From 46212d657e2e989dddd361a732e65b05748e8e91 Mon Sep 17 00:00:00 2001
From: Sean Harmer <sean.harmer@kdab.com>
Date: Fri, 20 Jul 2012 16:21:47 +0100
Subject: Improve the QOpenGLExtensionMatcher class
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Using a QSet<QByteArray> internally means that checking for the
presence of an extension no longer uses an O(N) search.

This patch also allows users of this class to easily get a list
of the supported extensions.

Change-Id: I02194e5345573c47be0876f3ea6eb6b69a2ead81
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>
---
 src/gui/opengl/qopengl.cpp | 33 ++++-----------------------------
 src/gui/opengl/qopengl_p.h | 28 +++++++---------------------
 2 files changed, 11 insertions(+), 50 deletions(-)

diff --git a/src/gui/opengl/qopengl.cpp b/src/gui/opengl/qopengl.cpp
index 290fcb287e..ce6cb8a691 100644
--- a/src/gui/opengl/qopengl.cpp
+++ b/src/gui/opengl/qopengl.cpp
@@ -46,11 +46,6 @@
 
 QT_BEGIN_NAMESPACE
 
-QOpenGLExtensionMatcher::QOpenGLExtensionMatcher(const char *str)
-{
-    init(str);
-}
-
 typedef const GLubyte * (QOPENGLF_APIENTRYP qt_glGetStringi)(GLenum, GLuint);
 
 #ifndef GL_NUM_EXTENSIONS
@@ -62,7 +57,9 @@ QOpenGLExtensionMatcher::QOpenGLExtensionMatcher()
     const char *extensionStr = reinterpret_cast<const char *>(glGetString(GL_EXTENSIONS));
 
     if (extensionStr) {
-        init(extensionStr);
+        QByteArray ba(extensionStr);
+        QList<QByteArray> extensions = ba.split(' ');
+        m_extensions = extensions.toSet();
     } else {
         // clear error state
         while (glGetError()) {}
@@ -79,32 +76,10 @@ QOpenGLExtensionMatcher::QOpenGLExtensionMatcher()
 
             for (int i = 0; i < numExtensions; ++i) {
                 const char *str = reinterpret_cast<const char *>(glGetStringi(GL_EXTENSIONS, i));
-
-                m_offsets << m_extensions.size();
-
-                while (*str != 0)
-                    m_extensions.append(*str++);
-                m_extensions.append(' ');
+                m_extensions.insert(str);
             }
         }
     }
 }
 
-void QOpenGLExtensionMatcher::init(const char *str)
-{
-    m_extensions = str;
-
-    // make sure extension string ends with a space
-    if (!m_extensions.endsWith(' '))
-        m_extensions.append(' ');
-
-    int index = 0;
-    int next = 0;
-    while ((next = m_extensions.indexOf(' ', index)) >= 0) {
-        m_offsets << index;
-        index = next + 1;
-    }
-}
-
-
 QT_END_NAMESPACE
diff --git a/src/gui/opengl/qopengl_p.h b/src/gui/opengl/qopengl_p.h
index 1860fb1683..b59e6c0fc5 100644
--- a/src/gui/opengl/qopengl_p.h
+++ b/src/gui/opengl/qopengl_p.h
@@ -44,9 +44,7 @@
 
 #include <qopengl.h>
 #include <private/qopenglcontext_p.h>
-
-#include <qthreadstorage.h>
-#include <qcache.h>
+#include <QtCore/qset.h>
 
 QT_BEGIN_HEADER
 
@@ -55,29 +53,17 @@ QT_BEGIN_NAMESPACE
 class QOpenGLExtensionMatcher
 {
 public:
-    QOpenGLExtensionMatcher(const char *str);
     QOpenGLExtensionMatcher();
 
-    bool match(const char *str) const {
-        int str_length = qstrlen(str);
-
-        Q_ASSERT(str);
-        Q_ASSERT(str_length > 0);
-        Q_ASSERT(str[str_length-1] != ' ');
-
-        for (int i = 0; i < m_offsets.size(); ++i) {
-            const char *extension = m_extensions.constData() + m_offsets.at(i);
-            if (qstrncmp(extension, str, str_length) == 0 && extension[str_length] == ' ')
-                return true;
-        }
-        return false;
+    bool match(const QByteArray &extension) const
+    {
+        return m_extensions.contains(extension);
     }
 
-private:
-    void init(const char *str);
+    QSet<QByteArray> extensions() const { return m_extensions; }
 
-    QByteArray m_extensions;
-    QVector<int> m_offsets;
+private:
+    QSet<QByteArray> m_extensions;
 };
 
 QT_END_NAMESPACE
-- 
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