/*

 * 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>

void readFileData(void* theSource) {

    char buffer[10];

    size_t estimated = dispatch_source_get_data(theSource);

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

    ssize_t actual = read(dispatch_source_get_handle(theSource), 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(theSource);

        }       

    }

}

void cancelSource(void* theSource) {

        close(dispatch_source_get_handle(theSource));

        dispatch_release(theSource);                    

        dispatch_release(dispatch_get_current_queue());

        printf("Everything is finished, goodbye.\n");

        exit(0);

} 

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_f( fileSource, readFileData);

    dispatch_source_set_cancel_handler_f( fileSource, cancelSource);

    // setting the context pointer to point to the source itself means the functions will get the source

    // as a paremeter, from there they can get all the information they need.

    dispatch_set_context(fileSource, fileSource);

    dispatch_resume(fileSource);

    dispatch_main();

    return 0;

}