[glib: 1/3] Optimize g_str_has_*() functions to detect const arguments at compile-time
- From: Marco Trevisan <marcotrevi src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [glib: 1/3] Optimize g_str_has_*() functions to detect const arguments at compile-time
- Date: Tue, 18 Oct 2022 14:16:02 +0000 (UTC)
commit bbd3ad8c0069a44f84590a8f53e89c2c3f910c3e
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 | 49 ++++++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 48 insertions(+), 11 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 3c1dc45ecb..8c2f59cf50 100644
--- a/glib/gstrfuncs.h
+++ b/glib/gstrfuncs.h
@@ -33,6 +33,7 @@
#include <stdarg.h>
#include <string.h>
+
#include <glib/gmacros.h>
#include <glib/gtypes.h>
#include <glib/gerror.h>
@@ -139,11 +140,49 @@ 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);
-GLIB_AVAILABLE_IN_ALL
-gboolean g_str_has_prefix (const gchar *str,
- const gchar *prefix);
+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);
+
+#if G_GNUC_CHECK_VERSION (2, 0)
+
+/* A note on the 'x + !x' terms: These are added to workaround a false
+ * warning in gcc 10< which is ignoring the check 'x != NULL' that is
+ * set outside of the G_GNUC_EXTENSION scope. Without 'x + !x' it
+ * would complain that x may be NULL where strlen() and memcmp()
+ * both require non-null arguments. */
+
+#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 + !__str); \
+ const size_t __prefix_len = strlen (__prefix + !__prefix); \
+ (__str_len >= __prefix_len) ? \
+ memcmp (__str + !__str, \
+ __prefix + !__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 + !__str); \
+ const size_t __suffix_len = strlen (__suffix + !__suffix); \
+ (__str_len >= __suffix_len) ? \
+ memcmp (__str + !__str + __str_len - __suffix_len, \
+ __suffix + !__suffix, __suffix_len) == 0 : FALSE; \
+ }) \
+ : \
+ (g_str_has_suffix) (STR, SUFFIX))
+
+#endif /* G_GNUC_CHECK_VERSION (2, 0) */
/* String to/from double conversion functions */
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