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// Copyright 2019 The Go 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 main // import "golang.org/x/tools/cmd/digraph"
// TODO(adonovan):
// - support input files other than stdin
// - support alternative formats (AT&T GraphViz, CSV, etc),
// a comment syntax, etc.
// - allow queries to nest, like Blaze query language.
import (
"bufio"
"bytes"
_ "embed"
"errors"
"flag"
"fmt"
"io"
"os"
"sort"
"strconv"
"strings"
"unicode"
"unicode/utf8"
)
func usage() {
// Extract the content of the /* ... */ comment in doc.go.
_, after, _ := strings.Cut(doc, "/*")
doc, _, _ := strings.Cut(after, "*/")
io.WriteString(flag.CommandLine.Output(), doc)
flag.PrintDefaults()
os.Exit(2)
}
//go:embed doc.go
var doc string
func main() {
flag.Usage = usage
flag.Parse()
args := flag.Args()
if len(args) == 0 {
usage()
}
if err := digraph(args[0], args[1:]); err != nil {
fmt.Fprintf(os.Stderr, "digraph: %s\n", err)
os.Exit(1)
}
}
type nodelist []string
func (l nodelist) println(sep string) {
for i, node := range l {
if i > 0 {
fmt.Fprint(stdout, sep)
}
fmt.Fprint(stdout, node)
}
fmt.Fprintln(stdout)
}
type nodeset map[string]bool
func (s nodeset) sort() nodelist {
nodes := make(nodelist, len(s))
var i int
for node := range s {
nodes[i] = node
i++
}
sort.Strings(nodes)
return nodes
}
func (s nodeset) addAll(x nodeset) {
for node := range x {
s[node] = true
}
}
// A graph maps nodes to the non-nil set of their immediate successors.
type graph map[string]nodeset
func (g graph) addNode(node string) nodeset {
edges := g[node]
if edges == nil {
edges = make(nodeset)
g[node] = edges
}
return edges
}
func (g graph) addEdges(from string, to ...string) {
edges := g.addNode(from)
for _, to := range to {
g.addNode(to)
edges[to] = true
}
}
func (g graph) nodelist() nodelist {
nodes := make(nodeset)
for node := range g {
nodes[node] = true
}
return nodes.sort()
}
func (g graph) reachableFrom(roots nodeset) nodeset {
seen := make(nodeset)
var visit func(node string)
visit = func(node string) {
if !seen[node] {
seen[node] = true
for e := range g[node] {
visit(e)
}
}
}
for root := range roots {
visit(root)
}
return seen
}
func (g graph) transpose() graph {
rev := make(graph)
for node, edges := range g {
rev.addNode(node)
for succ := range edges {
rev.addEdges(succ, node)
}
}
return rev
}
func (g graph) sccs() []nodeset {
// Kosaraju's algorithm---Tarjan is overkill here.
// Forward pass.
S := make(nodelist, 0, len(g)) // postorder stack
seen := make(nodeset)
var visit func(node string)
visit = func(node string) {
if !seen[node] {
seen[node] = true
for e := range g[node] {
visit(e)
}
S = append(S, node)
}
}
for node := range g {
visit(node)
}
// Reverse pass.
rev := g.transpose()
var scc nodeset
seen = make(nodeset)
var rvisit func(node string)
rvisit = func(node string) {
if !seen[node] {
seen[node] = true
scc[node] = true
for e := range rev[node] {
rvisit(e)
}
}
}
var sccs []nodeset
for len(S) > 0 {
top := S[len(S)-1]
S = S[:len(S)-1] // pop
if !seen[top] {
scc = make(nodeset)
rvisit(top)
if len(scc) == 1 && !g[top][top] {
continue
}
sccs = append(sccs, scc)
}
}
return sccs
}
func (g graph) allpaths(from, to string) error {
// Mark all nodes to "to".
seen := make(nodeset) // value of seen[x] indicates whether x is on some path to "to"
var visit func(node string) bool
visit = func(node string) bool {
reachesTo, ok := seen[node]
if !ok {
reachesTo = node == to
seen[node] = reachesTo
for e := range g[node] {
if visit(e) {
reachesTo = true
}
}
if reachesTo && node != to {
seen[node] = true
}
}
return reachesTo
}
visit(from)
// For each marked node, collect its marked successors.
var edges []string
for n := range seen {
for succ := range g[n] {
if seen[succ] {
edges = append(edges, n+" "+succ)
}
}
}
// Sort (so that this method is deterministic) and print edges.
sort.Strings(edges)
for _, e := range edges {
fmt.Fprintln(stdout, e)
}
return nil
}
func (g graph) somepath(from, to string) error {
// Search breadth-first so that we return a minimal path.
