[Test] Add unit tests for fpconv

test/lua/unit/fpconv.lua

@@ -0,0 +1,96 @@
+-- fpconv tests
+
+context("Fpconv printf functions", function()
+  local ffi = require("ffi")
+  local u = require "rspamd_util"
+  local niter_fuzz = 100000
+  local function small_double()
+    return math.random()
+  end
+  local function large_double()
+    return math.random() * math.random(2^52)
+  end
+  local function huge_double()
+    return math.random(2^52) * math.random(2^52)
+  end
+  local function tiny_double()
+    return math.random() / math.random(2^52)
+  end
+  ffi.cdef[[
+int snprintf(char *str, size_t size, const char *format, ...);
+long rspamd_snprintf(char *str, size_t size, const char *format, ...);
+long rspamd_printf(const char *format, ...);
+]]
+  local benchmarks = {
+    {'tiny fixed', small_double, '%f'},
+    {'small fixed', tiny_double, '%f'},
+    {'large fixed', large_double, '%.3f'},
+    {'huge fixed', huge_double, '%.3f'},
+    {'tiny scientific', small_double, '%g'},
+    {'small scientific', tiny_double, '%g'},
+    {'large scientific', large_double, '%g'},
+    {'huge scientific', huge_double, '%g'},
+  }
+
+  local generic = {
+    {0, '%f', '0'},
+    {0, '%.1f', '0.0'},
+    {0, '%.2f', '0.00'},
+    {0, '%.32f', '0.000000000000000000000000000'}, -- max
+    {0, '%.150f', '0.000000000000000000000000000'}, -- too large
+    {1/3, '%f', '0.3333333333333333'},
+    {1/3, '%.1f', '0.3'},
+    {1/3, '%.2f', '0.33'},
+    {-1/3, '%.32f', '-0.333333333333333300000000000'},
+    {-1/3, '%.150f', '-0.333333333333333300000000000'},
+    {-3.6817595395344857e-68, '%f', '-3.6817595395344857e-68'},
+    {3.5844466002796428e+298, '%f', '3.5844466002796428e+298'},
+    {9223372036854775808, '%f', '9223372036854776000'}, -- 2^63 with precision lost
+    {2^50 + 0.2, '%f', '1125899906842624.3'}, -- 2^50 with precision lost
+    {2^50 + 0.2, '%.2f', '1125899906842624.30'}, -- 2^50 with precision lost
+    {-3.6817595395344857e-68, '%.3f', '-0.000'}, -- not enough precision
+    {3.5844466002796428e+298, '%.3f', '3.5844466002796428e+298'},
+    {9223372036854775808, '%.3f', '9223372036854776000.000'}, -- 2^63 with precision lost
+    {math.huge, '%f', 'inf'},
+    {-math.huge, '%f', '-inf'},
+    {0.0/0.0, '%f', 'nan'},
+    {math.huge, '%.1f', 'inf'},
+    {-math.huge, '%.2f', '-inf'},
+    {0.0/0.0, '%.3f', 'nan'},
+    {math.huge, '%g', 'inf'},
+    {-math.huge, '%g', '-inf'},
+    {0.0/0.0, '%g', 'nan'},
+  }
+
+  local buf = ffi.new("char[64]")
+  local buf2 = ffi.new("char[64]")
+
+  for i,c in ipairs(generic) do
+    test("Generic fp test fmt: " .. c[2] .. '; ' .. tostring(c[1]), function()
+      ffi.C.rspamd_snprintf(buf, 64, c[2], c[1])
+      local sbuf = ffi.string(buf)
+      assert_equal(sbuf, c[3], c[3] .. " but test returned " .. sbuf)
+    end)
+  end
+  for i,c in ipairs(benchmarks) do
+    test("Fuzz fp test " .. c[1], function()
+      for _=1,niter_fuzz do
+        local sign = 1
+        if math.random() > 0.5 then
+          sign = -1
+        end
+        local d = c[2]() * sign
+        ffi.C.snprintf(buf, 64, c[3], d)
+        ffi.C.rspamd_snprintf(buf2, 64, c[3], d)
+
+        local sbuf = ffi.string(buf)
+        local sbuf2 = ffi.string(buf2)
+
+        assert_less_than(math.abs(d -  tonumber(sbuf2))/math.abs(d),
+            0.00001,
+            string.format('rspamd emitted: %s, libc emitted: %s, original number: %g',
+              sbuf2, sbuf, d))
+      end
+    end)
+  end
+end)