func()

in encoding/simplifiedchinese/hzgb2312.go [131:245]

• 99 lines of code
• 35 McCabe index (conditional complexity)

func (e *hzGB2312Encoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
	r, size := rune(0), 0
	for ; nSrc < len(src); nSrc += size {
		r = rune(src[nSrc])

		// Decode a 1-byte rune.
		if r < utf8.RuneSelf {
			size = 1
			if r == '~' {
				if nDst+2 > len(dst) {
					err = transform.ErrShortDst
					break
				}
				dst[nDst+0] = '~'
				dst[nDst+1] = '~'
				nDst += 2
				continue
			} else if *e != asciiState {
				if nDst+3 > len(dst) {
					err = transform.ErrShortDst
					break
				}
				*e = asciiState
				dst[nDst+0] = '~'
				dst[nDst+1] = '}'
				nDst += 2
			} else if nDst >= len(dst) {
				err = transform.ErrShortDst
				break
			}
			dst[nDst] = uint8(r)
			nDst += 1
			continue

		}

		// Decode a multi-byte rune.
		r, size = utf8.DecodeRune(src[nSrc:])
		if size == 1 {
			// All valid runes of size 1 (those below utf8.RuneSelf) were
			// handled above. We have invalid UTF-8 or we haven't seen the
			// full character yet.
			if !atEOF && !utf8.FullRune(src[nSrc:]) {
				err = transform.ErrShortSrc
				break
			}
		}

		// func init checks that the switch covers all tables.
		switch {
		case encode0Low <= r && r < encode0High:
			if r = rune(encode0[r-encode0Low]); r != 0 {
				goto writeGB
			}
		case encode1Low <= r && r < encode1High:
			if r = rune(encode1[r-encode1Low]); r != 0 {
				goto writeGB
			}
		case encode2Low <= r && r < encode2High:
			if r = rune(encode2[r-encode2Low]); r != 0 {
				goto writeGB
			}
		case encode3Low <= r && r < encode3High:
			if r = rune(encode3[r-encode3Low]); r != 0 {
				goto writeGB
			}
		case encode4Low <= r && r < encode4High:
			if r = rune(encode4[r-encode4Low]); r != 0 {
				goto writeGB
			}
		}

	terminateInASCIIState:
		// Switch back to ASCII state in case of error so that an ASCII
		// replacement character can be written in the correct state.
		if *e != asciiState {
			if nDst+2 > len(dst) {
				err = transform.ErrShortDst
				break
			}
			dst[nDst+0] = '~'
			dst[nDst+1] = '}'
			nDst += 2
		}
		err = internal.ErrASCIIReplacement
		break

	writeGB:
		c0 := uint8(r>>8) - 0x80
		c1 := uint8(r) - 0x80
		if c0 < 0x21 || 0x7e <= c0 || c1 < 0x21 || 0x7f <= c1 {
			goto terminateInASCIIState
		}
		if *e == asciiState {
			if nDst+4 > len(dst) {
				err = transform.ErrShortDst
				break
			}
			*e = gbState
			dst[nDst+0] = '~'
			dst[nDst+1] = '{'
			nDst += 2
		} else if nDst+2 > len(dst) {
			err = transform.ErrShortDst
			break
		}
		dst[nDst+0] = c0
		dst[nDst+1] = c1
		nDst += 2
		continue
	}
	// TODO: should one always terminate in ASCII state to make it safe to
	// concatenate two HZ-GB2312-encoded strings?
	return nDst, nSrc, err
}