tools/buzstats: add initial buzhash query tool

CMakeLists.txt

@@ -542,7 +542,7 @@ endif ()
 
 
 ###############################################################################
-foreach (tool cpuid poisson macro scratch)
+foreach (tool buzstats cpuid poisson macro scratch)
     add_executable (util_${tool} tools/${tool}.cpp)
     set_target_properties (util_${tool} PROPERTIES OUTPUT_NAME ${tool})
     target_link_libraries (util_${tool} cruft)

tools/buzstats.cpp

@@ -0,0 +1,32 @@
+#include "hash/buzhash.hpp"
+#include "io.hpp"
+
+#include <iostream>
+
+int main (int argc, char const **argv)
+{
+    (void)argc;
+
+    cruft::mapped_file src (argv[1]);
+    cruft::view bytes (src);
+
+    static constexpr std::size_t BITS = 16;
+    std::vector<std::size_t> counts (BITS, 0);
+
+    static constexpr std::size_t WINDOW = 48;
+    cruft::hash::buzhash<u64> h (WINDOW, bytes);
+
+    for (auto const &val: bytes.consume (WINDOW)) {
+        auto const res = h (&val);
+
+        std::size_t mask = ~u64(0) >> (64 - BITS);
+        for (std::size_t i = 0; i < BITS; ++i) {
+            if ((res & mask) == 0)
+                counts[i]++;
+            mask >>= 1;
+        }
+    }
+
+    for (auto const &i: counts)
+        std::cout << i << '\n';
+}