go/pointer/util.go - tools - Git at Google

 // Copyright 2013 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 pointer

 import (
 	"bytes"
 	"fmt"
 	"go/types"
 	exec "golang.org/x/sys/execabs"
 	"log"
 	"os"
 	"runtime"
 	"time"

 	"golang.org/x/tools/container/intsets"
 )

 // CanPoint reports whether the type T is pointerlike,
 // for the purposes of this analysis.
 func CanPoint(T types.Type) bool {
 	switch T := T.(type) {
 	case *types.Named:
 		if obj := T.Obj(); obj.Name() == "Value" && obj.Pkg().Path() == "reflect" {
 			return true // treat reflect.Value like interface{}
 		}
 		return CanPoint(T.Underlying())
 	case *types.Pointer, *types.Interface, *types.Map, *types.Chan, *types.Signature, *types.Slice:
 		return true
 	}

 	return false // array struct tuple builtin basic
 }

 // CanHaveDynamicTypes reports whether the type T can "hold" dynamic types,
 // i.e. is an interface (incl. reflect.Type) or a reflect.Value.
 func CanHaveDynamicTypes(T types.Type) bool {
 	switch T := T.(type) {
 	case *types.Named:
 		if obj := T.Obj(); obj.Name() == "Value" && obj.Pkg().Path() == "reflect" {
 			return true // reflect.Value
 		}
 		return CanHaveDynamicTypes(T.Underlying())
 	case *types.Interface:
 		return true
 	}
 	return false
 }

 func isInterface(T types.Type) bool { return types.IsInterface(T) }

 // mustDeref returns the element type of its argument, which must be a
 // pointer; panic ensues otherwise.
 func mustDeref(typ types.Type) types.Type {
 	return typ.Underlying().(*types.Pointer).Elem()
 }

 // deref returns a pointer's element type; otherwise it returns typ.
 func deref(typ types.Type) types.Type {
 	if p, ok := typ.Underlying().(*types.Pointer); ok {
 		return p.Elem()
 	}
 	return typ
 }

 // A fieldInfo describes one subelement (node) of the flattening-out
 // of a type T: the subelement's type and its path from the root of T.
 //
 // For example, for this type:
 //
 //	type line struct{ points []struct{x, y int} }
 //
 // flatten() of the inner struct yields the following []fieldInfo:
 //
 //	struct{ x, y int }                      ""
 //	int                                     ".x"
 //	int                                     ".y"
 //
 // and flatten(line) yields:
 //
 //	struct{ points []struct{x, y int} }     ""
 //	struct{ x, y int }                      ".points[*]"
 //	int                                     ".points[*].x
 //	int                                     ".points[*].y"
 type fieldInfo struct {
 	typ types.Type

 	// op and tail describe the path to the element (e.g. ".a#2.b[*].c").
 	op   interface{} // *Array: true; *Tuple: int; *Struct: *types.Var; *Named: nil
 	tail *fieldInfo
 }

 // path returns a user-friendly string describing the subelement path.
 func (fi *fieldInfo) path() string {
 	var buf bytes.Buffer
 	for p := fi; p != nil; p = p.tail {
 		switch op := p.op.(type) {
 		case bool:
 			fmt.Fprintf(&buf, "[*]")
 		case int:
 			fmt.Fprintf(&buf, "#%d", op)
 		case *types.Var:
 			fmt.Fprintf(&buf, ".%s", op.Name())
 		}
 	}
 	return buf.String()
 }

