readFile.c   [plain text]

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