import { decoderError } from "../../encoding/encodings";
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import { finished } from "../../encoding/finished";
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import { end_of_stream } from "../../encoding/terminology";
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import { inRange } from "../../encoding/utilities";
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import { convertCodeUnitToBytes } from "./converCodeUnitToBytes";
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/**
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* @constructor
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* @implements {Decoder}
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* @param {boolean} utf16_be True if big-endian, false if little-endian.
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* @param {{fatal: boolean}} options
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*/
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export class UTF16Decoder {
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constructor(utf16_be, options) {
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this.utf16_be = utf16_be;
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this.fatal = options.fatal;
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/** @type {?number} */ this.utf16_lead_byte = null;
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/** @type {?number} */ this.utf16_lead_surrogate = null;
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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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* @return {?(number|!Array.<number>)} The next code point(s)
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* decoded, or null if not enough data exists in the input
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* stream to decode a complete code point.
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*/
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handler(stream, bite) {
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// 1. If byte is end-of-stream and either utf-16 lead byte or
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// utf-16 lead surrogate is not null, set utf-16 lead byte and
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// utf-16 lead surrogate to null, and return error.
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if (bite === end_of_stream && (this.utf16_lead_byte !== null ||
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this.utf16_lead_surrogate !== null)) {
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return decoderError(this.fatal);
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}
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// 2. If byte is end-of-stream and utf-16 lead byte and utf-16
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// lead surrogate are null, return finished.
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if (bite === end_of_stream && this.utf16_lead_byte === null &&
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this.utf16_lead_surrogate === null) {
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return finished;
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}
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// 3. If utf-16 lead byte is null, set utf-16 lead byte to byte
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// and return continue.
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if (this.utf16_lead_byte === null) {
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this.utf16_lead_byte = bite;
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return null;
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}
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// 4. Let code unit be the result of:
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let code_unit;
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if (this.utf16_be) {
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// utf-16be decoder flag is set
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// (utf-16 lead byte << 8) + byte.
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code_unit = (this.utf16_lead_byte << 8) + bite;
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}
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else {
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// utf-16be decoder flag is unset
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// (byte << 8) + utf-16 lead byte.
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code_unit = (bite << 8) + this.utf16_lead_byte;
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}
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// Then set utf-16 lead byte to null.
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this.utf16_lead_byte = null;
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// 5. If utf-16 lead surrogate is not null, let lead surrogate
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// be utf-16 lead surrogate, set utf-16 lead surrogate to null,
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// and then run these substeps:
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if (this.utf16_lead_surrogate !== null) {
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const lead_surrogate = this.utf16_lead_surrogate;
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this.utf16_lead_surrogate = null;
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// 1. If code unit is in the range U+DC00 to U+DFFF,
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// inclusive, return a code point whose value is 0x10000 +
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// ((lead surrogate − 0xD800) << 10) + (code unit − 0xDC00).
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if (inRange(code_unit, 0xDC00, 0xDFFF)) {
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return 0x10000 + (lead_surrogate - 0xD800) * 0x400 +
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(code_unit - 0xDC00);
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}
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// 2. Prepend the sequence resulting of converting code unit
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// to bytes using utf-16be decoder flag to stream and return
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// error.
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stream.prepend(convertCodeUnitToBytes(code_unit, this.utf16_be));
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return decoderError(this.fatal);
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}
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// 6. If code unit is in the range U+D800 to U+DBFF, inclusive,
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// set utf-16 lead surrogate to code unit and return continue.
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if (inRange(code_unit, 0xD800, 0xDBFF)) {
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this.utf16_lead_surrogate = code_unit;
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return null;
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}
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// 7. If code unit is in the range U+DC00 to U+DFFF, inclusive,
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// return error.
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if (inRange(code_unit, 0xDC00, 0xDFFF))
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return decoderError(this.fatal);
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// 8. Return code point code unit.
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return code_unit;
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}
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}
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//# sourceMappingURL=UTF16Decoder.js.map
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