Add DqnVHashTable, hash table backed by virtual memory

DqnUnitTest.cpp

@@ -140,6 +140,7 @@ void LogHeader(char const *funcName)
 #include "DqnFixedString.cpp"
 #include "DqnOS.cpp"
 #include "DqnJson.cpp"
+#include "DqnVHashTable.cpp"
 
 void HandmadeMathVerifyMat4(DqnMat4 dqnMat, hmm_mat4 hmmMat)
 {
@@ -2901,6 +2902,7 @@ int main(void)
     DqnJson_Test();
 
 #ifdef DQN_PLATFORM_HEADER
+    DqnVHashTable_Test();
     DqnOS_Test();
     DqnFile_Test();
     DqnTimer_Test();

DqnVHashTable.cpp

@@ -0,0 +1,27 @@
+void DqnVHashTable_Test()
+{
+    LOG_HEADER();
+    struct Block
+    {
+        int x;
+    };
+    using Height = u32;
+    Block block  = {};
+
+    DqnVHashTable<Height, Block> table = {};
+    table.Set(12, block);
+
+    Block *getResult      = table.Get(12);
+    Block *operatorResult = table[12];
+    DQN_ASSERT(operatorResult == getResult);
+    DQN_ASSERT(operatorResult != nullptr);
+    Log(Status::Ok, "Set and get element using key");
+
+    table.Erase(12);
+    getResult      = table.Get(12);
+    operatorResult = table[12];
+
+    DQN_ASSERT(operatorResult == getResult);
+    DQN_ASSERT(operatorResult == nullptr);
+    Log(Status::Ok, "Erase element using key");
+}

dqn.h

@@ -48,6 +48,7 @@
 
 // #XPlatform (Win32 & Unix)
 // #DqnVArray     Array backed by virtual memory
+// #DqnVHashTable Hash Table using templates backed by virtual memory
 // #DqnFile       File I/O (Read, Write, Delete)
 // #DqnTimer      High Resolution Timer
 // #DqnLock       Mutex Synchronisation
@@ -1127,6 +1128,7 @@ DQN_FILE_SCOPE void *DqnMem_Realloc(void *memory, usize newSize);
 DQN_FILE_SCOPE void  DqnMem_Free   (void *memory);
 DQN_FILE_SCOPE void  DqnMem_Copy   (void *dest, void const *src, usize numBytesToCopy);
 DQN_FILE_SCOPE void *DqnMem_Set    (void *dest, u8 value,        usize numBytesToSet);
+DQN_FILE_SCOPE int   DqnMem_Cmp(void const *src, void const *dest, usize numBytes);
 
 // #DqnMemAPI API
 // =================================================================================================
@@ -2327,6 +2329,25 @@ int DqnFixedString<MAX>::SprintfAppend(char const *fmt, ...)
     return result;
 }
 
+template <typename Key> using DqnVHashTableHashingProc = isize(*)(isize count, Key const &data);
+template <typename Key> using DqnVHashTableEqualsProc  = bool (*)(Key const &a, Key const &b);
+
+#define DQN_VHASH_TABLE_HASHING_PROC(name) template <typename Key> inline isize name(isize count, Key const &key)
+DQN_VHASH_TABLE_HASHING_PROC(DqnVHashTableDefaultHash)
+{
+    const u64 SEED = 0x9747B28CAB3F8A7B;
+    u64 index64    = DqnHash_Murmur64Seed(&key, sizeof(key), SEED);
+    isize result   = index64 % count;
+    return result;
+}
+
+#define DQN_VHASH_TABLE_EQUALS_PROC(name) template <typename Key> inline bool name(Key const &a, Key const &b)
+DQN_VHASH_TABLE_EQUALS_PROC(DqnVHashTableDefaultEquals)
+{
+    bool result = (DqnMem_Cmp(&a, &b, sizeof(a)) == 0);
+    return result;
+}
+
 // TODO(doyle): Load factor
 // #DqnHashTable API
 // =================================================================================================
@@ -2938,6 +2959,119 @@ template <typename T> void DqnVArray<T>::EraseStable(isize index)
     count--;
 }
 
