1 files changed, 151 insertions, 0 deletions
diff --git a/src/net/http/cookiejar/punycode.go b/src/net/http/cookiejar/punycode.go
new file mode 100644
index 0000000..c7f438d
--- /dev/null
+++ b/src/net/http/cookiejar/punycode.go
@@ -0,0 +1,151 @@
+// Copyright 2012 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 cookiejar
+
+// This file implements the Punycode algorithm from RFC 3492.
+
+import (
+	"fmt"
+	"net/http/internal/ascii"
+	"strings"
+	"unicode/utf8"
+)
+
+// These parameter values are specified in section 5.
+//
+// All computation is done with int32s, so that overflow behavior is identical
+// regardless of whether int is 32-bit or 64-bit.
+const (
+	base        int32 = 36
+	damp        int32 = 700
+	initialBias int32 = 72
+	initialN    int32 = 128
+	skew        int32 = 38
+	tmax        int32 = 26
+	tmin        int32 = 1
+)
+
+// encode encodes a string as specified in section 6.3 and prepends prefix to
+// the result.
+//
+// The "while h < length(input)" line in the specification becomes "for
+// remaining != 0" in the Go code, because len(s) in Go is in bytes, not runes.
+func encode(prefix, s string) (string, error) {
+	output := make([]byte, len(prefix), len(prefix)+1+2*len(s))
+	copy(output, prefix)
+	delta, n, bias := int32(0), initialN, initialBias
+	b, remaining := int32(0), int32(0)
+	for _, r := range s {
+		if r < utf8.RuneSelf {
+			b++
+			output = append(output, byte(r))
+		} else {
+			remaining++
+		}
+	}
+	h := b
+	if b > 0 {
+		output = append(output, '-')
+	}
+	for remaining != 0 {
+		m := int32(0x7fffffff)
+		for _, r := range s {
+			if m > r && r >= n {
+				m = r
+			}
+		}
+		delta += (m - n) * (h + 1)
+		if delta < 0 {
+			return "", fmt.Errorf("cookiejar: invalid label %q", s)
+		}
+		n = m
+		for _, r := range s {
+			if r < n {
+				delta++
+				if delta < 0 {
+					return "", fmt.Errorf("cookiejar: invalid label %q", s)
+				}
+				continue
+			}
+			if r > n {
+				continue
+			}
+			q := delta
+			for k := base; ; k += base {
+				t := k - bias
+				if t < tmin {
+					t = tmin
+				} else if t > tmax {
+					t = tmax
+				}
+				if q < t {
+					break
+				}
+				output = append(output, encodeDigit(t+(q-t)%(base-t)))
+				q = (q - t) / (base - t)
+			}
+			output = append(output, encodeDigit(q))
+			bias = adapt(delta, h+1, h == b)
+			delta = 0
+			h++
+			remaining--
+		}
+		delta++
+		n++
+	}
+	return string(output), nil
+}
+
+func encodeDigit(digit int32) byte {
+	switch {
+	case 0 <= digit && digit < 26:
+		return byte(digit + 'a')
+	case 26 <= digit && digit < 36:
+		return byte(digit + ('0' - 26))
+	}
+	panic("cookiejar: internal error in punycode encoding")
+}
+
+// adapt is the bias adaptation function specified in section 6.1.
+func adapt(delta, numPoints int32, firstTime bool) int32 {
+	if firstTime {
+		delta /= damp
+	} else {
+		delta /= 2
+	}
+	delta += delta / numPoints
+	k := int32(0)
+	for delta > ((base-tmin)*tmax)/2 {
+		delta /= base - tmin
+		k += base
+	}
+	return k + (base-tmin+1)*delta/(delta+skew)
+}
+
+// Strictly speaking, the remaining code below deals with IDNA (RFC 5890 and
+// friends) and not Punycode (RFC 3492) per se.
+
+// acePrefix is the ASCII Compatible Encoding prefix.
+const acePrefix = "xn--"
+
+// toASCII converts a domain or domain label to its ASCII form. For example,
+// toASCII("bücher.example.com") is "xn--bcher-kva.example.com", and
+// toASCII("golang") is "golang".
+func toASCII(s string) (string, error) {
+	if ascii.Is(s) {
+		return s, nil
+	}
+	labels := strings.Split(s, ".")
+	for i, label := range labels {
+		if !ascii.Is(label) {
+			a, err := encode(acePrefix, label)
+			if err != nil {
+				return "", err
+			}
+			labels[i] = a
+		}
+	}
+	return strings.Join(labels, "."), nil
+}