1 files changed, 60 insertions, 0 deletions
diff --git a/branch.go b/branch.go
new file mode 100644
index 0000000..77cc1ca
--- /dev/null
+++ b/branch.go
@@ -0,0 +1,60 @@
+package bolt
+
+import (
+	"bytes"
+	"sort"
+	"unsafe"
+)
+
+// branch represents a temporary in-memory branch page.
+type branch struct {
+	parent *branch
+	items branchItems
+}
+
+// insert inserts a new item after a given pgid.
+func (b *branch) insert(key []byte, previd pgid, id pgid) {
+	// Find previous insertion index.
+	index := sort.Search(len(b.items), func(i int) bool { return b.items[i].pgid >= previd })
+
+	// If there is no existing key then add a new item.
+	b.items = append(b.items, branchItem{})
+	if index < len(b.items) {
+		copy(b.items[index+1:], b.items[index:])
+	}
+
+	b.items[index].pgid = id
+	b.items[index].key = key
+}
+
+// replace swaps out an existing node id for a new one id.
+func (b *branch) replace(oldid pgid, newid pgid, key []byte) {
+	index := sort.Search(len(b.items), func(i int) bool { return b.items[i].pgid >= oldid })
+	b.items[index].pgid = newid
+	b.items[index].key = key
+}
+
+// read initializes the item data from an on-disk page.
+func (b *branch) read(page *page) {
+	ncount := int(page.count)
+	b.items = make(branchItems, ncount)
+	bnodes := (*[maxNodesPerPage]bnode)(unsafe.Pointer(&page.ptr))
+	for i := 0; i < ncount; i++ {
+		bnode := &bnodes[i]
+		item := &b.items[i]
+		item.key = bnode.key()
+	}
+}
+
+
+type branchItems []branchItem
+
+type branchItem struct {
+	pgid pgid
+	key   []byte
+}
+
+func (s branchItems) Len() int           { return len(s) }
+func (s branchItems) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+func (s branchItems) Less(i, j int) bool { return bytes.Compare(s[i].key, s[j].key) == -1 }
+