const Minipass = require('minipass')
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const _flush = Symbol('_flush')
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const _flushed = Symbol('_flushed')
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const _flushing = Symbol('_flushing')
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class Flush extends Minipass {
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constructor (opt = {}) {
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if (typeof opt === 'function')
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opt = { flush: opt }
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super(opt)
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// or extend this class and provide a 'flush' method in your subclass
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if (typeof opt.flush !== 'function' && typeof this.flush !== 'function')
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throw new TypeError('must provide flush function in options')
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this[_flush] = opt.flush || this.flush
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}
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emit (ev, ...data) {
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if ((ev !== 'end' && ev !== 'finish') || this[_flushed])
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return super.emit(ev, ...data)
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if (this[_flushing])
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return
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this[_flushing] = true
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const afterFlush = er => {
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this[_flushed] = true
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er ? super.emit('error', er) : super.emit('end')
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}
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const ret = this[_flush](afterFlush)
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if (ret && ret.then)
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ret.then(() => afterFlush(), er => afterFlush(er))
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}
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}
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module.exports = Flush
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