//
// aegis - project change supervisor
// Copyright (C) 2002-2006, 2008, 2012 Peter Miller
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published
// by the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//

#include <common/ac/assert.h>
#include <common/ac/errno.h>
#include <common/ac/stddef.h>
#include <common/ac/sys/types.h>
#include <sys/wait.h>

#include <common/trace.h>
#include <libaegis/os.h>


int
os_waitpid(int child, int *status_p)
{
    struct ret_ty
    {
        int             pid;
        int             status;
    };

    static size_t   nret;
    static size_t   nret_max;
    static ret_ty   *ret;
    int             pid;
    int             status;
    int             result;

    //
    // see if we already have it
    //
    trace(("os_waitpid(child = %d)\n{\n", child));
    assert(child > 0);
    result = 0;
    for (size_t j = 0; j < nret; ++j)
    {
        if (ret[j].pid != child)
            continue;
        *status_p = ret[j].status;
        ret[j] = ret[--nret];
        goto done;
    }

    //
    // new one, go hunting
    //
    for (;;)
    {
        //
        // block until a child terminates,
        // or there are no more children
        //
        pid = wait(&status);
        if (pid == -1)
        {
            if (errno == EINTR)
                continue;
            result = -1;
            break;
        }

        //
        // stop if this is the child
        // we are looking for
        //
        if (pid == child)
        {
            *status_p = status;
            break;
        }

        //
        // remember and keep going
        //
        if (nret >= nret_max)
        {
            nret_max = nret_max * 2 + 8;
            ret_ty *new_ret  = new ret_ty [nret_max];
            for (size_t k = 0; k < nret; ++k)
                new_ret[k] = ret[k];
            delete [] ret;
            ret = new_ret;
        }
        ret[nret].pid = pid;
        ret[nret].status = status;
        ++nret;
    }

    //
    // here for all exits
    //
    done:
    trace(("return %d;\n", result));
    trace(("}\n"));
    return result;
}


// vim: set ts=8 sw=4 et :