// A path is a linked list whose head is a candidate "to" node
// and whose tail is the path ending in the "from" node.
type path struct {
node string
tail *path
}
seen := nodeset{from: true}
var queue []*path
queue = append(queue, &path{node: from, tail: nil})
for len(queue) > 0 {
p := queue[0]
queue = queue[1:]
if p.node == to {
// Found a path. Print, tail first.
var print func(p *path)
print = func(p *path) {
if p.tail != nil {
print(p.tail)
fmt.Fprintln(stdout, p.tail.node+" "+p.node)
}
}
print(p)
return nil
}
for succ := range g[p.node] {
if !seen[succ] {
seen[succ] = true
queue = append(queue, &path{node: succ, tail: p})
}
}
}
return fmt.Errorf("no path from %q to %q", from, to)
}
func (g graph) toDot(w *bytes.Buffer) {
fmt.Fprintln(w, "digraph {")
for _, src := range g.nodelist() {
for _, dst := range g[src].sort() {
// Dot's quoting rules appear to align with Go's for escString,
// which is the syntax of node IDs. Labels require significantly
// more quoting, but that appears not to be necessary if the node ID
// is implicitly used as the label.
fmt.Fprintf(w, "\t%q -> %q;\n", src, dst)
}
}
fmt.Fprintln(w, "}")
}
func parse(rd io.Reader) (graph, error) {
g := make(graph)
var linenum int
// We avoid bufio.Scanner as it imposes a (configurable) limit
// on line length, whereas Reader.ReadString does not.
in := bufio.NewReader(rd)
for {
linenum++
line, err := in.ReadString('\n')
eof := false
if err == io.EOF {
eof = true
} else if err != nil {
return nil, err
}
// Split into words, honoring double-quotes per Go spec.
words, err := split(line)
if err != nil {
return nil, fmt.Errorf("at line %d: %v", linenum, err)
}
if len(words) > 0 {
g.addEdges(words[0], words[1:]...)
}
if eof {
break
}
}
return g, nil
}
// Overridable for redirection.
var stdin io.Reader = os.Stdin
var stdout io.Writer = os.Stdout
func digraph(cmd string, args []string) error {
// Parse the input graph.
g, err := parse(stdin)
if err != nil {
return err
}
// Parse the command line.
switch cmd {
case "nodes":
if len(args) != 0 {
return fmt.Errorf("usage: digraph nodes")
}
g.nodelist().println("\n")
case "degree":
if len(args) != 0 {
return fmt.Errorf("usage: digraph degree")
}
nodes := make(nodeset)
for node := range g {
nodes[node] = true
}
rev := g.transpose()
for _, node := range nodes.sort() {
fmt.Fprintf(stdout, "%d\t%d\t%s\n", len(rev[node]), len(g[node]), node)
}
case "transpose":
if len(args) != 0 {
return fmt.Errorf("usage: digraph transpose")
}
var revEdges []string
for node, succs := range g.transpose() {
for succ := range succs {
revEdges = append(revEdges, fmt.Sprintf("%s %s", node, succ))
}
}
sort.Strings(revEdges) // make output deterministic
for _, e := range revEdges {
fmt.Fprintln(stdout, e)
}
case "succs", "preds":
if len(args) == 0 {
return fmt.Errorf("usage: digraph %s <node> ... ", cmd)
}
g := g
if cmd == "preds" {
g = g.transpose()
}
result := make(nodeset)
for _, root := range args {
edges := g[root]
if edges == nil {
return fmt.Errorf("no such node %q", root)
}
result.addAll(edges)
}
result.sort().println("\n")
case "forward", "reverse":
if len(args) == 0 {
return fmt.Errorf("usage: digraph %s <node> ... ", cmd)
}
roots := make(nodeset)
for _, root := range args {
if g[root] == nil {
return fmt.Errorf("no such node %q", root)
}
roots[root] = true
}
g := g
if cmd == "reverse" {
g = g.transpose()
}
g.reachableFrom(roots).sort().println("\n")
case "somepath":
if len(args) != 2 {
return fmt.Errorf("usage: digraph somepath <from> <to>")
}
from, to := args[0], args[1]
if g[from] == nil {
return fmt.Errorf("no such 'from' node %q", from)
}
if g[to] == nil {
return fmt.Errorf("no such 'to' node %q", to)
}
if err := g.somepath(from, to); err != nil {
return err
}
case "allpaths":
if len(args) != 2 {
return fmt.Errorf("usage: digraph allpaths <from> <to>")
}
from, to := args[0], args[1]
if g[from] == nil {
return fmt.Errorf("no such 'from' node %q", from)
}
if g[to] == nil {
return fmt.Errorf("no such 'to' node %q", to)
}
if err := g.allpaths(from, to); err != nil {
return err
}
case "sccs":
if len(args) != 0 {
