mirror of https://go.googlesource.com/go
584 lines
16 KiB
Go
584 lines
16 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package base32 implements base32 encoding as specified by RFC 4648.
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package base32
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import (
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"io"
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"slices"
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"strconv"
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)
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/*
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* Encodings
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*/
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// An Encoding is a radix 32 encoding/decoding scheme, defined by a
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// 32-character alphabet. The most common is the "base32" encoding
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// introduced for SASL GSSAPI and standardized in RFC 4648.
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// The alternate "base32hex" encoding is used in DNSSEC.
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type Encoding struct {
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encode [32]byte // mapping of symbol index to symbol byte value
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decodeMap [256]uint8 // mapping of symbol byte value to symbol index
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padChar rune
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}
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const (
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StdPadding rune = '=' // Standard padding character
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NoPadding rune = -1 // No padding
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)
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const (
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decodeMapInitialize = "" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
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invalidIndex = '\xff'
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)
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// NewEncoding returns a new padded Encoding defined by the given alphabet,
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// which must be a 32-byte string that contains unique byte values and
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// does not contain the padding character or CR / LF ('\r', '\n').
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// The alphabet is treated as a sequence of byte values
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// without any special treatment for multi-byte UTF-8.
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// The resulting Encoding uses the default padding character ('='),
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// which may be changed or disabled via [Encoding.WithPadding].
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func NewEncoding(encoder string) *Encoding {
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if len(encoder) != 32 {
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panic("encoding alphabet is not 32-bytes long")
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}
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e := new(Encoding)
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e.padChar = StdPadding
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copy(e.encode[:], encoder)
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copy(e.decodeMap[:], decodeMapInitialize)
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for i := 0; i < len(encoder); i++ {
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// Note: While we document that the alphabet cannot contain
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// the padding character, we do not enforce it since we do not know
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// if the caller intends to switch the padding from StdPadding later.
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switch {
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case encoder[i] == '\n' || encoder[i] == '\r':
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panic("encoding alphabet contains newline character")
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case e.decodeMap[encoder[i]] != invalidIndex:
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panic("encoding alphabet includes duplicate symbols")
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}
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e.decodeMap[encoder[i]] = uint8(i)
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}
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return e
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}
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// StdEncoding is the standard base32 encoding, as defined in RFC 4648.
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var StdEncoding = NewEncoding("ABCDEFGHIJKLMNOPQRSTUVWXYZ234567")
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// HexEncoding is the “Extended Hex Alphabet” defined in RFC 4648.
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// It is typically used in DNS.
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var HexEncoding = NewEncoding("0123456789ABCDEFGHIJKLMNOPQRSTUV")
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// WithPadding creates a new encoding identical to enc except
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// with a specified padding character, or NoPadding to disable padding.
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// The padding character must not be '\r' or '\n',
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// must not be contained in the encoding's alphabet,
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// must not be negative, and must be a rune equal or below '\xff'.
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// Padding characters above '\x7f' are encoded as their exact byte value
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// rather than using the UTF-8 representation of the codepoint.
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func (enc Encoding) WithPadding(padding rune) *Encoding {
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switch {
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case padding < NoPadding || padding == '\r' || padding == '\n' || padding > 0xff:
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panic("invalid padding")
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case padding != NoPadding && enc.decodeMap[byte(padding)] != invalidIndex:
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panic("padding contained in alphabet")
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}
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enc.padChar = padding
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return &enc
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}
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/*
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* Encoder
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*/
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// Encode encodes src using the encoding enc,
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// writing [Encoding.EncodedLen](len(src)) bytes to dst.
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//
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// The encoding pads the output to a multiple of 8 bytes,
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// so Encode is not appropriate for use on individual blocks
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// of a large data stream. Use [NewEncoder] instead.
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func (enc *Encoding) Encode(dst, src []byte) {
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if len(src) == 0 {
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return
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}
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// enc is a pointer receiver, so the use of enc.encode within the hot
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// loop below means a nil check at every operation. Lift that nil check
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// outside of the loop to speed up the encoder.
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_ = enc.encode
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di, si := 0, 0
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n := (len(src) / 5) * 5
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for si < n {
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// Combining two 32 bit loads allows the same code to be used
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// for 32 and 64 bit platforms.
