encoding/base32: new package

R=rsc
CC=Miek Gieben, golang-dev
https://golang.org/cl/3926041

src/pkg/Makefile

@@ -58,6 +58,7 @@ DIRS=\
 	debug/proc\
 	ebnf\
 	encoding/ascii85\
+	encoding/base32\
 	encoding/base64\
 	encoding/binary\
 	encoding/git85\

src/pkg/encoding/base32/Makefile

@@ -0,0 +1,11 @@
+# Copyright 2009 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.
+
+include $(GOROOT)/src/Make.inc
+
+TARG=encoding/base32
+GOFILES=\
+	base32.go\
+
+include $(GOROOT)/src/Make.pkg

src/pkg/encoding/base32/base32.go

@@ -0,0 +1,368 @@
+// 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 base32 implements base32 encoding as specified by RFC 4648.
+package base32
+
+import (
+	"io"
+	"os"
+	"strconv"
+)
+
+/*
+ * Encodings
+ */
+
+// An Encoding is a radix 32 encoding/decoding scheme, defined by a
+// 32-character alphabet.  The most common is the "base32" encoding
+// introduced for SASL GSSAPI and standardized in RFC 4648.
+// The alternate "base32hex" encoding is used in DNSSEC.
+type Encoding struct {
+	encode    string
+	decodeMap [256]byte
+}
+
+const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
+const encodeHex = "0123456789ABCDEFGHIJKLMNOPQRSTUV"
+
+// NewEncoding returns a new Encoding defined by the given alphabet,
+// which must be a 32-byte string.
+func NewEncoding(encoder string) *Encoding {
+	e := new(Encoding)
+	e.encode = encoder
+	for i := 0; i < len(e.decodeMap); i++ {
+		e.decodeMap[i] = 0xFF
+	}
+	for i := 0; i < len(encoder); i++ {
+		e.decodeMap[encoder[i]] = byte(i)
+	}
+	return e
+}
+
+// StdEncoding is the standard base32 encoding, as defined in
+// RFC 4648.
+var StdEncoding = NewEncoding(encodeStd)
+
+// HexEncoding is the ``Extended Hex Alphabet'' defined in RFC 4648.
+// It is typically used in DNS.
+var HexEncoding = NewEncoding(encodeHex)
+
+/*
+ * Encoder
+ */
+
+// Encode encodes src using the encoding enc, writing
+// EncodedLen(len(src)) bytes to dst.
+//
+// The encoding pads the output to a multiple of 8 bytes,
+// so Encode is not appropriate for use on individual blocks
+// of a large data stream.  Use NewEncoder() instead.
+func (enc *Encoding) Encode(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
+
+	for len(src) > 0 {
+		dst[0] = 0
+		dst[1] = 0
+		dst[2] = 0
+		dst[3] = 0
+		dst[4] = 0
+		dst[5] = 0
+		dst[6] = 0
+		dst[7] = 0
+
+		// Unpack 8x 5-bit source blocks into a 5 byte
+		// destination quantum
+		switch len(src) {
+		default:
+			dst[7] |= src[4] & 0x1F
+			dst[6] |= src[4] >> 5
+			fallthrough
+		case 4:
+			dst[6] |= (src[3] << 3) & 0x1F
+			dst[5] |= (src[3] >> 2) & 0x1F
+			dst[4] |= src[3] >> 7
+			fallthrough
+		case 3:
+			dst[4] |= (src[2] << 1) & 0x1F
+			dst[3] |= (src[2] >> 4) & 0x1F
+			fallthrough
+		case 2:
+			dst[3] |= (src[1] << 4) & 0x1F
+			dst[2] |= (src[1] >> 1) & 0x1F
+			dst[1] |= (src[1] >> 6) & 0x1F
+			fallthrough
+		case 1:
+			dst[1] |= (src[0] << 2) & 0x1F
+			dst[0] |= src[0] >> 3
+		}
+
+		// Encode 5-bit blocks using the base32 alphabet
+		for j := 0; j < 8; j++ {
+			dst[j] = enc.encode[dst[j]]
+		}
+
