+#include <ccan/htable/htable.h>
+#include <ccan/compiler/compiler.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <assert.h>
+
+/* This means a struct htable takes at least 512 bytes / 1k (32/64 bits). */
+#define HTABLE_BASE_BITS 7
+
+/* We use 0x1 as deleted marker. */
+#define HTABLE_DELETED (0x1)
+
+struct htable {
+ size_t (*rehash)(const void *elem, void *priv);
+ void *priv;
+ unsigned int bits;
+ size_t elems, max;
+ /* These are the bits which are the same in all pointers. */
+ uintptr_t common_mask, common_bits;
+ uintptr_t *table;
+};
+
+/* We clear out the bits which are always the same, and put metadata there. */
+static inline uintptr_t get_extra_ptr_bits(const struct htable *ht,
+ uintptr_t e)
+{
+ return e & ht->common_mask;
+}
+
+static inline void *get_raw_ptr(const struct htable *ht, uintptr_t e)
+{
+ return (void *)((e & ~ht->common_mask) | ht->common_bits);
+}
+
+static inline uintptr_t make_hval(const struct htable *ht,
+ const void *p, uintptr_t bits)
+{
+ return ((uintptr_t)p & ~ht->common_mask) | bits;
+}
+
+static inline bool entry_is_valid(uintptr_t e)
+{
+ return e > HTABLE_DELETED;
+}
+
+static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
+ size_t hash)
+{
+ /* Shuffling the extra bits (as specified in mask) down the
+ * end is quite expensive. But the lower bits are redundant, so
+ * we fold the value first. */
+ return (hash ^ (hash >> ht->bits)) & ht->common_mask;
+}
+
+struct htable *htable_new(size_t (*rehash)(const void *elem, void *priv),
+ void *priv)
+{
+ struct htable *ht = malloc(sizeof(struct htable));
+ if (ht) {
+ ht->bits = HTABLE_BASE_BITS;
+ ht->rehash = rehash;
+ ht->priv = priv;
+ ht->elems = 0;
+ ht->max = (1 << ht->bits) * 3 / 4;
+ /* This guarantees we enter update_common first add. */
+ ht->common_mask = -1;
+ ht->common_bits = 0;
+ ht->table = calloc(1 << ht->bits, sizeof(uintptr_t));
+ if (!ht->table) {
+ free(ht);
+ ht = NULL;
+ }
+ }
+ return ht;
+}
+
+void htable_free(const struct htable *ht)
+{
+ free((void *)ht->table);
+ free((void *)ht);
+}
+
+static size_t hash_bucket(const struct htable *ht, size_t h)
+{
+ return h & ((1 << ht->bits)-1);
+}
+
+static void *htable_val(const struct htable *ht,
+ struct htable_iter *i, size_t hash)
+{
+ uintptr_t h2 = get_hash_ptr_bits(ht, hash);
+
+ while (ht->table[i->off]) {
+ if (ht->table[i->off] != HTABLE_DELETED) {
+ if (get_extra_ptr_bits(ht, ht->table[i->off]) == h2)
+ return get_raw_ptr(ht, ht->table[i->off]);
+ }
+ i->off = (i->off + 1) & ((1 << ht->bits)-1);
+ }
+ return NULL;
+}
+
+void *htable_firstval(const struct htable *ht,
+ struct htable_iter *i, size_t hash)
+{
+ i->off = hash_bucket(ht, hash);
+ return htable_val(ht, i, hash);
+}
+
+void *htable_nextval(const struct htable *ht,
+ struct htable_iter *i, size_t hash)
+{
+ i->off = (i->off + 1) & ((1 << ht->bits)-1);
+ return htable_val(ht, i, hash);
+}
+
+void *htable_first(const struct htable *ht, struct htable_iter *i)
+{
+ for (i->off = 0; i->off < (size_t)1 << ht->bits; i->off++) {
+ if (entry_is_valid(ht->table[i->off]))
+ return get_raw_ptr(ht, ht->table[i->off]);
+ }
+ return NULL;
+}
+
+void *htable_next(const struct htable *ht, struct htable_iter *i)
+{
+ for (i->off++; i->off < (size_t)1 << ht->bits; i->off++) {
