Question: Recently I've been working on making some API calls to a 3rd party. I couldn't find anything available to use, so I had to do it from the ground up. Now I'm wondering whether it would be okay for me to rewrite all the platform specific parts and release that as open source (I'd say that would change ~50% of the code)?

Now the API doc that the other company gave me says "proprietary and confidential", but I assume that would apply only to the doc itself. Also when I asked them for help at one point they told me they don't support the language I am using. I have not signed a NDA specific to this, I have a general one in regards to client's data and info (and these are not clients). I am a bit hesitant to ask someone from my company about this since I have 0 experience when it comes to this sort of stuff, and I don't know whether they'd view it negatively..

**edit**

Thank you all for the advice. I do know that the code I write belongs to my employer, but I thought since most of what we do is platform dependent I'd have to majorly restructure it so it can work independently, and the rest could be considered a common way to do things. As for the proprietary API to which it would become a wrapper, it has wsdl and xsd schemas which can be accessed publicly (albeit you'd have to know where to get them), based on which a person can figure out how to use it. I guess the best thing really would be to speak to someone.. I'll let you know how it goes

Answer: 
The short answer is **not without express permission**.

You need to ask your superiors. Quite possibly your manager may need to pass the question up the chain. 

If you are lucky, the company has a process for this. If not, it may be helpful to find out if this has previously been done. Ask your coworkers. A previous example of having code released is a very helpful precedent. An example from another company may also help as will resources from the Free Software and Open Source Community that explain the process and implications. Anything that helps your superiors to make this easier.

Before releasing any code, the company needs to audit it to make sure that the code is fully owned by the company.

For the more detailed legal implications and resources to help ease the process, you may get more helpful answers on <https://opensource.stackexchange.com/>
In my company we have an open source policy. 

To use open source, the license has to be cleared for use, and all the restrictions stipulated.

To contribute to open source, the code has to be prepared and submitted for review and approved.

You need to find out the policies in Your company.