[WebRTC] Add ScreenCapturerDifferWrapper to share Differ across ScreenCapturers

webrtc/modules/desktop_capture/differ_block.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/modules/desktop_capture/differ_block.h"
 
 #include <string.h>
 
 #include "webrtc/typedefs.h"
-#include "webrtc/modules/desktop_capture/differ_block_sse2.h"
+#include "webrtc/modules/desktop_capture/differ_vector_sse2.h"
 #include "webrtc/system_wrappers/include/cpu_features_wrapper.h"
 
 namespace webrtc {
 
-bool BlockDifference_C(const uint8_t* image1,
-                       const uint8_t* image2,
-                       int stride) {
-  int width_bytes = kBlockSize * kBytesPerPixel;
+namespace {
 
-  for (int y = 0; y < kBlockSize; y++) {
-    if (memcmp(image1, image2, width_bytes) != 0)
+bool VectorDifference_C(const uint8_t* image1,
+                        const uint8_t* image2) {
+  return memcmp(image1, image2, kBlockSize * kBytesPerPixel) != 0;
+}
+
+}  // namespace
+
+bool VectorDifference(const uint8_t* image1, const uint8_t* image2) {
+  static bool (*diff_proc)(const uint8_t*, const uint8_t*) = nullptr;
+
+  if (!diff_proc) {
+#if defined(WEBRTC_ARCH_ARM_FAMILY) || defined(WEBRTC_ARCH_MIPS_FAMILY)
+    // For ARM and MIPS processors, always use C version.
+    // TODO(hclam): Implement a NEON version.
+    diff_proc = &VectorDifference_C;
+#else
+    bool have_sse2 = WebRtc_GetCPUInfo(kSSE2) != 0;
+    // For x86 processors, check if SSE2 is supported.
+    if (have_sse2 && kBlockSize == 32) {
+      diff_proc = &VectorDifference_SSE2_W32;
+    } else if (have_sse2 && kBlockSize == 16) {
+      diff_proc = &VectorDifference_SSE2_W16;
+    } else {
+      diff_proc = &VectorDifference_C;
+    }
+#endif
+  }
+
+  return diff_proc(image1, image2);
+}
+
+bool BlockDifference(const uint8_t* image1,
+                     const uint8_t* image2,
+                     int height,
+                     int stride) {
+  for (int i = 0; i < height; i++) {
+    if (VectorDifference(image1, image2)) {
       return true;
+    }
     image1 += stride;
     image2 += stride;
   }
   return false;
 }
 
 bool BlockDifference(const uint8_t* image1,
                      const uint8_t* image2,
                      int stride) {
-  static bool (*diff_proc)(const uint8_t*, const uint8_t*, int) = NULL;
-
-  if (!diff_proc) {
-#if defined(WEBRTC_ARCH_ARM_FAMILY) || defined(WEBRTC_ARCH_MIPS_FAMILY)
-    // For ARM and MIPS processors, always use C version.
-    // TODO(hclam): Implement a NEON version.
-    diff_proc = &BlockDifference_C;
-#else
-    bool have_sse2 = WebRtc_GetCPUInfo(kSSE2) != 0;
-    // For x86 processors, check if SSE2 is supported.
-    if (have_sse2 && kBlockSize == 32) {
-      diff_proc = &BlockDifference_SSE2_W32;
-    } else if (have_sse2 && kBlockSize == 16) {
-      diff_proc = &BlockDifference_SSE2_W16;
-    } else {
-      diff_proc = &BlockDifference_C;
-    }
-#endif
-  }
-
-  return diff_proc(image1, image2, stride);
+  return BlockDifference(image1, image2, kBlockSize, stride);
 }
 
 }  // namespace webrtc