Initial commit

.travis.yml

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+language: go
+
+go:
+  - master
+
+script:
+ - go test -v ./

AUTHORS

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+Milan Nikolic <gen2brain@gmail.com>

LICENSE

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+  Copyright (C) 2018 Milan Nikolic (gen2brain)
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.

README.md

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+## shm
+[![TravisCI Build Status](https://travis-ci.org/gen2brain/shm.svg?branch=master)](https://travis-ci.org/gen2brain/shm) 
+[![GoDoc](https://godoc.org/github.com/gen2brain/shm?status.svg)](https://godoc.org/github.com/gen2brain/shm) 
+[![Go Report Card](https://goreportcard.com/badge/github.com/gen2brain/shm?branch=master)](https://goreportcard.com/report/github.com/gen2brain/shm) 
+
+`shm` implements System V shared memory functions (`shmctl`, `shmget`, `shmat`, `shmdt`) in pure Go.
+
+### Installation
+
+    go get -u github.com/gen2brain/shm
+
+### More
+
+For System V Message Queue IPC (i.e. `msgctl`, `msgget`, `msgrcv`, `msgsnd`) see [ipc](https://github.com/siadat/ipc).

shm.go

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+// +build darwin dragonfly linux netbsd openbsd
+
+// Package shm implements System V shared memory functions (shmctl, shmget, shmat, shmdt).
+package shm
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const (
+	// Mode bits for `shmget`.
+
+	// Create key if key does not exist.
+	IPC_CREAT = 01000
+	// Fail if key exists.
+	IPC_EXCL = 02000
+	// Return error on wait.
+	IPC_NOWAIT = 04000
+
+	// Special key values.
+
+	// Private key.
+	IPC_PRIVATE = 0
+
+	// Flags for `shmat`.
+
+	// 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
+
+	// Commands for `shmctl`.
+
+	// Lock segment (root only).
+	SHM_LOCK = 1
+	// Unlock segment (root only).
+	SHM_UNLOCK = 12
+
+	// Control commands for `shmctl`.
+
+	// Remove identifier.
+	IPC_RMID = 0
+	// Set `ipc_perm` options.
+	IPC_SET = 1
+	// Get `ipc_perm' options.
+	IPC_STAT = 2
+)
+
+// 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.
+func Get(key int, size int, shmFlg int) (shmId int, err error) {
+	id, _, errno := syscall.Syscall(syscall.SYS_SHMGET, uintptr(int32(key)), uintptr(int32(size)), uintptr(int32(shmFlg)))
+	if int(id) == -1 {
+		return -1, errno
+	}
+
+	return int(id), nil
+}
+
+// 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 At(shmId int, shmAddr uintptr, shmFlg int) (data []byte, err error) {
+	addr, _, errno := syscall.Syscall(syscall.SYS_SHMAT, uintptr(int32(shmId)), shmAddr, uintptr(int32(shmFlg)))
+	if int(addr) == -1 {
+		return nil, errno
+	}
+
+	length, err := Size(shmId)
+	if err != nil {
+		return nil, err
+	}
+
+	var b = struct {
+		addr uintptr
+		len  int
+		cap  int
+	}{addr, length, length}
+
+	data = *(*[]byte)(unsafe.Pointer(&b))
+	return data, nil
+}
+
+// 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 Dt(data []byte) error {
+	result, _, errno := syscall.Syscall(syscall.SYS_SHMDT, uintptr(unsafe.Pointer(&data[0])), 0, 0)
+	if int(result) == -1 {
+		return errno
+	}
+
+	return nil
+}
+
+// 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 Ctl(shmId int, cmd int, buf *IdDs) (int, error) {
+	result, _, errno := syscall.Syscall(syscall.SYS_SHMCTL, uintptr(int32(shmId)), uintptr(int32(cmd)), uintptr(unsafe.Pointer(buf)))
+	if int(result) == -1 {
+		return -1, errno
+	}
+
+	return int(result), nil
+}
+
+// Rm removes the shared memory segment.
+func Rm(shmId int) error {
+	_, err := Ctl(shmId, IPC_RMID, nil)
+	return err
+}
+
+// Size returns size of shared memory segment.
+func Size(shmId int) (int, error) {
+	var idDs IdDs
+
+	_, err := Ctl(shmId, IPC_STAT, &idDs)
+	if err != nil {
+		return 0, err
+	}
+
+	return int(idDs.SegSz), nil
+}

