gristlabs_grist-core/sandbox/grist/sandbox.py

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"""
Implements the python side of the data engine sandbox, which allows us to register functions on
the python side and call them from Node.js.
Usage:
import sandbox
sandbox.register(func_name, func)
sandbox.call_external("hello", 1, 2, 3)
sandbox.run()
"""
import os
import marshal
import sys
import traceback
def log(msg):
sys.stderr.write(str(msg) + "\n")
sys.stderr.flush()
class Sandbox(object):
"""
This class works in conjunction with Sandbox.js to allow function calls
between the Node process and this sandbox.
The sandbox provides two pipes (on fds 3 and 4) to send data to and from the sandboxed
process. Data on these is serialized using `marshal` module. All messages are comprised of a
msgCode followed immediatedly by msgBody, with the following msgCodes:
CALL = call to the other side. The data must be an array of [func_name, arguments...]
DATA = data must be a value to return to a call from the other side
EXC = data must be an exception to return to a call from the other side
"""
CALL = None
DATA = True
EXC = False
def __init__(self, external_input, external_output):
self._functions = {}
self._external_input = external_input
self._external_output = external_output
@classmethod
def connected_to_js_pipes(cls):
"""
Send data on two specially-opened side channels.
"""
external_input = os.fdopen(3, "rb", 64 * 1024)
external_output = os.fdopen(4, "wb", 64 * 1024)
return cls(external_input, external_output)
@classmethod
def use_common_pipes(cls):
"""
Send data via stdin/stdout, rather than specially-opened side channels.
Duplicate stdin/stdout, close, and reopen as binary file objects.
"""
os.dup2(0, 3)
os.dup2(1, 4)
os.close(0)
os.close(1)
sys.stdout = sys.stderr
return Sandbox.connected_to_js_pipes()
def _send_to_js(self, msgCode, msgBody):
# (Note that marshal version 2 is the default; we specify it explicitly for clarity. The
# difference with version 0 is that version 2 uses a faster binary format for floats.)
# For large data, JS's Unmarshaller is very inefficient parsing it if it gets it piecewise.
# It's much better to ensure the whole blob is sent as one write. We marshal the resulting
# buffer again so that the reader can quickly tell how many bytes to expect.
buf = marshal.dumps((msgCode, msgBody), 2)
marshal.dump(buf, self._external_output, 2)
self._external_output.flush()
def call_external(self, name, *args):
self._send_to_js(Sandbox.CALL, (name,) + args)
(msgCode, data) = self.run(break_on_response=True)
if msgCode == Sandbox.EXC:
raise Exception(data)
return data
def register(self, func_name, func):
self._functions[func_name] = func
def run(self, break_on_response=False):
while True:
try:
msgCode = marshal.load(self._external_input)
data = marshal.load(self._external_input)
except EOFError:
break
if msgCode != Sandbox.CALL:
if break_on_response:
return (msgCode, data)
continue
if not isinstance(data, list) or len(data) < 1:
raise ValueError("Bad call " + data)
try:
fname = data[0]
args = data[1:]
ret = self._functions[fname](*args)
self._send_to_js(Sandbox.DATA, ret)
except Exception as e:
traceback.print_exc()
self._send_to_js(Sandbox.EXC, "%s %s" % (type(e).__name__, e))
if break_on_response:
raise Exception("Sandbox disconnected unexpectedly")
default_sandbox = None
def get_default_sandbox():
global default_sandbox
if default_sandbox is None:
if os.environ.get('PIPE_MODE') == 'minimal':
default_sandbox = Sandbox.use_common_pipes()
else:
default_sandbox = Sandbox.connected_to_js_pipes()
return default_sandbox
def call_external(name, *args):
return get_default_sandbox().call_external(name, *args)
def register(func_name, func):
get_default_sandbox().register(func_name, func)
def run():
get_default_sandbox().run()