+ if (entry_is_valid(ht->table[i->off]))
+ return get_raw_ptr(ht, ht->table[i->off]);
+ }
+ return NULL;
+}
+
+/* This does not expand the hash table, that's up to caller. */
+static void ht_add(struct htable *ht, const void *new, size_t h)
+{
+ size_t i;
+
+ i = hash_bucket(ht, h);
+
+ while (entry_is_valid(ht->table[i]))
+ i = (i + 1) & ((1 << ht->bits)-1);
+
+ ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h));
+}
+
+static COLD_ATTRIBUTE bool double_table(struct htable *ht)
+{
+ unsigned int i;
+ size_t oldnum = (size_t)1 << ht->bits;
+ size_t *oldtable, e;
+
+ oldtable = ht->table;
+ ht->table = calloc(1 << (ht->bits+1), sizeof(size_t));
+ if (!ht->table) {
+ ht->table = oldtable;
+ return false;
+ }
+ ht->bits++;
+ ht->max *= 2;
+
+ for (i = 0; i < oldnum; i++) {
+ if (entry_is_valid(e = oldtable[i])) {
+ void *p = get_raw_ptr(ht, e);
+ ht_add(ht, p, ht->rehash(p, ht->priv));
+ }
+ }
+ free(oldtable);
+ return true;
+}
+
+/* We stole some bits, now we need to put them back... */
+static COLD_ATTRIBUTE void update_common(struct htable *ht, const void *p)
+{
+ unsigned int i;
+ uintptr_t maskdiff, bitsdiff;
+
+ if (ht->elems == 0) {
+ ht->common_mask = -1;
+ ht->common_bits = (uintptr_t)p;
+ return;
+ }
+
+ /* Find bits which are unequal to old common set. */
+ maskdiff = ht->common_bits ^ ((uintptr_t)p & ht->common_mask);
+
+ /* These are the bits which go there in existing entries. */
+ bitsdiff = ht->common_bits & maskdiff;
+
+ for (i = 0; i < (size_t)1 << ht->bits; i++) {
+ if (!entry_is_valid(ht->table[i]))
+ continue;
+ /* Clear the bits no longer in the mask, set them as
+ * expected. */
+ ht->table[i] &= ~maskdiff;
+ ht->table[i] |= bitsdiff;
+ }
+
+ /* Take away those bits from our mask and set. */
+ ht->common_mask &= ~maskdiff;
+ ht->common_bits &= ~maskdiff;
+}
+
+bool htable_add(struct htable *ht, size_t hash, const void *p)
+{
+ if (ht->elems+1 > ht->max && !double_table(ht))
+ return false;
+ assert(p);
+ if (((uintptr_t)p & ht->common_mask) != ht->common_bits)
+ update_common(ht, p);
+
+ ht_add(ht, p, hash);
+ ht->elems++;
+ return true;
+}
+
+/* If every one of the following buckets are DELETED (up to the next unused
+ one), we can actually mark them all unused. */
+static void delete_run(struct htable *ht, unsigned int num)
+{
+ unsigned int i, last = num + 1;
+ size_t mask = (((size_t)1 << ht->bits)-1);
+
+ while (ht->table[last & mask]) {
+ if (entry_is_valid(ht->table[last & mask]))
+ return;
+ last++;
+ }
+
+ /* Now see if we can step backwards to find previous deleted ones. */
+ for (i = num-1; ht->table[i & mask] == HTABLE_DELETED; i--);
+
+ for (i++; i < last; i++)
+ ht->table[i & ((1 << ht->bits)-1)] = 0;
+}
+
+bool htable_del(struct htable *ht, size_t h, const void *p)
+{
+ struct htable_iter i;
+ void *c;
+
+ for (c = htable_firstval(ht,&i,h); c; c = htable_nextval(ht,&i,h)) {
+ if (c == p) {
+ htable_delval(ht, &i);
+ return true;
+ }
+ }
+ return false;
+}
+
+void htable_delval(struct htable *ht, struct htable_iter *i)
+{
+ assert(i->off < (size_t)1 << ht->bits);
+ assert(entry_is_valid(ht->table[i->off]));
+
+ ht->elems--;
+ ht->table[i->off] = HTABLE_DELETED;
+ delete_run(ht, i->off);
+}
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