forgejo/vendor/github.com/gogs/chardet/multi_byte.go

package chardet

import (
	"errors"
	"math"
)

type recognizerMultiByte struct {
	charset     string
	language    string
	decoder     charDecoder
	commonChars []uint16
}

type charDecoder interface {
	DecodeOneChar([]byte) (c uint16, remain []byte, err error)
}

func (r *recognizerMultiByte) Match(input *recognizerInput) (output recognizerOutput) {
	return recognizerOutput{
		Charset:    r.charset,
		Language:   r.language,
		Confidence: r.matchConfidence(input),
	}
}

func (r *recognizerMultiByte) matchConfidence(input *recognizerInput) int {
	raw := input.raw
	var c uint16
	var err error
	var totalCharCount, badCharCount, singleByteCharCount, doubleByteCharCount, commonCharCount int
	for c, raw, err = r.decoder.DecodeOneChar(raw); len(raw) > 0; c, raw, err = r.decoder.DecodeOneChar(raw) {
		totalCharCount++
		if err != nil {
			badCharCount++
		} else if c <= 0xFF {
			singleByteCharCount++
		} else {
			doubleByteCharCount++
			if r.commonChars != nil && binarySearch(r.commonChars, c) {
				commonCharCount++
			}
		}
		if badCharCount >= 2 && badCharCount*5 >= doubleByteCharCount {
			return 0
		}
	}

	if doubleByteCharCount <= 10 && badCharCount == 0 {
		if doubleByteCharCount == 0 && totalCharCount < 10 {
			return 0
		} else {
			return 10
		}
	}

	if doubleByteCharCount < 20*badCharCount {
		return 0
	}
	if r.commonChars == nil {
		confidence := 30 + doubleByteCharCount - 20*badCharCount
		if confidence > 100 {
			confidence = 100
		}
		return confidence
	}
	maxVal := math.Log(float64(doubleByteCharCount) / 4)
	scaleFactor := 90 / maxVal
	confidence := int(math.Log(float64(commonCharCount)+1)*scaleFactor + 10)
	if confidence > 100 {
		confidence = 100
	}
	if confidence < 0 {
		confidence = 0
	}
	return confidence
}

func binarySearch(l []uint16, c uint16) bool {
	start := 0
	end := len(l) - 1
	for start <= end {
		mid := (start + end) / 2
		if c == l[mid] {
			return true
		} else if c < l[mid] {
			end = mid - 1
		} else {
			start = mid + 1
		}
	}
	return false
}

var eobError = errors.New("End of input buffer")
var badCharError = errors.New("Decode a bad char")

type charDecoder_sjis struct {
}

func (charDecoder_sjis) DecodeOneChar(input []byte) (c uint16, remain []byte, err error) {
	if len(input) == 0 {
		return 0, nil, eobError
	}
	first := input[0]
	c = uint16(first)
	remain = input[1:]
	if first <= 0x7F || (first > 0xA0 && first <= 0xDF) {
		return
	}
	if len(remain) == 0 {
		return c, remain, badCharError
	}
	second := remain[0]
	remain = remain[1:]
	c = c<<8 | uint16(second)
	if (second >= 0x40 && second <= 0x7F) || (second >= 0x80 && second <= 0xFE) {
	} else {
		err = badCharError
	}
	return
}

var commonChars_sjis = []uint16{
	0x8140, 0x8141, 0x8142, 0x8145, 0x815b, 0x8169, 0x816a, 0x8175, 0x8176, 0x82a0,
	0x82a2, 0x82a4, 0x82a9, 0x82aa, 0x82ab, 0x82ad, 0x82af, 0x82b1, 0x82b3, 0x82b5,
	0x82b7, 0x82bd, 0x82be, 0x82c1, 0x82c4, 0x82c5, 0x82c6, 0x82c8, 0x82c9, 0x82cc,
	0x82cd, 0x82dc, 0x82e0, 0x82e7, 0x82e8, 0x82e9, 0x82ea, 0x82f0, 0x82f1, 0x8341,
	0x8343, 0x834e, 0x834f, 0x8358, 0x835e, 0x8362, 0x8367, 0x8375, 0x8376, 0x8389,
	0x838a, 0x838b, 0x838d, 0x8393, 0x8e96, 0x93fa, 0x95aa,
}

