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decode.go
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decode.go
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// Copyright ©2017 The gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package dot
import (
"fmt"
"gonum.org/v1/gonum/graph"
"gonum.org/v1/gonum/graph/formats/dot"
"gonum.org/v1/gonum/graph/formats/dot/ast"
"gonum.org/v1/gonum/graph/internal/set"
)
// Builder is a graph that can have user-defined nodes and edges added.
type Builder interface {
graph.Graph
graph.Builder
// NewNode adds a new node with a unique node ID to the graph.
NewNode() graph.Node
// NewEdge adds a new edge from the source to the destination node to the
// graph, or returns the existing edge if already present.
NewEdge(from, to graph.Node) graph.Edge
}
// UnmashalerAttrs is implemented by graph values that can unmarshal global
// DOT attributes.
type UnmarshalerAttrs interface {
// DOTUnmarshalerAttrs returns the global attribute unmarshalers.
DOTUnmarshalerAttrs() (graph, node, edge UnmarshalerAttr)
}
// UnmarshalerAttr is implemented by types that can unmarshal a DOT
// attribute description of themselves.
type UnmarshalerAttr interface {
// UnmarshalDOTAttr decodes a single DOT attribute.
UnmarshalDOTAttr(attr Attribute) error
}
// UnmarshalerID is implemented by types that can unmarshal a DOT ID.
type UnmarshalerID interface {
// UnmarshalDOTID decodes a single DOT ID.
UnmarshalDOTID(id string)
}
// Unmarshal parses the Graphviz DOT-encoded data and stores the result in dst.
func Unmarshal(data []byte, dst Builder) error {
file, err := dot.ParseBytes(data)
if err != nil {
return err
}
if len(file.Graphs) != 1 {
return fmt.Errorf("invalid number of graphs; expected 1, got %d", len(file.Graphs))
}
return copyGraph(dst, file.Graphs[0])
}
// copyGraph copies the nodes and edges from the Graphviz AST source graph to
// the destination graph. Edge direction is maintained if present.
func copyGraph(dst Builder, src *ast.Graph) (err error) {
defer func() {
switch e := recover().(type) {
case nil:
case error:
err = e
default:
panic(e)
}
}()
gen := &generator{
directed: src.Directed,
ids: make(map[string]graph.Node),
}
if a, ok := dst.(UnmarshalerAttrs); ok {
gen.graphAttr, gen.nodeAttr, gen.edgeAttr = a.DOTUnmarshalerAttrs()
}
for _, stmt := range src.Stmts {
gen.addStmt(dst, stmt)
}
return err
}
// A generator keeps track of the information required for generating a gonum
// graph from a dot AST graph.
type generator struct {
// Directed graph.
directed bool
// Map from dot AST node ID to gonum node.
ids map[string]graph.Node
// Nodes processed within the context of a subgraph, that is to be used as a
// vertex of an edge.
subNodes []graph.Node
// Stack of start indices into the subgraph node slice. The top element
// corresponds to the start index of the active (or inner-most) subgraph.
subStart []int
// graphAttr, nodeAttr and edgeAttr are global graph attributes.
graphAttr, nodeAttr, edgeAttr UnmarshalerAttr
}
// node returns the gonum node corresponding to the given dot AST node ID,
// generating a new such node if none exist.
func (gen *generator) node(dst Builder, id string) graph.Node {
if n, ok := gen.ids[id]; ok {
return n
}
n := dst.NewNode()
if n, ok := n.(UnmarshalerID); ok {
n.UnmarshalDOTID(id)
}
gen.ids[id] = n
// Check if within the context of a subgraph, that is to be used as a vertex
// of an edge.
if gen.isInSubgraph() {
// Append node processed within the context of a subgraph, that is to be
// used as a vertex of an edge
gen.appendSubgraphNode(n)
}
return n
}
// addStmt adds the given statement to the graph.
