[glib/wip/3v1n0/g_str_has_optimization: 1/7] Optimize g_str_has_*() functions to detect const arguments at compile-time

[Marco Trevisan <marcotrevi src gnome org>]

commit 0f4be1429d41de234f6a849c9b76445f61dd4a1e
Author: Emmanuel Fleury <emmanuel fleury gmail com>
Date:   Fri Aug 19 18:00:19 2022 +0200

    Optimize g_str_has_*() functions to  detect const arguments at compile-time
    
    Compilers can emit optimized code for str|strn|mem)cmp(str,"literal")
    at compile-time. This commit use the preprocessor to introduce this
    kind of optimization for the functions g_str_has_prefix() and
    g_str_has_suffix().
    
    Original work by Ben @bdejean
    
    Closes issue #24

 glib/gstrfuncs.c | 10 ++++------
 glib/gstrfuncs.h | 34 ++++++++++++++++++++++++++++++----
 2 files changed, 34 insertions(+), 10 deletions(-)
---
diff --git a/glib/gstrfuncs.c b/glib/gstrfuncs.c
index ee934e5d76..3030114e33 100644
--- a/glib/gstrfuncs.c
+++ b/glib/gstrfuncs.c
@@ -2928,9 +2928,8 @@ g_strrstr_len (const gchar *haystack,
  *
  * Since: 2.2
  */
-gboolean
-g_str_has_suffix (const gchar *str,
-                  const gchar *suffix)
+gboolean (g_str_has_suffix) (const gchar *str,
+                             const gchar *suffix)
 {
   gsize str_len;
   gsize suffix_len;
@@ -2958,9 +2957,8 @@ g_str_has_suffix (const gchar *str,
  *
  * Since: 2.2
  */
-gboolean
-g_str_has_prefix (const gchar *str,
-                  const gchar *prefix)
+gboolean (g_str_has_prefix) (const gchar *str,
+                             const gchar *prefix)
 {
   g_return_val_if_fail (str != NULL, FALSE);
   g_return_val_if_fail (prefix != NULL, FALSE);
diff --git a/glib/gstrfuncs.h b/glib/gstrfuncs.h
index 37d2728d89..88c8c3cf7d 100644
--- a/glib/gstrfuncs.h
+++ b/glib/gstrfuncs.h
@@ -32,6 +32,8 @@
 #endif
 
 #include <stdarg.h>
+#include <string.h>
+
 #include <glib/gmacros.h>
 #include <glib/gtypes.h>
 #include <glib/gerror.h>
@@ -137,11 +139,35 @@ gchar *               g_strrstr_len    (const gchar  *haystack,
                                        const gchar  *needle);
 
 GLIB_AVAILABLE_IN_ALL
-gboolean              g_str_has_suffix (const gchar  *str,
-                                       const gchar  *suffix);
+gboolean g_str_has_suffix (const gchar *str,
+                           const gchar *suffix);
 GLIB_AVAILABLE_IN_ALL
-gboolean              g_str_has_prefix (const gchar  *str,
-                                       const gchar  *prefix);
+gboolean g_str_has_prefix (const gchar *str,
+                           const gchar *prefix);
+
+#if defined(__GNUC__) && (__GNUC__ > 2)
+
+#define g_str_has_prefix(STR, PREFIX)                                                     \
+  ((STR != NULL && PREFIX != NULL && __builtin_constant_p (PREFIX)) ? G_GNUC_EXTENSION ({ \
+    const char *const __str = STR;                                                        \
+    const char *const __prefix = PREFIX;                                                  \
+    const size_t __str_len = strlen (__str);                                              \
+    const size_t __prefix_len = strlen (__prefix);                                        \
+    (__str_len >= __prefix_len) ? memcmp (__str, __prefix, __prefix_len) == 0 : FALSE;    \
+  })                                                                                      \
+                                                                    : (g_str_has_prefix) (STR, PREFIX))
+
+#define g_str_has_suffix(STR, SUFFIX)                                                                        
     \
+  ((STR != NULL && SUFFIX != NULL && __builtin_constant_p (SUFFIX)) ? G_GNUC_EXTENSION ({                    
     \
+    const char *const __str = STR;                                                                           
     \
+    const char *const __suffix = SUFFIX;                                                                     
     \
+    const size_t __str_len = strlen (__str);                                                                 
     \
+    const size_t __suffix_len = strlen (__suffix);                                                           
     \
+    (__str_len >= __suffix_len) ? memcmp (__str + __str_len - __suffix_len, __suffix, __suffix_len) == 0 : 
FALSE; \
+  })                                                                                                         
     \
+                                                                    : (g_str_has_suffix) (STR, SUFFIX))
+
+#endif
 
 /* String to/from double conversion functions */