forked from jhillyerd/enmime
/
quotedprint.go
86 lines (79 loc) · 1.76 KB
/
quotedprint.go
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package coding
import (
"bufio"
"fmt"
"io"
)
// QPCleaner scans quoted printable content for invalid characters and encodes them so that
// Go's quoted-printable decoder does not abort with an error.
type QPCleaner struct {
in *bufio.Reader
}
// Assert QPCleaner implements io.Reader.
var _ io.Reader = &QPCleaner{}
// NewQPCleaner returns a QPCleaner for the specified reader.
func NewQPCleaner(r io.Reader) *QPCleaner {
return &QPCleaner{
in: bufio.NewReader(r),
}
}
// Read method for io.Reader interface.
func (qp *QPCleaner) Read(dest []byte) (n int, err error) {
// Ensure room to write a byte or =XX string.
destLen := len(dest) - 3
// Loop over bytes in qp.in ByteReader.
for n < destLen {
b, err := qp.in.ReadByte()
if err != nil {
return n, err
}
switch {
case b == '=':
// Pass valid hex bytes through.
hexBytes, err := qp.in.Peek(2)
if err != nil && err != io.EOF {
return 0, err
}
if validHexBytes(hexBytes) {
dest[n] = b
n++
} else {
s := fmt.Sprintf("=%02X", b)
n += copy(dest[n:], s)
}
case b == '\t' || b == '\r' || b == '\n':
// Valid special character.
dest[n] = b
n++
case b < ' ' || '~' < b:
// Invalid character, render quoted-printable into buffer.
s := fmt.Sprintf("=%02X", b)
n += copy(dest[n:], s)
default:
// Acceptable character.
dest[n] = b
n++
}
}
return n, err
}
func validHexByte(b byte) bool {
return '0' <= b && b <= '9' || 'A' <= b && b <= 'F' || 'a' <= b && b <= 'f'
}
func validHexBytes(v []byte) bool {
if len(v) < 1 {
return false
}
if v[0] == '\n' {
// Soft line break.
return true
}
if len(v) < 2 {
return false
}
if v[0] == '\r' && v[1] == '\n' {
// Soft line break.
return true
}
return validHexByte(v[0]) && validHexByte(v[1])
}