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- Subject: Lua 5.2 - How do I resume an interrupted parse?
- From: <StephenSimpson@...>
- Date: Sun, 29 Jan 2012 19:00:09 -0500
I'm working with a large and very complex C++ application that has its
own memory management.
I'm reimplementing the Lua interpreter as a telnet daemon inside this
Typical telnet daemons are terminal centric, ie. the daemon responds to
data "committed" by a user hitting <Enter>.
I want the daemon to handle this traditional line-by-line input,
AND big but potentially syntactically incomplete blocks from eg. a pipe
directed to a ptty.
Is it possible to drive the Lua API so that a parse can be "put on ice"
while waiting for the arrival of new data from the comms stack.
I want to call lua_load with a lua_Reader that serialises the source
code data for the Lua parser from various chunks of memory bubbling up
the comms stack.
Now when I run out of data on the comms stack, I want to return NULL
from the lua_Reader to signal the parser to continue the opportunistic
ie. maybe the data is complete.
The trouble is that the parser throws when the data is correct but
"incomplete". This throw ends up unwinding the all the Lua state formed
from the initial lua_load call.
This is a bummer, since that means I need to (a) reparse from the
beginning, and (b) hang on to all the memory from the comms stack!
Is there some "approved" way of detecting the "incomplete source" syntax
error AND storing the mid-parse Lua state so that I can simply resume
once more data arrives???
Is there a better way?
Am I barking up the wrong tree? (wave's his noob flag)
btw. I didn't like the way lua.c dealt with detecting "incomplete data"
since it checks for a hardcoded "<eof>" in the stack return data.
This "<eof>" is a replication of static string data from llex.c. I'd
much rather look for the EOZ token on the return stack.