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Source file src/cmd/compile/internal/types/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  	Imported bool // export data of this package was parsed
    35  	Direct   bool // imported directly
    36  }
    37  
    38  // NewPkg returns a new Pkg for the given package path and name.
    39  // Unless name is the empty string, if the package exists already,
    40  // the existing package name and the provided name must match.
    41  func NewPkg(path, name string) *Pkg {
    42  	if p := pkgMap[path]; p != nil {
    43  		if name != "" && p.Name != name {
    44  			panic(fmt.Sprintf("conflicting package names %s and %s for path %q", p.Name, name, path))
    45  		}
    46  		return p
    47  	}
    48  
    49  	p := new(Pkg)
    50  	p.Path = path
    51  	p.Name = name
    52  	p.Prefix = objabi.PathToPrefix(path)
    53  	p.Syms = make(map[string]*Sym)
    54  	pkgMap[path] = p
    55  
    56  	return p
    57  }
    58  
    59  // ImportedPkgList returns the list of directly imported packages.
    60  // The list is sorted by package path.
    61  func ImportedPkgList() []*Pkg {
    62  	var list []*Pkg
    63  	for _, p := range pkgMap {
    64  		if p.Direct {
    65  			list = append(list, p)
    66  		}
    67  	}
    68  	sort.Sort(byPath(list))
    69  	return list
    70  }
    71  
    72  type byPath []*Pkg
    73  
    74  func (a byPath) Len() int           { return len(a) }
    75  func (a byPath) Less(i, j int) bool { return a[i].Path < a[j].Path }
    76  func (a byPath) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
    77  
    78  var nopkg = &Pkg{
    79  	Syms: make(map[string]*Sym),
    80  }
    81  
    82  func (pkg *Pkg) Lookup(name string) *Sym {
    83  	s, _ := pkg.LookupOK(name)
    84  	return s
    85  }
    86  
    87  var InitSyms []*Sym
    88  
    89  // LookupOK looks up name in pkg and reports whether it previously existed.
    90  func (pkg *Pkg) LookupOK(name string) (s *Sym, existed bool) {
    91  	// TODO(gri) remove this check in favor of specialized lookup
    92  	if pkg == nil {
    93  		pkg = nopkg
    94  	}
    95  	if s := pkg.Syms[name]; s != nil {
    96  		return s, true
    97  	}
    98  
    99  	s = &Sym{
   100  		Name: name,
   101  		Pkg:  pkg,
   102  	}
   103  	if name == "init" {
   104  		InitSyms = append(InitSyms, s)
   105  	}
   106  	pkg.Syms[name] = s
   107  	return s, false
   108  }
   109  
   110  func (pkg *Pkg) LookupBytes(name []byte) *Sym {
   111  	// TODO(gri) remove this check in favor of specialized lookup
   112  	if pkg == nil {
   113  		pkg = nopkg
   114  	}
   115  	if s := pkg.Syms[string(name)]; s != nil {
   116  		return s
   117  	}
   118  	str := InternString(name)
   119  	return pkg.Lookup(str)
   120  }
   121  
   122  var (
   123  	internedStringsmu sync.Mutex // protects internedStrings
   124  	internedStrings   = map[string]string{}
   125  )
   126  
   127  func InternString(b []byte) string {
   128  	internedStringsmu.Lock()
   129  	s, ok := internedStrings[string(b)] // string(b) here doesn't allocate
   130  	if !ok {
   131  		s = string(b)
   132  		internedStrings[s] = s
   133  	}
   134  	internedStringsmu.Unlock()
   135  	return s
   136  }
   137  
   138  // CleanroomDo invokes f in an environment with with no preexisting packages.
   139  // For testing of import/export only.
   140  func CleanroomDo(f func()) {
   141  	saved := pkgMap
   142  	pkgMap = make(map[string]*Pkg)
   143  	f()
   144  	pkgMap = saved
   145  }
   146  

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