github.com/sc0rp1us/gb@v0.4.1-0.20160319180011-4ba8cf1baa5a/vendor/discovery.go (about)

     1  // Copyright 2012 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 vendor
     6  
     7  import (
     8  	"encoding/xml"
     9  	"fmt"
    10  	"io"
    11  	"strings"
    12  )
    13  
    14  // charsetReader returns a reader for the given charset. Currently
    15  // it only supports UTF-8 and ASCII. Otherwise, it returns a meaningful
    16  // error which is printed by go get, so the user can find why the package
    17  // wasn't downloaded if the encoding is not supported. Note that, in
    18  // order to reduce potential errors, ASCII is treated as UTF-8 (i.e. characters
    19  // greater than 0x7f are not rejected).
    20  func charsetReader(charset string, input io.Reader) (io.Reader, error) {
    21  	switch strings.ToLower(charset) {
    22  	case "ascii":
    23  		return input, nil
    24  	default:
    25  		return nil, fmt.Errorf("can't decode XML document using charset %q", charset)
    26  	}
    27  }
    28  
    29  type metaImport struct {
    30  	Prefix, VCS, RepoRoot string
    31  }
    32  
    33  // parseMetaGoImports returns meta imports from the HTML in r.
    34  // Parsing ends at the end of the <head> section or the beginning of the <body>.
    35  func parseMetaGoImports(r io.Reader) (imports []metaImport, err error) {
    36  	d := xml.NewDecoder(r)
    37  	d.CharsetReader = charsetReader
    38  	d.Strict = false
    39  	var t xml.Token
    40  	for {
    41  		t, err = d.Token()
    42  		if err != nil {
    43  			if err == io.EOF {
    44  				err = nil
    45  			}
    46  			return
    47  		}
    48  		if e, ok := t.(xml.StartElement); ok && strings.EqualFold(e.Name.Local, "body") {
    49  			return
    50  		}
    51  		if e, ok := t.(xml.EndElement); ok && strings.EqualFold(e.Name.Local, "head") {
    52  			return
    53  		}
    54  		e, ok := t.(xml.StartElement)
    55  		if !ok || !strings.EqualFold(e.Name.Local, "meta") {
    56  			continue
    57  		}
    58  		if attrValue(e.Attr, "name") != "go-import" {
    59  			continue
    60  		}
    61  		if f := strings.Fields(attrValue(e.Attr, "content")); len(f) == 3 {
    62  			imports = append(imports, metaImport{
    63  				Prefix:   f[0],
    64  				VCS:      f[1],
    65  				RepoRoot: f[2],
    66  			})
    67  		}
    68  	}
    69  }
    70  
    71  // attrValue returns the attribute value for the case-insensitive key
    72  // `name', or the empty string if nothing is found.
    73  func attrValue(attrs []xml.Attr, name string) string {
    74  	for _, a := range attrs {
    75  		if strings.EqualFold(a.Name.Local, name) {
    76  			return a.Value
    77  		}
    78  	}
    79  	return ""
    80  }