105 lines
2.6 KiB
C++
105 lines
2.6 KiB
C++
//
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// Created by Cigerxwin Chaker on 05.11.19.
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//
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#include <cstdio>
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#include <cstdlib>
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#include <cstring>
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#include <iostream>
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#include <sys/ipc.h>
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#include <sys/sem.h>
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#include <sys/shm.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include "SharedMemoryAccess.h" /* header is important for the shmID. name could be different. maybe not needed cause: (shmget(memory_access_key, NULL, 0)) */
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#include "internal.h"
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constexpr int PERM = 0666; /* access rights */
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constexpr int LOCK = -1;
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constexpr int UNLOCK = 1;
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constexpr int SEM_KEY = 123458L;
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//int memoryAccessKey; /* var type is int. but could be another type. */ //TODO: look after type in sharedmemory group
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int semId;
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struct sembuf semaphore;
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std::vector<char> localSharedMemory;
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int initSemaphore() {
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/* Testen, ob das Semaphor bereits existiert */
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semId = semget(SEM_KEY, 0, IPC_PRIVATE);
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if (semId < 0) {
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/* ... existiert noch nicht, also anlegen */
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/* Alle Zugriffsrechte der Dateikreierungsmaske */
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/* erlauben */
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umask(0);
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semId = semget(SEM_KEY, 1, IPC_CREAT | IPC_EXCL | PERM);
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if (semId < 0) {
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return -1;
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}
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/* Semaphor mit 1 initialisieren */
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if (semctl(semId, 0, SETVAL, 1) == -1){
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return -1;
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}
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}
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return 1;
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}
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int semaphoreOperation(int op) {
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semaphore.sem_op = static_cast<int16_t>(op);
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semaphore.sem_flg = SEM_UNDO;
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if (semop(semId, &semaphore, 1) == -1) {
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perror(" semop ");
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return -1;
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}
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return 1;
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}
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void writeSharedMemory(char *data, int size, int offset) {
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lockSharedMemory();
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memcpy(getSharedMemory() + offset, data, size);
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unlockSharedMemory();
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}
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char *getSharedMemory() {
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bool useLocal = false;
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if(!useLocal){
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int shmId = shmget(impl.sharedMemoryKey, NULL, 0);
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if(shmId < 0) {
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//no shared memory found
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useLocal = true;
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} else {
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return (char *) shmat(shmId, NULL, 0);
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}
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}
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if(useLocal) {
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//using a local buffer for shared memory testing
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if (localSharedMemory.empty()) {
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initSemaphore();
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localSharedMemory.resize(impl.sharedMemorySize * 1024);
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}
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return &localSharedMemory[0];
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}
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}
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void getSharedMemory(char *address, int size, int offset) {
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lockSharedMemory();
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memcpy(address, getSharedMemory() + offset, size);
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unlockSharedMemory();
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}
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int getSharedMemorySize() {
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return impl.sharedMemorySize;
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}
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void lockSharedMemory() {
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semaphoreOperation(LOCK);
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}
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void unlockSharedMemory() {
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semaphoreOperation(UNLOCK);
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}
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