| 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 | // Although it might seem convenient for this package to live alongside |
| 11 | // go/types in the standard library, this would cause version skew |
| 12 | // problems for developer tools that use it, since they must be able to |
| 13 | // consume the outputs of the gc compiler both before and after a Go |
| 14 | // update such as from Go 1.7 to Go 1.8. Because this package lives in |
| 15 | // golang.org/x/tools, sites can update their version of this repo some |
| 16 | // time before the Go 1.8 release and rebuild and redeploy their |
| 17 | // developer tools, which will then be able to consume both Go 1.7 and |
| 18 | // Go 1.8 export data files, so they will work before and after the |
| 19 | // Go update. (See discussion at https://golang.org/issue/15651.) |
| 20 | package gcexportdata // import "golang.org/x/tools/go/gcexportdata" |
| 21 | |
| 22 | import ( |
| 23 | "bufio" |
| 24 | "bytes" |
| 25 | "encoding/json" |
| 26 | "fmt" |
| 27 | "go/token" |
| 28 | "go/types" |
| 29 | "io" |
| 30 | "os/exec" |
| 31 | |
| 32 | "golang.org/x/tools/internal/gcimporter" |
| 33 | ) |
| 34 | |
| 35 | // Find returns the name of an object (.o) or archive (.a) file |
| 36 | // containing type information for the specified import path, |
| 37 | // using the go command. |
| 38 | // If no file was found, an empty filename is returned. |
| 39 | // |
| 40 | // A relative srcDir is interpreted relative to the current working directory. |
| 41 | // |
| 42 | // Find also returns the package's resolved (canonical) import path, |
| 43 | // reflecting the effects of srcDir and vendoring on importPath. |
| 44 | // |
| 45 | // Deprecated: Use the higher-level API in golang.org/x/tools/go/packages, |
| 46 | // which is more efficient. |
| 47 | func Find(importPath, srcDir string) (filename, path string) { |
| 48 | cmd := exec.Command("go", "list", "-json", "-export", "--", importPath) |
| 49 | cmd.Dir = srcDir |
| 50 | out, err := cmd.CombinedOutput() |
| 51 | if err != nil { |
| 52 | return "", "" |
| 53 | } |
| 54 | var data struct { |
| 55 | ImportPath string |
| 56 | Export string |
| 57 | } |
| 58 | json.Unmarshal(out, &data) |
| 59 | return data.Export, data.ImportPath |
| 60 | } |
| 61 | |
| 62 | // NewReader returns a reader for the export data section of an object |
| 63 | // (.o) or archive (.a) file read from r. The new reader may provide |
| 64 | // additional trailing data beyond the end of the export data. |
| 65 | func NewReader(r io.Reader) (io.Reader, error) { |
| 66 | buf := bufio.NewReader(r) |
| 67 | _, size, err := gcimporter.FindExportData(buf) |
| 68 | if err != nil { |
| 69 | return nil, err |
| 70 | } |
| 71 | |
| 72 | if size >= 0 { |
| 73 | // We were given an archive and found the __.PKGDEF in it. |
| 74 | // This tells us the size of the export data, and we don't |
| 75 | // need to return the entire file. |
| 76 | return &io.LimitedReader{ |
| 77 | R: buf, |
| 78 | N: size, |
| 79 | }, nil |
| 80 | } else { |
| 81 | // We were given an object file. As such, we don't know how large |
| 82 | // the export data is and must return the entire file. |
| 83 | return buf, nil |
| 84 | } |
| 85 | } |
| 86 | |
| 87 | // readAll works the same way as io.ReadAll, but avoids allocations and copies |
| 88 | // by preallocating a byte slice of the necessary size if the size is known up |
| 89 | // front. This is always possible when the input is an archive. In that case, |
| 90 | // NewReader will return the known size using an io.LimitedReader. |
| 91 | func readAll(r io.Reader) ([]byte, error) { |
| 92 | if lr, ok := r.(*io.LimitedReader); ok { |
| 93 | data := make([]byte, lr.N) |
| 94 | _, err := io.ReadFull(lr, data) |
| 95 | return data, err |
| 96 | } |
| 97 | return io.ReadAll(r) |
| 98 | } |
| 99 | |
| 100 | // Read reads export data from in, decodes it, and returns type |
