Re: [Psidev-ms-dev] mzData issues

[simon a. (B. <sim...@bb...>]

On 29 Nov 2005, at 12:01, Andy Jones wrote:

> Hi,
> I=92m trying to convert data from various different instruments into=20=

> mzData and I have a few questions.
> =A0
> 	1 	One of the instruments produces plain text output for =
the peak=20
> list (peak [tab] intensity). Does anyone have a script or some code=20
> for turning this into the mzData base 64 binary. Otherwise, any advice=20=

> for how best to do this would be welcome.

You didn't mention which language you were using to do your processing.=20=

  When I was decoding Base64 in Java I used this nice little (free)=20
library, which also does encoding.

http://iharder.sourceforge.net/base64/

Before the Base64 encoding you'll need to convert your float/double=20
values to byte arrays (4 bytes per float or 8 bytes per double), then=20
encode the byte array.  The Float and Double classes have built-in=20
methods to convert to int / long and then you just need to split these=20=

down to their component bytes.

eg for a float f, to get the 4 little endian bytes would be

int i =3D Float.float.ToIntBits(f);

byte [] bytes =3D new byte[4];

bytes[0] =3D (i & 0xFF);
bytes[1] =3D (i >> 8) & 0xFF;
bytes[2] =3D (i>>16) & 0xFF;
bytes[3] =3D (i>>24) & 0xFF;

You'd then encode this to get the string you include in the mzData file:

String s =3D Base64.encodeBytes(bytes);


Hope this helps

Simon.

--=20
Simon Andrews PhD
Bioinformatics Dept.
The Babraham Institute

sim...@bb...
+44 (0) 1223 496463