nitowa
27 lines
1023 B
JavaScript
27 lines
1023 B
JavaScript
'use strict'
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var assert = require('assert')
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var BigNumber = require('bignumber.js')
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/*
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The quality, as stored in the last 64 bits of a directory index, is stored as
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the quotient of TakerPays/TakerGets. It uses drops (1e-6 XRP) for XRP values.
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*/
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function adjustQualityForXRP(quality, takerGetsCurrency, takerPaysCurrency) {
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var numeratorShift = (takerPaysCurrency === 'XRP' ? -6 : 0)
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var denominatorShift = (takerGetsCurrency === 'XRP' ? -6 : 0)
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var shift = numeratorShift - denominatorShift
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return shift === 0 ? (new BigNumber(quality)).toString() :
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(new BigNumber(quality)).shiftedBy(shift).toString()
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}
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function parseQuality(qualityHex, takerGetsCurrency, takerPaysCurrency) {
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assert(qualityHex.length === 16)
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var mantissa = new BigNumber(qualityHex.substring(2), 16)
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var offset = parseInt(qualityHex.substring(0, 2), 16) - 100
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var quality = mantissa.toString() + 'e' + offset.toString()
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return adjustQualityForXRP(quality, takerGetsCurrency, takerPaysCurrency)
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}
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module.exports = parseQuality
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