[vlc-devel] [PATCH 2/7] core: utils: add vlc_qsort

[Hugo Beauzée-Luyssen]

On Mon, Jan 21, 2019, at 5:43 PM, Thomas Guillem wrote:
> Following the upcoming POSIX prototype.
> ---
>  include/vlc_utils.h | 36 ++++++++++++++++++++++++++++
>  src/Makefile.am     |  2 ++
>  src/libvlccore.sym  |  1 +
>  src/misc/utils.c    | 58 +++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 97 insertions(+)
>  create mode 100644 include/vlc_utils.h
>  create mode 100644 src/misc/utils.c
> 
> diff --git a/include/vlc_utils.h b/include/vlc_utils.h
> new file mode 100644
> index 0000000000..46a331a1aa
> --- /dev/null
> +++ b/include/vlc_utils.h
> @@ -0,0 +1,36 @@
> +/******************************************************************************
> + * vlc_utils.h
> + ******************************************************************************
> + * Copyright © 2019 VLC authors and VideoLAN
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU Lesser General Public License as published by
> + * the Free Software Foundation; either version 2.1 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public License
> + * along with this program; if not, write to the Free Software Foundation,
> + * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
> + *****************************************************************************/
> +
> +#ifndef VLC_UTILS_H
> +#define VLC_UTILS_H
> +
> +#include <stdlib.h>
> +#include <stddef.h>
> +
> +/**
> + * Sort an array with reentrancy, following the upcoming POSIX prototype
> + *
> + * cf. POSIX qsort_r
> + */
> +VLC_API void vlc_qsort(void *base, size_t nmemb, size_t size,
> +                       int (*compar)(const void *, const void *, void *),
> +                       void *arg);
> +
> +#endif
> diff --git a/src/Makefile.am b/src/Makefile.am
> index aec931cdd4..a98f5fdac1 100644
> --- a/src/Makefile.am
> +++ b/src/Makefile.am
> @@ -100,6 +100,7 @@ pluginsinclude_HEADERS = \
>  	../include/vlc_thumbnailer.h \
>  	../include/vlc_tls.h \
>  	../include/vlc_url.h \
> +	../include/vlc_utils.h \
>  	../include/vlc_variables.h \
>  	../include/vlc_vector.h \
>  	../include/vlc_viewpoint.h \
> @@ -388,6 +389,7 @@ libvlccore_la_SOURCES = \
>  	misc/text_style.c \
>  	misc/subpicture.c \
>  	misc/subpicture.h \
> +	misc/utils.c \
>  	misc/medialibrary.c
>  libvlccore_la_LIBADD = $(LIBS_libvlccore) \
>  	../compat/libcompat.la \
> diff --git a/src/libvlccore.sym b/src/libvlccore.sym
> index a7bf98ecc1..629b3ec9eb 100644
> --- a/src/libvlccore.sym
> +++ b/src/libvlccore.sym
> @@ -671,6 +671,7 @@ vlc_rand_bytes
>  vlc_drand48
>  vlc_lrand48
>  vlc_mrand48
> +vlc_qsort
>  vlc_restorecancel
>  vlc_rwlock_destroy
>  vlc_rwlock_init
> diff --git a/src/misc/utils.c b/src/misc/utils.c
> new file mode 100644
> index 0000000000..3d5d9f357f
> --- /dev/null
> +++ b/src/misc/utils.c
> @@ -0,0 +1,58 @@
> +/******************************************************************************
> + * utils.c: compat utils back-end
> + ******************************************************************************
> + * Copyright © 2019 VLC authors and VideoLAN
> + * Copyright © 2018 Rémi Denis-Courmont
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU Lesser General Public License as published by
> + * the Free Software Foundation; either version 2.1 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public License
> + * along with this program; if not, write to the Free Software Foundation,
> + * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
> + *****************************************************************************/
> +
> +#ifdef HAVE_CONFIG_H
> +# include <config.h>
> +#endif
> +
> +#include <vlc_common.h>
> +#include <vlc_utils.h>
> +
> +static _Thread_local struct

Any reason not to use "thread_local" ?

> +{
> +    int (*compar)(const void *, const void *, void *);
> +    void *arg;
> +} state;
> +
> +static int compar_wrapper(const void *a, const void *b)
> +{
> +    return state.compar(a, b, state.arg);
> +}
> +
> +/* Follow the upcoming POSIX prototype, coming from GNU/libc.
> + * Note that this differs from the BSD prototype. */
> +
> +VLC_WEAK void vlc_qsort(void *base, size_t nmemb, size_t size,
> +                        int (*compar)(const void *, const void *, void *),
> +                        void *arg)

Any particular reason to use VLC_WEAK instead of the usual per-platform implementation?

> +{
> +    int (*saved_compar)(const void *, const void *, void *) = state.compar;
> +    void *saved_arg = state.arg;
> +
> +    state.compar = compar;
> +    state.arg = arg;
> +
> +    qsort(base, nmemb, size, compar_wrapper);
> +
> +    /* Restore state for nested reentrant calls */
> +    state.compar = saved_compar;
> +    state.arg = saved_arg;
> +}
> -- 
> 2.20.1
> 
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-- 
  Hugo Beauzée-Luyssen
  hugo at beauzee.fr