pkg.go

     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  // MaxPkgHeight is a height greater than any likely package height.
    19  const MaxPkgHeight = 1e9
    20  
    21  type Pkg struct {
    22  	Path    string // string literal used in import statement, e.g. "runtime/internal/sys"
    23  	Name    string // package name, e.g. "sys"
    24  	Prefix  string // escaped path for use in symbol table
    25  	Syms    map[string]*Sym
    26  	Pathsym *obj.LSym
    27  
    28  	// Height is the package's height in the import graph. Leaf
    29  	// packages (i.e., packages with no imports) have height 0,
    30  	// and all other packages have height 1 plus the maximum
    31  	// height of their imported packages.
    32  	Height int
    33  
    34  	Direct bool // imported directly
    35  }
    36  
    37  // NewPkg returns a new Pkg for the given package path and name.
    38  // Unless name is the empty string, if the package exists already,
    39  // the existing package name and the provided name must match.
    40  func NewPkg(path, name string) *Pkg {
    41  	if p := pkgMap[path]; p != nil {
    42  		if name != "" && p.Name != name {
    43  			panic(fmt.Sprintf("conflicting package names %s and %s for path %q", p.Name, name, path))
    44  		}
    45  		return p
    46  	}
    47  
    48  	p := new(Pkg)
    49  	p.Path = path
    50  	p.Name = name
    51  	if path == "go.shape" {
    52  		// Don't escape "go.shape", since it's not needed (it's a builtin
    53  		// package), and we don't want escape codes showing up in shape type
    54  		// names, which also appear in names of function/method
    55  		// instantiations.
    56  		p.Prefix = path
    57  	} else {
    58  		p.Prefix = objabi.PathToPrefix(path)
    59  	}
    60  	p.Syms = make(map[string]*Sym)
    61  	pkgMap[path] = p
    62  
    63  	return p
    64  }
    65  
    66  // ImportedPkgList returns the list of directly imported packages.
    67  // The list is sorted by package path.
    68  func ImportedPkgList() []*Pkg {
    69  	var list []*Pkg
    70  	for _, p := range pkgMap {
    71  		if p.Direct {
    72  			list = append(list, p)
    73  		}
    74  	}
    75  	sort.Sort(byPath(list))
    76  	return list
    77  }
    78  
    79  type byPath []*Pkg
    80  
    81  func (a byPath) Len() int           { return len(a) }
    82  func (a byPath) Less(i, j int) bool { return a[i].Path < a[j].Path }
    83  func (a byPath) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
    84  
    85  var nopkg = &Pkg{
    86  	Syms: make(map[string]*Sym),
    87  }
    88  
    89  func (pkg *Pkg) Lookup(name string) *Sym {
    90  	s, _ := pkg.LookupOK(name)
    91  	return s
    92  }
    93  
    94  // LookupOK looks up name in pkg and reports whether it previously existed.
    95  func (pkg *Pkg) LookupOK(name string) (s *Sym, existed bool) {
    96  	// TODO(gri) remove this check in favor of specialized lookup
    97  	if pkg == nil {
    98  		pkg = nopkg
    99  	}
   100  	if s := pkg.Syms[name]; s != nil {
   101  		return s, true
   102  	}
   103  
   104  	s = &Sym{
   105  		Name: name,
   106  		Pkg:  pkg,
   107  	}
   108  	pkg.Syms[name] = s
   109  	return s, false
   110  }
   111  
   112  func (pkg *Pkg) LookupBytes(name []byte) *Sym {
   113  	// TODO(gri) remove this check in favor of specialized lookup
   114  	if pkg == nil {
   115  		pkg = nopkg
   116  	}
   117  	if s := pkg.Syms[string(name)]; s != nil {
   118  		return s
   119  	}
   120  	str := InternString(name)
   121  	return pkg.Lookup(str)
   122  }
   123  
   124  var (
   125  	internedStringsmu sync.Mutex // protects internedStrings
   126  	internedStrings   = map[string]string{}
   127  )
   128  
   129  func InternString(b []byte) string {
   130  	internedStringsmu.Lock()
   131  	s, ok := internedStrings[string(b)] // string(b) here doesn't allocate
   132  	if !ok {
   133  		s = string(b)
   134  		internedStrings[s] = s
   135  	}
   136  	internedStringsmu.Unlock()
   137  	return s
   138  }
   139  
   140  // CleanroomDo invokes f in an environment with no preexisting packages.
   141  // For testing of import/export only.
   142  func CleanroomDo(f func()) {
   143  	saved := pkgMap
   144  	pkgMap = make(map[string]*Pkg)
   145  	f()
   146  	pkgMap = saved
   147  }
   148
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