putting a integer into a string in ruby

Question

I want to send a file on a socket, and need to pass its length in the first four bytes.

Here is what I want to do in C:

struct { int lenght; //four bytes char msg[40]; }dataBuf; write(fd, &databuf, sizeof(dataBuf))

How do I push an integer onto a socket, so it receives it as an integer at other end, not as an ASCII value?

I don't want to hardcode it like "\x04\X03" and I tried to do it with pack(L*). That only works with array and I don't have a way to break my four byte integer into a four byte array.

Is this what you want to do? stackoverflow.com/questions/941856/write-binary-file-in-ruby — HeatfanJohn
– HeatfanJohn, Commented Jul 24, 2012 at 21:00

Phrogz · Accepted Answer · 2012-07-24 22:47:16Z

4

Try putting the integer into an array and then using pack. For example:

socket.write( [0xffff].pack("L") )

edited Jul 24, 2012 at 22:47

Phrogz

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answered Jul 24, 2012 at 20:58

staticfloat

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Comments

the Tin Man · Accepted Answer · 2012-11-05 16:57:23Z

Look at the BinData gem.

Your example might look like this:

class DataBuf < BinData::Record uint32 :length array :msg, :initial_length => 40 do uint8 end end io = File.open(...) r = DataBuf.read(io) puts "Data buffer is #{r.length} length and it has '#{r.msg}' message"

I'm not sure about message, you should look at the String section of BinData documentation.

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