Shared Memory & Semaphore

NOTE: BinarySemaphore is the same as Mutex (for one shared resource).

1. SharedMemoryBinarySemaphoreWriter & SharedMemoryBinarySemaphoreReader
First, run SharedMemoryBinarySemaphoreWriter.exe (this only writes data on the shared memory segment.)

SharedMemoryBinarySemaphoreWriter

Then, run SharedMemoryBinarySemaphoreReader.exe (it only reads data from the shared memory segment.)

SharedMemoryBinarySemaphoreReader

2. SharedMemoryBinarySemaphoreMasterSlave (Both master/slaves write/reads data to/from the shared memory segment.)
First, run SharedMemoryBinarySemaphoreMasterSlave.exe –master
Then, run SharedMemoryBinarySemaphoreMasterSlave.exe

SharedMemoryBinarySemaphoreMasterSlave

 

NOTE: Semaphore allows a specific number of processes/threads to enter.

3. SharedMemoryGeneralSemaphoreMasterSlave (classic reader-writer problem)

The writer fills data until the buffer is full. It waits emptyBufferSemaphore (e–) to be available. If so, it fills data. After that, it signals fullBufferSemaphore(f++) ready.

The reader reads data until the buffer is empty. It waits fullBufferSemaphore(f–) to be available. If so, it reads data. After that, it signals emptyBufferSemaphore(e++) to be ready.

1 master is the writer (fills data the shared memory buffer).

2 slaves are the readers (read data from the shared memory buffer; but their reader index must be synchronized).
First, run SharedMemoryGeneralSemaphoreMasterSlave.exe –master
Next, run SharedMemoryGeneralSemaphoreMasterSlave.exe
Then, run SharedMemoryGeneralSemaphoreMasterSlave.exe

SharedMemoryGeneralSemaphoreMasterSlave

 

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