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// Copyright 2014 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 (
"bytes"
"fmt"
"go/constant"
"go/token"
"go/types"
"io"
"math/big"
)
// TODO(gri) use tabwriter for alignment?
func print(w io.Writer, pkg *types.Package, filter func(types.Object) bool) {
var p printer
p.pkg = pkg
p.printPackage(pkg, filter)
p.printGccgoExtra(pkg)
io.Copy(w, &p.buf)
}
type printer struct {
pkg *types.Package
buf bytes.Buffer
indent int // current indentation level
last byte // last byte written
}
func (p *printer) print(s string) {
// Write the string one byte at a time. We care about the presence of
// newlines for indentation which we will see even in the presence of
// (non-corrupted) Unicode; no need to read one rune at a time.
for i := 0; i < len(s); i++ {
ch := s[i]
if ch != '\n' && p.last == '\n' {
// Note: This could lead to a range overflow for very large
// indentations, but it's extremely unlikely to happen for
// non-pathological code.
p.buf.WriteString("\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"[:p.indent])
}
p.buf.WriteByte(ch)
p.last = ch
}
}
func (p *printer) printf(format string, args ...interface{}) {
p.print(fmt.Sprintf(format, args...))
}
// methodsFor returns the named type and corresponding methods if the type
// denoted by obj is not an interface and has methods. Otherwise it returns
// the zero value.
func methodsFor(obj *types.TypeName) (*types.Named, []*types.Selection) {
named, _ := obj.Type().(*types.Named)
if named == nil {
// A type name's type can also be the
// exported basic type unsafe.Pointer.
return nil, nil
}
if _, ok := named.Underlying().(*types.Interface); ok {
// ignore interfaces
return nil, nil
}
methods := combinedMethodSet(named)
if len(methods) == 0 {
return nil, nil
}
return named, methods
}
func (p *printer) printPackage(pkg *types.Package, filter func(types.Object) bool) {
// collect objects by kind
var (
consts []*types.Const
typem []*types.Named // non-interface types with methods
typez []*types.TypeName // interfaces or types without methods
vars []*types.Var
funcs []*types.Func
builtins []*types.Builtin
methods = make(map[*types.Named][]*types.Selection) // method sets for named types
)
scope := pkg.Scope()
for _, name := range scope.Names() {
obj := scope.Lookup(name)
if obj.Exported() {
// collect top-level exported and possibly filtered objects
if filter == nil || filter(obj) {
switch obj := obj.(type) {
case *types.Const:
consts = append(consts, obj)
case *types.TypeName:
// group into types with methods and types without
if named, m := methodsFor(obj); named != nil {
typem = append(typem, named)
methods[named] = m
} else {
typez = append(typez, obj)
}
case *types.Var:
vars = append(vars, obj)
case *types.Func:
funcs = append(funcs, obj)
case *types.Builtin:
// for unsafe.Sizeof, etc.
builtins = append(builtins, obj)
}
}
} else if filter == nil {
// no filtering: collect top-level unexported types with methods
if obj, _ := obj.(*types.TypeName); obj != nil {
// see case *types.TypeName above
if named, m := methodsFor(obj); named != nil {
typem = append(typem, named)
methods[named] = m
}
}
}
}
p.printf("package %s // %q\n", pkg.Name(), pkg.Path())
p.printDecl("const", len(consts), func() {
for _, obj := range consts {
p.printObj(obj)
p.print("\n")
}
})
p.printDecl("var", len(vars), func() {
for _, obj := range vars {
p.printObj(obj)
p.print("\n")
}
})
p.printDecl("type", len(typez), func() {
for _, obj := range typez {
p.printf("%s ", obj.Name())
typ := obj.Type()
if isAlias(obj) {
p.print("= ")
p.writeType(p.pkg, typ)
} else {
p.writeType(p.pkg, typ.Underlying())
}
p.print("\n")
}
})
// non-interface types with methods
for _, named := range typem {
first := true
if obj := named.Obj(); obj.Exported() {
if first {
p.print("\n")
first = false
}
p.printf("type %s ", obj.Name())
p.writeType(p.pkg, named.Underlying())
p.print("\n")
}
for _, m := range methods[named] {
if obj := m.Obj(); obj.Exported() {
if first {
p.print("\n")
first = false
}
p.printFunc(m.Recv(), obj.(*types.Func))
p.print("\n")
}
}
}
if len(funcs) > 0 {
p.print("\n")
for _, obj := range funcs {
p.printFunc(nil, obj)
p.print("\n")
}
}
// TODO(gri) better handling of builtins (package unsafe only)
if len(builtins) > 0 {
p.print("\n")
for _, obj := range builtins {
p.printf("func %s() // builtin\n", obj.Name())
}
}
p.print("\n")
}
func (p *printer) printDecl(keyword string, n int, printGroup func()) {
switch n {
case 0:
// nothing to do
case 1:
p.printf("\n%s ", keyword)
printGroup()
default:
p.printf("\n%s (\n", keyword)
p.indent++
printGroup()
p.indent--
p.print(")\n")
}
}
// absInt returns the absolute value of v as a *big.Int.