+		// Pad the final quantum
+		if len(src) < 5 {
+			dst[7] = '='
+			if len(src) < 4 {
+				dst[6] = '='
+				dst[5] = '='
+				if len(src) < 3 {
+					dst[4] = '='
+					if len(src) < 2 {
+						dst[3] = '='
+						dst[2] = '='
+					}
+				}
+			}
+			break
+		}
+		src = src[5:]
+		dst = dst[8:]
+	}
+}
+
+type encoder struct {
+	err  os.Error
+	enc  *Encoding
+	w    io.Writer
+	buf  [5]byte    // buffered data waiting to be encoded
+	nbuf int        // number of bytes in buf
+	out  [1024]byte // output buffer
+}
+
+func (e *encoder) Write(p []byte) (n int, err os.Error) {
+	if e.err != nil {
+		return 0, e.err
+	}
+
+	// Leading fringe.
+	if e.nbuf > 0 {
+		var i int
+		for i = 0; i < len(p) && e.nbuf < 5; i++ {
+			e.buf[e.nbuf] = p[i]
+			e.nbuf++
+		}
+		n += i
+		p = p[i:]
+		if e.nbuf < 5 {
+			return
+		}
+		e.enc.Encode(e.out[0:], e.buf[0:])
+		if _, e.err = e.w.Write(e.out[0:8]); e.err != nil {
+			return n, e.err
+		}
+		e.nbuf = 0
+	}
+
+	// Large interior chunks.
+	for len(p) >= 5 {
+		nn := len(e.out) / 8 * 5
+		if nn > len(p) {
+			nn = len(p)
+		}
+		nn -= nn % 5
+		if nn > 0 {
+			e.enc.Encode(e.out[0:], p[0:nn])
+			if _, e.err = e.w.Write(e.out[0 : nn/5*8]); e.err != nil {
+				return n, e.err
+			}
+		}
+		n += nn
+		p = p[nn:]
+	}
+
+	// Trailing fringe.
+	for i := 0; i < len(p); i++ {
+		e.buf[i] = p[i]
+	}
+	e.nbuf = len(p)
+	n += len(p)
+	return
+}
+
+// Close flushes any pending output from the encoder.
+// It is an error to call Write after calling Close.
+func (e *encoder) Close() os.Error {
+	// If there's anything left in the buffer, flush it out
+	if e.err == nil && e.nbuf > 0 {
+		e.enc.Encode(e.out[0:], e.buf[0:e.nbuf])
+		e.nbuf = 0
+		_, e.err = e.w.Write(e.out[0:8])
+	}
+	return e.err
+}
+
+// NewEncoder returns a new base32 stream encoder.  Data written to
+// the returned writer will be encoded using enc and then written to w.
+// Base32 encodings operate in 5-byte blocks; when finished
+// writing, the caller must Close the returned encoder to flush any
+// partially written blocks.
+func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser {
+	return &encoder{enc: enc, w: w}
+}
+
+// EncodedLen returns the length in bytes of the base32 encoding
+// of an input buffer of length n.
+func (enc *Encoding) EncodedLen(n int) int { return (n + 4) / 5 * 8 }
+
+/*
+ * Decoder
+ */
+
+type CorruptInputError int64
+
+func (e CorruptInputError) String() string {
+	return "illegal base32 data at input byte " + strconv.Itoa64(int64(e))
+}
+
+// decode is like Decode but returns an additional 'end' value, which
+// indicates if end-of-message padding was encountered and thus any
+// additional data is an error.  decode also assumes len(src)%8==0,
+// since it is meant for internal use.
+func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err os.Error) {
+	for i := 0; i < len(src)/8 && !end; i++ {
+		// Decode quantum using the base32 alphabet
+		var dbuf [8]byte
+		dlen := 8
+
+		// do the top bytes contain any data?
+	dbufloop:
+		for j := 0; j < 8; j++ {
+			in := src[i*8+j]
