34 lines
No EOL
491 B
Markdown
34 lines
No EOL
491 B
Markdown
```
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GLOB_MUTEX and R_MUTEX semaphores init. at 1
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R a shared register init. at 0
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begin_read() :=
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PR_MUTEX.down()
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R_MUTEX.down()
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R++ # currently active readers
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if R = 1 then
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W_MUTEX.down()
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GLOB_MUTEX.down()
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R_MUTEX.up()
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PR_MUTEX.up()
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return
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end_read() :=
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R_MUTEX.down()
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R--
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if R = 0 then GLOB_MUTEX.up()
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R_MUTEX.up()
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return
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begin_write() :=
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W_MUTEX.down()
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W_MUTEX.up()
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PR_MUTEX.down()
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GLOB_MUTEX.down()
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return
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end_write() :=
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PR_MUTEX.up()
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GLOB_MUTEX.up()
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return
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``` |