From 5dbda8f519faeeac457cf376fc186352ec3148d7 Mon Sep 17 00:00:00 2001
From: Dennis Luxen <info@project-osrm.org>
Date: Wed, 13 Aug 2014 11:20:19 +0200
Subject: [PATCH] refactoring of IteratorBasedCRC32, fixes #1140

---
 Algorithms/IteratorBasedCRC32.h | 105 ++++++++++++++------------------
 Contractor/Prepare.cpp          |  11 +++-
 2 files changed, 57 insertions(+), 59 deletions(-)

diff --git a/Algorithms/IteratorBasedCRC32.h b/Algorithms/IteratorBasedCRC32.h
index 6c2767f0d..dd693f831 100644
--- a/Algorithms/IteratorBasedCRC32.h
+++ b/Algorithms/IteratorBasedCRC32.h
@@ -28,41 +28,59 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef ITERATOR_BASED_CRC32_H
 #define ITERATOR_BASED_CRC32_H
 
-#include "../Util/SimpleLogger.h"
-
-#include <iostream>
-
 #if defined(__x86_64__) && !defined(__MINGW64__)
 #include <cpuid.h>
 #endif
 
 #include <boost/crc.hpp> // for boost::crc_32_type
 
-#if defined(__MINGW64__)
-inline void __get_cpuid(int param, unsigned *eax, unsigned *ebx, unsigned *ecx, unsigned *edx)
+#include <iterator>
+
+class IteratorbasedCRC32
 {
-    *ecx = 0;
-}
-#endif
+  public:
+    bool using_hardware() const { return use_hardware_implementation; }
 
-template <class ContainerT> class IteratorbasedCRC32
-{
-  private:
-    typedef typename ContainerT::iterator IteratorType;
-    unsigned crc;
+    IteratorbasedCRC32() : crc(0) { use_hardware_implementation = detect_hardware_support(); }
 
-    bool use_SSE42_CRC_function;
-
-    boost::crc_optimal<32, 0x1EDC6F41, 0x0, 0x0, true, true> CRC32_processor;
-
-    unsigned SoftwareBasedCRC32(char *str, unsigned len)
+    template <class Iterator> unsigned operator()(Iterator iter, const Iterator end)
     {
-        CRC32_processor.process_bytes(str, len);
-        return CRC32_processor.checksum();
+        unsigned crc = 0;
+        while (iter != end)
+        {
+            typedef typename std::iterator_traits<Iterator>::value_type value_type;
+            char *data = (char *)(&(*iter));
+
+            if (use_hardware_implementation)
+            {
+                crc = compute_in_hardware(data, sizeof(value_type));
+            }
+            else
+            {
+                crc = compute_in_software(data, sizeof(value_type));
+            }
+            ++iter;
+        }
+        return crc;
+    }
+
+  private:
+    bool detect_hardware_support() const
+    {
+        static const int sse42_bit = 0x00100000;
+        const unsigned ecx = cpuid();
+        const bool sse42_found = (ecx & sse42_bit) != 0;
+        return sse42_found;
+    }
+
+    unsigned compute_in_software(char *str, unsigned len)
+    {
+        crc_processor.process_bytes(str, len);
+        return crc_processor.checksum();
     }
 
     // adapted from http://byteworm.com/2010/10/13/crc32/
-    unsigned SSE42BasedCRC32(char *str, unsigned len)
+    unsigned compute_in_hardware(char *str, unsigned len)
     {
 #if defined(__x86_64__)
         unsigned q = len / sizeof(unsigned);
@@ -97,45 +115,16 @@ template <class ContainerT> class IteratorbasedCRC32
         __get_cpuid(1, &eax, &ebx, &ecx, &edx);
         return ecx;
     }
-
-    bool DetectNativeCRC32Support()
+#if defined(__MINGW64__)
+    inline void __get_cpuid(int param, unsigned *eax, unsigned *ebx, unsigned *ecx, unsigned *edx) const
     {
-        static const int SSE42_BIT = 0x00100000;
-        const unsigned ecx = cpuid();
-        const bool has_SSE42 = (ecx & SSE42_BIT) != 0;
-        if (has_SSE42)
-        {
-            SimpleLogger().Write() << "using hardware based CRC32 computation";
-        }
-        else
-        {
-            SimpleLogger().Write() << "using software based CRC32 computation";
-        }
-        return has_SSE42;
+        *ecx = 0;
     }
+#endif
 
-  public:
-    IteratorbasedCRC32() : crc(0) { use_SSE42_CRC_function = DetectNativeCRC32Support(); }
-
-    unsigned operator()(IteratorType iter, const IteratorType end)
-    {
-        unsigned crc = 0;
-        while (iter != end)
-        {
-            char *data = reinterpret_cast<char *>(&(*iter));
-
-            if (use_SSE42_CRC_function)
-            {
-                crc = SSE42BasedCRC32(data, sizeof(typename ContainerT::value_type));
-            }
-            else
-            {
-                crc = SoftwareBasedCRC32(data, sizeof(typename ContainerT::value_type));
-            }
-            ++iter;
-        }
-        return crc;
-    }
+    boost::crc_optimal<32, 0x1EDC6F41, 0x0, 0x0, true, true> crc_processor;
+    unsigned crc;
+    bool use_hardware_implementation;
 };
 
 #endif /* ITERATOR_BASED_CRC32_H */
diff --git a/Contractor/Prepare.cpp b/Contractor/Prepare.cpp
index 3b1b98574..d5c0208f6 100644
--- a/Contractor/Prepare.cpp
+++ b/Contractor/Prepare.cpp
@@ -172,7 +172,16 @@ int Prepare::Process(int argc, char *argv[])
 
     BuildRTree(node_based_edge_list);
 
-    IteratorbasedCRC32<std::vector<EdgeBasedNode>> crc32;
+    IteratorbasedCRC32 crc32;
+    if (crc32.using_hardware())
+    {
+        SimpleLogger().Write() << "using hardware based CRC32 computation";
+    }
+    else
+    {
+        SimpleLogger().Write() << "using software based CRC32 computation";
+    }
+
     const unsigned node_based_edge_list_CRC32 =
         crc32(node_based_edge_list.begin(), node_based_edge_list.end());
     node_based_edge_list.clear();