XrdSys::shm Struct Reference

#include <XrdSysShmem.hh>

Collaboration diagram for XrdSys::shm:

Static Public Member Functions
static std::tuple< void *, size_t >	create (const std::string &name, size_t size)
template<typename T >
static std::tuple< T *, size_t >	get (const std::string &name)
template<typename T >
static std::tuple< T *, size_t >	make_array (const std::string &name, size_t count)
template<typename T , typename... Args>
static std::tuple< T *, size_t >	make_array (const std::string &name, size_t count, Args &&... args)

Detailed Description

Utility class for creating and obtaining shared emory

Definition at line 54 of file XrdSysShmem.hh.

Member Function Documentation

create()

static std::tuple< void *, size_t > XrdSys::shm::create ( const std::string &  name, size_t  size  )

inlinestatic

Helper function for creating shared memory block

Parameters

name	: name of the shared memory block (shared memory object should be identified by a name of the form /somename)
size	: size of the shared memory segment

Returns

: pointer to the shared memory and its size

Definition at line 65 of file XrdSysShmem.hh.

    {
          int fd = shm_open( name.c_str(), O_CREAT | O_RDWR, 0600 );
      if( fd < 0 )
            throw shm_error( errno );
          if( ftruncate( fd, size ) < 0 )
          {
        if( errno != EINVAL )
          throw shm_error( errno );
          }
          struct stat statbuf;
          if( fstat( fd, &statbuf ) < 0 )
            throw shm_error( errno );
          size = statbuf.st_size;
          void *mem = map_shm( fd, size );
          close( fd );
          return std::make_tuple( mem, size );
    }

References close, fstat, ftruncate, and stat.

Referenced by make_array(), and make_array().

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get()

template<typename T >

static std::tuple< T *, size_t > XrdSys::shm::get ( const std::string &  name )

inlinestatic

Helper function for getting shared memory block

Parameters

name	: name of the shared memory block (shared memory object should be identified by a name of the form /somename)

Returns

: pointer to the shared memory and its size

Definition at line 93 of file XrdSysShmem.hh.

    {
      int fd = shm_open( name.c_str(), O_RDWR, 0600 );
      if( fd < 0 )
        throw shm_error( errno );
      struct stat statbuf;
      if( fstat( fd, &statbuf ) < 0 )
        throw shm_error( errno );
      size_t size = statbuf.st_size;
      void *mem = map_shm( fd, size );
      close( fd );
      return std::make_tuple( reinterpret_cast<T*>( mem ), size );
    }

References close, fstat, and stat.

make_array() [1/2]

template<typename T >

static std::tuple< T *, size_t > XrdSys::shm::make_array ( const std::string &  name, size_t  count  )

inlinestatic

Helper function for creating a shared memory block and constructing an array of objects of type T (constructed with default constructor) within the block.

Parameters

name	: name of the shared memory block (shared memory object should be identified by a name of the form /somename)
count	: size of the array

Returns

: pointer to the shared memory and its size

Definition at line 119 of file XrdSysShmem.hh.

    {
      auto tpl = create( name, count * sizeof( T ) );
      T* arr = reinterpret_cast<T*>( std::get<0>( tpl ) );
      size_t size = std::get<1>( tpl );
      for( size_t i = 0; i < count; ++i )
        new( arr + i ) T();
      return std::make_tuple( arr, size );
    }

References create().

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make_array() [2/2]

template<typename T , typename... Args>

static std::tuple< T *, size_t > XrdSys::shm::make_array ( const std::string &  name, size_t  count, Args &&...  args  )

inlinestatic

Helper function for creating a shared memory block and constructing an array of objects of type T (constructed with using arguments args) within the block.

Parameters

name	: name of the shared memory block (shared memory object should be identified by a name of the form /somename)
count	: size of the array
args	: the arguments for the T constructor

Returns

: pointer to the shared memory and its size

Definition at line 142 of file XrdSysShmem.hh.

    {
      auto tpl = create( name, count * sizeof( T ) );
      T* arr = reinterpret_cast<T*>( std::get<0>( tpl ) );
      size_t size = std::get<1>( tpl );
      for( size_t i = 0; i < count; ++i )
        new( arr + i ) T( std::forward<Args...>( args... ) );
      return std::make_tuple( arr, size );
    }

References create().

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The documentation for this struct was generated from the following file:

• XrdSysShmem.hh