text: // Copyright 2011 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package json
  
  import (
  	"strings"
  )
  
  // tagOptions is the string following a comma in a struct field's "json"
  // tag, or the empty string. It does not include the leading comma.
  type tagOptions string
  
  // parseTag splits a struct field's json tag into its name and
  // comma-separated options.
  func parseTag(tag string) (string, tagOptions) {
  	if idx := strings.Index(tag, ","); idx != -1 {
  		return tag[:idx], tagOptions(tag[idx+1:])
  	}
  	return tag, tagOptions("")
  }
  
  // Contains reports whether a comma-separated list of options
  // contains a particular substr flag. substr must be surrounded by a
  // string boundary or commas.
  func (o tagOptions) Contains(optionName string) bool {
  	if len(o) == 0 {
  		return false
  	}
  	s := string(o)
  	for s != "" {
  		var next string
  		i := strings.Index(s, ",")
  		if i >= 0 {
  			s, next = s[:i], s[i+1:]
  		}
  		if s == optionName {
  			return true
  		}
  		s = next
  	}
  	return false
  }
  