How to store a binary object in redis using node?

问题:

I am trying to save a binary object in redis and then serve it back as an image.

Here is the code I am using to save the data:

var buff=new Buffer(data.data,'base64');
client.set(key,new Buffer(data.data,'base64'));

Here is the code to dump the data out:

client.get(key,function(err,reply){
        var data = reply;
        response.writeHead(200, {"Content-Type": "image/png"});
        response.end(data,'binary');

});

The first few byte of the data seem to be corrupted. The magic number is incorrect.

Did some experimenting:

when I do the following:

var buff=new Buffer(data.data,'base64');
console.log(buff.toString('binary'));

I get this:

0000000: c289 504e 470d 0a1a 0a00 0000 0d49 4844

when I do this

 var buff=new Buffer(data.data,'base64');
 console.log(buff);

I get the following:

Buffer 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 00

I am not sure where the c2 is coming from

回答1:

The problem is that the Redis client for Node converts responses to JavaScript strings by default.

I solved this by setting the return_buffers option to true when creating the client.

var client = redis.createClient(7000, '127.0.0.1', {'return_buffers': true});

See here for more details.

回答2:

I was unable to figure out how to get the binary string to store.

Here is my workaround:

Where data is the data in base64 string

client.set(count,data);

to serve the data:

 client.get(last,function(err,reply){
   var data = reply;
   response.writeHead(200, {"Content-Type": "image/png"});
   var buff=new Buffer(data,'base64');
   response.end(buff);
});

This isn't ideal since you have to do the conversion every time, but it seem to work.

回答3:

The problem with return_buffers is when you are not using pure buffer data's then you'll have to do something to convert other buffers to strings. While detect_buffers could be an option it is too unreliable.

If you don't mind the extra computing cycles. You could also try:

// convert your buffer to hex string
client.set(key, mybuffer.toString('hex'));
// create a new buffer from hex string
client.get(key, function (err, val) {
   var bin = new Buffer(val, 'hex');
});

回答4:

What worked for me is to use data.toString('binary') if it is a Buffer. Also make sure not to reinterpret it as utf-8, but also as binary.