Initialize a segment of persistant shared memory. Note that as shared memory is a system wide rather than an application wide resource, the rules concerning program Unix User ID and access permissions apply.

Declared in file: hzProcess.h
Defined in file : hzProcess.cpp

Function Logic:

Function body:

hzEcode hzShmem::Init (const char* name)uint32_t size, uint32_t mask, 
{
   //  Category: System
   //  
   //  Initialize a segment of persistant shared memory.
   //  
   //  Arguments: 1) name Name of segment
   //     2) size No of bytes
   //     3) mask Access permissions
   //  
   //  Returns: E_INITDUP If shared memory segment is already initialized
   //     E_ARGUMENT If no name is supplied
   //     E_INITFAIL If the shared memory segment could not be set to the requested size
   //  
   //  Note that as shared memory is a system wide rather than an application wide resource, the rules concerning program Unix User ID and access permissions apply.
   _hzfunc("hzShmem::Init") ;
   //  Test the instance is not already initialized
   if (m_name)
   {
       hzerr(E_INITDUP, "Shared memory segment %s already initialized", *m_name) ;
       return E_INITDUP ;
   }
   if (!name || !name[0])
   {
       hzerr(E_ARGUMENT, "No name supplied") ;
       return E_ARGUMENT ;
   }
   m_name = name ;
   m_size = ((size/4096)+1)*4096;
   m_perm = mask ;
   //  Open shared memory
   m_fd = shm_open(name, O_RDWR | O_CREAT, 0666);
   threadLog("Set fd to %d\n", m_fd) ;
   //  Set to requested size
   if (ftruncate(m_fd, m_size) != 0)
   {
       hzerr(E_INITFAIL, "Shared memory could not be sized to %d bytes", m_size) ;
       return E_INITFAIL ;
   }
   threadLog("Set size to %d\n", m_size) ;
   //  Obtain pointer to start of segment
   m_pStart = mmap(0,m_size, PROT_READ | PROT_WRITE, MAP_SHARED, m_fd, 0);
   if (!m_pStart || m_pStart == (void*)-1)
   {
       hzerr(E_INITFAIL, "Shared memory address at %p errno is %d\n", m_pStart, errno) ;
       return E_INITFAIL ;
   }
   threadLog("mem at %p\n", m_pStart) ;
   return E_OK ;
}