(n->u.n);
+			n->u.s = empty_str;
+			break;
+		}
+
+		parent = n;
+		if (n->u.n->byte_num < len) {
+			c = bytes[n->u.n->byte_num];
+			direction = (c >> n->u.n->bit_num) & 1;
+		} else
+			direction = 0;
+		n = &n->u.n->child[direction];
+	}
+
+	/* Did we find it? */
+	if (!streq(member, n->u.s))
+		return NULL;
+
+	ret = n->u.s;
+
+	if (!parent) {
+		/* We deleted last node. */
+		set->u.n = NULL;
+	} else {
+		struct node *old = parent->u.n;
+		/* Raise other node to parent. */
+		*parent = old->child[!direction];
+		free(old);
+	}
+
+	return (char *)ret;
+}
+
+static bool iterate(struct strset n,
+		    bool (*handle)(const char *, void *), void *data)
+{
+	if (n.u.s[0])
+		return handle(n.u.s, data);
+	if (unlikely(n.u.n->byte_num == (size_t)-1))
+		return handle(n.u.n->child[0].u.s, data);
+
+	return iterate(n.u.n->child[0], handle, data)
+		|| iterate(n.u.n->child[1], handle, data);
+}
+
+void strset_iterate_(const struct strset *set,
+		     bool (*handle)(const char *, void *), void *data)
+{
+	/* Empty set? */
+	if (!set->u.n)
+		return;
+
+	iterate(*set, handle, data);
+}
+
+const struct strset *strset_prefix(const struct strset *set, const char *prefix)
+{
+	const struct strset *n, *top;
+	size_t len = strlen(prefix);
+	const u8 *bytes = (const u8 *)prefix;
+
+	/* Empty set -> return empty set. */
+	if (!set->u.n)
+		return set;
+
+	top = n = set;
+
+	/* We walk to find the top, but keep going to check prefix matches. */
+	while (!n->u.s[0]) {
+		u8 c = 0, direction;
+
+		/* Special node which represents the empty string. */
+		if (unlikely(n->u.n->byte_num == (size_t)-1)) {
+			n = &n->u.n->child[0];
+			break;
+		}
+
+		if (n->u.n->byte_num < len)
+			c = bytes[n->u.n->byte_num];
+
+		direction = (c >> n->u.n->bit_num) & 1;
+		n = &n->u.n->child[direction];
+		if (c)
+			top = n;
+	}
+
+	if (!strstarts(n->u.s, prefix)) {
+		/* Convenient return for prefixes which do not appear in set. */
+		static const struct strset empty_set;
+		return &empty_set;
+	}
+
+	return top;
+}
+
+static void destroy(struct strset n)
+{
+	if (!n.u.s[0]) {
+		if (likely(n.u.n->byte_num != (size_t)-1)) {
+			destroy(n.u.n->child[0]);
+			destroy(n.u.n->child[1]);
+		}
+		free(n.u.n);
+	}
+}
+
+void strset_destroy(struct strset *set)
+{
+	if (set->u.n)
+		destroy(*set);
+	set->u.n = NULL;
+}