posix

Documentation

Index

• Constants
• type Flag
• type SharedMemorySegment
  • func AttachToShmSegment(shmID int, size uint, permission int) (*SharedMemorySegment, error)
  • func NewSharedMemorySegment(key int, size uint, permission int, flags ...Flag) (*SharedMemorySegment, error)
  • func (s *SharedMemorySegment) Clear()
  • func (s *SharedMemorySegment) Detach() error
  • func (s *SharedMemorySegment) Read(data []byte) error
  • func (s *SharedMemorySegment) Write(data []byte)

Constants

const (
	S_IRUSR = 0400         /* Read by owner.  */  //nolint:golint,stylecheck
	S_IWUSR = 0200         /* Write by owner.  */ //nolint:golint,stylecheck
	S_IRGRP = S_IRUSR >> 3 /* Read by group.  */  //nolint:golint,stylecheck
	S_IWGRP = S_IWUSR >> 3 /* Write by group.  */ //nolint:golint,stylecheck
)

Types

type Flag

type Flag int

const (
	/* resource get request flags */
	IPC_CREAT  Flag = 00001000 /* create if key is nonexistent */ //nolint:golint,stylecheck
	IPC_EXCL   Flag = 00002000 /* fail if key exists */           //nolint:golint,stylecheck
	IPC_NOWAIT Flag = 00004000 /* return error on wait */         //nolint:golint,stylecheck

	/* Permission flag for shmget.  */
	SHM_R Flag = 0400 /* or S_IRUGO from <linux/stat.h> */ //nolint:golint,stylecheck
	SHM_W Flag = 0200 /* or S_IWUGO from <linux/stat.h> */ //nolint:golint,stylecheck

	/* Flags for `shmat'.  */
	SHM_RDONLY Flag = 010000 /* attach read-only else read-write */ //nolint:golint,stylecheck
	SHM_RND    Flag = 020000 /* round attach address to SHMLBA */   //nolint:golint,stylecheck

	/* Commands for `shmctl'.  */
	SHM_REMAP Flag = 040000  /* take-over region on attach */ //nolint:golint,stylecheck
	SHM_EXEC  Flag = 0100000 /* execution access */           //nolint:golint,stylecheck

	SHM_LOCK   Flag = 11 /* lock segment (root only) */   //nolint:golint,stylecheck
	SHM_UNLOCK Flag = 12 /* unlock segment (root only) */ //nolint:golint,stylecheck
)

https://github.com/torvalds/linux/blob/master/include/uapi/linux/ipc.h

type SharedMemorySegment

type SharedMemorySegment struct {
	// contains filtered or unexported fields
}

func AttachToShmSegment

func AttachToShmSegment(shmID int, size uint, permission int) (*SharedMemorySegment, error)

AttachToShmSegment used to attach to the existing shared memory segment by shared memory ID. Shared memory ID can be known or you find it by typing the following command: ipcs -m --human. If there is no such shm segment by shmId, the error will be shown.

func NewSharedMemorySegment

func NewSharedMemorySegment(key int, size uint, permission int, flags ...Flag) (*SharedMemorySegment, error)

The args are:

key - int, used as uniques identifier for the shared memory segment size - uint, size in bytes to allocate permission - int, if passed zero, 0600 will be used by default flags - IPC_CREAT, IPC_EXCL, IPC_NOWAIT. More info can be found here https://github.com/torvalds/linux/blob/master/include/uapi/linux/ipc.h

func (*SharedMemorySegment) Clear

func (s *SharedMemorySegment) Clear()

Clear by behavior is similar to the std::memset(..., 0, ...)

func (*SharedMemorySegment) Detach

func (s *SharedMemorySegment) Detach() error

Detach used to detach from memory segment

func (*SharedMemorySegment) Read

func (s *SharedMemorySegment) Read(data []byte) error

Read data segment. Attention, the segment to read will be equal to data function arg len

func (*SharedMemorySegment) Write

func (s *SharedMemorySegment) Write(data []byte)

write is not thread safe operation should be protected via semaphore