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124 lines
3.7 KiB
JavaScript
124 lines
3.7 KiB
JavaScript
import { inRange, decoderError, encoderError, isASCIICodePoint,
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end_of_stream, finished, isASCIIByte, floor } from './text_decoder_utils.js'
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import index, { indexCodePointFor, indexPointerFor } from './text_decoder_indexes.js'
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//
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// 14. Legacy multi-byte Korean encodings
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//
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// 14.1 euc-kr
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// 14.1.1 euc-kr decoder
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/**
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* @implements {Decoder}
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*/
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export class EUCKRDecoder {
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constructor(options) {
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const { fatal } = options
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this.fatal = fatal
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// euc-kr's decoder has an associated euc-kr lead (initially 0x00).
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this.euckr_lead = 0x00
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}
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/**
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* @param {Stream} stream The stream of bytes being decoded.
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* @param {number} bite The next byte read from the stream.
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*/
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handler(stream, bite) {
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// 1. If byte is end-of-stream and euc-kr lead is not 0x00, set
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// euc-kr lead to 0x00 and return error.
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if (bite === end_of_stream && this.euckr_lead !== 0) {
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this.euckr_lead = 0x00
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return decoderError(this.fatal)
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}
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// 2. If byte is end-of-stream and euc-kr lead is 0x00, return
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// finished.
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if (bite === end_of_stream && this.euckr_lead === 0)
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return finished
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// 3. If euc-kr lead is not 0x00, let lead be euc-kr lead, let
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// pointer be null, set euc-kr lead to 0x00, and then run these
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// substeps:
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if (this.euckr_lead !== 0x00) {
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const lead = this.euckr_lead
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let pointer = null
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this.euckr_lead = 0x00
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// 1. If byte is in the range 0x41 to 0xFE, inclusive, set
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// pointer to (lead − 0x81) × 190 + (byte − 0x41).
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if (inRange(bite, 0x41, 0xFE))
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pointer = (lead - 0x81) * 190 + (bite - 0x41)
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// 2. Let code point be null, if pointer is null, and the
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// index code point for pointer in index euc-kr otherwise.
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const code_point = (pointer === null)
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? null : indexCodePointFor(pointer, index('euc-kr'))
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// 3. If code point is null and byte is an ASCII byte, prepend
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// byte to stream.
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if (pointer === null && isASCIIByte(bite))
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stream.prepend(bite)
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// 4. If code point is null, return error.
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if (code_point === null)
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return decoderError(this.fatal)
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// 5. Return a code point whose value is code point.
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return code_point
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}
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// 4. If byte is an ASCII byte, return a code point whose value
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// is byte.
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if (isASCIIByte(bite))
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return bite
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// 5. If byte is in the range 0x81 to 0xFE, inclusive, set
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// euc-kr lead to byte and return continue.
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if (inRange(bite, 0x81, 0xFE)) {
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this.euckr_lead = bite
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return null
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}
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// 6. Return error.
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return decoderError(this.fatal)
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}
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}
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// 14.1.2 euc-kr encoder
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/**
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* @implements {Encoder}
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*/
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export class EUCKREncoder {
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/**
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* @param {Stream} stream Input stream.
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* @param {number} code_point Next code point read from the stream.
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* @return {(number|!Array.<number>)} Byte(s) to emit.
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*/
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handler(stream, code_point) {
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// 1. If code point is end-of-stream, return finished.
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if (code_point === end_of_stream)
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return finished
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// 2. If code point is an ASCII code point, return a byte whose
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// value is code point.
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if (isASCIICodePoint(code_point))
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return code_point
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// 3. Let pointer be the index pointer for code point in index
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// euc-kr.
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const pointer = indexPointerFor(code_point, index('euc-kr'))
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// 4. If pointer is null, return error with code point.
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if (pointer === null)
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return encoderError(code_point)
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// 5. Let lead be floor(pointer / 190) + 0x81.
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const lead = floor(pointer / 190) + 0x81
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// 6. Let trail be pointer % 190 + 0x41.
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const trail = (pointer % 190) + 0x41
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// 7. Return two bytes whose values are lead and trail.
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return [lead, trail]
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}
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} |