Test and Set a Value Atomically

#Threads

ok = atomic.testandset(t, idx, vt, vs)

Test and set a table index value atomically.

Parameters Type Description
t table Table to modify
idx string The table index to check and set
vt integer The value to test for
vs integer The value to set

Returns ok == true if the t[idx] == vt, and then t[idx] = vs.

Equivalent to:

function atomic.testandset(t, idx, vt, vs)
 if t[idx] ~= vt then return false end
 t[idx] = vs
 return true
end

(But an internal mutex ensures that this happens atomically - i.e. the state is coherent even if multiple threads perform the same operation)