README
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Documentation
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Overview ¶
Package shm implements System V shared memory functions (shmctl, shmget, shmat, shmdt).
Index ¶
- Constants
- func At(shmId int, shmAddr uintptr, shmFlg int) (data []byte, err error)
- func Ctl(shmId int, cmd int, buf *IdDs) (int, error)
- func Dt(data []byte) error
- func Get(key int, size int, shmFlg int) (shmId int, err error)
- func Rm(shmId int) error
- func Size(shmId int) (int64, error)
- type IdDs
- type Perm
Constants ¶
const ( // Create key if key does not exist. IPC_CREAT = 01000 // Fail if key exists. IPC_EXCL = 02000 // Return error on wait. IPC_NOWAIT = 04000 // Private key. IPC_PRIVATE = 0 // Attach read-only access. SHM_RDONLY = 010000 // Round attach address to SHMLBA. SHM_RND = 020000 // Take-over region on attach. SHM_REMAP = 040000 // Execution access. SHM_EXEC = 0100000 // Lock segment (root only). SHM_LOCK = 1 // Unlock segment (root only). SHM_UNLOCK = 12 // Remove identifier. IPC_RMID = 0 // Set `ipc_perm` options. IPC_SET = 1 // Get `ipc_perm' options. IPC_STAT = 2 )
Constants.
Variables ¶
This section is empty.
Functions ¶
func At ¶
At attaches the shared memory segment identified by shmId.
Using At() with shmAddr equal to NULL is the preferred, portable way of attaching a shared memory segment.
func Ctl ¶
Ctl performs the control operation specified by cmd on the shared memory segment whose identifier is given in shmId.
The buf argument is a pointer to a IdDs structure.
func Dt ¶
Dt detaches the shared memory segment.
The to-be-detached segment must be currently attached with shmAddr equal to the value returned by the attaching At() call.
func Get ¶
Get allocates a shared memory segment.
Get() returns the identifier of the shared memory segment associated with the value of the argument key. A new shared memory segment is created if key has the value IPC_PRIVATE or key isn't IPC_PRIVATE, no shared memory segment corresponding to key exists, and IPC_CREAT is specified in shmFlg.
If shmFlg specifies both IPC_CREAT and IPC_EXCL and a shared memory segment already exists for key, then Get() fails with errno set to EEXIST.
Types ¶
type IdDs ¶
type IdDs struct {
// Operation permission struct.
Perm Perm
// Size of segment in bytes.
SegSz uint64
// Last attach time.
Atime int64
// Last detach time.
Dtime int64
// Last change time.
Ctime int64
// Pid of creator.
Cpid int32
// Pid of last shmat/shmdt.
Lpid int32
// Number of current attaches.
Nattch uint64
// Reserved.
GlibcReserved4 uint64
// Reserved.
GlibcReserved5 uint64
}
IdDs describes shared memory segment.
type Perm ¶
type Perm struct {
// Key.
Key int32
// Owner's user ID.
Uid uint32
// Owner's group ID.
Gid uint32
// Creator's user ID.
Cuid uint32
// Creator's group ID.
Cgid uint32
// Read/write permission.
Mode uint16
// Padding.
Pad1 uint16
// Sequence number.
Seq uint16
// Padding.
Pad2 uint16
// Padding.
PadCgo0 [4]byte
// Reserved.
GlibcReserved1 uint64
// Reserved.
GlibcReserved2 uint64
}
Perm is used to pass permission information to IPC operations.
Source Files