func newRecognizer_sjis() *recognizerMultiByte {
	return &recognizerMultiByte{
		"Shift_JIS",
		"ja",
		charDecoder_sjis{},
		commonChars_sjis,
	}
}

type charDecoder_euc struct {
}

func (charDecoder_euc) DecodeOneChar(input []byte) (c uint16, remain []byte, err error) {
	if len(input) == 0 {
		return 0, nil, eobError
	}
	first := input[0]
	remain = input[1:]
	c = uint16(first)
	if first <= 0x8D {
		return uint16(first), remain, nil
	}
	if len(remain) == 0 {
		return 0, nil, eobError
	}
	second := remain[0]
	remain = remain[1:]
	c = c<<8 | uint16(second)
	if first >= 0xA1 && first <= 0xFE {
		if second < 0xA1 {
			err = badCharError
		}
		return
	}
	if first == 0x8E {
		if second < 0xA1 {
			err = badCharError
		}
		return
	}
	if first == 0x8F {
		if len(remain) == 0 {
			return 0, nil, eobError
		}
		third := remain[0]
		remain = remain[1:]
		c = c<<0 | uint16(third)
		if third < 0xa1 {
			err = badCharError
		}
	}
	return
}

var commonChars_euc_jp = []uint16{
	0xa1a1, 0xa1a2, 0xa1a3, 0xa1a6, 0xa1bc, 0xa1ca, 0xa1cb, 0xa1d6, 0xa1d7, 0xa4a2,
	0xa4a4, 0xa4a6, 0xa4a8, 0xa4aa, 0xa4ab, 0xa4ac, 0xa4ad, 0xa4af, 0xa4b1, 0xa4b3,
	0xa4b5, 0xa4b7, 0xa4b9, 0xa4bb, 0xa4bd, 0xa4bf, 0xa4c0, 0xa4c1, 0xa4c3, 0xa4c4,
	0xa4c6, 0xa4c7, 0xa4c8, 0xa4c9, 0xa4ca, 0xa4cb, 0xa4ce, 0xa4cf, 0xa4d0, 0xa4de,
	0xa4df, 0xa4e1, 0xa4e2, 0xa4e4, 0xa4e8, 0xa4e9, 0xa4ea, 0xa4eb, 0xa4ec, 0xa4ef,
	0xa4f2, 0xa4f3, 0xa5a2, 0xa5a3, 0xa5a4, 0xa5a6, 0xa5a7, 0xa5aa, 0xa5ad, 0xa5af,
	0xa5b0, 0xa5b3, 0xa5b5, 0xa5b7, 0xa5b8, 0xa5b9, 0xa5bf, 0xa5c3, 0xa5c6, 0xa5c7,
	0xa5c8, 0xa5c9, 0xa5cb, 0xa5d0, 0xa5d5, 0xa5d6, 0xa5d7, 0xa5de, 0xa5e0, 0xa5e1,
	0xa5e5, 0xa5e9, 0xa5ea, 0xa5eb, 0xa5ec, 0xa5ed, 0xa5f3, 0xb8a9, 0xb9d4, 0xbaee,
	0xbbc8, 0xbef0, 0xbfb7, 0xc4ea, 0xc6fc, 0xc7bd, 0xcab8, 0xcaf3, 0xcbdc, 0xcdd1,
}