+// #XPlatform > #DqnVHashTable API
+// =================================================================================================
+#define DQN_VHASH_TABLE_TEMPLATE                                                                   \
+    template <typename Key,                                                                        \
+              typename Item,                                                                       \
+              DqnVHashTableHashingProc<Key> Hash  = DqnVHashTableDefaultHash<Key>,                 \
+              DqnVHashTableEqualsProc<Key> Equals = DqnVHashTableDefaultEquals<Key>>
+
+#define DQN_VHASH_TABLE_DECL DqnVHashTable<Key, Item, Hash, Equals>
+
+DQN_VHASH_TABLE_TEMPLATE struct DqnVHashTable
+{
+    struct Entry
+    {
+        Key  key;
+        Item item;
+    };
+
+    struct Bucket
+    {
+        Entry entries[4];
+        isize entryIndex;
+    };
+
+    Bucket    *buckets;
+    isize      numBuckets;
+    isize      bucketsUsed;
+
+     DqnVHashTable() = default;
+     DqnVHashTable(isize size) { LazyInitialise(size); }
+    ~DqnVHashTable()           { if (buckets) DqnOS_VFree(buckets, sizeof(buckets) * numBuckets); }
+
+    void       Erase(Key const &key);
+    Item      *Set  (Key const &key, Item const &item);
+    Item      *Get  (Key const &key);
+
+    Item *operator[](Key const &key) { return Get(key); }
+
+private:
+    void LazyInitialise(isize size) { *this = {}; numBuckets = size; buckets = static_cast<Bucket *>(DqnOS_VAlloc(numBuckets * sizeof(*buckets))); DQN_ASSERT(buckets); }
+};
+
+DQN_VHASH_TABLE_TEMPLATE Item *DQN_VHASH_TABLE_DECL::Set(Key const &key, Item const &item)
+{
+    if (!buckets) LazyInitialise(1024);
+
+    isize index       = Hash(this->numBuckets, key);
+    Bucket *bucket    = this->buckets + index;
+    Entry *entry      = nullptr;
+
+    for (isize i = 0; i < bucket->entryIndex && !entry; i++)
+    {
+        Entry *check = bucket->entries + i;
+        entry        = Equals(check->key, key) ? check : nullptr;
+    }
+
+    if (!entry)
+    {
+        DQN_ASSERT(bucket->entryIndex < DQN_ARRAY_COUNT(bucket->entries));
+        this->bucketsUsed = (bucket->entryIndex == 0) ? this->bucketsUsed + 1 : this->bucketsUsed;
+        entry             = bucket->entries + bucket->entryIndex++;
+    }
+
+    entry->key  = key;
+    entry->item = item;
+    return &entry->item;
+}
+
+DQN_VHASH_TABLE_TEMPLATE Item *DQN_VHASH_TABLE_DECL::Get(Key const &key)
+{
+    Item *result = nullptr;
+    if (!buckets)
+    {
+        return result;
+    }
+
+    isize index    = Hash(this->numBuckets, key);
+    Bucket *bucket = this->buckets + index;
+
+    for (isize i = 0; i < bucket->entryIndex && !result; i++)
+    {
+        Entry *entry = bucket->entries + i;
+        result       = Equals(entry->key, key) ? &entry->item : nullptr;
+    }
+
+    return result;
+}
+
+DQN_VHASH_TABLE_TEMPLATE void DQN_VHASH_TABLE_DECL::Erase(Key const &key)
+{
+    if (!buckets)
+    {
+        return;
+    }
+
+    isize index    = Hash(this->numBuckets, key);
+    Bucket *bucket = this->buckets + index;
+
+    for (isize i = 0; i < bucket->entryIndex; ++i)
+    {
+        Entry *check  = bucket->entries + i;
+        if (Equals(check->key, key))
+        {
+            for (isize j = i; j < (bucket->entryIndex - 1); ++j)
+                bucket->entries[j] = bucket->entries[j + 1];
+
+            --bucket->entryIndex;
+            DQN_ASSERT(bucket->entryIndex >= 0);
+            return;
+        }
+    }
+}
+
 // XPlatform > #DqnFile API
 // =================================================================================================
 struct DqnFile
@@ -3356,6 +3490,22 @@ DQN_FILE_SCOPE void *DqnMem_Set(void *dest, u8 value, usize numBytesToSet)
     return dest;
 }
 
+DQN_FILE_SCOPE int DqnMem_Cmp(void const *src, void const *dest, usize numBytes)
+{
+    auto const *srcPtr  = static_cast<char const *>(src);
+    auto const *destPtr = static_cast<char const *>(dest);
+
+    usize i;
+    for (i = 0; i < numBytes; ++i)
+    {
+        if (srcPtr[i] != destPtr[i])
+            break;
+    }
+
+    i = DQN_MIN(i, (numBytes - 1));
+    return (srcPtr[i] - destPtr[i]);
+}
+
 // #DqnMemAPI
 // =================================================================================================
 FILE_SCOPE void DqnMemAPIInternal_ValidateRequest(DqnMemAPI::Request request_)