path: root/vendor/golang.org/x/text/encoding/japanese/shiftjis.go

// Copyright 2013 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 japanese

import (
    "errors"
    "unicode/utf8"

    "golang.org/x/text/encoding"
    "golang.org/x/text/encoding/internal"
    "golang.org/x/text/encoding/internal/identifier"
    "golang.org/x/text/transform"
)

// ShiftJIS is the Shift JIS encoding, also known as Code Page 932 and
// Windows-31J.
var ShiftJIS encoding.Encoding = &shiftJIS

var shiftJIS = internal.Encoding{
    &internal.SimpleEncoding{shiftJISDecoder{}, shiftJISEncoder{}},
    "Shift JIS",
    identifier.ShiftJIS,
}

var errInvalidShiftJIS = errors.New("japanese: invalid Shift JIS encoding")

type shiftJISDecoder struct{ transform.NopResetter }

func (shiftJISDecoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
    r, size := rune(0), 0
loop:
    for ; nSrc < len(src); nSrc += size {
        switch c0 := src[nSrc]; {
        case c0 < utf8.RuneSelf:
            r, size = rune(c0), 1

        case 0xa1 <= c0 && c0 < 0xe0:
            r, size = rune(c0)+(0xff61-0xa1), 1

        case (0x81 <= c0 && c0 < 0xa0) || (0xe0 <= c0 && c0 < 0xfd):
            if c0 <= 0x9f {
                c0 -= 0x70
            } else {
                c0 -= 0xb0
            }
            c0 = 2*c0 - 0x21

            if nSrc+1 >= len(src) {
                err = transform.ErrShortSrc
                break loop
            }
            c1 := src[nSrc+1]
            switch {
            case c1 < 0x40:
                err = errInvalidShiftJIS
                break loop
            case c1 < 0x7f:
                c0--
                c1 -= 0x40
            case c1 == 0x7f:
                err = errInvalidShiftJIS
                break loop
            case c1 < 0x9f:
                c0--
                c1 -= 0x41
            case c1 < 0xfd:
                c1 -= 0x9f
            default:
                err = errInvalidShiftJIS
                break loop
            }
            r, size = '\ufffd', 2
            if i := int(c0)*94 + int(c1); i < len(jis0208Decode) {
                r = rune(jis0208Decode[i])
                if r == 0 {
                    r = '\ufffd'
                }
            }

        default:
            err = errInvalidShiftJIS
            break loop
        }

        if nDst+utf8.RuneLen(r) > len(dst) {
            err = transform.ErrShortDst
            break loop
        }
        nDst += utf8.EncodeRune(dst[nDst:], r)
    }
    if atEOF && err == transform.ErrShortSrc {
        err = errInvalidShiftJIS
    }
    return nDst, nSrc, err
}

type shiftJISEncoder struct{ transform.NopResetter }

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

        // Decode a 1-byte rune.
        if r < utf8.RuneSelf {
            size = 1

        } else {
            // 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 loop
                }
            }

            // func init checks that the switch covers all tables.
            switch {
            case encode0Low <= r && r < encode0High:
                if r = rune(encode0[r-encode0Low]); r>>tableShift == jis0208 {
                    goto write2
                }
            case encode1Low <= r && r < encode1High:
                if r = rune(encode1[r-encode1Low]); r>>tableShift == jis0208 {
                    goto write2
                }
            case encode2Low <= r && r < encode2High:
                if r = rune(encode2[r-encode2Low]); r>>tableShift == jis0208 {
                    goto write2
                }
            case encode3Low <= r && r < encode3High:
                if r = rune(encode3[r-encode3Low]); r>>tableShift == jis0208 {
                    goto write2
                }
            case encode4Low <= r && r < encode4High:
                if r = rune(encode4[r-encode4Low]); r>>tableShift == jis0208 {
                    goto write2
                }
            case encode5Low <= r && r < encode5High:
                if 0xff61 <= r && r < 0xffa0 {
                    r -= 0xff61 - 0xa1
                    goto write1
                }
                if r = rune(encode5[r-encode5Low]); r>>tableShift == jis0208 {
                    goto write2
                }
            }
            err = internal.ErrASCIIReplacement
            break
        }

    write1:
        if nDst >= len(dst) {
            err = transform.ErrShortDst
            break
        }
        dst[nDst] = uint8(r)
        nDst++
        continue

    write2:
        j1 := uint8(r>>codeShift) & codeMask
        j2 := uint8(r) & codeMask
        if nDst+2 > len(dst) {
            err = transform.ErrShortDst
            break loop
        }
        if j1 <= 61 {
            dst[nDst+0] = 129 + j1/2
        } else {
            dst[nDst+0] = 193 + j1/2
        }
        if j1&1 == 0 {
            dst[nDst+1] = j2 + j2/63 + 64
        } else {
            dst[nDst+1] = j2 + 159
        }
        nDst += 2
        continue
    }
    return nDst, nSrc, err
}