97 lines
2.2 KiB
JavaScript
97 lines
2.2 KiB
JavaScript
'use strict'
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var codes = require('./character/codes.js')
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var constants = require('./constant/constants.js')
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var search = /[\0\t\n\r]/g
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function preprocess() {
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var start = true
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var column = 1
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var buffer = ''
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var atCarriageReturn
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return preprocessor
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function preprocessor(value, encoding, end) {
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var chunks = []
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var match
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var next
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var startPosition
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var endPosition
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var code
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value = buffer + value.toString(encoding)
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startPosition = 0
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buffer = ''
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if (start) {
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if (value.charCodeAt(0) === codes.byteOrderMarker) {
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startPosition++
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}
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start = undefined
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}
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while (startPosition < value.length) {
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search.lastIndex = startPosition
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match = search.exec(value)
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endPosition = match ? match.index : value.length
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code = value.charCodeAt(endPosition)
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if (!match) {
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buffer = value.slice(startPosition)
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break
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}
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if (
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code === codes.lf &&
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startPosition === endPosition &&
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atCarriageReturn
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) {
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chunks.push(codes.carriageReturnLineFeed)
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atCarriageReturn = undefined
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} else {
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if (atCarriageReturn) {
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chunks.push(codes.carriageReturn)
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atCarriageReturn = undefined
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}
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if (startPosition < endPosition) {
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chunks.push(value.slice(startPosition, endPosition))
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column += endPosition - startPosition
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}
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if (code === codes.nul) {
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chunks.push(codes.replacementCharacter)
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column++
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} else if (code === codes.ht) {
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next = Math.ceil(column / constants.tabSize) * constants.tabSize
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chunks.push(codes.horizontalTab)
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while (column++ < next) chunks.push(codes.virtualSpace)
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} else if (code === codes.lf) {
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chunks.push(codes.lineFeed)
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column = 1
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}
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// Must be carriage return.
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else {
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atCarriageReturn = true
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column = 1
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}
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}
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startPosition = endPosition + 1
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}
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if (end) {
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if (atCarriageReturn) chunks.push(codes.carriageReturn)
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if (buffer) chunks.push(buffer)
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chunks.push(codes.eof)
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}
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return chunks
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}
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}
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module.exports = preprocess
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