#! /usr/bin/env python
"""Generate C code for the jump table of the threaded code interpreter
(for compilers supporting computed gotos or "labels-as-values", such as gcc).
"""

import os
import sys


try:
 from importlib.machinery import SourceFileLoader
except ImportError:
 import imp

 def find_module(modname):
 """Finds and returns a module in the local dist/checkout.
 """
 modpath = os.path.join(
 os.path.dirname(os.path.dirname(__file__)), "Lib")
 return imp.load_module(modname, *imp.find_module(modname, [modpath]))
else:
 def find_module(modname):
 """Finds and returns a module in the local dist/checkout.
 """
 modpath = os.path.join(
 os.path.dirname(os.path.dirname(__file__)), "Lib", modname + ".py")
 return SourceFileLoader(modname, modpath).load_module()


def write_contents(f):
 """Write C code contents to the target file object.
 """
 opcode = find_module('opcode')
 targets = ['_unknown_opcode'] * 256
 for opname, op in opcode.opmap.items():
 targets[op] = "TARGET_%s" % opname
 f.write("static void *opcode_targets[256] = {\n")
 f.write(",\n".join([" &&%s" % s for s in targets]))
 f.write("\n};\n")


def main():
 if len(sys.argv) >= 3:
 sys.exit("Too many arguments")
 if len(sys.argv) == 2:
 target = sys.argv[1]
 else:
 target = "Python/opcode_targets.h"
 with open(target, "w") as f:
 write_contents(f)
 print("Jump table written into %s" % target)


if __name__ == "__main__":
 main()