Check for multiple pinned blocks in a single pass.

Provide a new method, Pinner.CheckIfPinned(), which will check if
any of the arguments are pinned.  Previously IsPinned would need to be
called once for each block.  The new method will speed up the checking
of multiple pinned blocks from O(p*n) to O(p) (where p is the number
of pinned blocks and n is the number of blocks to be check)

Use the new method in "block rm".

License: MIT
Signed-off-by: Kevin Atkinson <k@kevina.org>

pin.go

@@ -75,6 +75,10 @@ type Pinner interface {
 	Pin(context.Context, *mdag.Node, bool) error
 	Unpin(context.Context, key.Key, bool) error
 
+	// Check if a set of keys are pinned, more efficient than
+	// calling IsPinned for each key
+	CheckIfPinned(keys ...key.Key) ([]Pinned, error)
+
 	// PinWithMode is for manually editing the pin structure. Use with
 	// care! If used improperly, garbage collection may not be
 	// successful.
@@ -90,6 +94,12 @@ type Pinner interface {
 	InternalPins() []key.Key
 }
 
+type Pinned struct {
+	Key  key.Key
+	Mode PinMode
+	Via  key.Key
+}
+
 // pinner implements the Pinner interface
 type pinner struct {
 	lock       sync.RWMutex
@@ -255,6 +265,70 @@ func (p *pinner) isPinnedWithType(k key.Key, mode PinMode) (string, bool, error)
 	return "", false, nil
 }
 
+func (p *pinner) CheckIfPinned(keys ...key.Key) ([]Pinned, error) {
+	p.lock.RLock()
+	defer p.lock.RUnlock()
+	pinned := make([]Pinned, 0, len(keys))
+	toCheck := make(map[key.Key]struct{})
+
+	// First check for non-Indirect pins directly
+	for _, k := range keys {
+		if p.recursePin.HasKey(k) {
+			pinned = append(pinned, Pinned{Key: k, Mode: Recursive})
+		} else if p.directPin.HasKey(k) {
+			pinned = append(pinned, Pinned{Key: k, Mode: Direct})
+		} else if p.isInternalPin(k) {
+			pinned = append(pinned, Pinned{Key: k, Mode: Internal})
+		} else {
+			toCheck[k] = struct{}{}
+		}
+	}
+
+	// Now walk all recursive pins to check for indirect pins
+	var checkChildren func(key.Key, key.Key) error
+	checkChildren = func(rk key.Key, parentKey key.Key) error {
+		parent, err := p.dserv.Get(context.Background(), parentKey)
+		if err != nil {
+			return err
+		}
+		for _, lnk := range parent.Links {
+			k := key.Key(lnk.Hash)
+
+			if _, found := toCheck[k]; found {
+				pinned = append(pinned,
+					Pinned{Key: k, Mode: Indirect, Via: rk})
+				delete(toCheck, k)
+			}
+
+			err := checkChildren(rk, k)
+			if err != nil {
+				return err
+			}
+
+			if len(toCheck) == 0 {
+				return nil
+			}
+		}
+		return nil
+	}
+	for _, rk := range p.recursePin.GetKeys() {
+		err := checkChildren(rk, rk)
+		if err != nil {
+			return nil, err
+		}
+		if len(toCheck) == 0 {
+			break
+		}
+	}
+
+	// Anything left in toCheck is not pinned
+	for k, _ := range toCheck {
+		pinned = append(pinned, Pinned{Key: k, Mode: NotPinned})
+	}
+
+	return pinned, nil
+}
+
 func (p *pinner) RemovePinWithMode(key key.Key, mode PinMode) {
 	p.lock.Lock()
 	defer p.lock.Unlock()