Refactor locks package to build on non-Linux

Move SHM specific code into a subpackage. Within the main locks
package, move the manager to be linux-only and add a non-Linux
unsupported build file.

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

libpod/lock/shm/shm_lock.go

@@ -1,4 +1,4 @@
-package lock
+package shm
 
 // #cgo LDFLAGS: -lrt -lpthread
 // #include "shm_lock.h"
@@ -72,6 +72,11 @@ func OpenSHMLock(numLocks uint32) (*SHMLocks, error) {
 	return locks, nil
 }
 
+// GetMaxLocks returns the maximum number of locks in the SHM
+func (locks *SHMLocks) GetMaxLocks() uint32 {
+	return locks.maxLocks
+}
+
 // Close closes an existing shared-memory segment.
 // The segment will be rendered unusable after closing.
 // WARNING: If you Close() while there are still locks locked, these locks may

libpod/lock/shm/shm_lock_test.go

@@ -1,4 +1,4 @@
-package lock
+package shm
 
 import (
 	"fmt"

libpod/lock/shm_lock_manager_linux.go

@@ -1,3 +1,5 @@
+// +build linux
+
 package lock
 
 import (
@@ -7,16 +9,17 @@ import (
 	"syscall"
 
 	"github.com/pkg/errors"
+	"github.com/projectatomic/libpod/libpod/lock/shm"
 )
 
 // SHMLockManager manages shared memory locks.
 type SHMLockManager struct {
-	locks *SHMLocks
+	locks *shm.SHMLocks
 }
 
 // NewSHMLockManager makes a new SHMLockManager with the given number of locks.
 func NewSHMLockManager(numLocks uint32) (Manager, error) {
-	locks, err := CreateSHMLock(numLocks)
+	locks, err := shm.CreateSHMLock(numLocks)
 	if err != nil {
 		return nil, err
 	}
@@ -29,8 +32,8 @@ func NewSHMLockManager(numLocks uint32) (Manager, error) {
 
 // OpenSHMLockManager opens an existing SHMLockManager with the given number of
 // locks.
-func OpenSHMLockManager(numLocks uint32) (LockManager, error) {
-	locks, err := OpenSHMLock(numLocks)
+func OpenSHMLockManager(numLocks uint32) (Manager, error) {
+	locks, err := shm.OpenSHMLock(numLocks)
 	if err != nil {
 		return nil, err
 	}
@@ -59,20 +62,20 @@ func (m *SHMLockManager) AllocateLock() (Locker, error) {
 func (m *SHMLockManager) RetrieveLock(id string) (Locker, error) {
 	intID, err := strconv.ParseInt(id, 16, 64)
 	if err != nil {
-		return errors.Wrapf(err, "given ID %q is not a valid SHMLockManager ID - cannot be parsed as int", id)
+		return nil, errors.Wrapf(err, "given ID %q is not a valid SHMLockManager ID - cannot be parsed as int", id)
 	}
 
 	if intID < 0 {
-		return errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - must be positive", id)
+		return nil, errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - must be positive", id)
 	}
 
 	if intID > math.MaxUint32 {
-		return errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - too large", id)
+		return nil, errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - too large", id)
 	}
 
 	var u32ID uint32 = uint32(intID)
-	if u32ID >= m.locks.maxLocks {
-		return errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - too large to fit", id)
+	if u32ID >= m.locks.GetMaxLocks() {
+		return nil, errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - too large to fit", id)
 	}
 
 	lock := new(SHMLock)

libpod/lock/shm_lock_manager_unsupported.go

@@ -0,0 +1,29 @@
+// +build !linux
+
+package lock
+
+import "fmt"
+
+// SHMLockManager is a shared memory lock manager.
+// It is not supported on non-Unix platforms.
+type SHMLockManager struct{}
+
+// NewSHMLockManager is not supported on this platform
+func NewSHMLockManager(numLocks uint32) (Manager, error) {
+	return nil, fmt.Errorf("not supported")
+}
+
+// OpenSHMLockManager is not supported on this platform
+func OpenSHMLockManager(numLocks uint32) (Manager, error) {
+	return nil, fmt.Errorf("not supported")
+}
+
+// AllocateLock is not supported on this platform
+func (m *SHMLockManager) AllocateLock() (Locker, error) {
+	return nil, fmt.Errorf("not supported")
+}
+
+// RetrieveLock is not supported on this platform
+func (m *SHMLockManager) RetrieveLock(id string) (Locker, error) {
+	return nil, fmt.Errorf("not supported")
+}