 // flatten returns a list of directly contained fields in the preorder
 // traversal of the type tree of t.  The resulting elements are all
 // scalars (basic types or pointerlike types), except for struct/array
 // "identity" nodes, whose type is that of the aggregate.
 //
 // reflect.Value is considered pointerlike, similar to interface{}.
 //
 // Callers must not mutate the result.
 func (a *analysis) flatten(t types.Type) []*fieldInfo {
 	fl, ok := a.flattenMemo[t]
 	if !ok {
 		switch t := t.(type) {
 		case *types.Named:
 			u := t.Underlying()
 			if isInterface(u) {
 				// Debuggability hack: don't remove
 				// the named type from interfaces as
 				// they're very verbose.
 				fl = append(fl, &fieldInfo{typ: t})
 			} else {
 				fl = a.flatten(u)
 			}

 		case *types.Basic,
 			*types.Signature,
 			*types.Chan,
 			*types.Map,
 			*types.Interface,
 			*types.Slice,
 			*types.Pointer:
 			fl = append(fl, &fieldInfo{typ: t})

 		case *types.Array:
 			fl = append(fl, &fieldInfo{typ: t}) // identity node
 			for _, fi := range a.flatten(t.Elem()) {
 				fl = append(fl, &fieldInfo{typ: fi.typ, op: true, tail: fi})
 			}

 		case *types.Struct:
 			fl = append(fl, &fieldInfo{typ: t}) // identity node
 			for i, n := 0, t.NumFields(); i < n; i++ {
 				f := t.Field(i)
 				for _, fi := range a.flatten(f.Type()) {
 					fl = append(fl, &fieldInfo{typ: fi.typ, op: f, tail: fi})
 				}
 			}

 		case *types.Tuple:
 			// No identity node: tuples are never address-taken.
 			n := t.Len()
 			if n == 1 {
 				// Don't add a fieldInfo link for singletons,
 				// e.g. in params/results.
 				fl = append(fl, a.flatten(t.At(0).Type())...)
 			} else {
 				for i := 0; i < n; i++ {
 					f := t.At(i)
 					for _, fi := range a.flatten(f.Type()) {
 						fl = append(fl, &fieldInfo{typ: fi.typ, op: i, tail: fi})
 					}
 				}
 			}

 		default:
 			panic(fmt.Sprintf("cannot flatten unsupported type %T", t))
 		}

 		a.flattenMemo[t] = fl
 	}

 	return fl
 }

 // sizeof returns the number of pointerlike abstractions (nodes) in the type t.
 func (a *analysis) sizeof(t types.Type) uint32 {
 	return uint32(len(a.flatten(t)))
 }

 // shouldTrack reports whether object type T contains (recursively)
 // any fields whose addresses should be tracked.
 func (a *analysis) shouldTrack(T types.Type) bool {
 	if a.track == trackAll {
 		return true // fast path
 	}
 	track, ok := a.trackTypes[T]
 	if !ok {
 		a.trackTypes[T] = true // break cycles conservatively
 		// NB: reflect.Value, reflect.Type are pre-populated to true.
 		for _, fi := range a.flatten(T) {
 			switch ft := fi.typ.Underlying().(type) {
 			case *types.Interface, *types.Signature:
 				track = true // needed for callgraph
 			case *types.Basic:
 				// no-op
 			case *types.Chan:
 				track = a.track&trackChan != 0 || a.shouldTrack(ft.Elem())
 			case *types.Map:
 				track = a.track&trackMap != 0 || a.shouldTrack(ft.Key()) || a.shouldTrack(ft.Elem())
 			case *types.Slice:
 				track = a.track&trackSlice != 0 || a.shouldTrack(ft.Elem())
 			case *types.Pointer:
 				track = a.track&trackPtr != 0 || a.shouldTrack(ft.Elem())
 			case *types.Array, *types.Struct:
 				// No need to look at field types since they will follow (flattened).
 			default:
 				// Includes *types.Tuple, which are never address-taken.
 				panic(ft)
 			}
 			if track {
 				break
 			}
 		}
 		a.trackTypes[T] = track
 		if !track && a.log != nil {
 			fmt.Fprintf(a.log, "\ttype not tracked: %s\n", T)
 		}
 	}
 	return track
 }

