WIP Add file backend

chainsyncer/backend_file.py

@@ -0,0 +1,163 @@
+# standard imports
+import os
+import uuid
+import shutil
+import logging
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger().getChild(__name__)
+
+
+def data_dir_for(chain_spec, object_id, base_dir='/var/lib'):
+    base_data_dir = os.path.join(base_dir, 'chainsyncer')
+    chain_dir = str(chain_spec).replace(':', '/')
+    return os.path.join(base_data_dir, chain_dir, object_id)
+
+
+class SyncerFileBackend:
+
+    def __init__(self, chain_spec, object_id=None, base_dir='/var/lib'):
+        self.object_data_dir = data_dir_for(chain_spec, object_id, base_dir=base_dir)
+
+        self.block_height_offset = 0
+        self.tx_index_offset = 0
+
+        self.block_height_cursor = 0
+        self.tx_index_cursor = 0
+
+        self.block_height_target = 0
+        self.tx_index_target = 0
+
+        self.object_id = object_id
+        self.db_object = None
+        self.db_object_filter = None
+        self.chain_spec = chain_spec
+
+        if self.object_id != None:
+            self.connect()
+            self.disconnect()
+
+
+    @staticmethod
+    def create_object(chain_spec, object_id=None, base_dir='/var/lib'):
+        if object_id == None:
+            object_id = str(uuid.uuid4())
+
+        object_data_dir = data_dir_for(chain_spec, object_id, base_dir=base_dir)
+
+        if os.path.isdir(object_data_dir):
+            raise FileExistsError(object_data_dir)
+
+        os.makedirs(object_data_dir)
+
+        object_id_path = os.path.join(object_data_dir, 'object_id')
+        f = open(object_id_path, 'wb')
+        f.write(object_id.encode('utf-8'))
+        f.close()
+
+        init_value = 0
+        b = init_value.to_bytes(16, byteorder='big')
+        offset_path = os.path.join(object_data_dir, 'offset')
+        f = open(offset_path, 'wb')
+        f.write(b)
+        f.close()
+
+        target_path = os.path.join(object_data_dir, 'target')
+        f = open(target_path, 'wb')
+        f.write(b'\x00' * 16)
+        f.close()
+
+        cursor_path = os.path.join(object_data_dir, 'cursor')
+        f = open(cursor_path, 'wb')
+        f.write(b'\x00' * 16)
+        f.close()
+
+        return object_id
+
+
+    def load(self):
+        offset_path = os.path.join(self.object_data_dir, 'offset')
+        f = open(offset_path, 'rb')
+        b = f.read(16)
+        f.close()
+        self.block_height_offset = int.from_bytes(b[:8], byteorder='big')
+        self.tx_index_offset = int.from_bytes(b[8:], byteorder='big')
+
+        target_path = os.path.join(self.object_data_dir, 'target')
+        f = open(target_path, 'rb')
+        b = f.read(16)
+        f.close()
+        self.block_height_target = int.from_bytes(b[:8], byteorder='big')
+        self.tx_index_target = int.from_bytes(b[8:], byteorder='big')
+
+        cursor_path = os.path.join(self.object_data_dir, 'cursor')
+        f = open(cursor_path, 'rb')
+        b = f.read(16)
+        f.close()
+        self.block_height_cursor = int.from_bytes(b[:8], byteorder='big')
+        self.tx_index_cursor = int.from_bytes(b[8:], byteorder='big')
+
+
+    def connect(self):
+        object_path = os.path.join(self.object_data_dir, 'object_id') 
+        f = open(object_path, 'r')
+        object_id = f.read()
+        f.close()
+        if object_id != self.object_id:
+            raise ValueError('data corruption in store for id {}'.format(object_id))
+
+        self.load()
+
+
+    def disconnect(self):
+        pass
+
+    
+    def purge(self):
+        shutil.rmtree(self.object_data_dir)
+
+
+    def get(self):
+        return (self.block_height_cursor, self.tx_index_cursor)
+
+
+
+    def set(self, block_height, tx_index):
+        return self.__set(block_height, tx_index, 'cursor')
+
+
+    def __set(self, block_height, tx_index, category):
+        cursor_path = os.path.join(self.object_data_dir, category)
+
+        block_height_bytes = block_height.to_bytes(8, byteorder='big')
+        tx_index_bytes = tx_index.to_bytes(8, byteorder='big')
+
+        f = open(cursor_path, 'wb')
+        b = f.write(block_height_bytes)
+        b = f.write(tx_index_bytes)
+        f.close()
+
+        setattr(self, 'block_height_' + category, block_height)
+        setattr(self, 'tx_index_' + category, tx_index)
+
+
+    @staticmethod
+    def initial(chain_spec, target_block_height, start_block_height=0, base_dir='/var/lib'):
+        if start_block_height >= target_block_height:
+            raise ValueError('start block height must be lower than target block height')
+       
+        uu = SyncerFileBackend.create_object(chain_spec, base_dir=base_dir)
+
+        o = SyncerFileBackend(chain_spec, uu, base_dir=base_dir)
+        o.__set(target_block_height, 0, 'target')
+        o.__set(start_block_height, 0, 'offset')
+
+        return uu
+
+
+    def target(self):
+        return ((self.block_height_target, self.tx_index_target), None,)
+
+
+    def start(self):
+        return ((self.block_height_offset, self.tx_index_offset), None,)