github.com/ltltlt/go-source-code@v0.0.0-20190830023027-95be009773aa/cmd/compile/internal/types/pkg.go (about)

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package types
     6  
     7  import (
     8  	"cmd/internal/obj"
     9  	"cmd/internal/objabi"
    10  	"fmt"
    11  	"sort"
    12  	"sync"
    13  )
    14  
    15  // pkgMap maps a package path to a package.
    16  var pkgMap = make(map[string]*Pkg)
    17  
    18  type Pkg struct {
    19  	Path     string // string literal used in import statement, e.g. "runtime/internal/sys"
    20  	Name     string // package name, e.g. "sys"
    21  	Pathsym  *obj.LSym
    22  	Prefix   string // escaped path for use in symbol table
    23  	Imported bool   // export data of this package was parsed
    24  	Direct   bool   // imported directly
    25  	Syms     map[string]*Sym
    26  }
    27  
    28  // NewPkg returns a new Pkg for the given package path and name.
    29  // Unless name is the empty string, if the package exists already,
    30  // the existing package name and the provided name must match.
    31  func NewPkg(path, name string) *Pkg {
    32  	if p := pkgMap[path]; p != nil {
    33  		if name != "" && p.Name != name {
    34  			panic(fmt.Sprintf("conflicting package names %s and %s for path %q", p.Name, name, path))
    35  		}
    36  		return p
    37  	}
    38  
    39  	p := new(Pkg)
    40  	p.Path = path
    41  	p.Name = name
    42  	p.Prefix = objabi.PathToPrefix(path)
    43  	p.Syms = make(map[string]*Sym)
    44  	pkgMap[path] = p
    45  
    46  	return p
    47  }
    48  
    49  // ImportedPkgList returns the list of directly imported packages.
    50  // The list is sorted by package path.
    51  func ImportedPkgList() []*Pkg {
    52  	var list []*Pkg
    53  	for _, p := range pkgMap {
    54  		if p.Direct {
    55  			list = append(list, p)
    56  		}
    57  	}
    58  	sort.Sort(byPath(list))
    59  	return list
    60  }
    61  
    62  type byPath []*Pkg
    63  
    64  func (a byPath) Len() int           { return len(a) }
    65  func (a byPath) Less(i, j int) bool { return a[i].Path < a[j].Path }
    66  func (a byPath) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
    67  
    68  var nopkg = &Pkg{
    69  	Syms: make(map[string]*Sym),
    70  }
    71  
    72  func (pkg *Pkg) Lookup(name string) *Sym {
    73  	s, _ := pkg.LookupOK(name)
    74  	return s
    75  }
    76  
    77  var InitSyms []*Sym
    78  
    79  // LookupOK looks up name in pkg and reports whether it previously existed.
    80  func (pkg *Pkg) LookupOK(name string) (s *Sym, existed bool) {
    81  	// TODO(gri) remove this check in favor of specialized lookup
    82  	if pkg == nil {
    83  		pkg = nopkg
    84  	}
    85  	if s := pkg.Syms[name]; s != nil {
    86  		return s, true
    87  	}
    88  
    89  	s = &Sym{
    90  		Name: name,
    91  		Pkg:  pkg,
    92  	}
    93  	if name == "init" {
    94  		InitSyms = append(InitSyms, s)
    95  	}
    96  	pkg.Syms[name] = s
    97  	return s, false
    98  }
    99  
   100  func (pkg *Pkg) LookupBytes(name []byte) *Sym {
   101  	// TODO(gri) remove this check in favor of specialized lookup
   102  	if pkg == nil {
   103  		pkg = nopkg
   104  	}
   105  	if s := pkg.Syms[string(name)]; s != nil {
   106  		return s
   107  	}
   108  	str := InternString(name)
   109  	return pkg.Lookup(str)
   110  }
   111  
   112  var (
   113  	internedStringsmu sync.Mutex // protects internedStrings
   114  	internedStrings   = map[string]string{}
   115  )
   116  
   117  func InternString(b []byte) string {
   118  	internedStringsmu.Lock()
   119  	s, ok := internedStrings[string(b)] // string(b) here doesn't allocate
   120  	if !ok {
   121  		s = string(b)
   122  		internedStrings[s] = s
   123  	}
   124  	internedStringsmu.Unlock()
   125  	return s
   126  }
   127  
   128  // CleanroomDo invokes f in an environment with with no preexisting packages.
   129  // For testing of import/export only.
   130  func CleanroomDo(f func()) {
   131  	saved := pkgMap
   132  	pkgMap = make(map[string]*Pkg)
   133  	f()
   134  	pkgMap = saved
   135  }