flesh out gradient shaders

core/fxge/skia/fx_skia_device_unittest.cpp

+// Copyright 2016 PDFium 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 "core/fxge/skia/fx_skia_device.cpp"
+#include "testing/fx_string_testhelpers.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+uint32_t _GetBits32(const uint8_t* pData, int bitpos, int nbits) {
+  int result = 0;
+  for (int i = 0; i < nbits; i++)
+    if (pData[(bitpos + i) / 8] & (1 << (7 - (bitpos + i) % 8))) {
+      result |= 1 << (nbits - i - 1);
+    }
+  return result;
+}
+
+}  // namespace
+
+TEST(fxge, GetBits32) {
+  unsigned char data[] = {0xDE, 0x3F, 0xB1, 0x7C, 0x12, 0x9A, 0x04, 0x56};
+  for (int nbits = 1; nbits <= 32; ++nbits) {
+    for (int bitpos = 0; bitpos < (int)sizeof(data) * 8 - nbits; ++bitpos) {
+      uint32_t ref = _GetBits32(data, bitpos, nbits);
+      uint32_t test = GetBits32(data, bitpos, nbits);
+      EXPECT_TRUE(ref == test);
+    }
+  }
+}