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writter.go
179 lines (160 loc) · 3.28 KB
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writter.go
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package uuencode
import (
"bufio"
"fmt"
"io"
"os"
)
var (
writeEnd = []byte{'`', '\n', 'e', 'n', 'd', '\n'}
)
type Writer struct {
inner *bufio.Writer
file string
mode os.FileMode
ln []byte
lnpos byte
lnsz byte
rem []byte
flushed bool
wroteHdr bool
}
func FileWriter(w *os.File, file string, mode os.FileMode) (*Writer, error) {
inf, err := w.Stat()
if err != nil {
return nil, err
}
return NewWriter(w, w.Name(), inf.Mode()), nil
}
func NewWriter(w io.Writer, file string, mode os.FileMode) *Writer {
bw, ok := w.(*bufio.Writer)
if !ok {
bw = bufio.NewWriter(w)
}
return &Writer{
inner: bw,
file: file,
mode: mode,
ln: make([]byte, 62),
lnpos: 1,
rem: make([]byte, 0, 3),
}
}
func (w *Writer) flushLine() error {
lnsz := w.lnsz // doesn't include newline or length
if lnsz == 0 {
w.ln[0] = '`' // 0-length line
} else {
w.ln[0] = byte(lnsz + 32)
}
w.ln[w.lnpos] = '\n'
if _, err := w.inner.Write(w.ln[:w.lnpos+1]); err != nil {
return err
}
w.lnsz = 0
w.lnpos = 1
return nil
}
func (w *Writer) writeHdr() error {
_, err := fmt.Fprintf(w.inner, "begin %03o %s\n", w.mode, w.file)
w.wroteHdr = true
return err
}
func (w *Writer) Write(b []byte) (n int, err error) {
if w.flushed {
return n, fmt.Errorf("uunecode: already flushed")
}
if !w.wroteHdr {
if err := w.writeHdr(); err != nil {
return n, err
}
}
bsz := len(b)
remsz := len(w.rem)
bpos := 0
if remsz > 0 {
if bsz+remsz < 3 {
w.rem = append(w.rem, b...)
return bsz, nil
} else {
bpos = 3 - remsz
out := append(w.rem, b[:bpos]...)
n = bpos
uupack(w.ln[w.lnpos:], out)
w.lnpos += 4
w.lnsz += 3
if w.lnpos >= 61 {
if err := w.flushLine(); err != nil {
return n, err
}
}
w.rem = w.rem[:0]
}
}
bend := bsz - ((bsz - bpos) % 3)
if bend >= 3 {
for ; n < bend; n += 3 {
uupack(w.ln[w.lnpos:], b[n:])
w.lnpos += 4
w.lnsz += 3
if w.lnpos >= 61 {
if err := w.flushLine(); err != nil {
return n, err
}
}
}
}
if bsz-bend > 0 {
w.rem = append(w.rem, b[bend:]...)
n += bsz - bend
}
return n, nil
}
func (w *Writer) Flush() error {
if w.flushed {
return fmt.Errorf("uunecode: already flushed")
}
if !w.wroteHdr {
if err := w.writeHdr(); err != nil {
return err
}
}
remsz := len(w.rem)
if remsz > 0 {
switch remsz {
case 2:
w.rem = append(w.rem, 0)
case 1:
w.rem = append(w.rem, 0, 0)
case 0:
default:
panic("unexpected rem size")
}
uupack(w.ln[w.lnpos:], w.rem)
w.lnsz += byte(remsz)
w.lnpos += 4
}
w.flushed = true
if err := w.flushLine(); err != nil {
return err
}
if _, err := w.inner.Write(writeEnd); err != nil {
return err
}
return w.inner.Flush()
}
var uuTable = [64]byte{
'`', '!', '"', '#', '$', '%', '&', '\'', '(', ')', '*', '+', ',', '-', '.', '/',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ':', ';', '<', '=', '>', '?',
'@', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '[', '\\', ']', '^', '_',
}
func uupack(into []byte, b []byte) {
// b0 = 000000 00
// b1 = 0000 0000
// b2 = 00 000000
into[0] = uuTable[b[0]>>2]
into[1] = uuTable[(b[0]<<4|b[1]>>4)&63]
into[2] = uuTable[(b[1]<<2|b[2]>>6)&63]
into[3] = uuTable[b[2]&63]
}