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Merge pull request #5 from eliot-akira/stream-files-by-line
Stream database file line by line to avoid string length limit in Node.js
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| module.exports = {} |
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| // Forked from https://github.com/jahewson/node-byline | ||
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| // Copyright (C) 2011-2015 John Hewson | ||
| // | ||
| // Permission is hereby granted, free of charge, to any person obtaining a copy | ||
| // of this software and associated documentation files (the "Software"), to | ||
| // deal in the Software without restriction, including without limitation the | ||
| // rights to use, copy, modify, merge, publish, distribute, sublicense, and/or | ||
| // sell copies of the Software, and to permit persons to whom the Software is | ||
| // furnished to do so, subject to the following conditions: | ||
| // | ||
| // The above copyright notice and this permission notice shall be included in | ||
| // all copies or substantial portions of the Software. | ||
| // | ||
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
| // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
| // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
| // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING | ||
| // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS | ||
| // IN THE SOFTWARE. | ||
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| const stream = require('stream') | ||
| const util = require('util') | ||
| const timers = require('timers') | ||
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| // convinience API | ||
| module.exports = function (readStream, options) { | ||
| return module.exports.createStream(readStream, options) | ||
| } | ||
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| // basic API | ||
| module.exports.createStream = function (readStream, options) { | ||
| if (readStream) { | ||
| return createLineStream(readStream, options) | ||
| } else { | ||
| return new LineStream(options) | ||
| } | ||
| } | ||
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| // deprecated API | ||
| module.exports.createLineStream = function (readStream) { | ||
| console.log('WARNING: byline#createLineStream is deprecated and will be removed soon') | ||
| return createLineStream(readStream) | ||
| } | ||
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| function createLineStream (readStream, options) { | ||
| if (!readStream) { | ||
| throw new Error('expected readStream') | ||
| } | ||
| if (!readStream.readable) { | ||
| throw new Error('readStream must be readable') | ||
| } | ||
| const ls = new LineStream(options) | ||
| readStream.pipe(ls) | ||
| return ls | ||
| } | ||
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| // | ||
| // using the new node v0.10 "streams2" API | ||
| // | ||
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| module.exports.LineStream = LineStream | ||
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| function LineStream (options) { | ||
| stream.Transform.call(this, options) | ||
| options = options || {} | ||
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| // use objectMode to stop the output from being buffered | ||
| // which re-concatanates the lines, just without newlines. | ||
| this._readableState.objectMode = true | ||
| this._lineBuffer = [] | ||
| this._keepEmptyLines = options.keepEmptyLines || false | ||
| this._lastChunkEndedWithCR = false | ||
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| // take the source's encoding if we don't have one | ||
| const self = this | ||
| this.on('pipe', function (src) { | ||
| if (!self.encoding) { | ||
| // but we can't do this for old-style streams | ||
| if (src instanceof stream.Readable) { | ||
| self.encoding = src._readableState.encoding | ||
| } | ||
| } | ||
| }) | ||
| } | ||
| util.inherits(LineStream, stream.Transform) | ||
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| LineStream.prototype._transform = function (chunk, encoding, done) { | ||
| // decode binary chunks as UTF-8 | ||
| encoding = encoding || 'utf8' | ||
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| if (Buffer.isBuffer(chunk)) { | ||
| if (encoding === 'buffer') { | ||
| chunk = chunk.toString() // utf8 | ||
| encoding = 'utf8' | ||
| } else { | ||
| chunk = chunk.toString(encoding) | ||
| } | ||
| } | ||
| this._chunkEncoding = encoding | ||
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| // see: http://www.unicode.org/reports/tr18/#Line_Boundaries | ||
| const lines = chunk.split(/\r\n|[\n\v\f\r\x85\u2028\u2029]/g) | ||
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| // don't split CRLF which spans chunks | ||
| if (this._lastChunkEndedWithCR && chunk[0] === '\n') { | ||
| lines.shift() | ||
| } | ||
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| if (this._lineBuffer.length > 0) { | ||
| this._lineBuffer[this._lineBuffer.length - 1] += lines[0] | ||
| lines.shift() | ||
| } | ||
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| this._lastChunkEndedWithCR = chunk[chunk.length - 1] === '\r' | ||
| this._lineBuffer = this._lineBuffer.concat(lines) | ||
| this._pushBuffer(encoding, 1, done) | ||
| } | ||
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| LineStream.prototype._pushBuffer = function (encoding, keep, done) { | ||
| // always buffer the last (possibly partial) line | ||
| while (this._lineBuffer.length > keep) { | ||
| const line = this._lineBuffer.shift() | ||
| // skip empty lines | ||
| if (this._keepEmptyLines || line.length > 0) { | ||
| if (!this.push(this._reencode(line, encoding))) { | ||
| // when the high-water mark is reached, defer pushes until the next tick | ||
| timers.setImmediate(() => { | ||
| this._pushBuffer(encoding, keep, done) | ||
| }) | ||
| return | ||
| } | ||
| } | ||
| } | ||
| done() | ||
| } | ||
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| LineStream.prototype._flush = function (done) { | ||
| this._pushBuffer(this._chunkEncoding, 0, done) | ||
| } | ||
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| // see Readable::push | ||
| LineStream.prototype._reencode = function (line, chunkEncoding) { | ||
| if (this.encoding && this.encoding !== chunkEncoding) { | ||
| return Buffer.from(line, chunkEncoding).toString(this.encoding) | ||
| } else if (this.encoding) { | ||
| // this should be the most common case, i.e. we're using an encoded source stream | ||
| return line | ||
| } else { | ||
| return Buffer.from(line, chunkEncoding) | ||
| } | ||
| } |
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