 // offsetOf returns the (abstract) offset of field index within struct
 // or tuple typ.
 func (a *analysis) offsetOf(typ types.Type, index int) uint32 {
 	var offset uint32
 	switch t := typ.Underlying().(type) {
 	case *types.Tuple:
 		for i := 0; i < index; i++ {
 			offset += a.sizeof(t.At(i).Type())
 		}
 	case *types.Struct:
 		offset++ // the node for the struct itself
 		for i := 0; i < index; i++ {
 			offset += a.sizeof(t.Field(i).Type())
 		}
 	default:
 		panic(fmt.Sprintf("offsetOf(%s : %T)", typ, typ))
 	}
 	return offset
 }

 // sliceToArray returns the type representing the arrays to which
 // slice type slice points.
 func sliceToArray(slice types.Type) *types.Array {
 	return types.NewArray(slice.Underlying().(*types.Slice).Elem(), 1)
 }

 // Node set -------------------------------------------------------------------

 type nodeset struct {
 	intsets.Sparse
 }

 func (ns *nodeset) String() string {
 	var buf bytes.Buffer
 	buf.WriteRune('{')
 	var space [50]int
 	for i, n := range ns.AppendTo(space[:0]) {
 		if i > 0 {
 			buf.WriteString(", ")
 		}
 		buf.WriteRune('n')
 		fmt.Fprintf(&buf, "%d", n)
 	}
 	buf.WriteRune('}')
 	return buf.String()
 }

 func (ns *nodeset) add(n nodeid) bool {
 	return ns.Sparse.Insert(int(n))
 }

 func (ns *nodeset) addAll(y *nodeset) bool {
 	return ns.UnionWith(&y.Sparse)
 }

 // Profiling & debugging -------------------------------------------------------

 var timers = make(map[string]time.Time)

 func start(name string) {
 	if debugTimers {
 		timers[name] = time.Now()
 		log.Printf("%s...\n", name)
 	}
 }

 func stop(name string) {
 	if debugTimers {
 		log.Printf("%s took %s\n", name, time.Since(timers[name]))
 	}
 }

 // diff runs the command "diff a b" and reports its success.
 func diff(a, b string) bool {
 	var cmd *exec.Cmd
 	switch runtime.GOOS {
 	case "plan9":
 		cmd = exec.Command("/bin/diff", "-c", a, b)
 	default:
 		cmd = exec.Command("/usr/bin/diff", "-u", a, b)
 	}
 	cmd.Stdout = os.Stderr
 	cmd.Stderr = os.Stderr
 	return cmd.Run() == nil
 }
	// Copyright 2013 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 pointer

	import (
	"bytes"
	"fmt"
	"go/types"
	exec "golang.org/x/sys/execabs"
	"log"
	"os"
	"runtime"
	"time"

	"golang.org/x/tools/container/intsets"
	)

	// CanPoint reports whether the type T is pointerlike,
	// for the purposes of this analysis.
	func CanPoint(T types.Type) bool {
	switch T := T.(type) {
	case *types.Named:
	if obj := T.Obj(); obj.Name() == "Value" && obj.Pkg().Path() == "reflect" {
	return true // treat reflect.Value like interface{}
	}
	return CanPoint(T.Underlying())
	case types.Pointer, types.Interface, types.Map, types.Chan, types.Signature, types.Slice:
	return true
	}

	return false // array struct tuple builtin basic
	}

	// CanHaveDynamicTypes reports whether the type T can "hold" dynamic types,
	// i.e. is an interface (incl. reflect.Type) or a reflect.Value.
	func CanHaveDynamicTypes(T types.Type) bool {
	switch T := T.(type) {
	case *types.Named:
	if obj := T.Obj(); obj.Name() == "Value" && obj.Pkg().Path() == "reflect" {
	return true // reflect.Value
	}
	return CanHaveDynamicTypes(T.Underlying())
	case *types.Interface:
	return true
	}
	return false
	}

	func isInterface(T types.Type) bool { return types.IsInterface(T) }

	// mustDeref returns the element type of its argument, which must be a
	// pointer; panic ensues otherwise.
	func mustDeref(typ types.Type) types.Type {
	return typ.Underlying().(*types.Pointer).Elem()
	}

