pkg.go

Documentation: cmd/compile/internal/types

     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  	p.Prefix = objabi.PathToPrefix(path)
    52  	p.Syms = make(map[string]*Sym)
    53  	pkgMap[path] = p
    54  
    55  	return p
    56  }
    57  
    58  // ImportedPkgList returns the list of directly imported packages.
    59  // The list is sorted by package path.
    60  func ImportedPkgList() []*Pkg {
    61  	var list []*Pkg
    62  	for _, p := range pkgMap {
    63  		if p.Direct {
    64  			list = append(list, p)
    65  		}
    66  	}
    67  	sort.Sort(byPath(list))
    68  	return list
    69  }
    70  
    71  type byPath []*Pkg
    72  
    73  func (a byPath) Len() int           { return len(a) }
    74  func (a byPath) Less(i, j int) bool { return a[i].Path < a[j].Path }
    75  func (a byPath) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
    76  
    77  var nopkg = &Pkg{
    78  	Syms: make(map[string]*Sym),
    79  }
    80  
    81  func (pkg *Pkg) Lookup(name string) *Sym {
    82  	s, _ := pkg.LookupOK(name)
    83  	return s
    84  }
    85  
    86  // LookupOK looks up name in pkg and reports whether it previously existed.
    87  func (pkg *Pkg) LookupOK(name string) (s *Sym, existed bool) {
    88  	// TODO(gri) remove this check in favor of specialized lookup
    89  	if pkg == nil {
    90  		pkg = nopkg
    91  	}
    92  	if s := pkg.Syms[name]; s != nil {
    93  		return s, true
    94  	}
    95  
    96  	s = &Sym{
    97  		Name: name,
    98  		Pkg:  pkg,
    99  	}
   100  	pkg.Syms[name] = s
   101  	return s, false
   102  }
   103  
   104  func (pkg *Pkg) LookupBytes(name []byte) *Sym {
   105  	// TODO(gri) remove this check in favor of specialized lookup
   106  	if pkg == nil {
   107  		pkg = nopkg
   108  	}
   109  	if s := pkg.Syms[string(name)]; s != nil {
   110  		return s
   111  	}
   112  	str := InternString(name)
   113  	return pkg.Lookup(str)
   114  }
   115  
   116  var (
   117  	internedStringsmu sync.Mutex // protects internedStrings
   118  	internedStrings   = map[string]string{}
   119  )
   120  
   121  func InternString(b []byte) string {
   122  	internedStringsmu.Lock()
   123  	s, ok := internedStrings[string(b)] // string(b) here doesn't allocate
   124  	if !ok {
   125  		s = string(b)
   126  		internedStrings[s] = s
   127  	}
   128  	internedStringsmu.Unlock()
   129  	return s
   130  }
   131  
   132  // CleanroomDo invokes f in an environment with no preexisting packages.
   133  // For testing of import/export only.
   134  func CleanroomDo(f func()) {
   135  	saved := pkgMap
   136  	pkgMap = make(map[string]*Pkg)
   137  	f()
   138  	pkgMap = saved
   139  }
   140  
   141  func IsDotAlias(sym *Sym) bool {
   142  	return sym.Def != nil && sym.Def.Sym() != sym
   143  }
   144
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