Audio Processing with Accelerate and vDSP_desamp()

I am totally new to the vdsp framework and I am trying to learn by building. My goal is for the signal to be processed in the following way:

1. 100th order Band Pass FIR


2. Downsampling by factor: 2

From what I could understand from Apple's documentation the function vDSP_desamp() is what I am looking for (it can do both steps at the same time, right?)

How would I use this correctly?

Here are my thoughts: Given an AudioBufferList *audio and an array of filter coefficients filterCoeffs with length [101]:

vDSP_desamp((float*)audio->mBuffers[0].mData, 2, &filterCoeffs, (float*)audio->mBuffers[0].mData, frames, 101);

would this be a correct use of the method? Do I need to implement a circular buffer for this process? Any guidance /direction /pointer to something to read would be very welcome. thanks