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Optimize g_str_has_*() functions to detect const arguments at compile-time

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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
This commit is contained in:
Emmanuel Fleury 2022-08-19 18:00:19 +02:00
parent 5215463a03
commit bbd3ad8c00
2 changed files with 47 additions and 10 deletions
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10
glib/gstrfuncs.c
View File

@ -2928,9 +2928,8 @@ g_strrstr_len (const gchar *haystack,
* *
* Since: 2.2 * Since: 2.2
*/ */
gboolean gboolean (g_str_has_suffix) (const gchar *str,
g_str_has_suffix (const gchar *str, const gchar *suffix)
const gchar *suffix)
{ {
gsize str_len; gsize str_len;
gsize suffix_len; gsize suffix_len;
@ -2958,9 +2957,8 @@ g_str_has_suffix (const gchar *str,
* *
* Since: 2.2 * Since: 2.2
*/ */
gboolean gboolean (g_str_has_prefix) (const gchar *str,
g_str_has_prefix (const gchar *str, const gchar *prefix)
const gchar *prefix)
{ {
g_return_val_if_fail (str != NULL, FALSE); g_return_val_if_fail (str != NULL, FALSE);
g_return_val_if_fail (prefix != NULL, FALSE); g_return_val_if_fail (prefix != NULL, FALSE);

47
glib/gstrfuncs.h
View File

@ -33,6 +33,7 @@
#include <stdarg.h> #include <stdarg.h>
#include <string.h> #include <string.h>
#include <glib/gmacros.h> #include <glib/gmacros.h>
#include <glib/gtypes.h> #include <glib/gtypes.h>
#include <glib/gerror.h> #include <glib/gerror.h>
@ -139,11 +140,49 @@ gchar * g_strrstr_len (const gchar *haystack,
const gchar *needle); const gchar *needle);
GLIB_AVAILABLE_IN_ALL GLIB_AVAILABLE_IN_ALL
gboolean g_str_has_suffix (const gchar *str, gboolean (g_str_has_suffix) (const gchar *str,
const gchar *suffix); const gchar *suffix);
GLIB_AVAILABLE_IN_ALL GLIB_AVAILABLE_IN_ALL
gboolean g_str_has_prefix (const gchar *str, gboolean (g_str_has_prefix) (const gchar *str,
const gchar *prefix); 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 */ /* String to/from double conversion functions */