Move HalfFloatMaker to media

media/video/half_float_maker_unittest.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <math.h>
+
+#include "media/video/half_float_maker.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+class HalfFloatMakerTest : public testing::Test {};
+
+// Convert an IEEE 754 half-float to a double value
+// that we can do math on.
+double FromHalfFloat(uint16_t half_float) {
+  if (!half_float)
+    return 0.0;
+  int sign = (half_float & 0x8000) ? -1 : 1;
+  int exponent = (half_float >> 10) & 0x1F;
+  int fraction = half_float & 0x3FF;
+  if (exponent == 0) {
+    return pow(2.0, -24.0) * fraction;
+  } else if (exponent == 0x1F) {
+    return sign * 1000000000000.0;
+  } else {
+    return pow(2.0, exponent - 25) * (0x400 + fraction);
+  }
+}
+
+TEST_F(HalfFloatMakerTest, MakeHalfFloatTest) {
+  unsigned short integers[1 << 16];
+  unsigned short half_floats[1 << 16];
+  for (int bits = 9; bits <= 16; bits++) {
+    std::unique_ptr<media::HalfFloatMaker> half_float_maker;
+    half_float_maker = media::HalfFloatMaker::NewHalfFloatMaker(bits);
+    int num_values = 1 << bits;
+    for (int i = 0; i < num_values; i++)
+      integers[i] = i;
+
+    half_float_maker->MakeHalfFloats(integers, num_values, half_floats);
+    // Multiplier to converting integers to 0.0..1.0 range.
+    double multiplier = 1.0 / (num_values - 1);
+
+    for (int i = 0; i < num_values; i++) {
+      // This value is in range 0..1
+      float value = integers[i] * multiplier;
+      // Reverse the effect of offset and multiplier to get the expected
+      // output value from the half-float converter.
+      float expected_value =
+          value / half_float_maker->Multiplier() + half_float_maker->Offset();
+      EXPECT_EQ(integers[i], i);
+
+      // We expect the result to be within +/- one least-significant bit.
+      // Within the range we care about, half-floats values and
+      // their representation both sort in the same order, so we
+      // can just add one to get the next bigger half-float.
+      float expected_precision =
+          FromHalfFloat(half_floats[i] + 1) - FromHalfFloat(half_floats[i]);
+      EXPECT_NEAR(FromHalfFloat(half_floats[i]), expected_value,
+                  expected_precision)
+          << "i = " << i << " bits = " << bits;
+    }
+  }
+}
+
+}  // namespace media