gopkg.in/alecthomas/gometalinter.v3@v3.0.0/_linters/src/golang.org/x/tools/go/gcexportdata/gcexportdata.go (about) 1 // Copyright 2016 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 gcexportdata provides functions for locating, reading, and 6 // writing export data files containing type information produced by the 7 // gc compiler. This package supports go1.7 export data format and all 8 // later versions. 9 // 10 // This package replaces the deprecated golang.org/x/tools/go/gcimporter15 11 // package, which will be deleted in October 2017. 12 // 13 // Although it might seem convenient for this package to live alongside 14 // go/types in the standard library, this would cause version skew 15 // problems for developer tools that use it, since they must be able to 16 // consume the outputs of the gc compiler both before and after a Go 17 // update such as from Go 1.7 to Go 1.8. Because this package lives in 18 // golang.org/x/tools, sites can update their version of this repo some 19 // time before the Go 1.8 release and rebuild and redeploy their 20 // developer tools, which will then be able to consume both Go 1.7 and 21 // Go 1.8 export data files, so they will work before and after the 22 // Go update. (See discussion at https://github.com/golang/go/issues/15651.) 23 // 24 package gcexportdata // import "golang.org/x/tools/go/gcexportdata" 25 26 import ( 27 "bufio" 28 "bytes" 29 "fmt" 30 "go/token" 31 "go/types" 32 "io" 33 "io/ioutil" 34 35 gcimporter "golang.org/x/tools/go/gcimporter15" 36 ) 37 38 // Find returns the name of an object (.o) or archive (.a) file 39 // containing type information for the specified import path, 40 // using the workspace layout conventions of go/build. 41 // If no file was found, an empty filename is returned. 42 // 43 // A relative srcDir is interpreted relative to the current working directory. 44 // 45 // Find also returns the package's resolved (canonical) import path, 46 // reflecting the effects of srcDir and vendoring on importPath. 47 func Find(importPath, srcDir string) (filename, path string) { 48 return gcimporter.FindPkg(importPath, srcDir) 49 } 50 51 // NewReader returns a reader for the export data section of an object 52 // (.o) or archive (.a) file read from r. The new reader may provide 53 // additional trailing data beyond the end of the export data. 54 func NewReader(r io.Reader) (io.Reader, error) { 55 buf := bufio.NewReader(r) 56 _, err := gcimporter.FindExportData(buf) 57 // If we ever switch to a zip-like archive format with the ToC 58 // at the end, we can return the correct portion of export data, 59 // but for now we must return the entire rest of the file. 60 return buf, err 61 } 62 63 // Read reads export data from in, decodes it, and returns type 64 // information for the package. 65 // The package name is specified by path. 66 // File position information is added to fset. 67 // 68 // Read may inspect and add to the imports map to ensure that references 69 // within the export data to other packages are consistent. The caller 70 // must ensure that imports[path] does not exist, or exists but is 71 // incomplete (see types.Package.Complete), and Read inserts the 72 // resulting package into this map entry. 73 // 74 // On return, the state of the reader is undefined. 75 func Read(in io.Reader, fset *token.FileSet, imports map[string]*types.Package, path string) (*types.Package, error) { 76 data, err := ioutil.ReadAll(in) 77 if err != nil { 78 return nil, fmt.Errorf("reading export data for %q: %v", path, err) 79 } 80 81 if bytes.HasPrefix(data, []byte("!<arch>")) { 82 return nil, fmt.Errorf("can't read export data for %q directly from an archive file (call gcexportdata.NewReader first to extract export data)", path) 83 } 84 85 // The App Engine Go runtime v1.6 uses the old export data format. 86 // TODO(adonovan): delete once v1.7 has been around for a while. 87 if bytes.HasPrefix(data, []byte("package ")) { 88 return gcimporter.ImportData(imports, path, path, bytes.NewReader(data)) 89 } 90 91 _, pkg, err := gcimporter.BImportData(fset, imports, data, path) 92 return pkg, err 93 } 94 95 // Write writes encoded type information for the specified package to out. 96 // The FileSet provides file position information for named objects. 97 func Write(out io.Writer, fset *token.FileSet, pkg *types.Package) error { 98 _, err := out.Write(gcimporter.BExportData(fset, pkg)) 99 return err 100 }