forked from bnclabs/gobtree
/
cow.go
62 lines (55 loc) · 2.14 KB
/
cow.go
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// Copyright (c) 2013 Couchbase, Inc.
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
// except in compliance with the License. You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software distributed under the
// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
// either express or implied. See the License for the specific language governing permissions
// and limitations under the License.
package btree
// Create a new copy of node by assigning a free file-position to it.
func (ln *lnode) copyOnWrite(store *Store) Node {
newkn := (&lnode{}).newNode(store)
newkn.ks = newkn.ks[:len(ln.ks)]
copy(newkn.ks, ln.ks)
newkn.ds = newkn.ds[:len(ln.ds)]
copy(newkn.ds, ln.ds)
newkn.vs = newkn.vs[:len(ln.vs)]
copy(newkn.vs, ln.vs)
newkn.size = len(ln.ks)
return newkn
}
// Refer above.
func (in *inode) copyOnWrite(store *Store) Node {
newin := (&inode{}).newNode(store)
newin.ks = newin.ks[:len(in.ks)]
copy(newin.ks, in.ks)
newin.ds = newin.ds[:len(in.ds)]
copy(newin.ds, in.ds)
newin.vs = newin.vs[:len(in.vs)]
copy(newin.vs, in.vs)
newin.size = len(in.ks)
return newin
}
// Create a new instance of `lnode`, an in-memory representation of btree leaf
// block.
// * `keys` slice must be half sized and zero valued, capacity of keys slice
// must be 1 larger to accomodate overflow-detection.
// * `values` slice must be half+1 sized and zero valued, capacity of value
// slice must be 1 larger to accomodate overflow-detection.
func (ln *lnode) newNode(store *Store) *lnode {
fpos := store.WStore.freelist.pop()
max := store.maxKeys() // always even
b := (&block{leaf: TRUE}).newBlock(max/2, max)
newkn := &lnode{block: *b, fpos: fpos, dirty: true}
return newkn
}
// Refer to the notes above.
func (in *inode) newNode(store *Store) *inode {
fpos := store.WStore.freelist.pop()
max := store.maxKeys() // always even
b := (&block{leaf: FALSE}).newBlock(max/2, max)
kn := lnode{block: *b, fpos: fpos, dirty: true}
newin := &inode{lnode: kn}
return newin
}