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const { end_of_stream, finished, isASCIIByte, decoderError, encoderError, isASCIICodePoint } = require('../utils');
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const { indexPointerFor } = require('../indexes');
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//
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// 10. Legacy single-byte encodings
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//
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// 10.1 single-byte decoder
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/**
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* @implements {Decoder}
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*/
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class SingleByteDecoder {
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/**
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* @param {!Array.<number>} index The encoding index.
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* @param {{fatal: boolean}} options
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*/
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constructor(index, options) {
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const { fatal } = options
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this.fatal = fatal
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this.index = index
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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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*/
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handler(stream, bite) {
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// 1. 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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// 2. If byte is an ASCII byte, return a code point whose value
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// is byte.
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if (isASCIIByte(bite))
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return bite
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// 3. Let code point be the index code point for byte − 0x80 in
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// index single-byte.
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var code_point = this.index[bite - 0x80]
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// 4. If code point is null, return error.
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if (code_point === null)
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return decoderError(this.fatal)
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// 5. 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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// 10.2 single-byte encoder
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/**
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* @implements {Encoder}
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*/
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class SingleByteEncoder {
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/**
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* @param {!Array.<?number>} index The encoding index.
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*/
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constructor(index) {
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this.index = index
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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. Let pointer be the index pointer for code point in index
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// single-byte.
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const pointer = indexPointerFor(code_point, this.index)
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// 4. If pointer is null, return error with code point.
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if (pointer === null)
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encoderError(code_point)
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// 5. Return a byte whose value is pointer + 0x80.
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return pointer + 0x80
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}
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}
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module.exports.SingleByteDecoder = SingleByteDecoder
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module.exports.SingleByteEncoder = SingleByteEncoder |
