[WebRTC] Add ScreenCapturerDifferWrapper to share Differ across ScreenCapturers

webrtc/modules/desktop_capture/differ_block.cc

Index: webrtc/modules/desktop_capture/differ_block.cc
diff --git a/webrtc/modules/desktop_capture/differ_block.cc b/webrtc/modules/desktop_capture/differ_block.cc
index d4cbda3601f44b4e5c65d3352fec816df2f84c03..bcdaa91246c04f9dce6b8fd04b20493930e14223 100644
--- a/webrtc/modules/desktop_capture/differ_block.cc
+++ b/webrtc/modules/desktop_capture/differ_block.cc
@@ -13,49 +13,62 @@
 #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)
-      return true;
-    image1 += stride;
-    image2 += stride;
-  }
-  return false;
+bool VectorDifference_C(const uint8_t* image1,
+                        const uint8_t* image2) {
+  return memcmp(image1, image2, kBlockSize * kBytesPerPixel) != 0;
 }
 
-bool BlockDifference(const uint8_t* image1,
-                     const uint8_t* image2,
-                     int stride) {
-  static bool (*diff_proc)(const uint8_t*, const uint8_t*, int) = NULL;
+}  // 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 = &BlockDifference_C;
+    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 = &BlockDifference_SSE2_W32;
+      diff_proc = &VectorDifference_SSE2_W32;
     } else if (have_sse2 && kBlockSize == 16) {
-      diff_proc = &BlockDifference_SSE2_W16;
+      diff_proc = &VectorDifference_SSE2_W16;
     } else {
-      diff_proc = &BlockDifference_C;
+      diff_proc = &VectorDifference_C;
     }
 #endif
   }
 
-  return diff_proc(image1, image2, stride);
+  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) {
+  return BlockDifference(image1, image2, kBlockSize, stride);
 }
 
 }  // namespace webrtc