// v must be a numeric value.
func absInt(v constant.Value) *big.Int {
// compute big-endian representation of v
b := constant.Bytes(v) // little-endian
for i, j := 0, len(b)-1; i < j; i, j = i+1, j-1 {
b[i], b[j] = b[j], b[i]
}
return new(big.Int).SetBytes(b)
}
var (
one = big.NewRat(1, 1)
ten = big.NewRat(10, 1)
)
// floatString returns the string representation for a
// numeric value v in normalized floating-point format.
func floatString(v constant.Value) string {
if constant.Sign(v) == 0 {
return "0.0"
}
// x != 0
// convert |v| into a big.Rat x
x := new(big.Rat).SetFrac(absInt(constant.Num(v)), absInt(constant.Denom(v)))
// normalize x and determine exponent e
// (This is not very efficient, but also not speed-critical.)
var e int
for x.Cmp(ten) >= 0 {
x.Quo(x, ten)
e++
}
for x.Cmp(one) < 0 {
x.Mul(x, ten)
e--
}
// TODO(gri) Values such as 1/2 are easier to read in form 0.5
// rather than 5.0e-1. Similarly, 1.0e1 is easier to read as
// 10.0. Fine-tune best exponent range for readability.
s := x.FloatString(100) // good-enough precision
// trim trailing 0's
i := len(s)
for i > 0 && s[i-1] == '0' {
i--
}
s = s[:i]
// add a 0 if the number ends in decimal point
if len(s) > 0 && s[len(s)-1] == '.' {
s += "0"
}
// add exponent and sign
if e != 0 {
s += fmt.Sprintf("e%+d", e)
}
if constant.Sign(v) < 0 {
s = "-" + s
}
// TODO(gri) If v is a "small" fraction (i.e., numerator and denominator
// are just a small number of decimal digits), add the exact fraction as
// a comment. For instance: 3.3333...e-1 /* = 1/3 */
return s
}
// valString returns the string representation for the value v.
// Setting floatFmt forces an integer value to be formatted in
// normalized floating-point format.
// TODO(gri) Move this code into package constant.
func valString(v constant.Value, floatFmt bool) string {
switch v.Kind() {
case constant.Int:
if floatFmt {
return floatString(v)
}
case constant.Float:
return floatString(v)
case constant.Complex:
re := constant.Real(v)
im := constant.Imag(v)
var s string
if constant.Sign(re) != 0 {
s = floatString(re)
if constant.Sign(im) >= 0 {
s += " + "
} else {
s += " - "
im = constant.UnaryOp(token.SUB, im, 0) // negate im
}
}
// im != 0, otherwise v would be constant.Int or constant.Float
return s + floatString(im) + "i"
}
return v.String()
}
func (p *printer) printObj(obj types.Object) {
p.print(obj.Name())
typ, basic := obj.Type().Underlying().(*types.Basic)
if basic && typ.Info()&types.IsUntyped != 0 {
// don't write untyped types
} else {
p.print(" ")
p.writeType(p.pkg, obj.Type())
}
if obj, ok := obj.(*types.Const); ok {
floatFmt := basic && typ.Info()&(types.IsFloat|types.IsComplex) != 0
p.print(" = ")
p.print(valString(obj.Val(), floatFmt))
}
}
func (p *printer) printFunc(recvType types.Type, obj *types.Func) {
p.print("func ")
sig := obj.Type().(*types.Signature)
if recvType != nil {
p.print("(")
p.writeType(p.pkg, recvType)
p.print(") ")
}
p.print(obj.Name())
p.writeSignature(p.pkg, sig)
}
// combinedMethodSet returns the method set for a named type T
// merged with all the methods of *T that have different names than
// the methods of T.
//
// combinedMethodSet is analogous to types/typeutil.IntuitiveMethodSet
// but doesn't require a MethodSetCache.
// TODO(gri) If this functionality doesn't change over time, consider
// just calling IntuitiveMethodSet eventually.
func combinedMethodSet(T *types.Named) []*types.Selection {
// method set for T
mset := types.NewMethodSet(T)
var res []*types.Selection
for i, n := 0, mset.Len(); i < n; i++ {
res = append(res, mset.At(i))
}
// add all *T methods with names different from T methods
pmset := types.NewMethodSet(types.NewPointer(T))
for i, n := 0, pmset.Len(); i < n; i++ {
pm := pmset.At(i)
if obj := pm.Obj(); mset.Lookup(obj.Pkg(), obj.Name()) == nil {
res = append(res, pm)
}
}
return res
}