Something

static void randomizeModifier_deformVerts(
                ModifierData *md, Object *ob, DerivedMesh *derivedData,
                float (*vertexCos)[3], int numVerts)
{
    RandomizeModifierData *rmd = (RandomizeModifierData*) md;

    int i;
    
    for(i = 0; i < numVerts; i++) {
        float *co = vertexCos[i];
           
        co[0] = co[0] + (BLI_frand()/rmd->factor); 
        co[1] = co[1] + (BLI_frand()/rmd->factor);
        co[2] = co[2] + (BLI_frand()/rmd->factor);   
		}
}