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remove.go
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remove.go
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package mkvs
import (
"context"
"fmt"
"github.com/oasisprotocol/oasis-core/go/storage/mkvs/node"
)
// Implements Tree.
func (t *tree) RemoveExisting(ctx context.Context, key []byte) ([]byte, error) {
t.cache.Lock()
defer t.cache.Unlock()
if t.cache.isClosed() {
return nil, ErrClosed
}
// If the key has already been removed locally, don't try to remove it again.
var entry *pendingEntry
if !t.withoutWriteLog {
if entry = t.pendingWriteLog[node.ToMapKey(key)]; entry != nil && entry.value == nil {
return nil, nil
}
}
// Remember where the path from root to target node ends (will end).
t.cache.markPosition()
newRoot, changed, existing, err := t.doRemove(ctx, t.cache.pendingRoot, 0, key)
if err != nil {
return nil, err
}
// Update the pending write log.
if !t.withoutWriteLog {
if entry == nil {
t.pendingWriteLog[node.ToMapKey(key)] = &pendingEntry{key, nil, changed, nil}
} else {
entry.value = nil
}
}
t.cache.setPendingRoot(newRoot)
return existing, nil
}
// Implements Tree.
func (t *tree) Remove(ctx context.Context, key []byte) error {
_, err := t.RemoveExisting(ctx, key)
return err
}
func (t *tree) doRemove(
ctx context.Context,
ptr *node.Pointer,
bitDepth node.Depth,
key node.Key,
) (*node.Pointer, bool, []byte, error) {
if ctx.Err() != nil {
return nil, false, nil, ctx.Err()
}
// Dereference the node, possibly making a remote request.
nd, err := t.cache.derefNodePtr(ctx, ptr, t.newFetcherSyncGet(key, true))
if err != nil {
return nil, false, nil, err
}
switch n := nd.(type) {
case nil:
// Remove from nil node.
return nil, false, nil, nil
case *node.InternalNode:
// Remove from internal node and recursively collapse the branch, if
// needed.
bitLength := bitDepth + n.LabelBitLength
var changed bool
var existing []byte
if key.BitLength() < bitLength {
// Lookup key is too short for the current n.Label, so it doesn't exist.
return ptr, false, nil, nil
} else if key.BitLength() == bitLength {
n.LeafNode, changed, existing, err = t.doRemove(ctx, n.LeafNode, bitLength, key)
} else if key.GetBit(bitLength) {
n.Right, changed, existing, err = t.doRemove(ctx, n.Right, bitLength, key)
} else {
n.Left, changed, existing, err = t.doRemove(ctx, n.Left, bitLength, key)
}
if err != nil {
return nil, false, existing, err
}
// Fetch and check the remaining children.
var remainingLeaf node.Node
if n.LeafNode != nil {
// NOTE: The leaf node is always included with the internal node.
remainingLeaf = n.LeafNode.Node
}
remainingLeft, err := t.cache.derefNodePtr(ctx, n.Left, t.newFetcherSyncGet(key, true))
if err != nil {
return nil, false, nil, err
}
remainingRight, err := t.cache.derefNodePtr(ctx, n.Right, t.newFetcherSyncGet(key, true))
if err != nil {
return nil, false, nil, err
}
// If exactly one child including LeafNode remains, collapse it.
if remainingLeaf != nil && remainingLeft == nil && remainingRight == nil {
ndLeaf := n.LeafNode
n.LeafNode = nil
t.pendingRemovedNodes = append(t.pendingRemovedNodes, n)
t.cache.removeNode(ptr)
return ndLeaf, true, existing, nil
} else if remainingLeaf == nil && (remainingLeft == nil || remainingRight == nil) {
var nodePtr *node.Pointer
var ndChild node.Node
if remainingLeft != nil {
nodePtr = n.Left
n.Left = nil
ndChild = remainingLeft
} else {
nodePtr = n.Right
n.Right = nil
ndChild = remainingRight
}
// If child is an internal node, also fix the label.
switch inode := ndChild.(type) {
case *node.InternalNode:
inode.Label = n.Label.Merge(n.LabelBitLength, inode.Label, inode.LabelBitLength)
inode.LabelBitLength += n.LabelBitLength
if inode.Clean {
// Node was clean so old node is eligible for removal.
t.pendingRemovedNodes = append(t.pendingRemovedNodes, inode.ExtractUnchecked())
}
inode.Clean = false
nodePtr.Clean = false
// No longer eligible for eviction as it is dirty.
t.cache.rollbackNode(nodePtr)
}
t.pendingRemovedNodes = append(t.pendingRemovedNodes, n)
t.cache.removeNode(ptr)
return nodePtr, true, existing, nil
}
// Two or more children including LeafNode remain, just mark dirty bit.
if changed {
if n.Clean {
// Node was clean so old node is eligible for removal.
t.pendingRemovedNodes = append(t.pendingRemovedNodes, n.ExtractUnchecked())
}
n.Clean = false
ptr.Clean = false
// No longer eligible for eviction as it is dirty.
t.cache.rollbackNode(ptr)
}
return ptr, changed, existing, nil
case *node.LeafNode:
// Remove from leaf node.
if n.Key.Equal(key) {
t.pendingRemovedNodes = append(t.pendingRemovedNodes, n)
t.cache.removeNode(ptr)
return nil, true, n.Value, nil
}
return ptr, false, nil, nil
default:
panic(fmt.Sprintf("mkvs: unknown node type: %+v", n))
}
}