1 files changed, 75 insertions, 0 deletions
diff --git a/impl/symtable.c b/impl/symtable.c
new file mode 100644
index 0000000..abef727
--- /dev/null
+++ b/impl/symtable.c
@@ -0,0 +1,75 @@
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the Unlicense for details.
+
+ * You may distribute and modify this code under the terms of the Unlicense,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://unlicense.org/>.
+
+ * Created: 2025-08-19
+ * Description: Symbol Table implementation
+ */
+
+#include <alisp.h>
+
+#include <malloc.h>
+#include <string.h>
+
+u64 djb2(sv_t string)
+{
+  u64 hash = 5381;
+  for (u64 i = 0; i < string.size; ++i)
+    hash = string.data[i] + (hash + (hash << 5));
+  return hash;
+}
+
+void sym_table_init(sym_table_t *table)
+{
+  table->capacity = MAX(table->capacity, SYM_TABLE_INIT_SIZE);
+  table->count    = 0;
+  vec_init(&table->entries, table->capacity * sizeof(sv_t));
+}
+
+char *sym_table_find(sym_table_t *table, sv_t sv)
+{
+  // Initialise the table if it's not done already
+  if (table->entries.capacity == 0)
+    sym_table_init(table);
+
+  // TODO: Deal with resizing this when table->count > table->size / 2
+  u64 index = djb2(sv) & (table->capacity - 1);
+
+  for (sv_t comp = VEC_GET(&table->entries, sv_t)[index]; comp.data; index += 1,
+            index = index & (table->capacity - 1),
+            comp  = VEC_GET(&table->entries, sv_t)[index])
+    // Is it present in the table?
+    if (sv.size == comp.size && strncmp(sv.data, comp.data, sv.size) == 0)
+      break;
+
+  // we couldn't find it in our linear search (worst case scenario)
+  if (!VEC_GET(&table->entries, sv_t)[index].data)
+  {
+    sv_t newsv                            = sv_copy(sv);
+    VEC_GET(&table->entries, sv_t)[index] = newsv;
+    ++table->count;
+  }
+
+  return VEC_GET(&table->entries, sv_t)[index].data;
+}
+
+void sym_table_cleanup(sym_table_t *table)
+{
+  // kill the data
+  sv_t current = {0};
+  for (u64 i = 0; i < table->capacity; ++i)
+  {
+    current = VEC_GET(&table->entries, sv_t)[i];
+    if (current.data)
+      free(current.data);
+  }
+  // kill the container
+  vec_free(&table->entries);
+  memset(table, 0, sizeof(*table));
+}