examples/Dispatch Samples/readFile.c

   1 /*
   2  * Copyright (c) 2008 Apple Inc.  All rights reserved.
   3  *
   4  * @APPLE_DTS_LICENSE_HEADER_START@
   5  *
   6  * IMPORTANT:  This Apple software is supplied to you by Apple Computer, Inc.
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   8  * use, installation, modification or redistribution of this Apple software
   9  * constitutes acceptance of these terms.  If you do not agree with these terms,
  10  * please do not use, install, modify or redistribute this Apple software.
  11  *
  12  * In consideration of your agreement to abide by the following terms, and
  13  * subject to these terms, Apple grants you a personal, non-exclusive license,
  14  * under Apple's copyrights in this original Apple software (the "Apple Software"),
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  17  * the Apple Software in its entirety and without modifications, you must retain
  18  * this notice and the following text and disclaimers in all such redistributions
  19  * of the Apple Software.  Neither the name, trademarks, service marks or logos of
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  23  * implied, are granted by Apple herein, including but not limited to any patent
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  25  * which the Apple Software may be incorporated.
  26  *
  27  * The Apple Software is provided by Apple on an "AS IS" basis.  APPLE MAKES NO
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  33  * IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR
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  42  */
  43
  44 #include <assert.h>
  45 #include <fcntl.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include <unistd.h>
  49 #include <string.h>
  50 #include <sys/errno.h>
  51
  52 #include <dispatch/dispatch.h>
  53
  54 int main(int argc, char* argv[])
  55 {
  56         int infd;
  57         dispatch_source_t fileSource;
  58
  59         if (argc != 2) {
  60                 fprintf(stderr, "usage: %s file ...\n", argv[0]);
  61                 exit(1);
  62         }
  63
  64
  65         infd = open(argv[1], O_RDONLY);
  66         if (infd == -1) {
  67                 perror(argv[1]);
  68                 exit(1);
  69         }
  70
  71         if (fcntl(infd, F_SETFL, O_NONBLOCK) != 0) {
  72                 perror(argv[1]);
  73                 exit(1);
  74         }
  75
  76         fileSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, infd, 0, dispatch_queue_create("read source queue",NULL));
  77
  78         dispatch_source_set_event_handler( fileSource, ^{
  79                 char buffer[10];
  80                 size_t estimated = dispatch_source_get_data(fileSource);
  81                 printf("Estimated bytes available: %ld\n", estimated);
  82                 ssize_t actual = read(infd, buffer, sizeof(buffer));
  83                 if (actual == -1) {
  84                         if (errno != EAGAIN) {
  85                                 perror("read");
  86                                 exit(-1);
  87                         }
  88                 } else {
  89                         if  (estimated>actual) {
  90                                 printf("  bytes read: %ld\n", actual);
  91                         } else {
  92                                 // end of file has been reached.
  93                                 printf("  last bytes read: %ld\n", actual);
  94                                 dispatch_source_cancel(fileSource);
  95                         }
  96                 }
  97         });
  98
  99         dispatch_source_set_cancel_handler( fileSource, ^{
 100                 // release all our associated dispatch data structures
 101                 dispatch_release(fileSource);
 102                 dispatch_release(dispatch_get_current_queue());
 103                 // close the file descriptor because we are done reading it
 104                 close(infd);
 105                 // and since we have nothing left to do, exit the tool
 106                 exit(0);
 107
 108         });
 109
 110         dispatch_resume(fileSource);
 111
 112         dispatch_main();
 113
 114         return 0;
 115 }