c

Author: linrongbin16

lua/commons/num.lua

@@ -79,6 +79,13 @@ M.le = function(a, b, rel_tol, abs_tol)
   return M.lt(a, b, rel_tol, abs_tol) or M.eq(a, b, rel_tol, abs_tol)
 end
 
+--- @param a integer
+--- @param b integer
+--- @return integer
+M.mod = function(a, b)
+  return math.floor(math.fmod(a, b))
+end
+
 --- @param value number
 --- @param left number?   lower bound, by default INT32_MIN
 --- @param right number?  upper bound, by default INT32_MAX
@@ -132,4 +139,34 @@ M.max = function(f, a, ...)
   return maximal_item, maximal_index
 end
 
+-- Drop-in 32-bit random replacement of `math.random`.
+--- @param m integer?
+--- @param n integer?
+--- @return number
+M.random = function(m, n)
+  local uv = vim.uv or vim.loop
+  local rand_result, rand_err = uv.random(4)
+  assert(rand_result ~= nil, rand_err)
+
+  local bytes = {
+    string.byte(rand_result --[[@as string]], 1, -1),
+  }
+  local total = 0
+  for _, b in ipairs(bytes) do
+    total = M.mod(total * 256 + b, M.INT32_MAX)
+  end
+  if m == nil and n == nil then
+    return total / M.INT32_MAX
+  elseif m ~= nil and n == nil then
+    assert(type(m) == "number")
+    assert(m >= 1)
+    return M.mod(total, m) + 1
+  else
+    assert(type(m) == "number")
+    assert(type(n) == "number")
+    assert(n >= m)
+    return M.mod(total, n - m + 1) + m
+  end
+end
+
 return M

spec/commons/num_spec.lua

@@ -115,5 +115,28 @@ describe("commons.num", function()
       assert_false(ok)
       assert_eq(num.min(string.len, "a"), "a")
     end)
+    it("mod", function()
+      assert_eq(num.mod(2, 7), 2)
+      assert_eq(num.mod(10, 7), 3)
+      assert_eq(num.mod(10, 1), 0)
+      assert_eq(num.mod(7, 6), 1)
+    end)
+    it("random", function()
+      for i = 1, 50 do
+        local actual1 = num.random()
+        print(string.format("random-1(%s):%s\n", vim.inspect(type(actual1)), vim.inspect(actual1)))
+        assert_true(actual1 >= 0 and actual1 < 1)
+      end
+      for i = 1, 50 do
+        local actual2 = num.random(10)
+        print(string.format("random-2(%s):%s\n", vim.inspect(type(actual2)), vim.inspect(actual2)))
+        assert_true(actual2 >= 1 and actual2 <= 10)
+      end
+      for i = 1, 50 do
+        local actual3 = num.random(10, 100)
+        print(string.format("random-3(%s):%s\n", vim.inspect(type(actual3)), vim.inspect(actual3)))
+        assert_true(actual3 >= 10 and actual3 <= 100)
+      end
+    end)
   end)
 end)