diff options
Diffstat (limited to 'vendor/github.com/emersion/go-imap/utf7/encoder.go')
-rw-r--r-- | vendor/github.com/emersion/go-imap/utf7/encoder.go | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/vendor/github.com/emersion/go-imap/utf7/encoder.go b/vendor/github.com/emersion/go-imap/utf7/encoder.go new file mode 100644 index 0000000..8414d10 --- /dev/null +++ b/vendor/github.com/emersion/go-imap/utf7/encoder.go @@ -0,0 +1,91 @@ +package utf7 + +import ( + "unicode/utf16" + "unicode/utf8" + + "golang.org/x/text/transform" +) + +type encoder struct{} + +func (e *encoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { + for i := 0; i < len(src); { + ch := src[i] + + var b []byte + if min <= ch && ch <= max { + b = []byte{ch} + if ch == '&' { + b = append(b, '-') + } + + i++ + } else { + start := i + + // Find the next printable ASCII code point + i++ + for i < len(src) && (src[i] < min || src[i] > max) { + i++ + } + + if !atEOF && i == len(src) { + err = transform.ErrShortSrc + return + } + + b = encode(src[start:i]) + } + + if nDst+len(b) > len(dst) { + err = transform.ErrShortDst + return + } + + nSrc = i + + for _, ch := range b { + dst[nDst] = ch + nDst++ + } + } + + return +} + +func (e *encoder) Reset() {} + +// Converts string s from UTF-8 to UTF-16-BE, encodes the result as base64, +// removes the padding, and adds UTF-7 shifts. +func encode(s []byte) []byte { + // len(s) is sufficient for UTF-8 to UTF-16 conversion if there are no + // control code points (see table below). + b := make([]byte, 0, len(s)+4) + for len(s) > 0 { + r, size := utf8.DecodeRune(s) + if r > utf8.MaxRune { + r, size = utf8.RuneError, 1 // Bug fix (issue 3785) + } + s = s[size:] + if r1, r2 := utf16.EncodeRune(r); r1 != repl { + b = append(b, byte(r1>>8), byte(r1)) + r = r2 + } + b = append(b, byte(r>>8), byte(r)) + } + + // Encode as base64 + n := b64Enc.EncodedLen(len(b)) + 2 + b64 := make([]byte, n) + b64Enc.Encode(b64[1:], b) + + // Strip padding + n -= 2 - (len(b)+2)%3 + b64 = b64[:n] + + // Add UTF-7 shifts + b64[0] = '&' + b64[n-1] = '-' + return b64 +} |