Adding "empty" function.

headers/ewah.h

@@ -80,6 +80,26 @@ template <class uword = uint32_t> class EWAHBoolArray {
     return false;
   }
 
+  /**
+  * Returns true if no bit is set.
+  */
+  bool empty() const {
+      size_t pointer(0);
+      while (pointer < buffer.size()) {
+        ConstRunningLengthWord<uword> rlw(buffer[pointer]);
+        if (rlw.getRunningBit()) {
+          if(rlw.getRunningLength() > 0) return false;
+        }
+        ++pointer;
+        for (size_t k = 0; k < rlw.getNumberOfLiteralWords(); ++k) {
+          if(buffer[pointer] != 0) return false;
+          ++pointer;
+        }
+      }
+      return true;
+  }
+
+
   /**
    * Set the ith bit to true (starting at zero).
    * Auto-expands the bitmap. It has constant running time complexity.

src/unit.cpp

@@ -54,7 +54,20 @@ template <class uword> bool testInEqualityEWAHBoolArray() {
   }
   return true;
 }
-
+template <class uword> bool testEmpty() {
+  cout << "[testing SizeInBits] sizeof(uword)=" << sizeof(uword) << endl;
+    EWAHBoolArray<uword> ewah0;
+    if(!ewah0.empty()) {
+      std::cout << "empty is buggy " << std::endl;
+      return false;
+    }
+    EWAHBoolArray<uword> ewah1 = EWAHBoolArray<uword>::bitmapOf(1, 1);
+    if(ewah1.empty()) {
+      std::cout << "empty is buggy " << std::endl;
+      return false;
+    }
+    return true;
+}
 template <class uword> bool testSizeInBits() {
   cout << "[testing SizeInBits] sizeof(uword)=" << sizeof(uword) << endl;
 
@@ -1646,7 +1659,14 @@ int main(void) {
   if (!funnytest()) {
     ++failures;
   }
-
+  if (!testEmpty<uint64_t>()) {
+    std::cout << failtext << __LINE__ << std::endl;
+    ++failures;
+  }
+  if (!testEmpty<uint16_t>()) {
+    std::cout << failtext << __LINE__ << std::endl;
+    ++failures;
+  }
   if (!testSizeInBits<uint64_t>()) {
     std::cout << failtext << __LINE__ << std::endl;
     ++failures;