139 lines
4.6 KiB
JavaScript
139 lines
4.6 KiB
JavaScript
import { inRange, decoderError, end_of_stream, finished, convertCodeUnitToBytes } from './text_decoder_utils.js'
|
||
|
||
// 15.2.1 shared utf-16 decoder
|
||
|
||
/**
|
||
* @implements {Decoder}
|
||
*/
|
||
export class UTF16Decoder {
|
||
/**
|
||
* @param {boolean} utf16_be True if big-endian, false if little-endian.
|
||
* @param {{fatal: boolean}} options
|
||
*/
|
||
constructor(utf16_be, options) {
|
||
const { fatal } = options
|
||
this.utf16_be = utf16_be
|
||
this.fatal = fatal
|
||
this.utf16_lead_byte = null
|
||
this.utf16_lead_surrogate = null
|
||
}
|
||
/**
|
||
* @param {Stream} stream The stream of bytes being decoded.
|
||
* @param {number} bite The next byte read from the stream.
|
||
*/
|
||
handler(stream, bite) {
|
||
// 1. If byte is end-of-stream and either utf-16 lead byte or
|
||
// utf-16 lead surrogate is not null, set utf-16 lead byte and
|
||
// utf-16 lead surrogate to null, and return error.
|
||
if (bite === end_of_stream && (this.utf16_lead_byte !== null ||
|
||
this.utf16_lead_surrogate !== null)) {
|
||
return decoderError(this.fatal)
|
||
}
|
||
|
||
// 2. If byte is end-of-stream and utf-16 lead byte and utf-16
|
||
// lead surrogate are null, return finished.
|
||
if (bite === end_of_stream && this.utf16_lead_byte === null &&
|
||
this.utf16_lead_surrogate === null) {
|
||
return finished
|
||
}
|
||
|
||
// 3. If utf-16 lead byte is null, set utf-16 lead byte to byte
|
||
// and return continue.
|
||
if (this.utf16_lead_byte === null) {
|
||
this.utf16_lead_byte = bite
|
||
return null
|
||
}
|
||
|
||
// 4. Let code unit be the result of:
|
||
let code_unit
|
||
if (this.utf16_be) {
|
||
// utf-16be decoder flag is set
|
||
// (utf-16 lead byte << 8) + byte.
|
||
code_unit = (this.utf16_lead_byte << 8) + bite
|
||
} else {
|
||
// utf-16be decoder flag is unset
|
||
// (byte << 8) + utf-16 lead byte.
|
||
code_unit = (bite << 8) + this.utf16_lead_byte
|
||
}
|
||
// Then set utf-16 lead byte to null.
|
||
this.utf16_lead_byte = null
|
||
|
||
// 5. If utf-16 lead surrogate is not null, let lead surrogate
|
||
// be utf-16 lead surrogate, set utf-16 lead surrogate to null,
|
||
// and then run these substeps:
|
||
if (this.utf16_lead_surrogate !== null) {
|
||
const lead_surrogate = this.utf16_lead_surrogate
|
||
this.utf16_lead_surrogate = null
|
||
|
||
// 1. If code unit is in the range U+DC00 to U+DFFF,
|
||
// inclusive, return a code point whose value is 0x10000 +
|
||
// ((lead surrogate − 0xD800) << 10) + (code unit − 0xDC00).
|
||
if (inRange(code_unit, 0xDC00, 0xDFFF)) {
|
||
return 0x10000 + (lead_surrogate - 0xD800) * 0x400 +
|
||
(code_unit - 0xDC00)
|
||
}
|
||
|
||
// 2. Prepend the sequence resulting of converting code unit
|
||
// to bytes using utf-16be decoder flag to stream and return
|
||
// error.
|
||
stream.prepend(convertCodeUnitToBytes(code_unit, this.utf16_be))
|
||
return decoderError(this.fatal)
|
||
}
|
||
|
||
// 6. If code unit is in the range U+D800 to U+DBFF, inclusive,
|
||
// set utf-16 lead surrogate to code unit and return continue.
|
||
if (inRange(code_unit, 0xD800, 0xDBFF)) {
|
||
this.utf16_lead_surrogate = code_unit
|
||
return null
|
||
}
|
||
|
||
// 7. If code unit is in the range U+DC00 to U+DFFF, inclusive,
|
||
// return error.
|
||
if (inRange(code_unit, 0xDC00, 0xDFFF))
|
||
return decoderError(this.fatal)
|
||
|
||
// 8. Return code point code unit.
|
||
return code_unit
|
||
}
|
||
}
|
||
|
||
// 15.2.2 shared utf-16 encoder
|
||
/**
|
||
* @implements {Encoder}
|
||
*/
|
||
export class UTF16Encoder {
|
||
/**
|
||
* @param {boolean} [utf16_be] True if big-endian, false if little-endian.
|
||
*/
|
||
constructor(utf16_be = false) {
|
||
this.utf16_be = utf16_be
|
||
}
|
||
/**
|
||
* @param {Stream} stream Input stream.
|
||
* @param {number} code_point Next code point read from the stream.
|
||
*/
|
||
handler(stream, code_point) {
|
||
// 1. If code point is end-of-stream, return finished.
|
||
if (code_point === end_of_stream)
|
||
return finished
|
||
|
||
// 2. If code point is in the range U+0000 to U+FFFF, inclusive,
|
||
// return the sequence resulting of converting code point to
|
||
// bytes using utf-16be encoder flag.
|
||
if (inRange(code_point, 0x0000, 0xFFFF))
|
||
return convertCodeUnitToBytes(code_point, this.utf16_be)
|
||
|
||
// 3. Let lead be ((code point − 0x10000) >> 10) + 0xD800,
|
||
// converted to bytes using utf-16be encoder flag.
|
||
const lead = convertCodeUnitToBytes(
|
||
((code_point - 0x10000) >> 10) + 0xD800, this.utf16_be)
|
||
|
||
// 4. Let trail be ((code point − 0x10000) & 0x3FF) + 0xDC00,
|
||
// converted to bytes using utf-16be encoder flag.
|
||
const trail = convertCodeUnitToBytes(
|
||
((code_point - 0x10000) & 0x3FF) + 0xDC00, this.utf16_be)
|
||
|
||
// 5. Return a byte sequence of lead followed by trail.
|
||
return lead.concat(trail)
|
||
}
|
||
} |