208 lines
6.4 KiB
JavaScript
208 lines
6.4 KiB
JavaScript
import { inRange, decoderError, isASCIICodePoint,
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end_of_stream, finished } from './text_decoder_utils.js'
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/**
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* @implements {Decoder}
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*/
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export class UTF8Decoder {
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/**
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* @param {{fatal: boolean}} options
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*/
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constructor(options) {
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const { fatal } = options
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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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let /** @type {number} */ utf8_code_point = 0,
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/** @type {number} */ utf8_bytes_seen = 0,
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/** @type {number} */ utf8_bytes_needed = 0,
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/** @type {number} */ utf8_lower_boundary = 0x80,
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/** @type {number} */ utf8_upper_boundary = 0xBF
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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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this.handler = function(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 && utf8_bytes_needed !== 0) {
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utf8_bytes_needed = 0
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return decoderError(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 (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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utf8_bytes_needed = 1
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// 2. Set UTF-8 code point to byte & 0x1F.
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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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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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utf8_upper_boundary = 0x9F
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// 3. Set utf-8 bytes needed to 2.
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utf8_bytes_needed = 2
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// 4. Set UTF-8 code point to byte & 0xF.
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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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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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utf8_upper_boundary = 0x8F
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// 3. Set utf-8 bytes needed to 3.
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utf8_bytes_needed = 3
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// 4. Set UTF-8 code point to byte & 0x7.
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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(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, utf8_lower_boundary, 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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utf8_code_point = utf8_bytes_needed = utf8_bytes_seen = 0
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utf8_lower_boundary = 0x80
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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(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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utf8_lower_boundary = 0x80
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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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utf8_code_point = (utf8_code_point << 6) | (bite & 0x3F)
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// 7. Increase utf-8 bytes seen by one.
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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 (utf8_bytes_seen !== 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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var code_point = 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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utf8_code_point = utf8_bytes_needed = 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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}
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// 9.1.2 utf-8 encoder
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/**
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* @implements {Encoder}
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*/
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export class UTF8Encoder {
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constructor() {
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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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this.handler = function(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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var 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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var 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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var 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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} |