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// Copyright 2010 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 armor
import (
"encoding/base64"
"io"
)
var armorHeaderSep = []byte(": ")
var blockEnd = []byte("\n=")
var newline = []byte("\n")
var armorEndOfLineOut = []byte("-----\n")
// writeSlices writes its arguments to the given Writer.
func writeSlices(out io.Writer, slices ...[]byte) (err error) {
for _, s := range slices {
_, err = out.Write(s)
if err != nil {
return err
}
}
return
}
// lineBreaker breaks data across several lines, all of the same byte length
// (except possibly the last). Lines are broken with a single '\n'.
type lineBreaker struct {
lineLength int
line []byte
used int
out io.Writer
haveWritten bool
}
func newLineBreaker(out io.Writer, lineLength int) *lineBreaker {
return &lineBreaker{
lineLength: lineLength,
line: make([]byte, lineLength),
used: 0,
out: out,
}
}
func (l *lineBreaker) Write(b []byte) (n int, err error) {
n = len(b)
if n == 0 {
return
}
if l.used == 0 && l.haveWritten {
_, err = l.out.Write([]byte{'\n'})
if err != nil {
return
}
}
if l.used+len(b) < l.lineLength {
l.used += copy(l.line[l.used:], b)
return
}
l.haveWritten = true
_, err = l.out.Write(l.line[0:l.used])
if err != nil {
return
}
excess := l.lineLength - l.used
l.used = 0
_, err = l.out.Write(b[0:excess])
if err != nil {
return
}
_, err = l.Write(b[excess:])
return
}
func (l *lineBreaker) Close() (err error) {
if l.used > 0 {
_, err = l.out.Write(l.line[0:l.used])
if err != nil {
return
}
}
return
}
// encoding keeps track of a running CRC24 over the data which has been written
// to it and outputs a OpenPGP checksum when closed, followed by an armor
// trailer.
//
// It's built into a stack of io.Writers:
// encoding -> base64 encoder -> lineBreaker -> out
type encoding struct {
out io.Writer
breaker *lineBreaker
b64 io.WriteCloser
crc uint32
blockType []byte
}
func (e *encoding) Write(data []byte) (n int, err error) {
e.crc = crc24(e.crc, data)
return e.b64.Write(data)
}
func (e *encoding) Close() (err error) {
err = e.b64.Close()
if err != nil {
return
}
e.breaker.Close()
var checksumBytes [3]byte
checksumBytes[0] = byte(e.crc >> 16)
checksumBytes[1] = byte(e.crc >> 8)
checksumBytes[2] = byte(e.crc)
var b64ChecksumBytes [4]byte
base64.StdEncoding.Encode(b64ChecksumBytes[:], checksumBytes[:])
return writeSlices(e.out, blockEnd, b64ChecksumBytes[:], newline, armorEnd, e.blockType, armorEndOfLine)
}
// Encode returns a WriteCloser which will encode the data written to it in
// OpenPGP armor.
func Encode(out io.Writer, blockType string, headers map[string]string) (w io.WriteCloser, err error) {
bType := []byte(blockType)
err = writeSlices(out, armorStart, bType, armorEndOfLineOut)
if err != nil {
return
}
for k, v := range headers {
err = writeSlices(out, []byte(k), armorHeaderSep, []byte(v), newline)
if err != nil {
return
}
}
_, err = out.Write(newline)
if err != nil {
return
}
e := &encoding{
out: out,
breaker: newLineBreaker(out, 64),
crc: crc24Init,
blockType: bType,
}
e.b64 = base64.NewEncoder(base64.StdEncoding, e.breaker)
return e, nil
}
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