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hi := uint32(src[si+0])<<24 | uint32(src[si+1])<<16 | uint32(src[si+2])<<8 | uint32(src[si+3])
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lo := hi<<8 | uint32(src[si+4])
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dst[di+0] = enc.encode[(hi>>27)&0x1F]
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dst[di+1] = enc.encode[(hi>>22)&0x1F]
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dst[di+2] = enc.encode[(hi>>17)&0x1F]
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dst[di+3] = enc.encode[(hi>>12)&0x1F]
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dst[di+4] = enc.encode[(hi>>7)&0x1F]
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dst[di+5] = enc.encode[(hi>>2)&0x1F]
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dst[di+6] = enc.encode[(lo>>5)&0x1F]
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dst[di+7] = enc.encode[(lo)&0x1F]
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si += 5
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di += 8
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}
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// Add the remaining small block
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remain := len(src) - si
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if remain == 0 {
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return
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}
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// Encode the remaining bytes in reverse order.
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val := uint32(0)
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switch remain {
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case 4:
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val |= uint32(src[si+3])
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dst[di+6] = enc.encode[val<<3&0x1F]
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dst[di+5] = enc.encode[val>>2&0x1F]
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fallthrough
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case 3:
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val |= uint32(src[si+2]) << 8
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dst[di+4] = enc.encode[val>>7&0x1F]
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fallthrough
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case 2:
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val |= uint32(src[si+1]) << 16
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dst[di+3] = enc.encode[val>>12&0x1F]
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dst[di+2] = enc.encode[val>>17&0x1F]
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fallthrough
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case 1:
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val |= uint32(src[si+0]) << 24
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dst[di+1] = enc.encode[val>>22&0x1F]
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dst[di+0] = enc.encode[val>>27&0x1F]
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}
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// Pad the final quantum
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if enc.padChar != NoPadding {
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nPad := (remain * 8 / 5) + 1
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for i := nPad; i < 8; i++ {
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dst[di+i] = byte(enc.padChar)
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}
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}
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}
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// AppendEncode appends the base32 encoded src to dst
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// and returns the extended buffer.
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func (enc *Encoding) AppendEncode(dst, src []byte) []byte {
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n := enc.EncodedLen(len(src))
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dst = slices.Grow(dst, n)
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enc.Encode(dst[len(dst):][:n], src)
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return dst[:len(dst)+n]
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}
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// EncodeToString returns the base32 encoding of src.
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func (enc *Encoding) EncodeToString(src []byte) string {
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buf := make([]byte, enc.EncodedLen(len(src)))
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enc.Encode(buf, src)
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return string(buf)
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}
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type encoder struct {
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err error
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enc *Encoding
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w io.Writer
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buf [5]byte // buffered data waiting to be encoded
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nbuf int // number of bytes in buf
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out [1024]byte // output buffer
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}
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func (e *encoder) Write(p []byte) (n int, err error) {
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if e.err != nil {
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return 0, e.err
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}
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// Leading fringe.
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if e.nbuf > 0 {
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var i int
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for i = 0; i < len(p) && e.nbuf < 5; i++ {
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e.buf[e.nbuf] = p[i]
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e.nbuf++
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}
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n += i
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p = p[i:]
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if e.nbuf < 5 {
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return
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}
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e.enc.Encode(e.out[0:], e.buf[0:])
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if _, e.err = e.w.Write(e.out[0:8]); e.err != nil {
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return n, e.err
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}
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e.nbuf = 0
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}
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// Large interior chunks.
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for len(p) >= 5 {
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nn := len(e.out) / 8 * 5
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if nn > len(p) {
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nn = len(p)
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nn -= nn % 5
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}
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e.enc.Encode(e.out[0:], p[0:nn])
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if _, e.err = e.w.Write(e.out[0 : nn/5*8]); e.err != nil {
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return n, e.err
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}
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n += nn
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p = p[nn:]
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}
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// Trailing fringe.
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copy(e.buf[:], p)
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e.nbuf = len(p)
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n += len(p)
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return
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}
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// Close flushes any pending output from the encoder.
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// It is an error to call Write after calling Close.
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func (e *encoder) Close() error {
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// If there's anything left in the buffer, flush it out
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if e.err == nil && e.nbuf > 0 {
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e.enc.Encode(e.out[0:], e.buf[0:e.nbuf])
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encodedLen := e.enc.EncodedLen(e.nbuf)
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e.nbuf = 0
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_, e.err = e.w.Write(e.out[0:encodedLen])
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}
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return e.err
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}
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// NewEncoder returns a new base32 stream encoder. Data written to
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// the returned writer will be encoded using enc and then written to w.
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// Base32 encodings operate in 5-byte blocks; when finished
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// writing, the caller must Close the returned encoder to flush any
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// partially written blocks.
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func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser {
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return &encoder{enc: enc, w: w}
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}
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// EncodedLen returns the length in bytes of the base32 encoding
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// of an input buffer of length n.
