slsDetectorPackage/slsDetectorSoftware/sharedMemory/SharedMemory.h

#pragma once
/************************************************
 * @file SharedMemory.h
 * @short functions basic implemenation of
 * shared memory
 ***********************************************/
/**
 *@short functions basic implemenation of shared memory
 */

#include <iostream>
#include <string>

template <typename T>
class SharedMemory{
public:
	/**
	 * Constructor
	 * creates the single/multi detector shared memory name
	 * @param multiId multi detector id
     * @param slsId sls detector id, -1 if a multi detector shared memory
 	 */
	SharedMemory(int multiId, int slsId);

	/**
	 * Destructor
	 */
	~SharedMemory();

    /**
     * Verify if it exists
     * @param name of shared memory
     * @return true if exists, else false
     */
    bool IsExisting();

	/**
	 * Get shared memory name
	 */
	std::string GetName();

    /**
     * Create Shared memory and call MapSharedMemory to map it to an address
     * throws a SharedMemoryException exception on failure to create, ftruncate or map
     * @param sz of shared memory
     */
    void CreateSharedMemory(size_t sz);

    /**
     * Open existing Shared memory and call MapSharedMemory to map it to an address
     * throws a SharedMemoryException exception on failure to open or map
     * @param sz of shared memory
     */
    void OpenSharedMemory(size_t sz);

    /**
     * Unmap shared memory from an address
     * throws a SharedMemoryException exception on failure
     */
    void UnmapSharedMemory();

	/**
	 * Remove existing Shared memory
	 */
	void RemoveSharedMemory();

    /**
     * Maximum length of name as from man pages
     */
    static const int NAME_MAX = 255;


    /*
    Using the call operator to access the pointer

    */
    T* operator()(){
        return shared_struct;
    }

    const T* operator()() const{
        return shared_struct;
    }

private:
    /**
     * Create Shared memory name
     * throws exception if name created is longer than required 255(manpages)
     * @param multiId multi detector id
     * @param slsId sls detector id, -1 if a multi detector shared memory
     * @returns shared memory name
     */
    std::string ConstructSharedMemoryName(int multiId, int slsId);

    /**
     * Map shared memory to an address
     * throws a SharedMemoryException exception on failure
     * @param sz of shared memory
     */
    T* MapSharedMemory(size_t sz);

    /**
     * Verify if existing shared memory size matches expected size
     * @param expectedSize expected size of shared memory, replaced with smaller size if size does not match
     * @return 0 for success, 1 for fail
     */
    int VerifySizeMatch(size_t expectedSize);

	/** Shared memory name */
	std::string name;

	/** File descriptor */
	int fd;

	/** shm size */
	size_t shmSize;

    T* shared_struct;

};