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Java Forum / General / October 2006reading bytes with BufferedReader?
Hi All, I have a simple client - server application (using sockets). 80% responses of server are plain text messages, 20% are mixed: they are text messages with binary attachments. The structure is very simple. If message is plain text the last line contains "END OF TRANSMISSION". If message has attachment (only 1 possible) it contains: BINATY ATTACHMENT: {SIZE IN BYTES} I'm reading messages with BufferedReader. BufferedReader can not read bytes. It has read() method but it reads ints - futher more it reads int in big-endian order (the transmission is little-endian). I pass socket.getInputStream() into constructor of my reading thread: public InputThread(InputStream in) { this.raw = in; this.in = new BufferedReader(new InputStreamReader(in)); } the beggining of the message is read with the BufferedReader, then (if attachment is present) I use the raw object (InputStream), it has read(byte[] buffer) method but when I use it it returns -1. System.out.println(raw.read(bytes)); Can streams be mixed? E.g. I read some text with BufferedReader and then I'll read some bytes with orginal InputStream? > Hi All, > [quoted text clipped - 27 lines] > then I'll read some bytes > with orginal InputStream? > Hi All, > [quoted text clipped - 12 lines] > ints - futher more > it reads int in big-endian order (the transmission is little-endian). First of all you should always stick to the internet standard of network byte order, which is big endian. Second of all write the size in text instead of as bytes, the same goes with the binary data format it using Base64 coding or something similar. The you can read and process everything as text and then convert to byte,integer, float etc, what you need to convert. Basically, stick to one format or the other, i.e. binary or text. It doesn't complicate things as much and it will be easier to extend the design of the protocol. > I pass socket.getInputStream() into constructor of my reading thread: > [quoted text clipped - 11 lines] > then I'll read some bytes > with orginal InputStream? you should never mix streams. It makes the code unmanageable and the functionality untrustworthy. Unless you are chaining them, as you have done with the this.in stream. And yes it is technically possible to open several readers and manipulate them independently, but as said its not advisable. An example is using a PushbackReader and when you find any bytes, you push it back and open a new InputStream from the pushback stream and read the raw bytes. But then you are going to have problems the next time you read from the BufferedReader, because the mark of the stream is at different places depending on whether you are using the inputstream stream or the BufferedReader stream. So as stated it is better to choose either complete binary or text protocol. tom > An example is using a PushbackReader and when you find any bytes, you > push it back and open a new InputStream from the pushback stream Well you can't even do that for a start, you can't put an InputStream on top of a Reader. In the OP's circumstance I would just use the dreaded DataInputStream.readLine() to read the lines and DataInputStream.read() to read the bytes. >> An example is using a PushbackReader and when you find any bytes, you >> push it back and open a new InputStream from the pushback stream > > Well you can't even do that for a start, you can't put an InputStream on > top of a Reader. No, but you can use the InputStream the Reader is based. Ok, its not opening up a new InputStream, but you are still using the underlying stream directly. tom >>> An example is using a PushbackReader and when you find any bytes, you >>> push it back and open a new InputStream from the pushback stream [quoted text clipped - 5 lines] > opening up a new InputStream, but you are still using the underlying > stream directly. ... but you still won't get any of the data pushed back into the PushbackInputStream! >>> An example is using a PushbackReader and when you find any bytes, you >>> push it back and open a new InputStream from the pushback stream [quoted text clipped - 5 lines] > opening up a new InputStream, but you are still using the underlying > stream directly. ... but you still won't get any data pushed back into the PushbackReader! > .... but you still won't get any data pushed back into the PushbackReader! I went back to the paragraph in the book I thought I read this, but I must have misread it. I apologise for the confusion on that claim. tom >>>> An example is using a PushbackReader and when you find any bytes, >>>> you push it back and open a new InputStream from the pushback stream [quoted text clipped - 7 lines] > > .... but you still won't get any data pushed back into the PushbackReader! I went back to the paragraph in the book I thought I read this, but I must have misread it. I apologise for the confusion on that claim. What you can do, though, is to use a PushbackInputStream. Your read some bytes, give it to a reader which parses it, when the reader reaches the binary data, it returns with a value stating how many bytes where consumed by the reader. What was not consumed is pushed back into the stream and you open up e.g. a DataInputStream to read the binary data. When the DataInputStream is finished you could potentially return and give control to the reader again, this way going back and forth between text and binary. Its a bit complicated and not as clean. It would be easier and cleaner to just use a complete binary or text based protocol instead. tom Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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