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Source file src/cmd/go/internal/get/discovery.go

Documentation: cmd/go/internal/get

     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 get
     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  // parseMetaGoImports returns meta imports from the HTML in r.
    30  // Parsing ends at the end of the <head> section or the beginning of the <body>.
    31  func parseMetaGoImports(r io.Reader) (imports []metaImport, err error) {
    32  	d := xml.NewDecoder(r)
    33  	d.CharsetReader = charsetReader
    34  	d.Strict = false
    35  	var t xml.Token
    36  	for {
    37  		t, err = d.RawToken()
    38  		if err != nil {
    39  			if err == io.EOF || len(imports) > 0 {
    40  				err = nil
    41  			}
    42  			return
    43  		}
    44  		if e, ok := t.(xml.StartElement); ok && strings.EqualFold(e.Name.Local, "body") {
    45  			return
    46  		}
    47  		if e, ok := t.(xml.EndElement); ok && strings.EqualFold(e.Name.Local, "head") {
    48  			return
    49  		}
    50  		e, ok := t.(xml.StartElement)
    51  		if !ok || !strings.EqualFold(e.Name.Local, "meta") {
    52  			continue
    53  		}
    54  		if attrValue(e.Attr, "name") != "go-import" {
    55  			continue
    56  		}
    57  		if f := strings.Fields(attrValue(e.Attr, "content")); len(f) == 3 {
    58  			imports = append(imports, metaImport{
    59  				Prefix:   f[0],
    60  				VCS:      f[1],
    61  				RepoRoot: f[2],
    62  			})
    63  		}
    64  	}
    65  }
    66  
    67  // attrValue returns the attribute value for the case-insensitive key
    68  // `name', or the empty string if nothing is found.
    69  func attrValue(attrs []xml.Attr, name string) string {
    70  	for _, a := range attrs {
    71  		if strings.EqualFold(a.Name.Local, name) {
    72  			return a.Value
    73  		}
    74  	}
    75  	return ""
    76  }
    77  

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