From: Aaron Smith <beingthexemplary@...>
Date: 2007-03-08T13:36:38+09:00
Subject: ruby / php operator differences.

I am trying to do some parsing of binary data.

Here is the psuedo code that parses what i'm looking for:
private int readInteger() throws IOException {
    int n = 0;
    int b = in.readUnsignedByte();
    int result = 0;

    while ((b & 0x80) != 0 && n < 3) {
        result <<= 7;
        result |= (b & 0x7f);
        b = in.readUnsignedByte();
        n++;
    }
    if (n < 3) {
        result <<= 7;
        result |= b;
    } else {
      /* Use all 8 bits from the 4th byte */
      result <<= 8;
      result |= b;

      /* Check if the integer should be negative */
      if ((result & 0x10000000) != 0) {
        /* and extend the sign bit */
        result |= 0xe0000000;
      }
    }

    return result;
}




Here is how I wrote it with Ruby:
def read_int
    n = 0;
    b = @input_stream.read_special(1,'C')
    result = 0

    while((b & 0x80) != 0 && n < 3)
        result <<= 7
        result |= (b & 0x7f)
        b = @input_stream.read_special(1,'C')
        n = n + 1
    end
    if (n < 3)
        result <<= 7
        result |= b
    else
      # Use all 8 bits from the 4th byte
      result <<= 8
      result |= b

      #Check if the integer should be negative
      if ((result & 0x10000000) != 0)
        # and extend the sign bit
        result |= 0xe0000000
      end
    end

    STDOUT.puts "READ INT: #{result}"
    return result
  end


When translating the Pseudo Code to PHP, it's verbatim except for
syntax. With ruby, I think i've found the problem with it not parsing
correclty. the |= operator. With PHP

$i |= 0xe0000000; //= -536870912

Now with Ruby:
i |= 0xe000000 #= true

Any ideas on a solution?

thanks.

-- 
Posted via http://www.ruby-forum.com/.