1 files changed, 106 insertions, 0 deletions
diff --git a/advent-of-code/2022/lib/htable.c b/advent-of-code/2022/lib/htable.c
new file mode 100644
index 0000000..d4b90a5
--- /dev/null
+++ b/advent-of-code/2022/lib/htable.c
@@ -0,0 +1,106 @@
+#include "htable.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#define HTFL_NUL 0
+#define HTFL_VAL 1
+#define HTFL_DEL 2
+
+static void* htable_end(HTable *ht) {
+    return ht->buf + ht->cap * (ht->elemsz + 1);
+}
+
+static void rebuild(HTable *ht) {
+    HTable newht;
+    htable_init(&newht, ht->elemsz, ht->size * 6, ht->hash, ht->eq);
+    void *iter = htable_begin(ht);
+    while (iter != NULL) {
+        htable_insert(&newht, iter);
+        iter = htable_next(ht, iter);
+    }
+    free(ht->buf);
+    *ht = newht;
+}
+
+static uint8_t getflag(void *iter) {
+    return *(uint8_t*)(iter - 1);
+}
+
+static void setflag(void *iter, uint8_t flag) {
+    *(uint8_t *)(iter - 1) = flag;
+}
+
+void htable_init(HTable *ht, int elemsz, int cap, uint32_t (*hash)(void*),
+                 bool (*eq)(void*, void*)) {
+    if (cap < 16) cap = 16;
+    ht->buf = malloc(cap * (elemsz + 1));
+    memset(ht->buf, 0, cap * (elemsz + 1));
+    ht->size = 0;
+    ht->cap = cap;
+    ht->taken = 0;
+    ht->begin = NULL;
+    ht->elemsz = elemsz;
+    ht->hash = hash;
+    ht->eq = eq;
+}
+
+bool htable_insert(HTable *ht, void* elem) {
+    if (ht->taken + 1 > ht->cap / 2) {
+        rebuild(ht);
+    }
+    ht->taken++;
+    ht->size++;
+    int hashcode = ht->hash(elem) % ht->cap;
+    void *pos = ht->buf + hashcode * (ht->elemsz + 1) + 1;
+    while (getflag(pos) != HTFL_NUL) {
+        if (getflag(pos) == HTFL_VAL && ht->eq(pos, elem)) return false;
+        pos += ht->elemsz + 1;
+        if (pos >= htable_end(ht)) { // arrived end, restart from beginning
+            pos = ht->buf + 1;
+        }
+    }
+    memcpy(pos, elem, ht->elemsz);
+    setflag(pos, HTFL_VAL);
+    if (pos < ht->begin || ht->begin == NULL) {
+        ht->begin = pos;
+    }
+    return true;
+}
+
+void htable_del(HTable *ht, void* iter) {
+    ht->size--;
+    setflag(iter, HTFL_DEL);
+    if (iter == ht->begin) {
+        ht->begin = htable_next(ht, iter);
+    }
+}
+
+void* htable_find(HTable *ht, void* elem) {
+    int hashcode = ht->hash(elem) % ht->cap;
+    void *pos = ht->buf + hashcode * (ht->elemsz + 1) + 1;
+    while (getflag(pos) != HTFL_NUL) {
+        if (getflag(pos) == HTFL_VAL && ht->eq(pos, elem)) return pos;
+        pos += ht->elemsz + 1;
+        if (pos >= htable_end(ht)) { // arrived end, restart from beginning
+            pos = ht->buf + 1;
+        }
+    }
+    return NULL;
+}
+
+void* htable_begin(HTable *ht) {
+    return ht->begin;
+}
+
+void* htable_next(HTable *ht, void *iter) {
+    void *pos = iter;
+    do {
+        pos += ht->elemsz + 1;
+        if (pos >= htable_end(ht)) { 
+            return NULL;
+        }
+    } while (getflag(pos) != HTFL_VAL);
+    return pos;
+}
+