Class: ProcessShared::Posix::SharedMemory

Inherits:
FFI::Pointer
  • Object
show all
Extended by:
OpenWithSelf
Includes:
ObjectBuffer, LibC, Foreign
Defined in:
lib/process_shared/posix/shared_memory.rb

Overview

Memory block shared across processes.

Defined Under Namespace

Modules: Foreign

Constant Summary

Constants included from LibC

LibC::MAP_FAILED, LibC::MAP_PRIVATE, LibC::MAP_SHARED, LibC::O_CREAT, LibC::O_EXCL, LibC::O_RDWR, LibC::PROT_EXEC, LibC::PROT_NONE, LibC::PROT_READ, LibC::PROT_WRITE

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from OpenWithSelf

open

Methods included from ObjectBuffer

#get_object, #put_object, #read_object, #write_object

Methods included from LibC

type_size

Methods included from Errno

#error_check

Constructor Details

#initialize(type_or_count = 1, count = 1) ⇒ SharedMemory

Returns a new instance of SharedMemory.



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# File 'lib/process_shared/posix/shared_memory.rb', line 44

def initialize(type_or_count = 1, count = 1)
  @type, @count = case type_or_count
                  when Symbol
                    [type_or_count, count]
                  else
                    [:uchar, type_or_count]
                  end

  @type_size = FFI.type_size(@type)
  @size = @type_size * @count

  name = "/ps-shm#{rand(10000)}"
  @fd = shm_open(name,
                 O_CREAT | O_RDWR | O_EXCL,
                 0777)
  shm_unlink(name)
  
  ftruncate(@fd, @size)
  @pointer = mmap(nil,
                  @size,
                  LibC::PROT_READ | LibC::PROT_WRITE,
                  LibC::MAP_SHARED,
                  @fd,
                  0).
    slice(0, size) # slice to get FFI::Pointer that knows its size
  # (and thus does bounds checking)

  @finalize = self.class.make_finalizer(@pointer.address, @size, @fd)
  ObjectSpace.define_finalizer(self, @finalize)

  super(@pointer)
end

Instance Attribute Details

#count ⇒ Object (readonly)

Returns the value of attribute count.



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# File 'lib/process_shared/posix/shared_memory.rb', line 34

def count
  @count
end

#fd ⇒ Object (readonly)

Returns the value of attribute fd.



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# File 'lib/process_shared/posix/shared_memory.rb', line 34

def fd
  @fd
end

#size ⇒ Object (readonly)

Returns the value of attribute size.



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# File 'lib/process_shared/posix/shared_memory.rb', line 34

def size
  @size
end

#type ⇒ Object (readonly)

Returns the value of attribute type.



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# File 'lib/process_shared/posix/shared_memory.rb', line 34

def type
  @type
end

#type_size ⇒ Object (readonly)

Returns the value of attribute type_size.



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# File 'lib/process_shared/posix/shared_memory.rb', line 34

def type_size
  @type_size
end

Class Method Details

.make_finalizer(addr, size, fd) ⇒ Object 



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# File 'lib/process_shared/posix/shared_memory.rb', line 36

def self.make_finalizer(addr, size, fd)
  proc do
    pointer = FFI::Pointer.new(addr)
    LibC.munmap(pointer, size)
    LibC.close(fd)
  end
end

Instance Method Details

#close ⇒ Object 



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# File 'lib/process_shared/posix/shared_memory.rb', line 77

def close
  ObjectSpace.undefine_finalizer(self)
  @finalize.call
end