104 lines
2.9 KiB
Go
104 lines
2.9 KiB
Go
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package buildutil
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import (
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"bufio"
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"bytes"
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"fmt"
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"go/build"
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"io"
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"io/ioutil"
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"path/filepath"
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"strconv"
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"strings"
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)
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// OverlayContext overlays a build.Context with additional files from
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// a map. Files in the map take precedence over other files.
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//
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// In addition to plain string comparison, two file names are
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// considered equal if their base names match and their directory
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// components point at the same directory on the file system. That is,
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// symbolic links are followed for directories, but not files.
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//
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// A common use case for OverlayContext is to allow editors to pass in
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// a set of unsaved, modified files.
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//
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// Currently, only the Context.OpenFile function will respect the
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// overlay. This may change in the future.
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func OverlayContext(orig *build.Context, overlay map[string][]byte) *build.Context {
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// TODO(dominikh): Implement IsDir, HasSubdir and ReadDir
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rc := func(data []byte) (io.ReadCloser, error) {
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return ioutil.NopCloser(bytes.NewBuffer(data)), nil
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}
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copy := *orig // make a copy
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ctxt := ©
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ctxt.OpenFile = func(path string) (io.ReadCloser, error) {
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// Fast path: names match exactly.
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if content, ok := overlay[path]; ok {
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return rc(content)
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}
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// Slow path: check for same file under a different
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// alias, perhaps due to a symbolic link.
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for filename, content := range overlay {
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if sameFile(path, filename) {
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return rc(content)
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}
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}
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return OpenFile(orig, path)
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}
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return ctxt
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}
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// ParseOverlayArchive parses an archive containing Go files and their
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// contents. The result is intended to be used with OverlayContext.
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//
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//
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// Archive format
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//
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// The archive consists of a series of files. Each file consists of a
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// name, a decimal file size and the file contents, separated by
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// newlinews. No newline follows after the file contents.
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func ParseOverlayArchive(archive io.Reader) (map[string][]byte, error) {
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overlay := make(map[string][]byte)
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r := bufio.NewReader(archive)
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for {
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// Read file name.
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filename, err := r.ReadString('\n')
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if err != nil {
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if err == io.EOF {
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break // OK
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}
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return nil, fmt.Errorf("reading archive file name: %v", err)
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}
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filename = filepath.Clean(strings.TrimSpace(filename))
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// Read file size.
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sz, err := r.ReadString('\n')
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if err != nil {
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return nil, fmt.Errorf("reading size of archive file %s: %v", filename, err)
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}
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sz = strings.TrimSpace(sz)
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size, err := strconv.ParseUint(sz, 10, 32)
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if err != nil {
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return nil, fmt.Errorf("parsing size of archive file %s: %v", filename, err)
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}
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// Read file content.
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content := make([]byte, size)
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if _, err := io.ReadFull(r, content); err != nil {
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return nil, fmt.Errorf("reading archive file %s: %v", filename, err)
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}
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overlay[filename] = content
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}
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return overlay, nil
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}
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