3 files changed, 43 insertions, 4 deletions
diff --git a/src/core/bufferfragment_p.h b/src/core/bufferfragment_p.h
index e2154a59..a86e2922 100644
--- a/src/core/bufferfragment_p.h
+++ b/src/core/bufferfragment_p.h
@@ -150,6 +150,11 @@ public:
         return (other.size() != (int)len || memcmp(d, other.constData(), len) != 0);
     }
 
+    bool operator==(const BufferFragment &other) const
+    {
+        return other.len == len && !memcmp(d, other.d, len);
+    }
+
     int indexOf(char c, unsigned int from = 0) const
     {
         const char *cursor = d + from - 1;
@@ -190,4 +195,21 @@ private:
     unsigned int len;
 };
 
+uint qHash(const KConfigIniBackend::BufferFragment &fragment)
+{
+    const uchar *p = reinterpret_cast<const uchar*>(fragment.constData());
+    const int len = fragment.length();
+
+    // This algorithm is copied from qhash.cpp (Qt5 version).
+    // Sadly this code is not accessible from the outside without going through abstraction
+    // layers. Even QByteArray::fromRawData would do an allocation internally...
+    uint h = 0;
+
+    for (int i = 0; i < len; ++i) {
+        h = 31 * h + p[i];
+    }
+
+    return h;
+}
+
 #endif
diff --git a/src/core/kconfigini.cpp b/src/core/kconfigini.cpp
index a882ee31..f4ce9410 100644
--- a/src/core/kconfigini.cpp
+++ b/src/core/kconfigini.cpp
@@ -44,6 +44,15 @@
 
 KCONFIGCORE_EXPORT bool kde_kiosk_exception = false; // flag to disable kiosk restrictions
 
+static QByteArray lookup(const KConfigIniBackend::BufferFragment &fragment, QHash<KConfigIniBackend::BufferFragment, QByteArray> *cache)
+{
+    QHash<KConfigIniBackend::BufferFragment, QByteArray>::iterator it = cache->find(fragment);
+    if (it == cache->end()) {
+        it = cache->insert(fragment, fragment.toByteArray());
+    }
+    return it.value();
+}
+
 QString KConfigIniBackend::warningProlog(const QFile &file, int line)
 {
     return QString::fromLatin1("KConfigIni: In file %2, line %1: ")
@@ -100,6 +109,14 @@ KConfigIniBackend::parseConfig(const QByteArray &currentLocale, KEntryMap &entry
     unsigned int len = contents.length();
     unsigned int startOfLine = 0;
 
+    // Reduce memory overhead by making use of implicit sharing
+    // This assumes that config files contain only a small amount of
+    // different fragments which are repeated often.
+    // This is often the case, especially sub groups will all have
+    // the same list of keys and similar values as well.
+    QHash<BufferFragment, QByteArray> cache;
+    cache.reserve(4096);
+
     while (startOfLine < len) {
         BufferFragment line = contents.split('\n', &startOfLine);
         line.trim();
@@ -265,9 +282,9 @@ KConfigIniBackend::parseConfig(const QByteArray &currentLocale, KEntryMap &entry
                 rawKey.reserve(aKey.length() + locale.length() + 2);
                 rawKey.append(aKey.toVolatileByteArray());
                 rawKey.append('[').append(locale.toVolatileByteArray()).append(']');
-                entryMap.setEntry(currentGroup, rawKey, line.toByteArray(), entryOptions);
+                entryMap.setEntry(currentGroup, rawKey, lookup(line, &cache), entryOptions);
             } else {
-                entryMap.setEntry(currentGroup, aKey.toByteArray(), line.toByteArray(), entryOptions);
+                entryMap.setEntry(currentGroup, lookup(aKey, &cache), lookup(line, &cache), entryOptions);
             }
         }
     next_line:
diff --git a/src/core/kconfigini_p.h b/src/core/kconfigini_p.h
index 492e1956..29f61090 100644
--- a/src/core/kconfigini_p.h
+++ b/src/core/kconfigini_p.h
@@ -33,10 +33,10 @@ class KConfigIniBackend : public KConfigBackend
 {
 Q_OBJECT
 private:
-    class BufferFragment;
-
     QLockFile *lockFile;
+
 public:
+    class BufferFragment;
 
     KConfigIniBackend();
     ~KConfigIniBackend();