github.com/graybobo/golang.org-package-offline-cache@v0.0.0-20200626051047-6608995c132f/x/blog/content/context/userip/userip.go (about)

     1  // Package userip provides functions for extracting a user IP address from a
     2  // request and associating it with a Context.
     3  package userip
     4  
     5  import (
     6  	"fmt"
     7  	"net"
     8  	"net/http"
     9  
    10  	"golang.org/x/net/context"
    11  )
    12  
    13  // FromRequest extracts the user IP address from req, if present.
    14  func FromRequest(req *http.Request) (net.IP, error) {
    15  	ip, _, err := net.SplitHostPort(req.RemoteAddr)
    16  	if err != nil {
    17  		return nil, fmt.Errorf("userip: %q is not IP:port", req.RemoteAddr)
    18  	}
    19  
    20  	userIP := net.ParseIP(ip)
    21  	if userIP == nil {
    22  		return nil, fmt.Errorf("userip: %q is not IP:port", req.RemoteAddr)
    23  	}
    24  	return userIP, nil
    25  }
    26  
    27  // The key type is unexported to prevent collisions with context keys defined in
    28  // other packages.
    29  type key int
    30  
    31  // userIPkey is the context key for the user IP address.  Its value of zero is
    32  // arbitrary.  If this package defined other context keys, they would have
    33  // different integer values.
    34  const userIPKey key = 0
    35  
    36  // NewContext returns a new Context carrying userIP.
    37  func NewContext(ctx context.Context, userIP net.IP) context.Context {
    38  	return context.WithValue(ctx, userIPKey, userIP)
    39  }
    40  
    41  // FromContext extracts the user IP address from ctx, if present.
    42  func FromContext(ctx context.Context) (net.IP, bool) {
    43  	// ctx.Value returns nil if ctx has no value for the key;
    44  	// the net.IP type assertion returns ok=false for nil.
    45  	userIP, ok := ctx.Value(userIPKey).(net.IP)
    46  	return userIP, ok
    47  }