Add evm connector

cic_syncer/client/evm/response.py

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+from cic_syncer.client import translate
+
+translations = {
+        'block_number': 'hex_to_int',
+        }
+
+
+class EVMResponse:
+
+    def __init__(self, item, response_object):
+        self.response_object = response_object
+        self.item = item
+        self.fn = getattr(translate, translations[self.item])
+
+
+    def get_error(self):
+        return self.response_object.get('error')
+
+
+    def get_result(self):
+        return self.fn(self.response_object.get('result'))

cic_syncer/client/evm/websocket.py

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+import uuid
+import json
+
+import websocket
+
+from .response import EVMResponse
+from cic_syncer.error import RequestError
+
+
+
+class EVMWebsocketClient:
+
+    def __init__(self, url):
+        self.url = url
+        self.conn = websocket.create_connection(url)
+
+
+    def __del__(self):
+        self.conn.close()
+
+
+    def block_number(self):
+        req_id = str(uuid.uuid4())
+        req = {
+                'jsonrpc': '2.0',
+                'method': 'eth_blockNumber',
+                'id': str(req_id),
+                'params': [],
+                }
+        self.conn.send(json.dumps(req))
+        r = self.conn.recv()
+        res = EVMResponse('block_number', json.loads(r))
+        err = res.get_error()
+        if err != None:
+            raise RequestError(err)
+
+        return res.get_result()

cic_syncer/client/translate.py

@@ -0,0 +1,21 @@
+import re
+
+re_hex = r'^[0-9a-fA-Z]+$'
+def is_hex(hx):
+    m = re.match(re_hex, hx)
+    if m == None:
+        raise ValueError('not valid hex {}'.format(hx))
+
+    return hx
+
+
+def strip_0x(hx):
+    if len(hx) >= 2 and hx[:2] == '0x':
+        hx = hx[2:]
+    return is_hex(hx)
+
+
+def hex_to_int(hx, endianness='big'):
+    hx = strip_0x(hx)
+    b = bytes.fromhex(hx)
+    return int.from_bytes(b, endianness)