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func (enc *Encoding) EncodedLen(n int) int {
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if enc.padChar == NoPadding {
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return n/5*8 + (n%5*8+4)/5
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}
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return (n + 4) / 5 * 8
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}
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/*
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* Decoder
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*/
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type CorruptInputError int64
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func (e CorruptInputError) Error() string {
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return "illegal base32 data at input byte " + strconv.FormatInt(int64(e), 10)
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}
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// decode is like Decode but returns an additional 'end' value, which
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// indicates if end-of-message padding was encountered and thus any
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// additional data is an error. This method assumes that src has been
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// stripped of all supported whitespace ('\r' and '\n').
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func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
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// Lift the nil check outside of the loop.
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_ = enc.decodeMap
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dsti := 0
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olen := len(src)
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for len(src) > 0 && !end {
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// Decode quantum using the base32 alphabet
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var dbuf [8]byte
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dlen := 8
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for j := 0; j < 8; {
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if len(src) == 0 {
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if enc.padChar != NoPadding {
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// We have reached the end and are missing padding
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return n, false, CorruptInputError(olen - len(src) - j)
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}
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// We have reached the end and are not expecting any padding
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dlen, end = j, true
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break
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}
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in := src[0]
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src = src[1:]
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if in == byte(enc.padChar) && j >= 2 && len(src) < 8 {
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// We've reached the end and there's padding
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if len(src)+j < 8-1 {
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// not enough padding
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return n, false, CorruptInputError(olen)
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}
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for k := 0; k < 8-1-j; k++ {
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if len(src) > k && src[k] != byte(enc.padChar) {
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// incorrect padding
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return n, false, CorruptInputError(olen - len(src) + k - 1)
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}
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}
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dlen, end = j, true
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// 7, 5 and 2 are not valid padding lengths, and so 1, 3 and 6 are not
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// valid dlen values. See RFC 4648 Section 6 "Base 32 Encoding" listing
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// the five valid padding lengths, and Section 9 "Illustrations and
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// Examples" for an illustration for how the 1st, 3rd and 6th base32
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// src bytes do not yield enough information to decode a dst byte.
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if dlen == 1 || dlen == 3 || dlen == 6 {
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return n, false, CorruptInputError(olen - len(src) - 1)
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}
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break
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}
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dbuf[j] = enc.decodeMap[in]
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if dbuf[j] == 0xFF {
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return n, false, CorruptInputError(olen - len(src) - 1)
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}
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j++
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}
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// Pack 8x 5-bit source blocks into 5 byte destination
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// quantum
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switch dlen {
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case 8:
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dst[dsti+4] = dbuf[6]<<5 | dbuf[7]
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n++
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fallthrough
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case 7:
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dst[dsti+3] = dbuf[4]<<7 | dbuf[5]<<2 | dbuf[6]>>3
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n++
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fallthrough
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case 5:
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dst[dsti+2] = dbuf[3]<<4 | dbuf[4]>>1
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n++
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fallthrough
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case 4:
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dst[dsti+1] = dbuf[1]<<6 | dbuf[2]<<1 | dbuf[3]>>4
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n++
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fallthrough
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case 2:
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dst[dsti+0] = dbuf[0]<<3 | dbuf[1]>>2
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n++
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}
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dsti += 5
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}
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return n, end, nil
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}
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// Decode decodes src using the encoding enc. It writes at most
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// [Encoding.DecodedLen](len(src)) bytes to dst and returns the number of bytes
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// written. If src contains invalid base32 data, it will return the
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// number of bytes successfully written and [CorruptInputError].
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// Newline characters (\r and \n) are ignored.
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func (enc *Encoding) Decode(dst, src []byte) (n int, err error) {
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buf := make([]byte, len(src))
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l := stripNewlines(buf, src)
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n, _, err = enc.decode(dst, buf[:l])
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return
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}
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// AppendDecode appends the base32 decoded src to dst
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// and returns the extended buffer.
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// If the input is malformed, it returns the partially decoded src and an error.
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func (enc *Encoding) AppendDecode(dst, src []byte) ([]byte, error) {
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// Compute the output size without padding to avoid over allocating.
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n := len(src)
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for n > 0 && rune(src[n-1]) == enc.padChar {
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n--
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}
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n = decodedLen(n, NoPadding)
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dst = slices.Grow(dst, n)
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n, err := enc.Decode(dst[len(dst):][:n], src)
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return dst[:len(dst)+n], err
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}
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// DecodeString returns the bytes represented by the base32 string s.