	// deref returns a pointer's element type; otherwise it returns typ.
	func deref(typ types.Type) types.Type {
	if p, ok := typ.Underlying().(*types.Pointer); ok {
	return p.Elem()
	}
	return typ
	}

	// A fieldInfo describes one subelement (node) of the flattening-out
	// of a type T: the subelement's type and its path from the root of T.
	//
	// For example, for this type:
	//
	// type line struct{ points []struct{x, y int} }
	//
	// flatten() of the inner struct yields the following []fieldInfo:
	//
	// struct{ x, y int } ""
	// int ".x"
	// int ".y"
	//
	// and flatten(line) yields:
	//
	// struct{ points []struct{x, y int} } ""
	// struct{ x, y int } ".points[*]"
	// int ".points[*].x
	// int ".points[*].y"
	type fieldInfo struct {
	typ types.Type

	// op and tail describe the path to the element (e.g. ".a#2.b[*].c").
	op interface{} // Array: true; Tuple: int; Struct: types.Var; *Named: nil
	tail *fieldInfo
	}

	// path returns a user-friendly string describing the subelement path.
	func (fi *fieldInfo) path() string {
	var buf bytes.Buffer
	for p := fi; p != nil; p = p.tail {
	switch op := p.op.(type) {
	case bool:
	fmt.Fprintf(&buf, "[*]")
	case int:
	fmt.Fprintf(&buf, "#%d", op)
	case *types.Var:
	fmt.Fprintf(&buf, ".%s", op.Name())
	}
	}
	return buf.String()
	}

	// flatten returns a list of directly contained fields in the preorder
	// traversal of the type tree of t. The resulting elements are all
	// scalars (basic types or pointerlike types), except for struct/array
	// "identity" nodes, whose type is that of the aggregate.
	//
	// reflect.Value is considered pointerlike, similar to interface{}.
	//
	// Callers must not mutate the result.
	func (a analysis) flatten(t types.Type) []fieldInfo {
	fl, ok := a.flattenMemo[t]
	if !ok {
	switch t := t.(type) {
	case *types.Named:
	u := t.Underlying()
	if isInterface(u) {
	// Debuggability hack: don't remove
	// the named type from interfaces as
	// they're very verbose.
	fl = append(fl, &fieldInfo{typ: t})
	} else {
	fl = a.flatten(u)
	}

	case *types.Basic,
	*types.Signature,
	*types.Chan,
	*types.Map,
	*types.Interface,
	*types.Slice,
	*types.Pointer:
	fl = append(fl, &fieldInfo{typ: t})

	case *types.Array:
	fl = append(fl, &fieldInfo{typ: t}) // identity node
	for _, fi := range a.flatten(t.Elem()) {
	fl = append(fl, &fieldInfo{typ: fi.typ, op: true, tail: fi})
	}

	case *types.Struct:
	fl = append(fl, &fieldInfo{typ: t}) // identity node
	for i, n := 0, t.NumFields(); i < n; i++ {
	f := t.Field(i)
	for _, fi := range a.flatten(f.Type()) {
	fl = append(fl, &fieldInfo{typ: fi.typ, op: f, tail: fi})
	}
	}

	case *types.Tuple:
	// No identity node: tuples are never address-taken.
	n := t.Len()
	if n == 1 {
	// Don't add a fieldInfo link for singletons,
	// e.g. in params/results.
	fl = append(fl, a.flatten(t.At(0).Type())...)
	} else {
	for i := 0; i < n; i++ {
	f := t.At(i)
	for _, fi := range a.flatten(f.Type()) {
	fl = append(fl, &fieldInfo{typ: fi.typ, op: i, tail: fi})
	}
	}
	}

	default:
	panic(fmt.Sprintf("cannot flatten unsupported type %T", t))
	}

	a.flattenMemo[t] = fl
	}

	return fl
	}

	// sizeof returns the number of pointerlike abstractions (nodes) in the type t.
	func (a *analysis) sizeof(t types.Type) uint32 {
	return uint32(len(a.flatten(t)))
	}

