async-line-reader
Version:
Read line-by-line from stream, using async.
199 lines • 8.37 kB
JavaScript
"use strict";
var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
return new (P || (P = Promise))(function (resolve, reject) {
function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
step((generator = generator.apply(thisArg, _arguments || [])).next());
});
};
var __generator = (this && this.__generator) || function (thisArg, body) {
var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
function verb(n) { return function (v) { return step([n, v]); }; }
function step(op) {
if (f) throw new TypeError("Generator is already executing.");
while (_) try {
if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
if (y = 0, t) op = [op[0] & 2, t.value];
switch (op[0]) {
case 0: case 1: t = op; break;
case 4: _.label++; return { value: op[1], done: false };
case 5: _.label++; y = op[1]; op = [0]; continue;
case 7: op = _.ops.pop(); _.trys.pop(); continue;
default:
if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
if (t[2]) _.ops.pop();
_.trys.pop(); continue;
}
op = body.call(thisArg, _);
} catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
}
};
Object.defineProperty(exports, "__esModule", { value: true });
/**
* Allows async line-wise reading from a stream.
*/
var AsyncLineReader = /** @class */ (function () {
/**
* Creates a new AsyncLineReader instance.
* @param stream The stream to read from.
* @param separator The line separator.
* @param bufferEncoding The encoding of the buffer, if the stream is a binary stream.
*/
function AsyncLineReader(stream, separator, bufferEncoding) {
var _this = this;
if (separator === void 0) { separator = '\n'; }
if (bufferEncoding === void 0) { bufferEncoding = 'utf-8'; }
this.stream = stream;
this.separator = separator;
this.bufferEncoding = bufferEncoding;
this.ended = false;
this.internalBuffer = '';
this.resolve = null;
this.reject = null;
this.stream.on('data', function (chunk) { return _this.onData(chunk); });
this.stream.on('end', function () { return _this.onEnd(); });
this.stream.on('error', function (err) { return _this.onError(err); });
}
/**
* Checks the type of a chunk and converts it to a string.
*/
AsyncLineReader.prototype.chunkToString = function (chunk) {
if (typeof chunk === 'string') {
return chunk;
}
if (chunk instanceof Buffer) {
return chunk.toString(this.bufferEncoding);
}
throw new Error("Invalid buffer type: " + typeof chunk);
};
/**
* Called on stream error.
*/
AsyncLineReader.prototype.onError = function (err) {
this.consumeError(err);
};
/**
* Called on stream end.
*/
AsyncLineReader.prototype.onEnd = function () {
this.ended = true;
this.tryNotifyWaiting();
};
/**
* Called in case there is new data in the stream.
*/
AsyncLineReader.prototype.onData = function (chunk) {
var data = this.chunkToString(chunk);
// Store the new data. This could be done faster.
this.internalBuffer = this.internalBuffer + data;
this.tryNotifyWaiting();
};
/**
* Notifies a waiting promise chain, if any.
*/
AsyncLineReader.prototype.tryNotifyWaiting = function () {
if (this.resolve) {
var line = this.readNextLineFromBuffer();
// If the stream has ended, we might send a null.
if (line !== null || this.ended) {
this.resolve(line);
this.reject = null;
this.resolve = null;
}
}
};
/**
* Either rejects a waiting promise with the given error,
* or stores it for later throwing.
*/
AsyncLineReader.prototype.consumeError = function (error) {
if (this.resolve) {
this.reject(error);
this.reject = null;
this.resolve = null;
}
else {
this.error = error;
}
};
/**
* Gets the next available line from the buffer. The line is removed from the buffer.
*
* Returns null when there is no data, regardless of the stream has ended or not.
*/
AsyncLineReader.prototype.readNextLineFromBuffer = function () {
var idx = this.internalBuffer.indexOf(this.separator);
if (idx >= 0) {
// There is at least one complete line in our buffer.
var line = this.internalBuffer.substring(0, idx);
// Update buffer, remove \n
this.internalBuffer = this.internalBuffer.substring(idx + this.separator.length, this.internalBuffer.length);
return line;
}
else if (this.ended) {
if (this.internalBuffer === '') {
return null;
}
// There is no complete line and the stream has ended.
var line = this.internalBuffer;
this.internalBuffer = '';
return line;
}
else {
// There is no complete line yet.
return null;
}
};
/**
* Gets the next line from the stream.
* Returns either a line, a promise that resolves
* when the next line becomes available, or null,
* if the stream has ended and was read completely.
* This method throws if the underlying stream errors.
*/
AsyncLineReader.prototype.readLine = function () {
return __awaiter(this, void 0, void 0, function () {
var err, line;
var _this = this;
return __generator(this, function (_a) {
if (this.error) {
err = this.error;
this.error = null;
throw err;
}
line = this.readNextLineFromBuffer();
if (line !== null) {
// There is data available, return it.
return [2 /*return*/, line];
}
else if (this.ended) {
// Stream is over, return null.
return [2 /*return*/, null];
}
else {
// No data, but stream ongoing. Async read operation.
return [2 /*return*/, new Promise(function (resolve, reject) {
if (_this.resolve !== null) {
reject('Another promise chain is already waiting for the next line.');
}
else {
_this.resolve = resolve;
_this.reject = reject;
}
})];
}
return [2 /*return*/];
});
});
};
return AsyncLineReader;
}());
exports.AsyncLineReader = AsyncLineReader;
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