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buffered-writer.js
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buffered-writer.js
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/**
* @name BufferedWriter.
* @description Fully configurable buffered writer.
*
* @author Gabriel Llamas
* @created 27/04/2012
* @modified 09/10/2012
* @version 0.1.12
*/
"use strict";
var EVENTS = require ("events");
var FS = require ("fs");
var Error = require ("errno-codes");
Error.create (Error.getNextAvailableErrno (), "INVALID_BUFFER_SIZE",
"The buffer size must be greater than 0.");
var BUFFER_SIZE = 16384;
var EOL = process.platform === "win32" ? new Buffer ([0x0D, 0x0A]) : new Buffer ([0x0A]);
var toHexArray = function (n){
var array = [];
do{
array.unshift (n & 0xFF);
n = n >>> 8;
}while (n);
return array;
};
var BufferedWriter = function (fileName, settings){
EVENTS.EventEmitter.call (this);
settings = settings || {};
if (settings.bufferSize === 0) settings.bufferSize = -1;
this._settings = {
bufferSize: settings.bufferSize || BUFFER_SIZE,
encoding: settings.encoding || null,
append: settings.append ? "a" : "w"
};
if (this._settings.bufferSize < 1) throw Error.get (Error.INVALID_BUFFER_SIZE);
this._fileName = fileName;
this._stream = null;
this._buffer = null;
//Marca la primera posicion libre del buffer donde escribir bytes
this._offset = 0;
this._closing = false;
};
BufferedWriter.prototype = Object.create (EVENTS.EventEmitter.prototype);
BufferedWriter.prototype.constructor = BufferedWriter;
BufferedWriter.prototype._flush = function (){
//Cuando se escribe un buffer en el stream internamente no se crea una copia, solo se guarda
//la referencia, por lo que si el buffer se modifica desde fuera internamente tambien
//se habra modificado. Es por eso que se instancia un nuevo buffer para escribir datos.
this._stream.write (new Buffer (this._offset !== this._settings.bufferSize ?
this._buffer.slice (0, this._offset) : this._buffer));
this._offset = 0;
};
BufferedWriter.prototype._write = function (data, offset, length){
var me = this;
if (!this._buffer){
this._buffer = new Buffer (this._settings.bufferSize);
}
this.touch (me._settings.append);
if (length === 0) return;
var bytes = length + this._offset > this._settings.bufferSize ?
this._settings.bufferSize - this._offset :
length;
data.copy (this._buffer, this._offset, offset, offset + bytes);
this._offset += bytes;
offset += bytes;
length -= bytes;
if (this._offset === this._settings.bufferSize){
this._flush ();
if (length !== 0){
//Mientras queden bytes por escribir en el buffer se van haciendo llamadas recursivas
this._write (data, offset, length);
}
}
};
BufferedWriter.prototype.close = function (cb){
if (this._closing || !this._stream) return;
if (cb) cb = cb.bind (this);
if (this._offset !== 0){
this._flush ();
}
var me = this;
this._stream.on ("close", function (){
me._stream = null;
me._buffer = null;
me._closing = false;
if (cb) cb ();
});
this._stream.destroySoon ();
this._closing = true;
};
BufferedWriter.prototype.newLine = function (){
this._write (EOL, 0, EOL.length);
return this;
};
BufferedWriter.prototype.touch = function (_append){
if (this._closing) return this;
_append = _append || "w";
var me = this;
this._stream = FS.createWriteStream (this._fileName, {
flags: _append,
encoding: me._settings.encoding
})
.on ("error", function (error){
me.emit ("error", error);
});
return this;
};
BufferedWriter.prototype.write = function (buffer, offset, length){
if (this._closing) return this;
var type = typeof buffer;
if (type === "number"){
offset = 0;
buffer = toHexArray (buffer);
length = buffer.length;
buffer = new Buffer (buffer);
}else if (type === "string"){
offset = 0;
length = Buffer.byteLength (buffer, this._settings.encoding);
buffer = new Buffer (buffer, this._settings.encoding);
}else{
if (Array.isArray (buffer)){
buffer = new Buffer (buffer);
}
var argsLen = arguments.length;
if (argsLen === 1){
offset = 0;
length = buffer.length === 0 ? 0 : 1;
}
}
this._write (buffer, offset, length);
return this;
};
module.exports = BufferedWriter;