return fmt.Errorf("usage: digraph sccs")
}
buf := new(bytes.Buffer)
oldStdout := stdout
stdout = buf
for _, scc := range g.sccs() {
scc.sort().println(" ")
}
lines := strings.SplitAfter(buf.String(), "\n")
sort.Strings(lines)
stdout = oldStdout
io.WriteString(stdout, strings.Join(lines, ""))
case "scc":
if len(args) != 1 {
return fmt.Errorf("usage: digraph scc <node>")
}
node := args[0]
if g[node] == nil {
return fmt.Errorf("no such node %q", node)
}
for _, scc := range g.sccs() {
if scc[node] {
scc.sort().println("\n")
break
}
}
case "focus":
if len(args) != 1 {
return fmt.Errorf("usage: digraph focus <node>")
}
node := args[0]
if g[node] == nil {
return fmt.Errorf("no such node %q", node)
}
edges := make(map[string]struct{})
for from := range g.reachableFrom(nodeset{node: true}) {
for to := range g[from] {
edges[fmt.Sprintf("%s %s", from, to)] = struct{}{}
}
}
gtrans := g.transpose()
for from := range gtrans.reachableFrom(nodeset{node: true}) {
for to := range gtrans[from] {
edges[fmt.Sprintf("%s %s", to, from)] = struct{}{}
}
}
edgesSorted := make([]string, 0, len(edges))
for e := range edges {
edgesSorted = append(edgesSorted, e)
}
sort.Strings(edgesSorted)
fmt.Fprintln(stdout, strings.Join(edgesSorted, "\n"))
case "to":
if len(args) != 1 || args[0] != "dot" {
return fmt.Errorf("usage: digraph to dot")
}
var b bytes.Buffer
g.toDot(&b)
stdout.Write(b.Bytes())
default:
return fmt.Errorf("no such command %q", cmd)
}
return nil
}
// -- Utilities --------------------------------------------------------
// split splits a line into words, which are generally separated by
// spaces, but Go-style double-quoted string literals are also supported.
// (This approximates the behaviour of the Bourne shell.)
//
// `one "two three"` -> ["one" "two three"]
// `a"\n"b` -> ["a\nb"]
func split(line string) ([]string, error) {
var (
words []string
inWord bool
current bytes.Buffer
)
for len(line) > 0 {
r, size := utf8.DecodeRuneInString(line)
if unicode.IsSpace(r) {
if inWord {
words = append(words, current.String())
current.Reset()
inWord = false
}
} else if r == '"' {
var ok bool
size, ok = quotedLength(line)
if !ok {
return nil, errors.New("invalid quotation")
}
s, err := strconv.Unquote(line[:size])
if err != nil {
return nil, err
}
current.WriteString(s)
inWord = true
} else {
current.WriteRune(r)
inWord = true
}
line = line[size:]
}
if inWord {
words = append(words, current.String())
}
return words, nil
}
// quotedLength returns the length in bytes of the prefix of input that
// contain a possibly-valid double-quoted Go string literal.
//
// On success, n is at least two (""); input[:n] may be passed to
// strconv.Unquote to interpret its value, and input[n:] contains the
// rest of the input.
//
// On failure, quotedLength returns false, and the entire input can be
// passed to strconv.Unquote if an informative error message is desired.
//
// quotedLength does not and need not detect all errors, such as
// invalid hex or octal escape sequences, since it assumes
// strconv.Unquote will be applied to the prefix. It guarantees only
// that if there is a prefix of input containing a valid string literal,
// its length is returned.
//
// TODO(adonovan): move this into a strconv-like utility package.
func quotedLength(input string) (n int, ok bool) {
var offset int
// next returns the rune at offset, or -1 on EOF.
// offset advances to just after that rune.
next := func() rune {
if offset < len(input) {
r, size := utf8.DecodeRuneInString(input[offset:])
offset += size
return r
}
return -1
}
if next() != '"' {
return // error: not a quotation
}
for {
r := next()
if r == '\n' || r < 0 {
return // error: string literal not terminated
}
if r == '"' {
return offset, true // success
}
if r == '\\' {
var skip int
switch next() {
case 'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', '"':
skip = 0
case '0', '1', '2', '3', '4', '5', '6', '7':
skip = 2
case 'x':
skip = 2
case 'u':
skip = 4
case 'U':
skip = 8
default:
return // error: invalid escape
}
for i := 0; i < skip; i++ {
next()
}
}
}
}
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