Utility function to get a vector of set bits

Template function to return a vector with the positions of all set bits in a variable.

slsDetectorSoftware/src/CmdProxy.cpp

@@ -1,4 +1,5 @@
 #include "CmdProxy.h"
+#include "bit_utils.h"
 #include "TimeHelper.h"
 #include "ToString.h"
 #include "container_utils.h"
@@ -1810,14 +1811,7 @@ std::string CmdProxy::Counters(int action) {
             WrongNumberOfParameters(0);
         }
         auto mask = det->getCounterMask({det_id}).squash(-1);
-        // scan counter enable mask to get vector
+        os << sls::ToString(getSetBits(mask)) << '\n';
-        std::vector<int> result;
-        for (size_t i = 0; i < 32; ++i) {
-            if (mask & (1 << i)) {
-                result.push_back(static_cast<int>(i));
-            }
-        }
-        os << sls::ToString(result) << '\n';
     } else if (action == defs::PUT_ACTION) {
         if (args.empty()) {
             WrongNumberOfParameters(1);

slsSupportLib/CMakeLists.txt

@@ -40,6 +40,7 @@ if(SLS_DEVEL_HEADERS)
         include/UdpRxSocket.h
         include/versionAPI.h
         include/ZmqSocket.h
+        include/bit_utils.h
     )
 endif()
 

slsSupportLib/include/bit_utils.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <vector>
+#include <bitset>
+namespace sls {
+template <typename T> std::vector<int> getSetBits(T val) {
+    constexpr size_t bitsPerByte = 8;
+    constexpr size_t numBits  = sizeof(T)*bitsPerByte;
+    std::bitset<numBits> bs(val);
+    std::vector<int> set_bits;
+    set_bits.reserve(bs.count());
+    for (size_t i = 0; i < bs.size(); ++i) {
+        if (bs[i]) {
+            set_bits.push_back(static_cast<int>(i));
+        }
+    }
+    return set_bits;
+}
+} // namespace sls

slsSupportLib/tests/CMakeLists.txt

@@ -1,4 +1,5 @@
 target_sources(tests PRIVATE 
+                ${CMAKE_CURRENT_SOURCE_DIR}/test-bit_utils.cpp
                 ${CMAKE_CURRENT_SOURCE_DIR}/test-container_utils.cpp
                 ${CMAKE_CURRENT_SOURCE_DIR}/test-network_utils.cpp
                 ${CMAKE_CURRENT_SOURCE_DIR}/test-string_utils.cpp

slsSupportLib/tests/test-bit_stuff.cpp

@@ -0,0 +1,39 @@
+#include "catch.hpp"
+#include <vector>
+#include "bit_utils.h"
+
+TEST_CASE("Get set bits from 0"){
+    auto vec = sls::getSetBits(0);
+    REQUIRE(vec.empty());
+}
+
+TEST_CASE("Get set bits from 1"){
+    auto vec = sls::getSetBits(1);
+    REQUIRE(vec.size() == 1);
+    REQUIRE(vec[0] == 0);
+}
+
+TEST_CASE("Get set bits from 2"){
+    auto vec = sls::getSetBits(2ul);
+    REQUIRE(vec.size() == 1);
+    REQUIRE(vec[0] == 1);
+}
+
+TEST_CASE("Get set bits from 3"){
+    auto vec = sls::getSetBits(3u);
+    REQUIRE(vec.size() == 2);
+    REQUIRE(vec[0] == 0);
+    REQUIRE(vec[1] == 1);
+}
+
+TEST_CASE("All bits set"){
+    uint8_t val = -1;
+    auto vec = sls::getSetBits(val);
+    REQUIRE(vec == std::vector<int>{0,1,2,3,4,5,6,7});
+}
+
+TEST_CASE("Get set bits from 523"){
+    //0b1000001011 == 523
+    auto vec = sls::getSetBits(523);
+    REQUIRE(vec == std::vector<int>{0,1,3,9});
+}