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From Jeff Trawick <traw...@attglobal.net>
Subject Re: [PATCH] Fix POD reading...
Date Sat, 21 Jul 2001 12:07:50 GMT
There is at least one problem with your testpipe program which affects
the results.  See comments below:

> void pipe_child()
> {
>     char b = ' ';
>     int one = 1;
>     int i = 0;
>     apr_status_t ret;
> #ifdef PIPE_AS_SOCKET
>     apr_socket_t *s;
>     apr_socket_from_file(&s, readp);
> #endif
>     while (i < 1000)
>     {

you must reset one to 1 here every time through the loop... otherwise,
if you ever hit the EAGAIN condition (where one is set to zero on exit
from APR), you'll never read any more data but you'll get APR_SUCCESS

I get EAGAIN on the first call before I start reading the data, so
this fix was crucial to me.

> #ifdef PIPE_AS_SOCKET
>         ret = apr_recv(s, &b, &one);
> #else
>         ret = apr_file_read(readp, &b, &one);
> #endif
>         if (APR_STATUS_IS_EAGAIN(ret)) {
...
> void go()
> {
>     fflush(stdout);
>     if (fork())
>     {
>         fork();
>         fork();
>         fork();
>         fork();
>         fork();
>         fork();
>         pipe_child();

too darn confusing :) since when does the parent run a function called
foo_child()?

I switched it around, got rid of the extra fork calls for easier
debugging, and had pipe_child() read more times than the parent
wrote.

Here is my copy of the program.  It seems to work properly whether or
not apr_file_read() is used.

I couldn't help but fix some of the warnings before running, even
knowing that they didn't affect the outcome.  Sorry :)

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000-2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

#include <stdio.h>
#include "apr_file_io.h"
#include "apr_errno.h"
#include "apr_general.h"
#include "apr_lib.h"
#include "apr_network_io.h"
#include <stdlib.h>
#include <unistd.h>

apr_file_t *readp = NULL;
apr_file_t *writep = NULL;

#define PIPE_AS_SOCKET
/*#define SOLARIS_HACK*/
/*#define PRINT_RET*/

static void pipe_child(void)
{
    char b = ' ';
    apr_size_t one = 1;
    int i = 0;
    apr_status_t ret;
#ifdef PIPE_AS_SOCKET
    apr_socket_t *s;
    apr_socket_from_file(&s, readp);
#endif
    while (i < 2000)
    {
        one = 1;
#ifdef PIPE_AS_SOCKET
        ret = apr_recv(s, &b, &one);
#else
        ret = apr_file_read(readp, &b, &one);
#endif
        printf("got %d/%" APR_SIZE_T_FMT " from read\n",
               ret, one);
        if (APR_STATUS_IS_EAGAIN(ret)) {
            /* It lost the lottery. It must continue to suffer
             * through a life of servitude. */
        }
        else {
#ifdef SOLARIS_HACK
            if (one == 1)
                printf("%c", b);
#elif defined(PRINT_RET)
            if (one != 1)
                printf("%d %d\n", ret, one);
#else
            printf("%c", b);
#endif
        }
        i++;
    }
}

static void pipe_parent(void)
{
    char c = '!';
    int one = 1;
    int i = 0;
    while (i < 1000)
    {
        apr_file_write(writep, &c, &one);
        i++;
    } 
printf("exiting parent\n");
}

static void go(void)
{
    fflush(stdout);
    if (!fork())
    {
        pipe_child();
    }
    else
    {
        pipe_parent();
    }
}

int main(void)
{
    apr_pool_t *context;
    apr_size_t nbytes;
    apr_status_t rv;
    char *buf;
    char msgbuf[120];

    if (apr_initialize() != APR_SUCCESS) {
        exit(-1);
    }
    atexit(apr_terminate);
    if (apr_pool_create(&context, NULL) != APR_SUCCESS) {
        exit(-1);
    }

    if ((rv = apr_file_pipe_create(&readp, &writep, context)) != APR_SUCCESS) {
        exit(-1);
    }
    if ((rv = apr_file_pipe_timeout_set(readp, 0)) != 
        APR_SUCCESS) {
        exit(-1);
    }        
    go();
    return 1;
}


-- 
Jeff Trawick | trawick@attglobal.net | PGP public key at web site:
       http://www.geocities.com/SiliconValley/Park/9289/
             Born in Roswell... married an alien...

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