241 lines
9.5 KiB
Plaintext
241 lines
9.5 KiB
Plaintext
# hashtable - Open-addressing hash table library
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# Linear probing for collision resolution, supports auto-resizing and tombstone deletion
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# Key type fixed as str (i8*), value type is void* (generic pointer)
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import t, c
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import string
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import memhub
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from stdint import *
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# Empty slot marker (hash == 0)
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_HT_EMPTY: t.CDefine = 0
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# Tombstone slot marker (hash == 1)
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_HT_TOMBSTONE: t.CDefine = 1
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# Default initial capacity (must be power of two)
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_HT_INIT_CAP: t.CDefine = 16
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# Slot memory layout: hash(8) + key pointer(8) + value pointer(8) = 24 bytes
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_HT_SLOT_SIZE: t.CDefine = 24
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# FNV-1a 64-bit constants
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_FNV_OFFSET: t.CUInt64T = 0xcbf29ce484222325
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_FNV_PRIME: t.CUInt64T = 0x100000001b3
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def _fnv1a_hash(key: str) -> t.CUInt64T:
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"""FNV-1a 64-bit hash function."""
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h: t.CUInt64T = _FNV_OFFSET
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k: str = key
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while k[0] != 0:
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h = h ^ t.CUInt64T(k[0])
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h = h * _FNV_PRIME
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k += 1
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# Ensure h >= 2 (avoids empty slot marker 0 and tombstone marker 1)
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if h < 2:
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h = 2
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return h
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class HashTable:
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"""Open-addressing hash table using linear probing for collision resolution.
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Key type fixed as str (i8*), value type is void* (generic pointer).
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Memory is managed via the mbuddy allocator. Automatically resizes when load factor exceeds 0.75.
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Usage:
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mb: memhub.MemBuddy = memhub.MemBuddy(arena, arena_size)
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ht: HashTable = HashTable(mb)
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ht.set_int("x", 42)
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p: t.CPtr = ht["x"]
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v: int = c.Deref(p)
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"""
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__slots__: t.CVoid | t.CPtr # Base address of slot array
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__count__: t.CSizeT = 0 # Number of occupied entries
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__capacity__: t.CSizeT = 16 # Total slot count (power of two)
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__tombstones__: t.CSizeT = 0 # Tombstone entry count
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__mbuddy__: memhub.MemBuddy | t.CPtr
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__iter_index__: t.CSizeT = 0
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def __new__(self, mb: memhub.MemBuddy | t.CPtr) -> t.CPtr:
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# Heap-allocate HashTable object (6 fields × 8 bytes = 48 bytes)
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return mb.alloc(48)
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def __init__(self, mb: memhub.MemBuddy | t.CPtr):
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self.__mbuddy__ = mb
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self.__capacity__ = _HT_INIT_CAP
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self.__count__ = 0
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self.__tombstones__ = 0
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self.__slots__ = mb.alloc(self.__capacity__ * _HT_SLOT_SIZE)
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# Initialize all slots to empty (hash = 0)
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string.memset(self.__slots__, 0, self.__capacity__ * _HT_SLOT_SIZE)
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def _slot_hash(self, idx: t.CSizeT) -> t.CUInt64T:
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"""Read hash value from target slot."""
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ptr: t.CUInt64T | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(self.__slots__) + idx * _HT_SLOT_SIZE)
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return ptr[0]
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def _slot_key(self, idx: t.CSizeT) -> str:
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"""Read key pointer from target slot."""
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ptr: str | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(self.__slots__) + idx * _HT_SLOT_SIZE + 8)
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return ptr[0]
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def _slot_value(self, idx: t.CSizeT) -> t.CPtr:
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"""Read value pointer from target slot."""
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ptr: t.CUInt64T | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(self.__slots__) + idx * _HT_SLOT_SIZE + 16)
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return ptr[0]
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def _set_slot(self, idx: t.CSizeT, h: t.CUInt64T, key: str, val: t.CPtr):
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"""Assign three fields of the target slot."""
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h_ptr: t.CUInt64T | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(self.__slots__) + idx * _HT_SLOT_SIZE)
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h_ptr[0] = h
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k_ptr: str | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(self.__slots__) + idx * _HT_SLOT_SIZE + 8)
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k_ptr[0] = key
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v_ptr: t.CUInt64T | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(self.__slots__) + idx * _HT_SLOT_SIZE + 16)
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v_ptr[0] = val
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def _find_slot(self, key: str, h: t.CUInt64T) -> t.CSizeT:
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"""Locate slot index for key insertion or lookup.
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Returns: Index of matching key if found; otherwise returns index of first usable empty/tombstone slot.
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"""
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mask: t.CSizeT = self.__capacity__ - 1
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idx: t.CSizeT = t.CSizeT(h) & mask
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first_tombstone: t.CSizeT = self.__capacity__
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i: t.CSizeT = 0
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while i < self.__capacity__:
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sh: t.CUInt64T = self._slot_hash(idx)
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if sh == _HT_EMPTY:
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if first_tombstone < self.__capacity__:
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return first_tombstone
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return idx
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if sh == _HT_TOMBSTONE:
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if first_tombstone >= self.__capacity__:
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first_tombstone = idx
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else:
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if sh == h:
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sk: str = self._slot_key(idx)
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if sk == key:
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return idx
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idx = (idx + 1) & mask
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i += 1
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if first_tombstone < self.__capacity__:
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return first_tombstone
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return self.__capacity__
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def _resize(self, new_cap: t.CSizeT):
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"""Resize table and rehash all entries."""