var commonChars_euc_kr = []uint16{
	0xb0a1, 0xb0b3, 0xb0c5, 0xb0cd, 0xb0d4, 0xb0e6, 0xb0ed, 0xb0f8, 0xb0fa, 0xb0fc,
	0xb1b8, 0xb1b9, 0xb1c7, 0xb1d7, 0xb1e2, 0xb3aa, 0xb3bb, 0xb4c2, 0xb4cf, 0xb4d9,
	0xb4eb, 0xb5a5, 0xb5b5, 0xb5bf, 0xb5c7, 0xb5e9, 0xb6f3, 0xb7af, 0xb7c2, 0xb7ce,
	0xb8a6, 0xb8ae, 0xb8b6, 0xb8b8, 0xb8bb, 0xb8e9, 0xb9ab, 0xb9ae, 0xb9cc, 0xb9ce,
	0xb9fd, 0xbab8, 0xbace, 0xbad0, 0xbaf1, 0xbbe7, 0xbbf3, 0xbbfd, 0xbcad, 0xbcba,
	0xbcd2, 0xbcf6, 0xbdba, 0xbdc0, 0xbdc3, 0xbdc5, 0xbec6, 0xbec8, 0xbedf, 0xbeee,
	0xbef8, 0xbefa, 0xbfa1, 0xbfa9, 0xbfc0, 0xbfe4, 0xbfeb, 0xbfec, 0xbff8, 0xc0a7,
	0xc0af, 0xc0b8, 0xc0ba, 0xc0bb, 0xc0bd, 0xc0c7, 0xc0cc, 0xc0ce, 0xc0cf, 0xc0d6,
	0xc0da, 0xc0e5, 0xc0fb, 0xc0fc, 0xc1a4, 0xc1a6, 0xc1b6, 0xc1d6, 0xc1df, 0xc1f6,
	0xc1f8, 0xc4a1, 0xc5cd, 0xc6ae, 0xc7cf, 0xc7d1, 0xc7d2, 0xc7d8, 0xc7e5, 0xc8ad,
}

func newRecognizer_euc_jp() *recognizerMultiByte {
	return &recognizerMultiByte{
		"EUC-JP",
		"ja",
		charDecoder_euc{},
		commonChars_euc_jp,
	}
}

func newRecognizer_euc_kr() *recognizerMultiByte {
	return &recognizerMultiByte{
		"EUC-KR",
		"ko",
		charDecoder_euc{},
		commonChars_euc_kr,
	}
}

type charDecoder_big5 struct {
}

func (charDecoder_big5) DecodeOneChar(input []byte) (c uint16, remain []byte, err error) {
	if len(input) == 0 {
		return 0, nil, eobError
	}
	first := input[0]
	remain = input[1:]
	c = uint16(first)
	if first <= 0x7F || first == 0xFF {
		return
	}
	if len(remain) == 0 {
		return c, nil, eobError
	}
	second := remain[0]
	remain = remain[1:]
	c = c<<8 | uint16(second)
	if second < 0x40 || second == 0x7F || second == 0xFF {
		err = badCharError
	}
	return
}

var commonChars_big5 = []uint16{
	0xa140, 0xa141, 0xa142, 0xa143, 0xa147, 0xa149, 0xa175, 0xa176, 0xa440, 0xa446,
	0xa447, 0xa448, 0xa451, 0xa454, 0xa457, 0xa464, 0xa46a, 0xa46c, 0xa477, 0xa4a3,
	0xa4a4, 0xa4a7, 0xa4c1, 0xa4ce, 0xa4d1, 0xa4df, 0xa4e8, 0xa4fd, 0xa540, 0xa548,
	0xa558, 0xa569, 0xa5cd, 0xa5e7, 0xa657, 0xa661, 0xa662, 0xa668, 0xa670, 0xa6a8,
	0xa6b3, 0xa6b9, 0xa6d3, 0xa6db, 0xa6e6, 0xa6f2, 0xa740, 0xa751, 0xa759, 0xa7da,
	0xa8a3, 0xa8a5, 0xa8ad, 0xa8d1, 0xa8d3, 0xa8e4, 0xa8fc, 0xa9c0, 0xa9d2, 0xa9f3,
	0xaa6b, 0xaaba, 0xaabe, 0xaacc, 0xaafc, 0xac47, 0xac4f, 0xacb0, 0xacd2, 0xad59,
	0xaec9, 0xafe0, 0xb0ea, 0xb16f, 0xb2b3, 0xb2c4, 0xb36f, 0xb44c, 0xb44e, 0xb54c,
	0xb5a5, 0xb5bd, 0xb5d0, 0xb5d8, 0xb671, 0xb7ed, 0xb867, 0xb944, 0xbad8, 0xbb44,
	0xbba1, 0xbdd1, 0xc2c4, 0xc3b9, 0xc440, 0xc45f,
}

