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