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old_slots: t.CVoid | t.CPtr = self.__slots__
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old_cap: t.CSizeT = self.__capacity__
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new_slots: t.CVoid | t.CPtr = self.__mbuddy__.alloc(new_cap * _HT_SLOT_SIZE)
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if new_slots == None:
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return
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string.memset(new_slots, 0, new_cap * _HT_SLOT_SIZE)
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self.__slots__ = new_slots
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self.__capacity__ = new_cap
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self.__count__ = 0
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self.__tombstones__ = 0
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i: t.CSizeT = 0
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while i < old_cap:
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old_h_ptr: t.CUInt64T | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(old_slots) + i * _HT_SLOT_SIZE)
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h: t.CUInt64T = old_h_ptr[0]
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if h != _HT_EMPTY and h != _HT_TOMBSTONE:
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old_k_ptr: str | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(old_slots) + i * _HT_SLOT_SIZE + 8)
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old_v_ptr: t.CUInt64T | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(old_slots) + i * _HT_SLOT_SIZE + 16)
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k: str = old_k_ptr[0]
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v: t.CPtr = old_v_ptr[0]
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idx: t.CSizeT = self._find_slot(k, h)
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self._set_slot(idx, h, k, v)
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self.__count__ += 1
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i += 1
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def __setitem__(self, key: str, val: t.CNeedPtr):
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"""Insert or update key-value pair. val automatically decays to pointer (t.CNeedPtr: no conversion if already pointer)."""
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h: t.CUInt64T = _fnv1a_hash(key)
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idx: t.CSizeT = self._find_slot(key, h)
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if idx >= self.__capacity__:
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return
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sh: t.CUInt64T = self._slot_hash(idx)
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if sh == _HT_EMPTY or sh == _HT_TOMBSTONE:
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if sh == _HT_TOMBSTONE:
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self.__tombstones__ -= 1
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self._set_slot(idx, h, key, val)
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self.__count__ += 1
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# Resize when load factor > 0.75
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load: t.CSizeT = self.__count__ + self.__tombstones__
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if load * 4 >= self.__capacity__ * 3:
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self._resize(self.__capacity__ * 2)
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else:
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self._set_slot(idx, h, key, val)
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def __getitem__(self, key: str) -> t.CPtr:
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"""Lookup key and return value pointer. Returns None if key not found."""
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h: t.CUInt64T = _fnv1a_hash(key)
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idx: t.CSizeT = self._find_slot(key, h)
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if idx >= self.__capacity__:
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return None
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sh: t.CUInt64T = self._slot_hash(idx)
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if sh == _HT_EMPTY or sh == _HT_TOMBSTONE:
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return None
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return self._slot_value(idx)
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def __contains__(self, key: str) -> t.CInt:
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"""Check whether key exists in table."""
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h: t.CUInt64T = _fnv1a_hash(key)
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idx: t.CSizeT = self._find_slot(key, h)
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if idx >= self.__capacity__:
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return 0
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sh: t.CUInt64T = self._slot_hash(idx)
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if sh == _HT_EMPTY or sh == _HT_TOMBSTONE:
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return 0
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return 1
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def __delitem__(self, key: str) -> t.CInt:
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"""Delete entry by key. Return 1 on success, 0 if key not present."""
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h: t.CUInt64T = _fnv1a_hash(key)
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idx: t.CSizeT = self._find_slot(key, h)
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if idx >= self.__capacity__:
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return 0
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sh: t.CUInt64T = self._slot_hash(idx)
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if sh == _HT_EMPTY or sh == _HT_TOMBSTONE:
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return 0
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h_ptr: t.CUInt64T | t.CPtr = (t.CVoid | t.CPtr)(t.CUInt64T(self.__slots__) + idx * _HT_SLOT_SIZE)
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h_ptr[0] = _HT_TOMBSTONE
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self.__count__ -= 1
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self.__tombstones__ += 1
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return 1
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def __len__(self) -> t.CSizeT:
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return self.__count__
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def __iter__(self) -> HashTable | t.CPtr:
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self.__iter_index__ = 0
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return self
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def __next__(self) -> str:
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while self.__iter_index__ < self.__capacity__:
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idx: t.CSizeT = self.__iter_index__
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self.__iter_index__ = idx + 1
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sh: t.CUInt64T = self._slot_hash(idx)
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if sh != _HT_EMPTY and sh != _HT_TOMBSTONE:
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return self._slot_key(idx)
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raise StopIteration
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def get(self, key: str, default: t.CPtr) -> t.CPtr:
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"""Return value pointer; return default pointer if key not found."""
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h: t.CUInt64T = _fnv1a_hash(key)
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idx: t.CSizeT = self._find_slot(key, h)
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if idx >= self.__capacity__:
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return default
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sh: t.CUInt64T = self._slot_hash(idx)
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if sh == _HT_EMPTY or sh == _HT_TOMBSTONE:
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return default
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return self._slot_value(idx)
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def set_int(self, key: str, val: int):
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"""Store integer value. Value is copied into mbuddy-managed storage."""
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storage: t.CVoid | t.CPtr = self.__mbuddy__.alloc(8)
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int_ptr: int | t.CPtr = t.CVoid(t.CUInt64T(storage), t.CPtr)
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int_ptr[0] = val
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self[key] = storage
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def set_str(self, key: str, val: str):
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"""Store string value. Directly store the string pointer."""
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self[key] = val
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