From 041e5efc85208bf02319a7e47ad797cbd107bbca Mon Sep 17 00:00:00 2001
From: Nigel Stewart <nigel.stewart@immersaview.com>
Date: Sat, 21 Feb 2015 23:29:40 +1000
Subject: [PATCH] [CoreSupport] Linux/GLX touch-ups for extension string
 parsing and enable lookup.

---
 auto/src/glew_head.c    | 24 ++++++++++++++++++++++--
 auto/src/glew_init_gl.c | 22 +++++++++++++---------
 2 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/auto/src/glew_head.c b/auto/src/glew_head.c
index 22da593..80d6cc1 100644
--- a/auto/src/glew_head.c
+++ b/auto/src/glew_head.c
@@ -7,6 +7,8 @@
 #endif
 
 #include <stddef.h>  /* For size_t */
+#include <string.h>  /* memset, etc */
+#include <stdlib.h>
 
 /*
  * Define glewGetContext and related helper macros.
@@ -202,7 +204,6 @@ static GLuint _glewStrCLen (const GLubyte* s, GLubyte c)
   return (s[i] == '\0' || s[i] == c) ? i : 0;
 }
 
-#if 0
 static GLboolean _glewStrSame (const GLubyte* a, const GLubyte* b, GLuint n)
 {
   GLuint i=0;
@@ -211,7 +212,6 @@ static GLboolean _glewStrSame (const GLubyte* a, const GLubyte* b, GLuint n)
   while (i < n && a[i] != '\0' && b[i] != '\0' && a[i] == b[i]) i++;
   return i == n ? GL_TRUE : GL_FALSE;
 }
-#endif
 
 static GLboolean _glewStrSame1 (const GLubyte** a, GLuint* na, const GLubyte* b, GLuint nb)
 {
@@ -265,3 +265,23 @@ static GLboolean _glewStrSame3 (const GLubyte** a, GLuint* na, const GLubyte* b,
   }
   return GL_FALSE;
 }
+
+/*
+ * Search for name in the extensions string. Use of strstr()
+ * is not sufficient because extension names can be prefixes of
+ * other extension names. Could use strtok() but the constant
+ * string returned by glGetString might be in read-only memory.
+ */
+static GLboolean _glewSearchExtension (const char* name, const GLubyte *start, const GLubyte *end)
+{
+  const GLubyte* p;
+  GLuint len = _glewStrLen((const GLubyte*)name);
+  p = start;
+  while (p < end)
+  {
+    GLuint n = _glewStrCLen(p, ' ');
+    if (len == n && _glewStrSame((const GLubyte*)name, p, n)) return GL_TRUE;
+    p += n+1;
+  }
+  return GL_FALSE;
+}
diff --git a/auto/src/glew_init_gl.c b/auto/src/glew_init_gl.c
index 336f9ea..c4548ad 100644
--- a/auto/src/glew_init_gl.c
+++ b/auto/src/glew_init_gl.c
@@ -2,7 +2,7 @@
 
 static int _glewExtensionCompare(const void *a, const void *b)
 {
-   return strcmp((const char *) a, *(const char**) b);
+   return strcmp((const char *) a, *(const char * const *) b);
 }
 
 static GLboolean *_glewGetExtensionString(const char *name)
@@ -67,11 +67,6 @@ GLenum GLEWAPIENTRY glewContextInit (GLEW_CONTEXT_ARG_DEF_LIST)
   const GLubyte* s;
   GLuint dot;
   GLint major, minor;
-  char *begin;
-  char *end;
-  char *i;
-  char *j;
-  GLboolean *enable;
 
   /* query opengl version */
   s = glGetString(GL_VERSION);
@@ -121,6 +116,7 @@ GLenum GLEWAPIENTRY glewContextInit (GLEW_CONTEXT_ARG_DEF_LIST)
     GLint i;
     PFNGLGETSTRINGIPROC getStringi;
     const char *ext;
+    GLboolean *enable;
 
     glGetIntegerv(GL_NUM_EXTENSIONS, &n);
 
@@ -144,10 +140,18 @@ GLenum GLEWAPIENTRY glewContextInit (GLEW_CONTEXT_ARG_DEF_LIST)
   }
   else
   {
-    begin = (char *) glGetString(GL_EXTENSIONS);
-    if (begin)
+    const char *ext;
+    char *begin;
+    char *end;
+    char *i;
+    char *j;
+    GLboolean *enable;
+
+    ext = (const char *) glGetString(GL_EXTENSIONS);
+
+    if (ext)
     {
-      begin = strdup(begin);
+      begin = strdup(ext);
       end = begin + strlen(begin);
       for (i=begin; i<end; i = j + 1)
       {