Shared_memory.cc

#include <iostream>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

#include "Shared_memory.h"

static int getSharedBlock(char * fileName, int size, unsigned int proj_id) {
  key_t key;

  // Request a key and link it to a filename
  key = ftok(fileName, proj_id);
  if (key == IPC_ERROR) {
    return IPC_ERROR;
  }
  // Create block or get it if it exists
  return shmget(key, size, IPC_CREAT | 0644);
}

message * attachBlock(char * fileName, int size, unsigned int proj_id) {
  message * result;

  // Request the shared block id
  int sharedBlockId = getSharedBlock(fileName, size, proj_id);
  if (sharedBlockId == IPC_ERROR)
    return NULL;
  
  // Map the shared block to the current proccess
  // and return a pointer to it
  result = (message *) shmat(sharedBlockId, NULL, 0);
  if (result == (message*)IPC_ERROR) {
    return NULL;
  }
  
  return result;
}

bool * attachFlagBlock(char * fileName, int size, unsigned int proj_id) {
  bool * result;

  // Request the shared block id
  int sharedBlockId = getSharedBlock(fileName, size, proj_id);

  if (sharedBlockId == IPC_ERROR)
    return NULL;

  /* 
  Map the shared block to the current proccess
  and return a pointer to it
  */
  result = (bool *)shmat(sharedBlockId, NULL, 0);
  if (result == (bool *)IPC_ERROR) {
    return NULL;
  }

  return result;
}

bool detachBlock(message * block) {
  return (shmdt(block) != IPC_ERROR);
}

bool detachBlock(bool *block) {
  return (shmdt(block) != IPC_ERROR);
}

bool destroyBlock(char * fileName, int size, unsigned int proj_id) {
  int sharedBlockId = getSharedBlock(fileName, size, proj_id);

  if (sharedBlockId == IPC_ERROR) {
    return NULL;
  }

  return(shmctl(sharedBlockId, IPC_RMID, NULL) != IPC_ERROR);
}

bool destroyBlock(char *fileName, unsigned int proj_id) {
  int sharedBlockId = getSharedBlock(fileName, sizeof(bool *), proj_id);

  if (sharedBlockId == IPC_ERROR) {
    return NULL;
  }

  return (shmctl(sharedBlockId, IPC_RMID, NULL) != IPC_ERROR);
}