from collections import namedtuple import bisect class Chunk: def __init__(self, start, end, data, height=0, leaf_count=1, age=0): self.start = start self.end = end self.data = data self.height = height self.leaf_count = leaf_count self.age = age def __len__(self): return self.end - self.start class Flush(Chunk): class Entry(Chunk): def __init__(self, start, end, chunk, path = []): super().__init__(start, end, chunk, height=0, leaf_count=1, age=chunk.age) self.path = [*path, self.data] if type(chunk) is Flush: self.leaf_count = 0 self.height = 0 for entry in self.flush_entries(): self.leaf_count += entry.leaf_count self.height = max(self.height, entry.height + 1) def flush_entries(self): assert type(self.data) is Flush return ( Flush.Entry(max(entry.start, self.start), min(entry.end, self.end), entry.data, self.path) for entry in self.data.data if entry.start < self.end and entry.end > self.start ) def chunk_data(self): assert type(self.data) is Chunk return self.data.data[self.start - self.data.start : self.end - self.data.start] def __init__(self, prev_flush = None): if prev_flush is not None: leaf_count = prev_flush.leaf_count self.max_height = leaf_count.bit_length() super().__init__(prev_flush.start, prev_flush.end, [], leaf_count=0, age=prev_flush.age+1) self.add(prev_flush) for entry in prev_flush.data: if entry.height >= self.max_height: self.add(entry) else: super().__init__(None, None, [], height=1, leaf_count=0) def add(self, *adjacents): adjacents = [ adjacent if type(adjacent) is Flush.Entry else Flush.Entry(adjacent.start, adjacent.end, adjacent) for adjacent in adjacents ] if self.start is None: self.start = adjacents[0].start self.end = adjacents[-1].end else: self.start = min(self.start, adjacents[0].start) self.end = max(self.end, adjacents[-1].end) # first idx with end > start start_idx = bisect.bisect_right([entry.end for entry in self.data], adjacents[0].start) # first idx with start >= end end_idx = bisect.bisect_left([entry.start for entry in self.data], adjacents[-1].end, start_idx) replaced = self.data[start_idx:end_idx] if len(replaced): if replaced[0].start < adjacents[0].start: adjacents.insert( 0, Flush.Entry( replaced[0].start, adjacents[0].start, replaced[0].data ) ) if start_idx > 0: # the trimmed entry may have fewer leaves and itself merge with its neighbor start_idx -= 1 replaced.insert(0, self.data[start_idx]) adjacents.insert(0, self.data[start_idx]) if replaced[-1].end > adjacents[-1].end: adjacents.append( Flush.Entry( adjacents[-1].end, replaced[-1].end, replaced[-1].data ) ) if end_idx < len(self.data): # the trimmed entry may have fewer leaves and itself merge with its neighbor replaced.append(self.data[end_idx]) adjacents.append(self.data[end_idx]) end_idx += 1 for idx, entry in reversed([*enumerate(adjacents)]): if entry.leaf_count == 0: # no leaves left in this branch, remove adjacents.pop(idx) continue count = 0 subentry = entry while count <= 1 and subentry is not None and type(subentry.data) is Flush: # make branches shallower by splicing out roots with only one child parent_entry = subentry count = 0 subentry = None for subentry in parent_entry.flush_entries(): count += 1 if count > 1: subentry = parent_entry break if subentry is not entry: # some internodes were removed assert subentry is not None # can likely remove assignment to None above if this removed adjacents[idx] = subentry for idx, (left_adjacent, right_adjacent) in reversed([*enumerate(zip(adjacents[:-1], adjacents[1:]))]): # merge writes if ( left_adjacent.age == self.age and right_adjacent.age == self.age and #type(left_adjacent.data) is Chunk and #type(right_adjacent.data) is Chunk and left_adjacent.end == right_adjacent.start ): left_adjacent.data = Chunk( left_adjacent.start, right_adjacent.end, left_adjacent.chunk_data() + right_adjacent.chunk_data() ) left_adjacent.end = right_adjacent.end adjacents.pop(idx+1) continue # merge branches with shared parents shared_parents = [ left_parent for left_parent, right_parent in zip(left_adjacent.path, right_adjacent.path) if left_parent is right_parent ] if len(shared_parents) > 0: import pdb; pdb.set_trace() '''this code path has not been hit before; does it work?''' print(shared_parents) if len(shared_parents) > 0 and left_adjacent.height + len(left_adjacent.parents) - len(shared_parents) < self.max_height and right_adjacent.height + len(right_adjacent.parents) - len(shared_parents) < self.max_height: if left_adjacent.end != right_adjacent.start: between_entry = Flush.Entry( left_adjacent.end, right_adjacent.start ) if between_entry.leaf_count > 0: # the shared root contains leaves in between that have been removed continue print(f'Merging {len(left_adjacent.path)}:{left_adjacent.height}, {len(right_adjacent.path)}:{right_adjacent.height} -> {len(shared_path)}:{left_adjacent.height + len(leaf_adjacent.path) - len(shared_parents)}') left_adjacent.end = right_adjacent.end left_adjacent.leaf_count += right_adjacent.leaf_count left_adjacent.height += len(left_adjacent.path) - len(shared_parents) left_adjacent.path = shared_parents left_adjacent.data = shared_parents[-1] adjacents.pop(idx+1) self.leaf_count += sum((adjacent.leaf_count for adjacent in adjacents)) self.leaf_count -= sum((old.leaf_count for old in replaced)) self.max_height = self.leaf_count.bit_length() self.data[start_idx:end_idx] = adjacents self.height = max((entry.height for entry in self.data)) + 1 #self.check_leaf_count(self.start, self.end) def write(self, offset, data): chunk = Chunk(offset, offset + len(data), data, age=self.age) return self.add(chunk) def read(self, start, max_end = float('inf')): # first idx with end > start idx = bisect.bisect_right([entry.end for entry in self.data], start) if idx == len(self.data): return bytes(4096) entry = self.data[idx] if entry.start > start: end = min(max_end, entry.start) return bytes(end - start) end = min(max_end, entry.end) if type(entry.data) is Flush: return entry.data.read(start, end) elif type(entry.data) is Chunk: datastart = start - entry.data.start dataend = end - entry.data.start return entry.data.data[datastart : dataend] #def check_leaf_count(self, start, end): # leaf_count = 0 # wrapper = Flush.Entry(start, end, self) # for entry in wrapper.flush_entries(): # if type(entry.data) is Flush: # entry_leaf_count = entry.data.check_leaf_count(entry.start, entry.end) # assert entry_leaf_count == entry.leaf_count # leaf_count += entry_leaf_count # else: # leaf_count += entry.data.leaf_count # assert leaf_count == wrapper.leaf_count # if start == self.start and end == self.end: # assert leaf_count == self.leaf_count # return leaf_count if __name__ == '__main__': import random random.seed(0) SIZE=4096 comparison = bytearray(SIZE) store = Flush() def compare(store, comparison): offset = 0 while offset < len(comparison): data = store.read(offset)[:len(comparison) - offset] assert data == comparison[offset:offset+len(data)] offset += len(data) #store.check_leaf_count(store.start, store.end) return True for flushes in range(1024): for writes in range(random.randint(1,16)): start = random.randint(0, SIZE) end = random.randint(0, SIZE) if end < start: start, end = end, start end = (end + start) // 2 size = end - start data = random.randint(0, (1<<(size*8))-1).to_bytes(size, 'little') store.write(start, data) comparison[start:end] = data #compare(store, comparison) #print('OK', flushes, writes)#, offset) compare(store, comparison) print('OK', len(store.data), 'x', store.height, 'count =', store.leaf_count, 'flushes =', flushes)#, writes)#, offset) store = Flush(prev_flush = store) compare(store, comparison)