/*

 * Copyright (c) 2008 Apple Inc.  All rights reserved.

 *

 * @APPLE_DTS_LICENSE_HEADER_START@

 * 

 * IMPORTANT:  This Apple software is supplied to you by Apple Computer, Inc.

 * ("Apple") in consideration of your agreement to the following terms, and your

 * use, installation, modification or redistribution of this Apple software

 * constitutes acceptance of these terms.  If you do not agree with these terms,

 * please do not use, install, modify or redistribute this Apple software.

 * 

 * In consideration of your agreement to abide by the following terms, and

 * subject to these terms, Apple grants you a personal, non-exclusive license,

 * under Apple's copyrights in this original Apple software (the "Apple Software"),

 * to use, reproduce, modify and redistribute the Apple Software, with or without

 * modifications, in source and/or binary forms; provided that if you redistribute

 * the Apple Software in its entirety and without modifications, you must retain

 * this notice and the following text and disclaimers in all such redistributions

 * of the Apple Software.  Neither the name, trademarks, service marks or logos of

 * Apple Computer, Inc. may be used to endorse or promote products derived from

 * the Apple Software without specific prior written permission from Apple.  Except

 * as expressly stated in this notice, no other rights or licenses, express or

 * implied, are granted by Apple herein, including but not limited to any patent

 * rights that may be infringed by your derivative works or by other works in

 * which the Apple Software may be incorporated.

 * 

 * The Apple Software is provided by Apple on an "AS IS" basis.  APPLE MAKES NO

 * WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED

 * WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN

 * COMBINATION WITH YOUR PRODUCTS. 

 * 

 * IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR

 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE

 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, MODIFICATION AND/OR

 * DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED AND WHETHER UNDER THEORY OF

 * CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT LIABILITY OR OTHERWISE, EVEN IF

 * APPLE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 * 

 * @APPLE_DTS_LICENSE_HEADER_END@

 */

#include <assert.h>

#include <fcntl.h>

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <sys/errno.h>

#include <dispatch/dispatch.h>

int main(int argc, char* argv[])

{

    int infd;

    dispatch_source_t fileSource;

    if (argc != 2) {

        fprintf(stderr, "usage: %s file ...\n", argv[0]);

        exit(1);

    }

    infd = open(argv[1], O_RDONLY);

    if (infd == -1) {

        perror(argv[1]);

        exit(1);

    }

    if (fcntl(infd, F_SETFL, O_NONBLOCK) != 0) {

        perror(argv[1]);

        exit(1);

    }

    fileSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, infd, 0, dispatch_queue_create("read source queue",NULL));

    dispatch_source_set_event_handler( fileSource, ^{

        char buffer[10];

        size_t estimated = dispatch_source_get_data(fileSource);

        printf("Estimated bytes available: %ld\n", estimated);

        ssize_t actual = read(infd, buffer, sizeof(buffer));

        if (actual == -1) {

            if (errno != EAGAIN) {

                perror("read");

                exit(-1);

            }

        } else {

            if  (estimated>actual) {

                printf("  bytes read: %ld\n", actual);

            } else {

                // end of file has been reached.

                printf("  last bytes read: %ld\n", actual);

                dispatch_source_cancel(fileSource);

            }       

        }

    });

    dispatch_source_set_cancel_handler( fileSource, ^{

        // release all our associated dispatch data structures

        dispatch_release(fileSource);                   

        dispatch_release(dispatch_get_current_queue());

        // close the file descriptor because we are done reading it

        close(infd);

        // and since we have nothing left to do, exit the tool

        exit(0);

    });

    dispatch_resume(fileSource);

    dispatch_main();

    return 0;

}