tidb texttree 代码
文件路径：/util/texttree/texttree.go
/ Copyright 2019 PingCAP, 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 texttree
const (
/ TreeBody indicates the current operator sub-tree is not finished, still
/ has child operators to be attached on.
TreeBody = '│'
/ TreeMiddleNode indicates this operator is not the last child of the
/ current sub-tree rooted by its parent.
TreeMiddleNode = '├'
/ TreeLastNode indicates this operator is the last child of the current
/ sub-tree rooted by its parent.
TreeLastNode = '└'
/ TreeGap is used to represent the gap between the branches of the tree.
TreeGap = ' '
/ TreeNodeIdentifier is used to replace the treeGap once we need to attach
/ a node to a sub-tree.
TreeNodeIdentifier = '─'
)
/ Indent4Child appends more blank to the `indent` string
func Indent4Child(indent string, isLastChild bool) string {
if !isLastChild {
return string(append([]rune(indent), TreeBody, TreeGap))
}
/ If the current node is the last node of the current operator tree, we
/ need to end this sub-tree by changing the closest treeBody to a treeGap.
indentBytes := []rune(indent)
for i := len(indentBytes) - 1; i >= 0; i-- {
if indentBytes[i] == TreeBody {
indentBytes[i] = TreeGap
break
}
}
return string(append(indentBytes, TreeBody, TreeGap))
}
/ PrettyIdentifier returns a pretty identifier which contains indent and tree node hierarchy indicator
func PrettyIdentifier(id, indent string, isLastChild bool) string {
if len(indent) == 0 {
return id
}
indentBytes := []rune(indent)
for i := len(indentBytes) - 1; i >= 0; i-- {
if indentBytes[i] != TreeBody {
continue
}
/ Here we attach a new node to the current sub-tree by changing
/ the closest treeBody to a:
/ 1. treeLastNode, if this operator is the last child.
/ 2. treeMiddleNode, if this operator is not the last child..
if isLastChild {
indentBytes[i] = TreeLastNode
} else {
indentBytes[i] = TreeMiddleNode
}
break
}
/ Replace the treeGap between the treeBody and the node to a
/ treeNodeIdentifier.
indentBytes[len(indentBytes)-1] = TreeNodeIdentifier
return string(indentBytes) + id
}