Based on how you do the casting, the entire buffer is of the same type. You can take advantage of that.

SV* new_sv_from_float_buffer(void* buffer, int i) {
    return newSVnv( (double)(((float*)buffer)[i]) );
}

...

{
    SV* (*new_sv_from_buffer)(void*, int);
    if ( fmt == 3 && bps == 32 ) {
        new_sv_from_buffer = &new_sv_from_float_buffer;
    }
    ...

    ... Call new_sv_from_buffer repeatedly ...
}
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