| 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 buildutil |
| 6 | |
| 7 | import ( |
| 8 | "bufio" |
| 9 | "bytes" |
| 10 | "fmt" |
| 11 | "go/build" |
| 12 | "io" |
| 13 | "io/ioutil" |
| 14 | "path/filepath" |
| 15 | "strconv" |
| 16 | "strings" |
| 17 | ) |
| 18 | |
| 19 | // OverlayContext overlays a build.Context with additional files from |
| 20 | // a map. Files in the map take precedence over other files. |
| 21 | // |
| 22 | // In addition to plain string comparison, two file names are |
| 23 | // considered equal if their base names match and their directory |
| 24 | // components point at the same directory on the file system. That is, |
| 25 | // symbolic links are followed for directories, but not files. |
| 26 | // |
| 27 | // A common use case for OverlayContext is to allow editors to pass in |
| 28 | // a set of unsaved, modified files. |
| 29 | // |
| 30 | // Currently, only the Context.OpenFile function will respect the |
| 31 | // overlay. This may change in the future. |
| 32 | func OverlayContext(orig *build.Context, overlay map[string][]byte) *build.Context { |
| 33 | // TODO(dominikh): Implement IsDir, HasSubdir and ReadDir |
| 34 | |
| 35 | rc := func(data []byte) (io.ReadCloser, error) { |
| 36 | return ioutil.NopCloser(bytes.NewBuffer(data)), nil |
| 37 | } |
| 38 | |
| 39 | copy := *orig // make a copy |
| 40 | ctxt := © |
| 41 | ctxt.OpenFile = func(path string) (io.ReadCloser, error) { |
| 42 | // Fast path: names match exactly. |
| 43 | if content, ok := overlay[path]; ok { |
| 44 | return rc(content) |
| 45 | } |
| 46 | |
| 47 | // Slow path: check for same file under a different |
| 48 | // alias, perhaps due to a symbolic link. |
| 49 | for filename, content := range overlay { |
| 50 | if sameFile(path, filename) { |
| 51 | return rc(content) |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | return OpenFile(orig, path) |
| 56 | } |
| 57 | return ctxt |
| 58 | } |
| 59 | |
| 60 | // ParseOverlayArchive parses an archive containing Go files and their |
| 61 | // contents. The result is intended to be used with OverlayContext. |
| 62 | // |
| 63 | // # Archive format |
| 64 | // |
| 65 | // The archive consists of a series of files. Each file consists of a |
| 66 | // name, a decimal file size and the file contents, separated by |
| 67 | // newlines. No newline follows after the file contents. |
| 68 | func ParseOverlayArchive(archive io.Reader) (map[string][]byte, error) { |
| 69 | overlay := make(map[string][]byte) |
| 70 | r := bufio.NewReader(archive) |
| 71 | for { |
| 72 | // Read file name. |
| 73 | filename, err := r.ReadString('\n') |
| 74 | if err != nil { |
| 75 | if err == io.EOF { |
| 76 | break // OK |
| 77 | } |
| 78 | return nil, fmt.Errorf("reading archive file name: %v", err) |
| 79 | } |
| 80 | filename = filepath.Clean(strings.TrimSpace(filename)) |
| 81 | |
| 82 | // Read file size. |
| 83 | sz, err := r.ReadString('\n') |
| 84 | if err != nil { |
| 85 | return nil, fmt.Errorf("reading size of archive file %s: %v", filename, err) |
| 86 | } |
| 87 | sz = strings.TrimSpace(sz) |
| 88 | size, err := strconv.ParseUint(sz, 10, 32) |
| 89 | if err != nil { |
| 90 | return nil, fmt.Errorf("parsing size of archive file %s: %v", filename, err) |
| 91 | } |
| 92 | |
| 93 | // Read file content. |
| 94 | content := make([]byte, size) |
| 95 | if _, err := io.ReadFull(r, content); err != nil { |
| 96 | return nil, fmt.Errorf("reading archive file %s: %v", filename, err) |
| 97 | } |
| 98 | overlay[filename] = content |
| 99 | } |
| 100 | |
| 101 | return overlay, nil |
| 102 | } |
| 103 |
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