shm_darwin.go

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+package shm
+
+// Perm is used to pass permission information to IPC operations.
+type Perm struct {
+	// 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
+	// Sequence number.
+	Seq uint16
+	// Key.
+	Key int32
+}
+
+// IdDs describes shared memory segment.
+type IdDs struct {
+	// Operation permission struct.
+	Perm Perm
+	// Size of segment in bytes.
+	SegSz uint64
+	// Pid of last shmat/shmdt.
+	Lpid int32
+	// Pid of creator.
+	Cpid int32
+	// Number of current attaches.
+	Nattch uint16
+	// Padding.
+	Pad_cgo_0 [2]byte
+	// Padding.
+	Pad_cgo_1 [8]byte
+	// Padding.
+	Pad_cgo_2 [8]byte
+	// Padding.
+	Pad_cgo_3 [8]byte
+	// Padding.
+	Pad_cgo_4 [8]byte
+}

shm_dragonfly.go

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+package shm

shm_linux_386.go

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+package shm
+
+// Perm is used to pass permission information to IPC operations.
+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.
+	X__pad1 uint16
+	// Sequence number.
+	X__seq uint16
+	// Padding.
+	X__pad2 uint16
+	// Reserved.
+	X__glibc_reserved1 uint32
+	// Reserved.
+	X__glibc_reserved2 uint32
+}
+
+// IdDs describes shared memory segment.
+type IdDs struct {
+	// Operation permission struct.
+	Perm Perm
+	// Size of segment in bytes.
+	SegSz uint32
+	// Last attach time.
+	Atime int32
+	// Reserved.
+	X__glibc_reserved1 uint32
+	// Last detach time.
+	Dtime int32
+	// Reserved.
+	X__glibc_reserved2 uint32
+	// Last change time.
+	Ctime int32
+	// Reserved.
+	X__glibc_reserved3 uint32
+	// Pid of creator.
+	Cpid int32
+	// Pid of last shmat/shmdt.
+	Lpid int32
+	// Number of current attaches.
+	Nattch uint32
+	// Reserved.
+	X__glibc_reserved4 uint32
+	// Reserved.
+	X__glibc_reserved5 uint32
+}

shm_linux_amd64.go

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+package shm
+
+// Perm is used to pass permission information to IPC operations.
+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.
+	X__pad1 uint16
+	// Sequence number.
+	Seq uint16
+	// Padding.
+	X__pad2 uint16
+	// Padding.
+	Pad_cgo_0 [4]byte
+	// Reserved.
+	X__glibc_reserved1 uint64
+	// Reserved.
+	X__glibc_reserved2 uint64
+}
+
+// IdDs describes shared memory segment.
+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.
+	X__glibc_reserved4 uint64
+	// Reserved.
+	X__glibc_reserved5 uint64
+}

shm_netbsd.go

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+package shm

shm_openbsd.go

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+package shm

shm_test.go

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+package shm
+
+import (
+	"testing"
+)
+
+func TestShm(t *testing.T) {
+	shmSize := 65536
+
+	shmId, err := Get(IPC_PRIVATE, shmSize, IPC_CREAT|0777)
+	if err != nil {
+		t.Errorf("Get: %v", err)
+	}
+
+	data, err := At(shmId, 0, 0)
+	if err != nil {
+		t.Errorf("At: %v", err)
+	}
+
+	size, err := Size(shmId)
+	if err != nil {
+		t.Errorf("Size: %v", err)
+	}
+
+	if size != shmSize {
+		t.Errorf("Wrong size got %d expected %d", size, shmSize)
+	}
+
+	err = Rm(shmId)
+	if err != nil {
+		t.Errorf("Rm: %v", err)
+	}
+
+	err = Dt(data)
+	if err != nil {
+		t.Errorf("Dt: %v", err)
+	}
+}