+			if in == '=' && j >= 2 && i == len(src)/8-1 {
+				// We've reached the end and there's
+				// padding, the rest should be padded
+				for k := j; k < 8; k++ {
+					if src[i*8+k] != '=' {
+						return n, false, CorruptInputError(i*8 + j)
+					}
+				}
+				dlen = j
+				end = true
+				break dbufloop
+			}
+			dbuf[j] = enc.decodeMap[in]
+			if dbuf[j] == 0xFF {
+				return n, false, CorruptInputError(i*8 + j)
+			}
+		}
+
+		// Pack 8x 5-bit source blocks into 5 byte destination
+		// quantum
+		switch dlen {
+		case 7, 8:
+			dst[i*5+4] = dbuf[6]<<5 | dbuf[7]
+			fallthrough
+		case 6, 5:
+			dst[i*5+3] = dbuf[4]<<7 | dbuf[5]<<2 | dbuf[6]>>3
+			fallthrough
+		case 4:
+			dst[i*5+2] = dbuf[3]<<4 | dbuf[4]>>1
+			fallthrough
+		case 3:
+			dst[i*5+1] = dbuf[1]<<6 | dbuf[2]<<1 | dbuf[3]>>4
+			fallthrough
+		case 2:
+			dst[i*5+0] = dbuf[0]<<3 | dbuf[1]>>2
+		}
+		switch dlen {
+		case 2:
+			n += 1
+		case 3, 4:
+			n += 2
+		case 5:
+			n += 3
+		case 6, 7:
+			n += 4
+		case 8:
+			n += 5
+		}
+	}
+	return n, end, nil
+}
+
+// Decode decodes src using the encoding enc.  It writes at most
+// DecodedLen(len(src)) bytes to dst and returns the number of bytes
+// written.  If src contains invalid base32 data, it will return the
+// number of bytes successfully written and CorruptInputError.
+func (enc *Encoding) Decode(dst, src []byte) (n int, err os.Error) {
+	if len(src)%8 != 0 {
+		return 0, CorruptInputError(len(src) / 8 * 8)
+	}
+
+	n, _, err = enc.decode(dst, src)
+	return
+}
+
+type decoder struct {
+	err    os.Error
+	enc    *Encoding
+	r      io.Reader
+	end    bool       // saw end of message
+	buf    [1024]byte // leftover input
+	nbuf   int
+	out    []byte // leftover decoded output
+	outbuf [1024 / 8 * 5]byte
+}
+
+func (d *decoder) Read(p []byte) (n int, err os.Error) {
+	if d.err != nil {
+		return 0, d.err
+	}
+
+	// Use leftover decoded output from last read.
+	if len(d.out) > 0 {
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+		return n, nil
+	}
+
+	// Read a chunk.
+	nn := len(p) / 5 * 8
+	if nn < 8 {
+		nn = 8
+	}
+	if nn > len(d.buf) {
+		nn = len(d.buf)
+	}
+	nn, d.err = io.ReadAtLeast(d.r, d.buf[d.nbuf:nn], 8-d.nbuf)
+	d.nbuf += nn
+	if d.nbuf < 8 {
+		return 0, d.err
+	}
+
+	// Decode chunk into p, or d.out and then p if p is too small.
+	nr := d.nbuf / 8 * 8
+	nw := d.nbuf / 8 * 5
+	if nw > len(p) {
+		nw, d.end, d.err = d.enc.decode(d.outbuf[0:], d.buf[0:nr])
+		d.out = d.outbuf[0:nw]
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+	} else {
+		n, d.end, d.err = d.enc.decode(p, d.buf[0:nr])
+	}
+	d.nbuf -= nr
+	for i := 0; i < d.nbuf; i++ {
+		d.buf[i] = d.buf[i+nr]
+	}
+
+	if d.err == nil {
+		d.err = err
+	}
+	return n, d.err
+}
+
+// NewDecoder constructs a new base32 stream decoder.
+func NewDecoder(enc *Encoding, r io.Reader) io.Reader {
+	return &decoder{enc: enc, r: r}
+}
+
+// DecodedLen returns the maximum length in bytes of the decoded data
+// corresponding to n bytes of base32-encoded data.
+func (enc *Encoding) DecodedLen(n int) int { return n / 8 * 5 }