| 101 | // information for the package. |
| 102 | // |
| 103 | // The package path (effectively its linker symbol prefix) is |
| 104 | // specified by path, since unlike the package name, this information |
| 105 | // may not be recorded in the export data. |
| 106 | // |
| 107 | // File position information is added to fset. |
| 108 | // |
| 109 | // Read may inspect and add to the imports map to ensure that references |
| 110 | // within the export data to other packages are consistent. The caller |
| 111 | // must ensure that imports[path] does not exist, or exists but is |
| 112 | // incomplete (see types.Package.Complete), and Read inserts the |
| 113 | // resulting package into this map entry. |
| 114 | // |
| 115 | // On return, the state of the reader is undefined. |
| 116 | func Read(in io.Reader, fset *token.FileSet, imports map[string]*types.Package, path string) (*types.Package, error) { |
| 117 | data, err := readAll(in) |
| 118 | if err != nil { |
| 119 | return nil, fmt.Errorf("reading export data for %q: %v", path, err) |
| 120 | } |
| 121 | |
| 122 | if bytes.HasPrefix(data, []byte("!<arch>")) { |
| 123 | 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) |
| 124 | } |
| 125 | |
| 126 | // The indexed export format starts with an 'i'; the older |
| 127 | // binary export format starts with a 'c', 'd', or 'v' |
| 128 | // (from "version"). Select appropriate importer. |
| 129 | if len(data) > 0 { |
| 130 | switch data[0] { |
| 131 | case 'i': |
| 132 | _, pkg, err := gcimporter.IImportData(fset, imports, data[1:], path) |
| 133 | return pkg, err |
| 134 | |
| 135 | case 'v', 'c', 'd': |
| 136 | _, pkg, err := gcimporter.BImportData(fset, imports, data, path) |
| 137 | return pkg, err |
| 138 | |
| 139 | case 'u': |
| 140 | _, pkg, err := gcimporter.UImportData(fset, imports, data[1:], path) |
| 141 | return pkg, err |
| 142 | |
| 143 | default: |
| 144 | l := len(data) |
| 145 | if l > 10 { |
| 146 | l = 10 |
| 147 | } |
| 148 | return nil, fmt.Errorf("unexpected export data with prefix %q for path %s", string(data[:l]), path) |
| 149 | } |
| 150 | } |
| 151 | return nil, fmt.Errorf("empty export data for %s", path) |
| 152 | } |
| 153 | |
| 154 | // Write writes encoded type information for the specified package to out. |
| 155 | // The FileSet provides file position information for named objects. |
| 156 | func Write(out io.Writer, fset *token.FileSet, pkg *types.Package) error { |
| 157 | if _, err := io.WriteString(out, "i"); err != nil { |
| 158 | return err |
| 159 | } |
| 160 | return gcimporter.IExportData(out, fset, pkg) |
| 161 | } |
| 162 | |
| 163 | // ReadBundle reads an export bundle from in, decodes it, and returns type |
| 164 | // information for the packages. |
| 165 | // File position information is added to fset. |
| 166 | // |
| 167 | // ReadBundle may inspect and add to the imports map to ensure that references |
| 168 | // within the export bundle to other packages are consistent. |
| 169 | // |
| 170 | // On return, the state of the reader is undefined. |
| 171 | // |
| 172 | // Experimental: This API is experimental and may change in the future. |
| 173 | func ReadBundle(in io.Reader, fset *token.FileSet, imports map[string]*types.Package) ([]*types.Package, error) { |
| 174 | data, err := readAll(in) |
| 175 | if err != nil { |
| 176 | return nil, fmt.Errorf("reading export bundle: %v", err) |
| 177 | } |
| 178 | return gcimporter.IImportBundle(fset, imports, data) |
| 179 | } |
| 180 | |
| 181 | // WriteBundle writes encoded type information for the specified packages to out. |
| 182 | // The FileSet provides file position information for named objects. |
| 183 | // |
| 184 | // Experimental: This API is experimental and may change in the future. |
| 185 | func WriteBundle(out io.Writer, fset *token.FileSet, pkgs []*types.Package) error { |
| 186 | return gcimporter.IExportBundle(out, fset, pkgs) |
| 187 | } |
| 188 |
Members