From: draygen@...
Date: 2009-01-30T10:23:16+09:00
Subject: Re: Reading a file in chunks, to a byte array

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Robert,=20



=C2=A0That did it! Thank you so much, very simple solution - I just need to=
 understand iteration/blocks a bit better for me to figure that out on my o=
wn.=20



=C2=A0thanks,=20



Brian=20


----- Original Message -----=20
From: "Robert Klemme" <shortcutter@googlemail.com>=20
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>=20
Sent: Thursday, January 29, 2009 4:57:37 PM GMT -05:00 US/Canada Eastern=20
Subject: Re: Reading a file in chunks, to a byte array=20

On 29.01.2009 22:23, draygen@comcast.net wrote:=20
> [Note: =C2=A0parts of this message were removed to make it a legal post.]=
=20
>=20
> Hi everyone,=20
>=20
> I'm pretty new to Ruby, I'm taking courses and reading as much info as I =
can, but I'm stuck on this one problem that may/may not have a simple answe=
r.=20
>=20
> A quick summary of what I'm trying to accomplish:=20
>=20
> I've written a simple SOAP client that interfaces with a web app used for=
 file transfer... It works great, however, if a file is over a certain size=
 it just hangs - and I know the reason why...=20
> The webapp receives the file as a chunk, in the form of a byte array, the=
 great thing about Ruby is that strings are basically an arrangement of arb=
itrary bytes, so I can just pass a string with the file object into the web=
 service and upload small files.=20
>=20
> But I'd like to split a file into "chunks" .. I know that I can do this:=
=20
>=20
> ---=20
>=20
> def get_chunk(bytearray)=20
> bytearray.read(61440) #read a 60kb chunk of the byte array=20
> end=20
>=20
> localFile =3D File.open('test.dat')=20
>=20
> get_chunk(localFile)=20
>=20
> ---=20
>=20
> But I need to keep track of more information .. The web app is looking fo=
r an offset integer , which basically works like this:=20
>=20
> (with a 60k chunksize)=20
>=20
> the first request will be:=20
> offset =3D 0=20
>=20
> second request:=20
> offset =3D 61440=20
>=20
> third request:=20
> offset =3D 122880=20
>=20
> Does anyone know how I could iterate over a bytearray, keeping track of t=
he offset, and read 60k chunks all at the same time?=20
> in pseudo code:=20
>=20
> get_chunk(bytearray)=20
>=20
> bytearray.read(61440)=20
> offset =3D 0=20
> puts bytearray.pos=20
> =3D> 61440=20
>=20
> bytearray.read(61440)=20
> offset +=3D 61440=20
> puts offset=20
> =3D> 61440=20
> puts bytearray.pos=20
> =3D> 122880=20
> ...=20
>=20
> After I have the proper offset, and chunks of a bytearray - I need to kee=
p calling the web service method with that data until the file =3D eof.=20
>=20
> I'm horrible at code blocks and iteration, if anyone has any suggestions,=
 it would be greatly appreciated.=20

It's not fully clear to me which one is the driving application here.=20
If it is your client application, it's easy=20

File.open "foo", "rb" do |io|=20
=C2=A0=C2=A0 pos =3D io.tell=20
=C2=A0=C2=A0 while buffer =3D io.read(CHUNK_SIZE)=20
=C2=A0=C2=A0 =C2=A0 send_to_web_app(pos, buffer)=20
=C2=A0=C2=A0 =C2=A0 pos =3D io.tell=20
=C2=A0=C2=A0 end=20
end=20

Kind regards=20

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0robert=20

--=20
remember.guy do |as, often| as.you_can - without end=20


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