examples/prodcons.lsp

   1 #!/usr/bin/newlisp
   2
   3 # prodcons.lsp -  Producer/consumer
   4 #
   5 # this program only runs on Linux/UNIX
   6 #
   7 # usage of 'fork', 'wait-pid', 'semaphore' and 'share'
   8
   9 (if (> (& (last (sys-info)) 0xF) 4)
  10         (begin
  11                 (println "this will not run on Win32")
  12                 (exit)))
  13
  14
  15 (constant 'wait -1 'signal 1 'release 0)
  16
  17 (define (consumer n)
  18         (set 'i 0)
  19         (while (< i n)
  20                 (semaphore cons-sem wait)
  21                 (println (set 'i (share data)) " <-")
  22                 (semaphore prod-sem signal))
  23         (exit))
  24
  25 (define (producer n)
  26         (for (i 1 n)
  27                 (semaphore prod-sem wait)
  28                 (println "-> " (share data i))
  29                 (semaphore cons-sem signal))
  30         (exit))
  31
  32
  33 (define (run n)
  34         (set 'data (share))
  35         (share data 0)
  36
  37         (set 'prod-sem (semaphore)) ; get semaphores
  38         (set 'cons-sem (semaphore))
  39
  40         (set 'prod-pid (fork (producer n))) ; start threads
  41         (set 'cons-pid (fork (consumer n)))
  42         (semaphore prod-sem signal) ; get producer started
  43
  44         (wait-pid prod-pid) ; wait for threads to finish
  45         (wait-pid cons-pid) ;
  46         (semaphore cons-sem release) ; release semaphores
  47         (semaphore prod-sem release))
  48
  49
  50 (run 10)
  51
  52 (exit)
  53