src/pkg/encoding/base32/base32_test.go

@@ -0,0 +1,194 @@
+// Copyright 2009 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 base32
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+type testpair struct {
+	decoded, encoded string
+}
+
+var pairs = []testpair{
+	// RFC 4648 examples
+	{"", ""},
+	{"f", "MY======"},
+	{"fo", "MZXQ===="},
+	{"foo", "MZXW6==="},
+	{"foob", "MZXW6YQ="},
+	{"fooba", "MZXW6YTB"},
+	{"foobar", "MZXW6YTBOI======"},
+
+
+	// Wikipedia examples, converted to base32
+	{"sure.", "ON2XEZJO"},
+	{"sure", "ON2XEZI="},
+	{"sur", "ON2XE==="},
+	{"su", "ON2Q===="},
+	{"leasure.", "NRSWC43VOJSS4==="},
+	{"easure.", "MVQXG5LSMUXA===="},
+	{"asure.", "MFZXK4TFFY======"},
+	{"sure.", "ON2XEZJO"},
+}
+
+var bigtest = testpair{
+	"Twas brillig, and the slithy toves",
+	"KR3WC4ZAMJZGS3DMNFTSYIDBNZSCA5DIMUQHG3DJORUHSIDUN53GK4Y=",
+}
+
+func testEqual(t *testing.T, msg string, args ...interface{}) bool {
+	if args[len(args)-2] != args[len(args)-1] {
+		t.Errorf(msg, args...)
+		return false
+	}
+	return true
+}
+
+func TestEncode(t *testing.T) {
+	for _, p := range pairs {
+		buf := make([]byte, StdEncoding.EncodedLen(len(p.decoded)))
+		StdEncoding.Encode(buf, []byte(p.decoded))
+		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, string(buf), p.encoded)
+	}
+}
+
+func TestEncoder(t *testing.T) {
+	for _, p := range pairs {
+		bb := &bytes.Buffer{}
+		encoder := NewEncoder(StdEncoding, bb)
+		encoder.Write([]byte(p.decoded))
+		encoder.Close()
+		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, bb.String(), p.encoded)
+	}
+}
+
+func TestEncoderBuffering(t *testing.T) {
+	input := []byte(bigtest.decoded)
+	for bs := 1; bs <= 12; bs++ {
+		bb := &bytes.Buffer{}
+		encoder := NewEncoder(StdEncoding, bb)
+		for pos := 0; pos < len(input); pos += bs {
+			end := pos + bs
+			if end > len(input) {
+				end = len(input)
+			}
+			n, err := encoder.Write(input[pos:end])
+			testEqual(t, "Write(%q) gave error %v, want %v", input[pos:end], err, os.Error(nil))
+			testEqual(t, "Write(%q) gave length %v, want %v", input[pos:end], n, end-pos)
+		}
+		err := encoder.Close()
+		testEqual(t, "Close gave error %v, want %v", err, os.Error(nil))
+		testEqual(t, "Encoding/%d of %q = %q, want %q", bs, bigtest.decoded, bb.String(), bigtest.encoded)
+	}
+}
+
+func TestDecode(t *testing.T) {
+	for _, p := range pairs {
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(p.encoded)))
+		count, end, err := StdEncoding.decode(dbuf, []byte(p.encoded))
+		testEqual(t, "Decode(%q) = error %v, want %v", p.encoded, err, os.Error(nil))
+		testEqual(t, "Decode(%q) = length %v, want %v", p.encoded, count, len(p.decoded))
+		if len(p.encoded) > 0 {
+			testEqual(t, "Decode(%q) = end %v, want %v", p.encoded, end, (p.encoded[len(p.encoded)-1] == '='))
