From b2ebca7a5e2db98276d1e26afbc93ad284355637 Mon Sep 17 00:00:00 2001
From: zhonghong <hzhong@mcorp.ae>
Date: Sat, 11 May 2024 18:30:27 +0800
Subject: [PATCH] B tree

---
 .gitignore |  1 +
 bTree.go   | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 go.mod     |  3 +++
 3 files changed, 75 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 bTree.go
 create mode 100644 go.mod

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..723ef36
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.idea
\ No newline at end of file
diff --git a/bTree.go b/bTree.go
new file mode 100644
index 0000000..3b8252b
--- /dev/null
+++ b/bTree.go
@@ -0,0 +1,71 @@
+package bluedb
+
+import "encoding/binary"
+
+// BNode
+// | type | nkeys |  pointers  |   offsets  | key-values
+// |  2B  |   2B  | nkeys * 8B | nkeys * 2B | ...
+// This is the format of the KV pair. Lengths followed by data.
+// | klen | vlen | key | val |
+// |  2B  |  2B  | ... | ... |
+type BNode struct {
+	data []byte
+}
+
+type BTree struct {
+	// 根节点指针
+	root uint64
+
+	// 获取BNode
+	get func(uint64) BNode
+	// 分配一个新页
+	new func(BNode) uint64
+	// 删除页
+	del func(BNode)
+}
+
+// 页配置
+const (
+	HEADER              = 4
+	BTREE_PAGE_SIZE     = 4096
+	BTREE_MAX_KEY_LEN   = 1000
+	BTREE_MAX_VALUE_LEN = 3000
+)
+
+func init() {
+	nodeMax := HEADER + 8 + 2 + 4 + BTREE_MAX_KEY_LEN + BTREE_MAX_VALUE_LEN
+	assert(nodeMax <= BTREE_PAGE_SIZE)
+}
+
+func assert(expression bool) {
+	if !expression {
+		panic("校验不通过")
+	}
+}
+
+// header
+func (node *BNode) dataType() uint16 {
+	return binary.LittleEndian.Uint16(node.data)
+}
+
+func (node *BNode) keyCount() uint16 {
+	return binary.LittleEndian.Uint16(node.data[2:4])
+}
+
+func (node *BNode) setHeader(dataType uint16, keyCount uint16) {
+	binary.LittleEndian.PutUint16(node.data[0:2], dataType)
+	binary.LittleEndian.PutUint16(node.data[2:4], keyCount)
+}
+
+// pointer
+func (node *BNode) getPointer(idNum uint16) uint64 {
+	assert(idNum < node.keyCount())
+	pos := HEADER + 8*idNum
+	return binary.LittleEndian.Uint64(node.data[pos:])
+}
+
+func (node *BNode) setPointer(idNum uint16, val uint64) {
+	assert(idNum < node.keyCount())
+	pos := HEADER + 8*idNum
+	binary.LittleEndian.PutUint64(node.data[pos:], val)
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..197e3e1
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module bluedb
+
+go 1.19