intmap: new module.

[ccan] / ccan / intmap / intmap.c

diff --git a/ccan/intmap/intmap.c b/ccan/intmap/intmap.c
new file mode 100644 (file)
index 0000000..d27b645
--- /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);
+}