# Newbie question

**URL:** <https://www.ruby-forum.com/t/newbie-question/94507>\
**Category:** Ruby\
**Created:** [January 6, 2006, 5:34am UTC](https://www.ruby-forum.com/t/newbie-question/94507 "2006-01-06T05:34:17Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![mac](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/cc9497/32.png) [@mac](https://www.ruby-forum.com/u/mac)\
**Post date:** [January 6, 2006, 5:34am UTC](https://www.ruby-forum.com/t/newbie-question/94507/1 "2006-01-06T05:34:17Z")

</div>

Hello all and happy new year. I hope this is the right mailing list for  
this question. If not please redirect me and accept my apologies. Thanks  
in  
advance.  
I just started learning Ruby. I have good experience in Java and Perl  
and  
have read most of the doc on Ruby that I can get my hands on. I started  
on a  
project to build the DICOM netwrok library as a way to learn Ruby. I  
have  
done quite bit of coding on this project and have a working code. Well  
when  
I say quite a bit, it is about 5% done!! What I am looking for is  
RubyIdioms  
and if there are better ways of doing things as opposed to what I have  
already done. Basically DICOM messages are binary and we need to read  
the  
data and manipulate byes. We will have to construct integers or floats  
from  
bytes or pair of bytes and the next few bytes could be a string etc. I  
have  
pasted some part of the code and want your opinion on this. Also, once  
this  
project has reached a point where it could be used, I will release it to  
the  
community.

What I am looking for is recomendation to improve the speed of the code  
in  
processing the bytes. is ‘slice’ the best way to do what I am doing. I  
am  
going to re-arrange the code, so dont worry about the neatness at this  
point.

Thans and here is the code.

session comes from

server = TCPServer.new(‘localhost’, port)  
p “waiting on connection”  
while (session = server.accept) …

def ae\_6 session  
#AE\_6  
p “Inside ae\_6”  
#stop ARTIM and issue and a-associate indiction primitive.

# all we have to do here is suck in the whole PDU, that amounts to

sending  
the indication primitive.  
pdu=session.getc # reserved, neglect this byte  
pduLen=session.read(4).unpack(‘N’)[0] # unsigned integer 4 bytes long  
print “PDU Length =”, pduLen,"\n"  
pdu=session.read(pduLen) # this is the full PDU  
#version=pdu.slice(0…1).unpack(‘n’)[0]  
#p version  
calledAETitle = pdu.slice(4…19) # string of 16 chars  
callingAETitle = pdu.slice(20…35) # string of 16 chars  
p calledAETitle  
p callingAETitle  
#pdu.each\_byte {|c| print c,"|" }  
#reserved=pdu.slice(36…67) # ignore this  
#next item type should be 10H which is “Application Context” which is  
always set to “1.2.840.10008.3.1.1.1”  
itemType=pdu.slice(68…68).unpack(‘C’)[0]  
#printf( “ItemType=%XH\n”, itemType)  
#ignore the next byte, byte # 69  
itemLength=pdu.slice(70…71).unpack(‘n’)[0]  
contextName=pdu.slice(72…72+itemLength-1)  
p contextName

# Next we read presentation context items

start = 72+itemLength  
finish = 0  
while finish \< pduLen  
finish = getNextPresentationContext(start, pdu)  
print “Finish = “,finish,” outside proc\n”  
start=finish+1  
end  
end

def getNextPresentationContext(start, pdu)  
finish = start  
itemType=pdu.slice(start…finish).unpack(‘C’)[0] #should be20H  
start = finish+2 # added 2 here since we need to skip on byte which is  
reserved  
finish = start + 1 # total of two bytes  
itemLength=pdu.slice(start…finish).unpack(‘n’)[0]  
#printf( “FIRST ItemType=%XH, itemLength=%d\n”, itemType,itemLength)  
start = finish+1  
finish = start  
presContextId=pdu.slice(start…finish).unpack(‘C’)[0]

# next 3 bytes needs to be ignored, they are reserved hence +4 below

start = finish +4  
finish = start  
itemType=pdu.slice(start…finish).unpack(‘C’)[0]  
start = finish+2 # added 2 here since we need to skip on byte which is  
reserved  
finish = start + 1 # total of two bytes  
itemLength=pdu.slice(start…finish).unpack(‘n’)[0]  
#printf( “SECOND ItemType=%XH, itemLength=%d\n”, itemType,itemLength)  
start = finish+1  
finish = start + itemLength-1 # total of two bytes  
abstractSyntax=pdu.slice(start…finish)

start = finish +1  
finish = start  
itemType=pdu.slice(start…finish).unpack(‘C’)[0]  
while itemType == 64  
start = finish+2 # added 2 here since we need to skip one byte which  
is  
reserved  
finish = start + 1 # total of two bytes  
itemLength=pdu.slice(start…finish).unpack(‘n’)[0]  
#printf( “LATER ItemType=%XH, itemLength=%d\n”, itemType,itemLength)  
start = finish+1  
finish = start + itemLength-1 # total of two bytes  
transferSyntax=pdu.slice(start…finish)  
printf(“id=%d, AbstractSyntax =%s, TxSyntax=%s\n”,  
presContextId,abstractSyntax,transferSyntax)  
start=finish+1  
finish = start  
itemType=pdu.slice(start…finish).unpack(‘C’)[0]  
end  
return finish-1