	// shouldTrack reports whether object type T contains (recursively)
	// any fields whose addresses should be tracked.
	func (a *analysis) shouldTrack(T types.Type) bool {
	if a.track == trackAll {
	return true // fast path
	}
	track, ok := a.trackTypes[T]
	if !ok {
	a.trackTypes[T] = true // break cycles conservatively
	// NB: reflect.Value, reflect.Type are pre-populated to true.
	for _, fi := range a.flatten(T) {
	switch ft := fi.typ.Underlying().(type) {
	case types.Interface, types.Signature:
	track = true // needed for callgraph
	case *types.Basic:
	// no-op
	case *types.Chan:
	track = a.track&trackChan != 0 \|\| a.shouldTrack(ft.Elem())
	case *types.Map:
	track = a.track&trackMap != 0 \|\| a.shouldTrack(ft.Key()) \|\| a.shouldTrack(ft.Elem())
	case *types.Slice:
	track = a.track&trackSlice != 0 \|\| a.shouldTrack(ft.Elem())
	case *types.Pointer:
	track = a.track&trackPtr != 0 \|\| a.shouldTrack(ft.Elem())
	case types.Array, types.Struct:
	// No need to look at field types since they will follow (flattened).
	default:
	// Includes *types.Tuple, which are never address-taken.
	panic(ft)
	}
	if track {
	break
	}
	}
	a.trackTypes[T] = track
	if !track && a.log != nil {
	fmt.Fprintf(a.log, "\ttype not tracked: %s\n", T)
	}
	}
	return track
	}

	// offsetOf returns the (abstract) offset of field index within struct
	// or tuple typ.
	func (a *analysis) offsetOf(typ types.Type, index int) uint32 {
	var offset uint32
	switch t := typ.Underlying().(type) {
	case *types.Tuple:
	for i := 0; i < index; i++ {
	offset += a.sizeof(t.At(i).Type())
	}
	case *types.Struct:
	offset++ // the node for the struct itself
	for i := 0; i < index; i++ {
	offset += a.sizeof(t.Field(i).Type())
	}
	default:
	panic(fmt.Sprintf("offsetOf(%s : %T)", typ, typ))
	}
	return offset
	}

	// sliceToArray returns the type representing the arrays to which
	// slice type slice points.
	func sliceToArray(slice types.Type) *types.Array {
	return types.NewArray(slice.Underlying().(*types.Slice).Elem(), 1)
	}

	// Node set -------------------------------------------------------------------

	type nodeset struct {
	intsets.Sparse
	}

	func (ns *nodeset) String() string {
	var buf bytes.Buffer
	buf.WriteRune('{')
	var space [50]int
	for i, n := range ns.AppendTo(space[:0]) {
	if i > 0 {
	buf.WriteString(", ")
	}
	buf.WriteRune('n')
	fmt.Fprintf(&buf, "%d", n)
	}
	buf.WriteRune('}')
	return buf.String()
	}

	func (ns *nodeset) add(n nodeid) bool {
	return ns.Sparse.Insert(int(n))
	}

	func (ns nodeset) addAll(y nodeset) bool {
	return ns.UnionWith(&y.Sparse)
	}

	// Profiling & debugging -------------------------------------------------------

	var timers = make(map[string]time.Time)

	func start(name string) {
	if debugTimers {
	timers[name] = time.Now()
	log.Printf("%s...\n", name)
	}
	}

	func stop(name string) {
	if debugTimers {
	log.Printf("%s took %s\n", name, time.Since(timers[name]))
	}
	}

	// diff runs the command "diff a b" and reports its success.
	func diff(a, b string) bool {
	var cmd *exec.Cmd
	switch runtime.GOOS {
	case "plan9":
	cmd = exec.Command("/bin/diff", "-c", a, b)
	default:
	cmd = exec.Command("/usr/bin/diff", "-u", a, b)
	}
	cmd.Stdout = os.Stderr
	cmd.Stderr = os.Stderr
	return cmd.Run() == nil
	}