--- /dev/null
+/* 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;
+}
projects / ccan / blobdiff