func newRecognizer_big5() *recognizerMultiByte {
	return &recognizerMultiByte{
		"Big5",
		"zh",
		charDecoder_big5{},
		commonChars_big5,
	}
}

type charDecoder_gb_18030 struct {
}

func (charDecoder_gb_18030) DecodeOneChar(input []byte) (c uint16, remain []byte, err error) {
	if len(input) == 0 {
		return 0, nil, eobError
	}
	first := input[0]
	remain = input[1:]
	c = uint16(first)
	if first <= 0x80 {
		return
	}
	if len(remain) == 0 {
		return 0, nil, eobError
	}
	second := remain[0]
	remain = remain[1:]
	c = c<<8 | uint16(second)
	if first >= 0x81 && first <= 0xFE {
		if (second >= 0x40 && second <= 0x7E) || (second >= 0x80 && second <= 0xFE) {
			return
		}

		if second >= 0x30 && second <= 0x39 {
			if len(remain) == 0 {
				return 0, nil, eobError
			}
			third := remain[0]
			remain = remain[1:]
			if third >= 0x81 && third <= 0xFE {
				if len(remain) == 0 {
					return 0, nil, eobError
				}
				fourth := remain[0]
				remain = remain[1:]
				if fourth >= 0x30 && fourth <= 0x39 {
					c = c<<16 | uint16(third)<<8 | uint16(fourth)
					return
				}
			}
		}
		err = badCharError
	}
	return
}

var commonChars_gb_18030 = []uint16{
	0xa1a1, 0xa1a2, 0xa1a3, 0xa1a4, 0xa1b0, 0xa1b1, 0xa1f1, 0xa1f3, 0xa3a1, 0xa3ac,
	0xa3ba, 0xb1a8, 0xb1b8, 0xb1be, 0xb2bb, 0xb3c9, 0xb3f6, 0xb4f3, 0xb5bd, 0xb5c4,
	0xb5e3, 0xb6af, 0xb6d4, 0xb6e0, 0xb7a2, 0xb7a8, 0xb7bd, 0xb7d6, 0xb7dd, 0xb8b4,
	0xb8df, 0xb8f6, 0xb9ab, 0xb9c9, 0xb9d8, 0xb9fa, 0xb9fd, 0xbacd, 0xbba7, 0xbbd6,
	0xbbe1, 0xbbfa, 0xbcbc, 0xbcdb, 0xbcfe, 0xbdcc, 0xbecd, 0xbedd, 0xbfb4, 0xbfc6,
	0xbfc9, 0xc0b4, 0xc0ed, 0xc1cb, 0xc2db, 0xc3c7, 0xc4dc, 0xc4ea, 0xc5cc, 0xc6f7,
	0xc7f8, 0xc8ab, 0xc8cb, 0xc8d5, 0xc8e7, 0xc9cf, 0xc9fa, 0xcab1, 0xcab5, 0xcac7,
	0xcad0, 0xcad6, 0xcaf5, 0xcafd, 0xccec, 0xcdf8, 0xceaa, 0xcec4, 0xced2, 0xcee5,
	0xcfb5, 0xcfc2, 0xcfd6, 0xd0c2, 0xd0c5, 0xd0d0, 0xd0d4, 0xd1a7, 0xd2aa, 0xd2b2,
	0xd2b5, 0xd2bb, 0xd2d4, 0xd3c3, 0xd3d0, 0xd3fd, 0xd4c2, 0xd4da, 0xd5e2, 0xd6d0,
}

func newRecognizer_gb_18030() *recognizerMultiByte {
	return &recognizerMultiByte{
		"GB18030",
		"zh",
		charDecoder_gb_18030{},
		commonChars_gb_18030,
	}
}