1 files changed, 190 insertions, 0 deletions
diff --git a/src/net/netip/slow_test.go b/src/net/netip/slow_test.go
new file mode 100644
index 0000000..d7c8025
--- /dev/null
+++ b/src/net/netip/slow_test.go
@@ -0,0 +1,190 @@
+// Copyright 2020 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 netip_test
+
+import (
+	"fmt"
+	. "net/netip"
+	"strconv"
+	"strings"
+)
+
+// zeros is a slice of eight stringified zeros. It's used in
+// parseIPSlow to construct slices of specific amounts of zero fields,
+// from 1 to 8.
+var zeros = []string{"0", "0", "0", "0", "0", "0", "0", "0"}
+
+// parseIPSlow is like ParseIP, but aims for readability above
+// speed. It's the reference implementation for correctness checking
+// and against which we measure optimized parsers.
+//
+// parseIPSlow understands the following forms of IP addresses:
+//   - Regular IPv4: 1.2.3.4
+//   - IPv4 with many leading zeros: 0000001.0000002.0000003.0000004
+//   - Regular IPv6: 1111:2222:3333:4444:5555:6666:7777:8888
+//   - IPv6 with many leading zeros: 00000001:0000002:0000003:0000004:0000005:0000006:0000007:0000008
+//   - IPv6 with zero blocks elided: 1111:2222::7777:8888
+//   - IPv6 with trailing 32 bits expressed as IPv4: 1111:2222:3333:4444:5555:6666:77.77.88.88
+//
+// It does not process the following IP address forms, which have been
+// varyingly accepted by some programs due to an under-specification
+// of the shapes of IPv4 addresses:
+//
+//   - IPv4 as a single 32-bit uint: 4660 (same as "1.2.3.4")
+//   - IPv4 with octal numbers: 0300.0250.0.01 (same as "192.168.0.1")
+//   - IPv4 with hex numbers: 0xc0.0xa8.0x0.0x1 (same as "192.168.0.1")
+//   - IPv4 in "class-B style": 1.2.52 (same as "1.2.3.4")
+//   - IPv4 in "class-A style": 1.564 (same as "1.2.3.4")
+func parseIPSlow(s string) (Addr, error) {
+	// Identify and strip out the zone, if any. There should be 0 or 1
+	// '%' in the string.
+	var zone string
+	fs := strings.Split(s, "%")
+	switch len(fs) {
+	case 1:
+		// No zone, that's fine.
+	case 2:
+		s, zone = fs[0], fs[1]
+		if zone == "" {
+			return Addr{}, fmt.Errorf("netaddr.ParseIP(%q): no zone after zone specifier", s)
+		}
+	default:
+		return Addr{}, fmt.Errorf("netaddr.ParseIP(%q): too many zone specifiers", s) // TODO: less specific?
+	}
+
+	// IPv4 by itself is easy to do in a helper.
+	if strings.Count(s, ":") == 0 {
+		if zone != "" {
+			return Addr{}, fmt.Errorf("netaddr.ParseIP(%q): IPv4 addresses cannot have a zone", s)
+		}
+		return parseIPv4Slow(s)
+	}
+
+	normal, err := normalizeIPv6Slow(s)
+	if err != nil {
+		return Addr{}, err
+	}
+
+	// At this point, we've normalized the address back into 8 hex
+	// fields of 16 bits each. Parse that.
+	fs = strings.Split(normal, ":")
+	if len(fs) != 8 {
+		return Addr{}, fmt.Errorf("netaddr.ParseIP(%q): wrong size address", s)
+	}
+	var ret [16]byte
+	for i, f := range fs {
+		a, b, err := parseWord(f)
+		if err != nil {
+			return Addr{}, err
+		}
+		ret[i*2] = a
+		ret[i*2+1] = b
+	}
+
+	return AddrFrom16(ret).WithZone(zone), nil
+}
+
+// normalizeIPv6Slow expands s, which is assumed to be an IPv6
+// address, to its canonical text form.
