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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/**
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* @constructor
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* @implements {Decoder}
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* @param {{fatal: boolean}} options
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*/
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export class UTF8Decoder {
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constructor(options) {
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this.fatal = options.fatal;
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// utf-8's decoder's has an associated utf-8 code point, utf-8
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// bytes seen, and utf-8 bytes needed (all initially 0), a utf-8
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// lower boundary (initially 0x80), and a utf-8 upper boundary
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// (initially 0xBF).
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/** @type {number} */ this.utf8_code_point = 0,
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/** @type {number} */ this.utf8_bytes_seen = 0,
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/** @type {number} */ this.utf8_bytes_needed = 0,
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/** @type {number} */ this.utf8_lower_boundary = 0x80,
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/** @type {number} */ this.utf8_upper_boundary = 0xBF;
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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 utf-8 bytes needed is not 0,
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// set utf-8 bytes needed to 0 and return error.
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if (bite === end_of_stream && this.utf8_bytes_needed !== 0) {
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this.utf8_bytes_needed = 0;
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return decoderError(this.fatal);
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}
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// 2. If byte is end-of-stream, return finished.
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if (bite === end_of_stream)
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return finished;
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// 3. If utf-8 bytes needed is 0, based on byte:
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if (this.utf8_bytes_needed === 0) {
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// 0x00 to 0x7F
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if (inRange(bite, 0x00, 0x7F)) {
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// Return a code point whose value is byte.
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return bite;
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}
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// 0xC2 to 0xDF
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else if (inRange(bite, 0xC2, 0xDF)) {
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// 1. Set utf-8 bytes needed to 1.
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this.utf8_bytes_needed = 1;
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// 2. Set UTF-8 code point to byte & 0x1F.
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this.utf8_code_point = bite & 0x1F;
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}
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// 0xE0 to 0xEF
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else if (inRange(bite, 0xE0, 0xEF)) {
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// 1. If byte is 0xE0, set utf-8 lower boundary to 0xA0.
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if (bite === 0xE0)
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this.utf8_lower_boundary = 0xA0;
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// 2. If byte is 0xED, set utf-8 upper boundary to 0x9F.
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if (bite === 0xED)
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this.utf8_upper_boundary = 0x9F;
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// 3. Set utf-8 bytes needed to 2.
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this.utf8_bytes_needed = 2;
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// 4. Set UTF-8 code point to byte & 0xF.
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this.utf8_code_point = bite & 0xF;
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}
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// 0xF0 to 0xF4
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else if (inRange(bite, 0xF0, 0xF4)) {
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// 1. If byte is 0xF0, set utf-8 lower boundary to 0x90.
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if (bite === 0xF0)
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this.utf8_lower_boundary = 0x90;
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// 2. If byte is 0xF4, set utf-8 upper boundary to 0x8F.
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if (bite === 0xF4)
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this.utf8_upper_boundary = 0x8F;
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// 3. Set utf-8 bytes needed to 3.
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this.utf8_bytes_needed = 3;
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// 4. Set UTF-8 code point to byte & 0x7.
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this.utf8_code_point = bite & 0x7;
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}
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// Otherwise
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else {
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// Return error.
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return decoderError(this.fatal);
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}
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// Return continue.
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return null;
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}
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// 4. If byte is not in the range utf-8 lower boundary to utf-8
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// upper boundary, inclusive, run these substeps:
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if (!inRange(bite, this.utf8_lower_boundary, this.utf8_upper_boundary)) {
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// 1. Set utf-8 code point, utf-8 bytes needed, and utf-8
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// bytes seen to 0, set utf-8 lower boundary to 0x80, and set
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// utf-8 upper boundary to 0xBF.
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this.utf8_code_point = this.utf8_bytes_needed = this.utf8_bytes_seen = 0;
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this.utf8_lower_boundary = 0x80;
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this.utf8_upper_boundary = 0xBF;
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// 2. Prepend byte to stream.
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stream.prepend(bite);
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// 3. Return error.
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return decoderError(this.fatal);
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}
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// 5. Set utf-8 lower boundary to 0x80 and utf-8 upper boundary
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// to 0xBF.
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this.utf8_lower_boundary = 0x80;
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this.utf8_upper_boundary = 0xBF;
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// 6. Set UTF-8 code point to (UTF-8 code point << 6) | (byte &
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// 0x3F)
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this.utf8_code_point = (this.utf8_code_point << 6) | (bite & 0x3F);
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// 7. Increase utf-8 bytes seen by one.
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this.utf8_bytes_seen += 1;
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// 8. If utf-8 bytes seen is not equal to utf-8 bytes needed,
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// continue.
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if (this.utf8_bytes_seen !== this.utf8_bytes_needed)
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return null;
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// 9. Let code point be utf-8 code point.
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const code_point = this.utf8_code_point;
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// 10. Set utf-8 code point, utf-8 bytes needed, and utf-8 bytes
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// seen to 0.
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this.utf8_code_point = this.utf8_bytes_needed = this.utf8_bytes_seen = 0;
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// 11. Return a code point whose value is code point.
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return code_point;
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}
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}
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//# sourceMappingURL=UTF8Decoder.js.map
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