improve combining in hash functions

specifically, use boost::hash_combine to combine values in hash
functions, except for a couple of places where I use the
small-prime-number strategy popular in the Java world, to avoid
including boost in header files that are widely shared.

Change-Id: I0e184c9ec8803bf09fc6e84fe20131b203e1652a
Reviewed-on: https://gerrit.libreoffice.org/70384
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

3 files changed, 20 insertions, 17 deletions

diff --git a/vcl/source/font/fontinstance.cxx b/vcl/source/font/fontinstance.cxx
index 595259731db1..bcbbe6d94d9d 100644
--- a/vcl/source/font/fontinstance.cxx
+++ b/vcl/source/font/fontinstance.cxx
@@ -32,9 +32,10 @@ namespace std
     {
         size_t operator()(const pair< sal_UCS4, FontWeight >& rData) const
         {
-            size_t h1 = hash<sal_UCS4>()(rData.first);
-            size_t h2 = hash<int>()(rData.second);
-            return h1 ^ h2;
+            std::size_t seed = 0;
+            boost::hash_combine(seed, rData.first);
+            boost::hash_combine(seed, rData.second);
+            return seed;
         }
     };
 }
diff --git a/vcl/unx/generic/glyphs/glyphcache.cxx b/vcl/unx/generic/glyphs/glyphcache.cxx
index 0aa8be45e84a..558e3d8c3323 100644
--- a/vcl/unx/generic/glyphs/glyphcache.cxx
+++ b/vcl/unx/generic/glyphs/glyphcache.cxx
@@ -85,15 +85,15 @@ size_t GlyphCache::IFSD_Hash::operator()(const rtl::Reference<LogicalFontInstanc
         nFontId ^= aFeatName.hashCode();
     }
 
-    size_t nHash = nFontId << 8;
-    nHash   += rFontSelData.mnHeight;
-    nHash   += rFontSelData.mnOrientation;
-    nHash   += size_t(rFontSelData.mbVertical);
-    nHash   += rFontSelData.GetItalic();
-    nHash   += rFontSelData.GetWeight();
-    nHash   += static_cast<sal_uInt16>(rFontSelData.meLanguage);
-
-    return nHash;
+    std::size_t seed = 0;
+    boost::hash_combine(seed, nFontId);
+    boost::hash_combine(seed, rFontSelData.mnHeight);
+    boost::hash_combine(seed, rFontSelData.mnOrientation);
+    boost::hash_combine(seed, size_t(rFontSelData.mbVertical));
+    boost::hash_combine(seed, rFontSelData.GetItalic());
+    boost::hash_combine(seed, rFontSelData.GetWeight());
+    boost::hash_combine(seed, static_cast<sal_uInt16>(rFontSelData.meLanguage));
+    return seed;
 }
 
 bool GlyphCache::IFSD_Equal::operator()(const rtl::Reference<LogicalFontInstance>& rAFontInstance,
diff --git a/vcl/unx/generic/printer/ppdparser.cxx b/vcl/unx/generic/printer/ppdparser.cxx
index 923d8612e7a1..aa99e3638580 100644
--- a/vcl/unx/generic/printer/ppdparser.cxx
+++ b/vcl/unx/generic/printer/ppdparser.cxx
@@ -54,6 +54,7 @@
 
 #include <config_dbus.h>
 #include <config_gio.h>
+#include <boost/functional/hash.hpp>
 
 namespace psp
 {
@@ -73,11 +74,12 @@ namespace psp
         struct LocaleHash
         {
             size_t operator()(const css::lang::Locale& rLocale) const
-            { return
-                  static_cast<size_t>(rLocale.Language.hashCode())
-                ^ static_cast<size_t>(rLocale.Country.hashCode())
-                ^ static_cast<size_t>(rLocale.Variant.hashCode())
-                ;
+            {
+                std::size_t seed = 0;
+                boost::hash_combine(seed, rLocale.Language.hashCode());
+                boost::hash_combine(seed, rLocale.Country.hashCode());
+                boost::hash_combine(seed, rLocale.Variant.hashCode());
+                return seed;
             }
         };