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base64-streamer.js
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base64-streamer.js
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var stream = require('stream');
/**
* Create a streamer that inherits from the base stream class.
* - base64 operates on 3 bytes at a time so chunk output along 3 byte boundaries
* - at the end send any remaining bytes.
*/
var base64EncodeStreamer = function () {
this.readable = true;
this.writable = true;
this.boundaryBytes = undefined;
};
//inherit from stream base class.
require('util').inherits(base64EncodeStreamer, stream);
base64EncodeStreamer.prototype.write = function (chunk,encoding) {
//convert string inputs into buffer since buffer provides base64 encoding.
if(!Buffer.isBuffer(chunk)) {
chunk = new Buffer(chunk);
}
if(Buffer.isBuffer(this.boundaryBytes)) {
//get boundaryBytes left over from last data write.
chunk = Buffer.concat([this.boundaryBytes, chunk], this.boundaryBytes.length + chunk.length);
this.boundaryBytes = undefined;
}
//test for 3 byte boundary and store any left over bytes
//in boundaryBytes for sending next data write
var remaining = chunk.length % 3;
if(remaining>0) {
this.boundaryBytes = chunk.slice(chunk.length - remaining);
chunk = chunk.slice(0, chunk.length - remaining);
}
//stream this data to listener.
this.emit('data',chunk.toString('base64'),'base64');
};
base64EncodeStreamer.prototype.end = function (chunk,encoding) {
//stream remaining boundaryBytes
if(Buffer.isBuffer(this.boundaryBytes)) {
this.emit('data', this.boundaryBytes.toString('base64'),'base64');
this.boundaryBytes = undefined;
}
this.emit('end');
};
module.exports.Encoder = function() {
return new base64EncodeStreamer();
}
/**
* Decoder just uses buffer class to decode on the fly.
*/
var base64DecodeStreamer = function () {
this.readable = true;
this.writable = true;
this.boundaryBytes = undefined;
};
require('util').inherits(base64DecodeStreamer, stream);
base64DecodeStreamer.prototype.write = function (chunk,encoding) {
//use buffer to decode.
this.emit('data',new Buffer(chunk.toString(),'base64'));
};
base64DecodeStreamer.prototype.end = function (chunk,encoding) {
args = Array.prototype.slice.call(arguments, 0);
this.emit.apply(this, ['end'].concat(args));
};
module.exports.Decoder = function() {
return new base64DecodeStreamer();
}