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func (enc *Encoding) DecodeString(s string) ([]byte, error) {
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buf := []byte(s)
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l := stripNewlines(buf, buf)
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n, _, err := enc.decode(buf, buf[:l])
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return buf[:n], err
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}
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type decoder struct {
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err error
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enc *Encoding
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r io.Reader
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end bool // saw end of message
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buf [1024]byte // leftover input
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nbuf int
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out []byte // leftover decoded output
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outbuf [1024 / 8 * 5]byte
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}
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func readEncodedData(r io.Reader, buf []byte, min int, expectsPadding bool) (n int, err error) {
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for n < min && err == nil {
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var nn int
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nn, err = r.Read(buf[n:])
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n += nn
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}
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// data was read, less than min bytes could be read
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if n < min && n > 0 && err == io.EOF {
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err = io.ErrUnexpectedEOF
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}
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// no data was read, the buffer already contains some data
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// when padding is disabled this is not an error, as the message can be of
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// any length
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if expectsPadding && min < 8 && n == 0 && err == io.EOF {
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err = io.ErrUnexpectedEOF
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}
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return
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}
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func (d *decoder) Read(p []byte) (n int, err error) {
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// Use leftover decoded output from last read.
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if len(d.out) > 0 {
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n = copy(p, d.out)
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d.out = d.out[n:]
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if len(d.out) == 0 {
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return n, d.err
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}
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return n, nil
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}
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if d.err != nil {
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return 0, d.err
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}
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// Read a chunk.
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nn := (len(p) + 4) / 5 * 8
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if nn < 8 {
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nn = 8
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}
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if nn > len(d.buf) {
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nn = len(d.buf)
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}
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// Minimum amount of bytes that needs to be read each cycle
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var min int
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var expectsPadding bool
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if d.enc.padChar == NoPadding {
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min = 1
|
|
expectsPadding = false
|
|
} else {
|
|
min = 8 - d.nbuf
|
|
expectsPadding = true
|
|
}
|
|
|
|
nn, d.err = readEncodedData(d.r, d.buf[d.nbuf:nn], min, expectsPadding)
|
|
d.nbuf += nn
|
|
if d.nbuf < min {
|
|
return 0, d.err
|
|
}
|
|
if nn > 0 && d.end {
|
|
return 0, CorruptInputError(0)
|
|
}
|
|
|
|
// Decode chunk into p, or d.out and then p if p is too small.
|
|
var nr int
|
|
if d.enc.padChar == NoPadding {
|
|
nr = d.nbuf
|
|
} else {
|
|
nr = d.nbuf / 8 * 8
|
|
}
|
|
nw := d.enc.DecodedLen(d.nbuf)
|
|
|
|
if nw > len(p) {
|
|
nw, d.end, 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, 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 err != nil && (d.err == nil || d.err == io.EOF) {
|
|
d.err = err
|
|
}
|
|
|
|
if len(d.out) > 0 {
|
|
// We cannot return all the decoded bytes to the caller in this
|
|
// invocation of Read, so we return a nil error to ensure that Read
|
|
// will be called again. The error stored in d.err, if any, will be
|
|
// returned with the last set of decoded bytes.
|
|
return n, nil
|
|
}
|
|
|
|
return n, d.err
|
|
}
|
|
|
|
type newlineFilteringReader struct {
|
|
wrapped io.Reader
|
|
}
|
|
|
|
// stripNewlines removes newline characters and returns the number
|
|
// of non-newline characters copied to dst.
|
|
func stripNewlines(dst, src []byte) int {
|
|
offset := 0
|
|
for _, b := range src {
|
|
if b == '\r' || b == '\n' {
|
|
continue
|
|
}
|
|
dst[offset] = b
|
|
offset++
|
|
}
|
|
return offset
|
|
}
|
|
|
|
func (r *newlineFilteringReader) Read(p []byte) (int, error) {
|
|
n, err := r.wrapped.Read(p)
|
|
for n > 0 {
|
|
s := p[0:n]
|
|
offset := stripNewlines(s, s)
|
|
if err != nil || offset > 0 {
|
|
return offset, err
|
|
}
|
|
// Previous buffer entirely whitespace, read again
|
|
n, err = r.wrapped.Read(p)
|
|
}
|
|
return n, err
|
|
}
|
|
|
|
// NewDecoder constructs a new base32 stream decoder.
|
|
func NewDecoder(enc *Encoding, r io.Reader) io.Reader {
|
|
return &decoder{enc: enc, r: &newlineFilteringReader{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 decodedLen(n, enc.padChar)
|
|
}
|
|
|
|
func decodedLen(n int, padChar rune) int {
|
|
if padChar == NoPadding {
|
|
return n/8*5 + n%8*5/8
|
|
}
|
|
return n / 8 * 5
|
|
}
|