Hi,
I have some data with binary numbers.
e.g. a 3 byte string could be 0x01216f which is 74095 decimal.
To do this conversion in ruby I've come up with:
def binum(bs)
n = e = 0
bs.reverse.each_byte do |c|
n += c * 256 ** e
e += 1
end
n
end
bs = ''
bs << 0x01 << 0x21 << 0x6f
puts binum(bs) => 74095
Now some data are signed binary numbers stored as two's complement.
e.g. 0xfede91 which is -74095 decimal.
How can I do this conversion in ruby?
Best regards,
Kim
def binum(bs)
result = 0
bs.unpack("cCC").each {|b| result = (result << 8) | b }
result
end
bs = ''
bs << 0x01 << 0x21 << 0x6f
puts binum(bs)
bs = ''
bs << 0xfe << 0xde << 0x91
puts binum(bs)
The above code extracts the first byte as a signed 8-bit integer and the
rest of the bytes as unsigned 8-bit integers. Each iteration through the
loop shift the result to construct the proper value.
--Dale Martenson
···
On Wednesday, August 02, 2006, at 5:46 AM, Kim Pedersen wrote:
Hi,
I have some data with binary numbers.
e.g. a 3 byte string could be 0x01216f which is 74095 decimal.
To do this conversion in ruby I've come up with:
def binum(bs)
n = e = 0
bs.reverse.each_byte do |c|
n += c * 256 ** e
e += 1
end
n
end
bs = ''
bs << 0x01 << 0x21 << 0x6f
puts binum(bs) => 74095
Now some data are signed binary numbers stored as two's complement.
e.g. 0xfede91 which is -74095 decimal.
How can I do this conversion in ruby?
--
Posted with http://DevLists.com. Sign up and save your mailbox.
That's just crying out for inject():
bs.unpack("cCC").inject(0) { |res, b| (res << 8) | b }
James Edward Gray II
···
On Aug 1, 2006, at 4:33 PM, Dale Martenson wrote:
def binum(bs)
result = 0
bs.unpack("cCC").each {|b| result = (result << 8) | b }
result
end
James Edward Gray II wrote:
···
On Aug 1, 2006, at 4:33 PM, Dale Martenson wrote:
def binum(bs)
result = 0
bs.unpack("cCC").each {|b| result = (result << 8) | b }
result
end
That's just crying out for inject():
bs.unpack("cCC").inject(0) { |res, b| (res << 8) | b }
James Edward Gray II
Thanks,
ps. just bought your ruby quiz book 
For variable length;
c.unpack("cC*").inject(0) { |res, b| (res << 8) | b }
···
On 8/2/06, Kim Pedersen <kimersen@online.no> wrote:
Dale Martenson wrote:
> On Wednesday, August 02, 2006, at 5:46 AM, Kim Pedersen wrote:
>
>> Hi,
>>
>> I have some data with binary numbers.
>> e.g. a 3 byte string could be 0x01216f which is 74095 decimal.
>> To do this conversion in ruby I've come up with:
>>
>> def binum(bs)
>> n = e = 0
>> bs.reverse.each_byte do |c|
>> n += c * 256 ** e
>> e += 1
>> end
>> n
>> end
>>
>> bs = ''
>> bs << 0x01 << 0x21 << 0x6f
>>
>> puts binum(bs) => 74095
>>
>> Now some data are signed binary numbers stored as two's complement.
>> e.g. 0xfede91 which is -74095 decimal.
>>
>> How can I do this conversion in ruby?
>>
>
> def binum(bs)
> result = 0
> bs.unpack("cCC").each {|b| result = (result << 8) | b }
> result
> end
>
> bs = ''
> bs << 0x01 << 0x21 << 0x6f
>
> puts binum(bs)
>
> bs = ''
> bs << 0xfe << 0xde << 0x91
>
> puts binum(bs)
>
> The above code extracts the first byte as a signed 8-bit integer and the
> rest of the bytes as unsigned 8-bit integers. Each iteration through the
> loop shift the result to construct the proper value.
>
> --Dale Martenson
>
Great!
Thanks
Kim
BTW, the length of the string may vary from 1 to 8. I'll have to adjust
for that.