From 0c6df62acd984c92a71e2ab4bcd630afe2752840 Mon Sep 17 00:00:00 2001
From: Miguel Lechon <miguel.lechon@gmail.com>
Date: Mon, 1 Mar 2021 18:35:02 +0100
Subject: [PATCH] Hash map proposal.

---
 source/map_proposal.c | 130 ++++++++++++++++++++++++++++++++++++++++++
 source/map_proposal.h |  35 ++++++++++++
 2 files changed, 165 insertions(+)
 create mode 100644 source/map_proposal.c
 create mode 100644 source/map_proposal.h

diff --git a/source/map_proposal.c b/source/map_proposal.c
new file mode 100644
index 0000000..8afeebe
--- /dev/null
+++ b/source/map_proposal.c
@@ -0,0 +1,130 @@
+/////////////////////////////////////////////
+//~ NOTE(mal): MD_Map functions. Same as MD_NodeTable except they ask for hash values to abstract the hash function away
+MD_PRIVATE_FUNCTION_IMPL void
+_MD_Map_Initialize(MD_Map *map)
+{
+    if(map->table_size == 0)
+    {
+        map->table_size = 4096;
+        map->table = _MD_PushArray(_MD_GetCtx(), MD_MapSlot *, map->table_size);
+    }
+}
+
+MD_FUNCTION_IMPL MD_MapSlot *
+_MD_Map_Lookup(MD_Map *map, MD_u64 hash)
+{
+    _MD_Map_Initialize(map);
+    
+    MD_MapSlot *slot = 0;
+    MD_u64 index = hash % map->table_size;
+    for(MD_MapSlot *candidate = map->table[index]; candidate; candidate = candidate->next)
+    {
+        if(candidate->hash == hash)
+        {
+            slot = candidate;
+            break;
+        }
+    }
+    return slot;
+}
+
+MD_FUNCTION_IMPL MD_b32
+_MD_Map_Insert(MD_StringMap *map, MD_MapCollisionRule collision_rule, MD_u64 hash, void *value)
+{
+    _MD_Map_Initialize(map);
+    
+    MD_MapSlot *slot = 0;
+    MD_u64 index = hash % map->table_size;
+    
+    for(MD_MapSlot *candidate = map->table[index]; candidate; candidate = candidate->next)
+    {
+        if(candidate->hash == hash)
+        {
+            slot = candidate;
+            break;
+        }
+    }
+    
+    if(slot == 0 || (slot != 0 && collision_rule == MD_MapCollisionRule_Chain))
+    {
+        slot = _MD_PushArray(_MD_GetCtx(), MD_MapSlot, 1);
+        if(slot)
+        {
+            slot->next = 0;
+            if(map->table[index])
+            {
+                for(MD_MapSlot *old_slot = map->table[index]; old_slot; old_slot = old_slot->next)
+                {
+                    if(old_slot->next == 0)
+                    {
+                        old_slot->next = slot;
+                        break;
+                    }
+                }
+            }
+            else
+            {
+                map->table[index] = slot;
+            }
+        }
+    }
+    
+    if(slot)
+    {
+        slot->value = value;
+        slot->hash = hash;
+    }
+    
+    return !!slot;
+}
+
+/////////////////////////////////////////////
+//~ NOTE(mal): MD_StringMap
+MD_FUNCTION_IMPL MD_MapSlot *
+MD_StringMap_Lookup(MD_StringMap *map, MD_String8 string)       // NOTE(mal): Or MD_PtrFromString
+{
+    MD_MapSlot *slot = _MD_Map_Lookup(map, MD_HashString(string));
+    return slot;
+}
+
+MD_FUNCTION_IMPL MD_b32
+MD_StringMap_Insert(MD_StringMap *map, MD_MapCollisionRule collision_rule, MD_String8 string, void *value)
+{
+    MD_b32 result = _MD_Map_Insert(map, collision_rule, MD_HashString(string), value);
+    return result;
+}
+
+// NOTE(mal): Original MD_NodeTable interface
+#define MD_NodeTable_Lookup(map, string) MD_StringMap_Lookup(map, string)
+#define MD_NodeTable_Insert(map, collision_rule, string, node) MD_StringMap_Insert(map, collision_rule, string, (void *) node)
+
+/////////////////////////////////////////////
+//~ NOTE(mal): MD_PtrMap
+
+// NOTE(mal): Generic 64-bit hash function (https://nullprogram.com/blog/2018/07/31/)
+//            Assumes all bits of the pointer matter and that there's a b
+MD_FUNCTION_IMPL MD_u64 
+MD_HashPointer(void *p)
+{
+    MD_u64 h = (MD_u64)p;
+    h = (h ^ (h >> 30)) * UINT64_C(0xbf58476d1ce4e5b9);
+    h = (h ^ (h >> 27)) * UINT64_C(0x94d049bb133111eb);
+    h = h ^ (h >> 31);
+    return h;
+}
+
+MD_FUNCTION_IMPL MD_MapSlot *
+MD_PtrMap_Lookup(MD_PtrMap *map, void *key)                     // NOTE(mal): Or MD_PtrFromPtr
+{
+    MD_MapSlot *slot = _MD_Map_Lookup(map, MD_HashPointer(key));
+    return slot;
+}
+
+// TODO(mal): Remove collision_rule parameter and assume MD_MapCollisionRule_Overwrite?
+MD_FUNCTION_IMPL MD_b32
+MD_PtrMap_Insert(MD_PtrMap *map, MD_MapCollisionRule collision_rule, void *key, void *value)
+{
+    MD_b32 result = _MD_Map_Insert(map, collision_rule, MD_HashPointer(key), value);
+    return result;
+}
+
diff --git a/source/map_proposal.h b/source/map_proposal.h
new file mode 100644
index 0000000..7c67406
--- /dev/null
+++ b/source/map_proposal.h
@@ -0,0 +1,35 @@
+/////////////////////////////////////////////
+//~ NOTE(mal): MD_Map. Same as MD_NodeTable except it stores void * values
+typedef enum MD_MapCollisionRule
+{
+    MD_MapCollisionRule_Chain,
+    MD_MapCollisionRule_Overwrite,
+}
+MD_MapCollisionRule;
+
+typedef struct MD_MapSlot MD_MapSlot;
+struct MD_MapSlot
+{
+    MD_MapSlot *next;
+    MD_u64 hash;
+    void *value;
+};
+
+typedef struct MD_Map MD_Map;
+struct MD_Map
+{
+    MD_u64 table_size;
+    MD_MapSlot **table;
+};
+
+/////////////////////////////////////////////
+//~ NOTE(mal): Helpers
+typedef MD_Map MD_StringMap;
+typedef MD_Map MD_PtrMap;
+
+// NOTE(mal): MD_NodeTable interface
+typedef MD_Map MD_NodeTable;
+typedef MD_MapSlot MD_NodeTableSlot;
+typedef MD_MapCollisionRule MD_NodeTableCollisionRule;
+#define MD_NodeTableCollisionRule_Chain MD_MapCollisionRule_Chain 
+#define MD_NodeTableCollisionRule_Overwrite MD_MapCollisionRule_Overwrite