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62 lines
2.2 KiB
JavaScript
62 lines
2.2 KiB
JavaScript
import { finished } from "../../encoding/finished";
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import { end_of_stream, isASCIICodePoint } 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 {Encoder}
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* @param {{fatal: boolean}} options
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*/
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export class UTF8Encoder {
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constructor(options) {
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this.fatal = options.fatal;
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}
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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. Set count and offset based on the range code point is in:
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let count, offset;
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// U+0080 to U+07FF, inclusive:
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if (inRange(code_point, 0x0080, 0x07FF)) {
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// 1 and 0xC0
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count = 1;
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offset = 0xC0;
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}
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// U+0800 to U+FFFF, inclusive:
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else if (inRange(code_point, 0x0800, 0xFFFF)) {
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// 2 and 0xE0
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count = 2;
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offset = 0xE0;
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}
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// U+10000 to U+10FFFF, inclusive:
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else if (inRange(code_point, 0x10000, 0x10FFFF)) {
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// 3 and 0xF0
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count = 3;
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offset = 0xF0;
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}
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// 4. Let bytes be a byte sequence whose first byte is (code
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// point >> (6 × count)) + offset.
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const bytes = [(code_point >> (6 * count)) + offset];
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// 5. Run these substeps while count is greater than 0:
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while (count > 0) {
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// 1. Set temp to code point >> (6 × (count − 1)).
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const temp = code_point >> (6 * (count - 1));
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// 2. Append to bytes 0x80 | (temp & 0x3F).
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bytes.push(0x80 | (temp & 0x3F));
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// 3. Decrease count by one.
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count -= 1;
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}
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// 6. Return bytes bytes, in order.
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return bytes;
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}
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}
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//# sourceMappingURL=UTF8Encoder.js.map
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