#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#include <OS.h>

const char* kInitialValue = "/dev/null";
const char* kChangedValue = "Argh!";

int
main(int argc, const char* const* argv)
{
        thread_id parent = find_thread(NULL);

        char* globalVar = NULL;
        area_id area = create_area("cow test", (void**)&globalVar,
                B_ANY_ADDRESS, B_PAGE_SIZE, B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);
        if (area < 0) {
                printf("failed to create area\n");
                return 1;
        }

        strcpy(globalVar, kInitialValue);

        printf("[%ld] parent: before fork(): globalVar(%p): \"%s\"\n", parent,
                globalVar, globalVar);

        pid_t child = fork();
        if (child == 0) {
                // child
                child = find_thread(NULL);

                // let the kernel read access the page
                struct stat st;
                stat(globalVar, &st);

                printf("[%ld] child: after kernel read: globalVar: \"%s\"\n",
                        child, globalVar);

                // write access the page from userland
                strcpy(globalVar, kChangedValue);

                printf("[%ld] child: after change: globalVar: \"%s\"\n", child,
                        globalVar);

        } else {
                // parent

                // wait for the child
                status_t exitVal;
                while (wait_for_thread(child, &exitVal) == B_INTERRUPTED);

                // check the value
                printf("[%ld] parent: after exit child: globalVar: \"%s\"\n",
                        parent, globalVar);

                if (strcmp(globalVar, kInitialValue) == 0)
                        printf("test OK\n");
                else
                        printf("test FAILED: child process changed parent's memory!\n");
        }

        return 0;
}