func (gen *generator) addStmt(dst Builder, stmt ast.Stmt) {
switch stmt := stmt.(type) {
case *ast.NodeStmt:
n, ok := gen.node(dst, stmt.Node.ID).(UnmarshalerAttr)
if !ok {
return
}
for _, attr := range stmt.Attrs {
a := Attribute{
Key: attr.Key,
Value: attr.Val,
}
if err := n.UnmarshalDOTAttr(a); err != nil {
panic(fmt.Errorf("unable to unmarshal node DOT attribute (%s=%s)", a.Key, a.Value))
}
}
case *ast.EdgeStmt:
gen.addEdgeStmt(dst, stmt)
case *ast.AttrStmt:
var n UnmarshalerAttr
var dst string
switch stmt.Kind {
case ast.KindGraph:
if gen.graphAttr == nil {
return
}
n = gen.graphAttr
dst = "graph"
case ast.KindNode:
if gen.nodeAttr == nil {
return
}
n = gen.nodeAttr
dst = "node"
case ast.KindEdge:
if gen.edgeAttr == nil {
return
}
n = gen.edgeAttr
dst = "edge"
default:
panic("unreachable")
}
for _, attr := range stmt.Attrs {
a := Attribute{
Key: attr.Key,
Value: attr.Val,
}
if err := n.UnmarshalDOTAttr(a); err != nil {
panic(fmt.Errorf("unable to unmarshal global %s DOT attribute (%s=%s)", dst, a.Key, a.Value))
}
}
case *ast.Attr:
// ignore.
case *ast.Subgraph:
for _, stmt := range stmt.Stmts {
gen.addStmt(dst, stmt)
}
default:
panic(fmt.Sprintf("unknown statement type %T", stmt))
}
}
// addEdgeStmt adds the given edge statement to the graph.
func (gen *generator) addEdgeStmt(dst Builder, e *ast.EdgeStmt) {
fs := gen.addVertex(dst, e.From)
ts := gen.addEdge(dst, e.To)
for _, f := range fs {
for _, t := range ts {
edge, ok := dst.NewEdge(f, t).(UnmarshalerAttr)
if !ok {
continue
}
for _, attr := range e.Attrs {
a := Attribute{
Key: attr.Key,
Value: attr.Val,
}
if err := edge.UnmarshalDOTAttr(a); err != nil {
panic(fmt.Errorf("unable to unmarshal edge DOT attribute (%s=%s)", a.Key, a.Value))
}
}
}
}
}
// addVertex adds the given vertex to the graph, and returns its set of nodes.
func (gen *generator) addVertex(dst Builder, v ast.Vertex) []graph.Node {
switch v := v.(type) {
case *ast.Node:
n := gen.node(dst, v.ID)
return []graph.Node{n}
case *ast.Subgraph:
gen.pushSubgraph()
for _, stmt := range v.Stmts {
gen.addStmt(dst, stmt)
}
return gen.popSubgraph()
default:
panic(fmt.Sprintf("unknown vertex type %T", v))
}
}
// addEdge adds the given edge to the graph, and returns its set of nodes.
func (gen *generator) addEdge(dst Builder, to *ast.Edge) []graph.Node {
if !gen.directed && to.Directed {
panic(fmt.Errorf("directed edge to %v in undirected graph", to.Vertex))
}
fs := gen.addVertex(dst, to.Vertex)
if to.To != nil {
ts := gen.addEdge(dst, to.To)
for _, f := range fs {
for _, t := range ts {
dst.NewEdge(f, t)
}
}
}
return fs
}
// pushSubgraph pushes the node start index of the active subgraph onto the
// stack.
func (gen *generator) pushSubgraph() {
gen.subStart = append(gen.subStart, len(gen.subNodes))
}
// popSubgraph pops the node start index of the active subgraph from the stack,
// and returns the nodes processed since.
func (gen *generator) popSubgraph() []graph.Node {
// Get nodes processed since the subgraph became active.
start := gen.subStart[len(gen.subStart)-1]
// TODO: Figure out a better way to store subgraph nodes, so that duplicates
// may not occur.
nodes := unique(gen.subNodes[start:])
// Remove subgraph from stack.
gen.subStart = gen.subStart[:len(gen.subStart)-1]
if len(gen.subStart) == 0 {
// Remove subgraph nodes when the bottom-most subgraph has been processed.
gen.subNodes = gen.subNodes[:0]
}
return nodes
}
// unique returns the set of unique nodes contained within ns.
func unique(ns []graph.Node) []graph.Node {
var nodes []graph.Node
seen := make(set.Ints)
for _, n := range ns {
id := n.ID()
if seen.Has(id) {
// skip duplicate node
continue
}
seen.Add(id)
nodes = append(nodes, n)
}
return nodes
}
// isInSubgraph reports whether the active context is within a subgraph, that is
// to be used as a vertex of an edge.
func (gen *generator) isInSubgraph() bool {
return len(gen.subStart) > 0
}
// appendSubgraphNode appends the given node to the slice of nodes processed
// within the context of a subgraph.
func (gen *generator) appendSubgraphNode(n graph.Node) {
gen.subNodes = append(gen.subNodes, n)
}