README.md

libinteractive

A tiny IDL translator that creates IPC shims to easily create interactive problems.

You can grab the latest .jar from the Releases page

Let's say your problem's name is sum. if you have your validator in Main.cpp and your solution in sum.py, you can do

$ ls
Main.cpp sum.py sum.idl input

$ cat Main.cpp
#include <stdio.h>
#include "sum.h"

int main(int argc, char* argv[]) {
    int a, b;
    scanf("%d %d\n", &a, &b);
    printf("%d\n", sum(a, b));
}

$ cat sum.py
def sum(a, b):
    print 'Hello, world!'
    return a + b
    
$ cat sum.idl
interface Main {
}

interface sum {
    int sum(int a, int b);
}

$ java -jar libinteractive.jar generate sum.idl cpp py --makefile
$ make run < input
[Main] 3
[ sum] Hello, world!

Memory:   5.023 MB
Time:     0.011 s

You can also add a --verbose flag to libinteractive to print a message every time an IPC call is made.

How it works

libinteractive parses the .idl file, which is a description of how the problemsetter and contestant's code are to be compiled, and which functions can be used to interact between them. It then generates all the necessary code that allows the code to communicate correctly. libinteractive uses Unix named pipes to send binary messages between the processes, which is much faster than reading and parsing text files.

One advantage of libinteractive is that since it separates the problemsetter and contestant's codes in different processes, they can be written in different programming languages. This means that you as a problemsetter will only need to write one program that reads the input and interacts with the contestant's code, and libinteractive will handle serializing and de-serializing the function calls.

libinteractive will also produce an executable called run, which will create the necessary pipes for communication, execute all the programs, relay the input to the Main program (if needed), and print out any output from the programs. Finally, it will print a summary of the maximum memory and total (user) time consumed by the contestant's code.

Since libinteractive was built with omegaUp in mind, all problems built using libinteractive will be omegaUp-compliant.

Conventions

• The first interface must be called Main, and the problemsetter's program must be in a file called Main.extension, where extension is one of c, cpp, rb, py, java, pas.
• The name of the .idl file must match the name of the contestant's code.
• Each interface will produce a separate binary and will run in a different process, which means that they will not be able to share anything.
• It is only possible to communicate between all the interfaces and Main, but not amongst them.
• Arrays are allowed, but the rules of array bounds in C must be followed: all array dimensions (except the first one) must be integer constants.
• Arrays may declare the first dimension to be a variable, but it must be a parameter of the function, and must appear before in the parameter list.

IDL Grammar

IDL is almost a subset of WebIDL, but with some syntax to help programming contests.

letter
    = "a" | "b" | ... | "y" | "z"
    | "A" | "B" | ... | "Y" | "Z"
    ;

digit
    = "0" | "1" | ... | "8" | "9"
    ;

ident
    = (letter | "_"), { letter | digit | "_" }
    ;

number
    = digit, { digit }
    ;

interface-list
    = interface, { interface }
    ;

interface
    = "interface", ident, "{", { function }, "}", ";"
    ;

function
    = return-type, ident, "(", param-list , ")", ";"
    ;

param-list
    = [ param, { ",", param } ]
    ;

type
    = array | primitive
    ;

primitive
    = "bool" | "int" | "short" | "float"
    | "char" | "string" | "long"
    ;

array
    = primitive, "[", expr, "]", { "[", expr, "]" }
    ;

return-type
    = primitive | "void"
    ;

expr
    = ident | number
    ;

param
    = { param-attribute }, type, ident
    ;

param-attribute
    = "[", range-attribute, "]"
    ;

range-attribute
    = "Range", "(", expression, ",", expression, ")"
    ;