examples/Dispatch Samples/readFileF.c

   1 /*
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  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
  55 void readFileData(void* theSource) {
  56         char buffer[10];
  57         size_t estimated = dispatch_source_get_data(theSource);
  58         printf("Estimated bytes available: %ld\n", estimated);
  59         ssize_t actual = read(dispatch_source_get_handle(theSource), buffer, sizeof(buffer));
  60         if (actual == -1) {
  61                 if (errno != EAGAIN) {
  62                         perror("read");
  63                         exit(-1);
  64                 }
  65         } else {
  66                 if  (estimated>actual) {
  67                         printf("  bytes read: %ld\n", actual);
  68                 } else {
  69                         // end of file has been reached.
  70                         printf("  last bytes read: %ld\n", actual);
  71                         dispatch_source_cancel(theSource);
  72                 }
  73         }
  74 }
  75
  76 void cancelSource(void* theSource) {
  77                 close(dispatch_source_get_handle(theSource));
  78                 dispatch_release(theSource);
  79                 dispatch_release(dispatch_get_current_queue());
  80                 printf("Everything is finished, goodbye.\n");
  81                 exit(0);
  82 }
  83
  84 int main(int argc, char* argv[])
  85 {
  86         int infd;
  87         dispatch_source_t       fileSource;
  88
  89         if (argc != 2) {
  90                 fprintf(stderr, "usage: %s file ...\n", argv[0]);
  91                 exit(1);
  92         }
  93
  94
  95         infd = open(argv[1], O_RDONLY);
  96         if (infd == -1) {
  97                 perror(argv[1]);
  98                 exit(1);
  99         }
 100
 101         if (fcntl(infd, F_SETFL, O_NONBLOCK) != 0) {
 102                 perror(argv[1]);
 103                 exit(1);
 104         }
 105
 106         fileSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, infd, 0, dispatch_queue_create("read source queue",NULL));
 107         dispatch_source_set_event_handler_f( fileSource, readFileData);
 108         dispatch_source_set_cancel_handler_f( fileSource, cancelSource);
 109         // setting the context pointer to point to the source itself means the functions will get the source
 110         // as a paremeter, from there they can get all the information they need.
 111         dispatch_set_context(fileSource, fileSource);
 112         dispatch_resume(fileSource);
 113
 114         dispatch_main();
 115
 116         return 0;
 117 }