diff options
| -rw-r--r-- | Makefile.am | 1 | ||||
| -rw-r--r-- | src/output/HttpdInternal.hxx | 3 | ||||
| -rw-r--r-- | src/tag/TagPool.cxx | 3 | ||||
| -rw-r--r-- | src/util/Cast.hxx | 58 |
4 files changed, 63 insertions, 2 deletions
diff --git a/Makefile.am b/Makefile.am index d851efad8..3541714c0 100644 --- a/Makefile.am +++ b/Makefile.am @@ -249,6 +249,7 @@ endif libutil_a_SOURCES = \ src/util/Macros.hxx \ + src/util/Cast.hxx \ src/util/Clamp.hxx \ src/util/Error.cxx src/util/Error.hxx \ src/util/Domain.hxx \ diff --git a/src/output/HttpdInternal.hxx b/src/output/HttpdInternal.hxx index 5a9ef8c19..8d35d35e9 100644 --- a/src/output/HttpdInternal.hxx +++ b/src/output/HttpdInternal.hxx @@ -30,6 +30,7 @@ #include "thread/Mutex.hxx" #include "event/ServerSocket.hxx" #include "event/DeferredMonitor.hxx" +#include "util/Cast.hxx" #ifdef _LIBCPP_VERSION /* can't use incomplete template arguments with libc++ */ @@ -157,7 +158,7 @@ public: #endif static constexpr HttpdOutput *Cast(audio_output *ao) { - return (HttpdOutput *)((char *)ao - offsetof(HttpdOutput, base)); + return ContainerCast(ao, HttpdOutput, base); } #if GCC_CHECK_VERSION(4,6) || defined(__clang__) diff --git a/src/tag/TagPool.cxx b/src/tag/TagPool.cxx index cc28ea9a6..8e1e670c9 100644 --- a/src/tag/TagPool.cxx +++ b/src/tag/TagPool.cxx @@ -20,6 +20,7 @@ #include "config.h" #include "TagPool.hxx" #include "TagItem.hxx" +#include "util/Cast.hxx" #include <glib.h> @@ -67,7 +68,7 @@ calc_hash(TagType type, const char *p) static inline struct slot * tag_item_to_slot(TagItem *item) { - return (struct slot*)(((char*)item) - offsetof(struct slot, item)); + return ContainerCast(item, slot, item); } static struct slot *slot_alloc(struct slot *next, diff --git a/src/util/Cast.hxx b/src/util/Cast.hxx new file mode 100644 index 000000000..69172e6de --- /dev/null +++ b/src/util/Cast.hxx @@ -0,0 +1,58 @@ +/* + * Copyright (C) 2013 Max Kellermann <max@duempel.org> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * - Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * - Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the + * distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, + * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED + * OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#ifndef CAST_HXX +#define CAST_HXX + +#include <stddef.h> + +/** + * Offset the given pointer by the specified number of bytes. + */ +static constexpr void * +OffsetPointer(void *p, ptrdiff_t offset) +{ + return (char *)p + offset; +} + +template<typename T, typename U> +static constexpr T * +OffsetCast(U *p, ptrdiff_t offset) +{ + return reinterpret_cast<T *>(OffsetPointer(p, offset)); +} + +/** + * Cast the given pointer to a struct member to its parent structure. + */ +#define ContainerCast(p, container, attribute) \ + OffsetCast<container, decltype(((container*)nullptr)->attribute)>\ + ((p), -ptrdiff_t(offsetof(container, attribute))) + +#endif |