+		}
+		testEqual(t, "Decode(%q) = %q, want %q", p.encoded,
+			string(dbuf[0:count]),
+			p.decoded)
+	}
+}
+
+func TestDecoder(t *testing.T) {
+	for _, p := range pairs {
+		decoder := NewDecoder(StdEncoding, bytes.NewBufferString(p.encoded))
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(p.encoded)))
+		count, err := decoder.Read(dbuf)
+		if err != nil && err != os.EOF {
+			t.Fatal("Read failed", err)
+		}
+		testEqual(t, "Read from %q = length %v, want %v", p.encoded, count, len(p.decoded))
+		testEqual(t, "Decoding of %q = %q, want %q", p.encoded, string(dbuf[0:count]), p.decoded)
+		if err != os.EOF {
+			count, err = decoder.Read(dbuf)
+		}
+		testEqual(t, "Read from %q = %v, want %v", p.encoded, err, os.EOF)
+	}
+}
+
+func TestDecoderBuffering(t *testing.T) {
+	for bs := 1; bs <= 12; bs++ {
+		decoder := NewDecoder(StdEncoding, bytes.NewBufferString(bigtest.encoded))
+		buf := make([]byte, len(bigtest.decoded)+12)
+		var total int
+		for total = 0; total < len(bigtest.decoded); {
+			n, err := decoder.Read(buf[total : total+bs])
+			testEqual(t, "Read from %q at pos %d = %d, %v, want _, %v", bigtest.encoded, total, n, err, os.Error(nil))
+			total += n
+		}
+		testEqual(t, "Decoding/%d of %q = %q, want %q", bs, bigtest.encoded, string(buf[0:total]), bigtest.decoded)
+	}
+}
+
+func TestDecodeCorrupt(t *testing.T) {
+	type corrupt struct {
+		e string
+		p int
+	}
+	examples := []corrupt{
+		{"!!!!", 0},
+		{"x===", 0},
+		{"AA=A====", 2},
+		{"AAA=AAAA", 3},
+		{"MMMMMMMMM", 8},
+		{"MMMMMM", 0},
+	}
+
+	for _, e := range examples {
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(e.e)))
+		_, err := StdEncoding.Decode(dbuf, []byte(e.e))
+		switch err := err.(type) {
+		case CorruptInputError:
+			testEqual(t, "Corruption in %q at offset %v, want %v", e.e, int(err), e.p)
+		default:
+			t.Error("Decoder failed to detect corruption in", e)
+		}
+	}
+}
+
+func TestBig(t *testing.T) {
+	n := 3*1000 + 1
+	raw := make([]byte, n)
+	const alpha = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	for i := 0; i < n; i++ {
+		raw[i] = alpha[i%len(alpha)]
+	}
+	encoded := new(bytes.Buffer)
+	w := NewEncoder(StdEncoding, encoded)
+	nn, err := w.Write(raw)
+	if nn != n || err != nil {
+		t.Fatalf("Encoder.Write(raw) = %d, %v want %d, nil", nn, err, n)
+	}
+	err = w.Close()
+	if err != nil {
+		t.Fatalf("Encoder.Close() = %v want nil", err)
+	}
+	decoded, err := ioutil.ReadAll(NewDecoder(StdEncoding, encoded))
+	if err != nil {
+		t.Fatalf("ioutil.ReadAll(NewDecoder(...)): %v", err)
+	}
+
+	if !bytes.Equal(raw, decoded) {
+		var i int
+		for i = 0; i < len(decoded) && i < len(raw); i++ {
+			if decoded[i] != raw[i] {
+				break
+			}
+		}
+		t.Errorf("Decode(Encode(%d-byte string)) failed at offset %d", n, i)
+	}
+}