HAL samples: renamed and added readme

samples/hal/README.md

+Custom HAL samples
+==================
+
+Samples in this folder are intended to demonstrate functionality replacement mechanism in the OpenCV library.
+
+The __c_hal__ is the example of pure C replacement library with all functions returning error. It can be used to verify error handling in the function switching code.
+
+The __slow_hal__ contains naive C++ implementations of the element-wise logical array operations (and, or, xor, not) making them twice slower than the default.
+
+Build custom HAL replacement library
+------------------------------------
+
+1. Create folder for build (for example `<home-dir>/my-hal-build`)
+2. Go to created folder and run cmake: `cmake <opencv-src>/samples/hal/slow_hal`
+3. Run make
+
+After build you will find static library in the build folder: `libslow_hal.a`
+
+Build OpenCV with HAL replacement
+---------------------------------
+
+1. Create folder for build (for example `<home-dir>/my-opencv-build`)
+2. Go to created folder and run cmake: 
+```
+cmake \
+    -DOPENCV_HAL_HEADERS="<opencv-src>/samples/hal/slow_hal/impl.hpp" \
+    -DOPENCV_HAL_LIBS="<home-dir>/my-hal-build/libslow_hal.a" \
+    <opencv-src>
+```
+3. Run make (or `make opencv_perf_core` to build the demonstration test executable only)
+4. After build you can run the tests and verify that some functions are slower now:
+```
+./bin/opencv_perf_core --gtest_filter=*bitwise_and*
+```

samples/hal/broken_hal/CMakeLists.txt → samples/hal/c_hal/CMakeLists.txt

@@ -6,6 +6,6 @@ if(UNIX)
   endif()
 endif()
 
-add_library(broken_hal broken.c)
+add_library(c_hal impl.c)
 set(OPENCV_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../..")
-target_include_directories(broken_hal PUBLIC ${CMAKE_CURRENT_SOURCE_DIR} ${OPENCV_SRC_DIR}/modules/core/include)
+target_include_directories(c_hal PUBLIC ${CMAKE_CURRENT_SOURCE_DIR} ${OPENCV_SRC_DIR}/modules/core/include)

samples/hal/simple_hal/CMakeLists.txt → samples/hal/slow_hal/CMakeLists.txt

@@ -6,6 +6,6 @@ if(UNIX)
   endif()
 endif()
 
-add_library(simple_hal simple.cpp)
+add_library(slow_hal impl.cpp)
 set(OPENCV_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../..")
-target_include_directories(simple_hal PUBLIC ${CMAKE_CURRENT_SOURCE_DIR} ${OPENCV_SRC_DIR}/modules/core/include)
+target_include_directories(slow_hal PUBLIC ${CMAKE_CURRENT_SOURCE_DIR} ${OPENCV_SRC_DIR}/modules/core/include)

samples/hal/simple_hal/simple.cpp → samples/hal/slow_hal/impl.cpp

-#include "simple.hpp"
+#include "impl.hpp"
 
 int slow_and8u(const uchar* src1, size_t step1, const uchar* src2, size_t step2, uchar* dst, size_t step, int width, int height)
 {
@@ -24,9 +24,9 @@ int slow_xor8u(const uchar* src1, size_t step1, const uchar* src2, size_t step2,
     return CV_HAL_ERROR_OK;
 }
 
-int slow_not8u(const uchar* src1, size_t step1, const uchar* src2, size_t step2, uchar* dst, size_t step, int width, int height)
+int slow_not8u(const uchar* src1, size_t step1, uchar* dst, size_t step, int width, int height)
 {
-    for(; height--; src1 = src1 + step1, src2 = src2 + step2, dst = dst + step)
+    for(; height--; src1 = src1 + step1, dst = dst + step)
         for(int x = 0 ; x < width; x++ )
             dst[x] = ~src1[x];
     return CV_HAL_ERROR_OK;

samples/hal/simple_hal/simple.hpp → samples/hal/slow_hal/impl.hpp

@@ -6,15 +6,15 @@
 int slow_and8u(const uchar* src1, size_t step1, const uchar* src2, size_t step2, uchar* dst, size_t step, int width, int height);
 int slow_or8u(const uchar* src1, size_t step1, const uchar* src2, size_t step2, uchar* dst, size_t step, int width, int height);
 int slow_xor8u(const uchar* src1, size_t step1, const uchar* src2, size_t step2, uchar* dst, size_t step, int width, int height);
-int slow_not8u(const uchar* src1, size_t step1, const uchar* src2, size_t step2, uchar* dst, size_t step, int width, int height);
+int slow_not8u(const uchar* src1, size_t step1, uchar* dst, size_t step, int width, int height);
 
-#undef hal_and8u
-#define hal_and8u slow_and8u
-#undef hal_or8u
-#define hal_or8u slow_or8u
-#undef hal_xor8u
-#define hal_xor8u slow_xor8u
-#undef hal_not8u
-#define hal_not8u slow_not8u
+#undef cv_hal_and8u
+#define cv_hal_and8u slow_and8u
+#undef cv_hal_or8u
+#define cv_hal_or8u slow_or8u
+#undef cv_hal_xor8u
+#define cv_hal_xor8u slow_xor8u
+#undef cv_hal_not8u
+#define cv_hal_not8u slow_not8u
 
 #endif