+//
+// The canonical form of an IPv6 address is 8 colon-separated fields,
+// where each field should be a hex value from 0 to ffff. This
+// function does not verify the contents of each field.
+//
+// This function performs two transformations:
+//   - The last 32 bits of an IPv6 address may be represented in
+//     IPv4-style dotted quad form, as in 1:2:3:4:5:6:7.8.9.10. That
+//     address is transformed to its hex equivalent,
+//     e.g. 1:2:3:4:5:6:708:90a.
+//   - An address may contain one "::", which expands into as many
+//     16-bit blocks of zeros as needed to make the address its correct
+//     full size. For example, fe80::1:2 expands to fe80:0:0:0:0:0:1:2.
+//
+// Both short forms may be present in a single address,
+// e.g. fe80::1.2.3.4.
+func normalizeIPv6Slow(orig string) (string, error) {
+	s := orig
+
+	// Find and convert an IPv4 address in the final field, if any.
+	i := strings.LastIndex(s, ":")
+	if i == -1 {
+		return "", fmt.Errorf("netaddr.ParseIP(%q): invalid IP address", orig)
+	}
+	if strings.Contains(s[i+1:], ".") {
+		ip, err := parseIPv4Slow(s[i+1:])
+		if err != nil {
+			return "", err
+		}
+		a4 := ip.As4()
+		s = fmt.Sprintf("%s:%02x%02x:%02x%02x", s[:i], a4[0], a4[1], a4[2], a4[3])
+	}
+
+	// Find and expand a ::, if any.
+	fs := strings.Split(s, "::")
+	switch len(fs) {
+	case 1:
+		// No ::, nothing to do.
+	case 2:
+		lhs, rhs := fs[0], fs[1]
+		// Found a ::, figure out how many zero blocks need to be
+		// inserted.
+		nblocks := strings.Count(lhs, ":") + strings.Count(rhs, ":")
+		if lhs != "" {
+			nblocks++
+		}
+		if rhs != "" {
+			nblocks++
+		}
+		if nblocks > 7 {
+			return "", fmt.Errorf("netaddr.ParseIP(%q): address too long", orig)
+		}
+		fs = nil
+		// Either side of the :: can be empty. We don't want empty
+		// fields to feature in the final normalized address.
+		if lhs != "" {
+			fs = append(fs, lhs)
+		}
+		fs = append(fs, zeros[:8-nblocks]...)
+		if rhs != "" {
+			fs = append(fs, rhs)
+		}
+		s = strings.Join(fs, ":")
+	default:
+		// Too many ::
+		return "", fmt.Errorf("netaddr.ParseIP(%q): invalid IP address", orig)
+	}
+
+	return s, nil
+}
+
+// parseIPv4Slow parses and returns an IPv4 address in dotted quad
+// form, e.g. "192.168.0.1". It is slow but easy to read, and the
+// reference implementation against which we compare faster
+// implementations for correctness.
+func parseIPv4Slow(s string) (Addr, error) {
+	fs := strings.Split(s, ".")
+	if len(fs) != 4 {
+		return Addr{}, fmt.Errorf("netaddr.ParseIP(%q): invalid IP address", s)
+	}
+	var ret [4]byte
+	for i := range ret {
+		val, err := strconv.ParseUint(fs[i], 10, 8)
+		if err != nil {
+			return Addr{}, err
+		}
+		ret[i] = uint8(val)
+	}
+	return AddrFrom4([4]byte{ret[0], ret[1], ret[2], ret[3]}), nil
+}
+
+// parseWord converts a 16-bit hex string into its corresponding
+// two-byte value.
+func parseWord(s string) (byte, byte, error) {
+	ret, err := strconv.ParseUint(s, 16, 16)
+	if err != nil {
+		return 0, 0, err
+	}
+	return uint8(ret >> 8), uint8(ret), nil
+}