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alignment.h
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2014-03-02
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4KB
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125 lines
// Avisynth C Interface Version 0.20
// Copyright 2003 Kevin Atkinson
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA, or visit
// http://www.gnu.org/copyleft/gpl.html .
//
// As a special exception, I give you permission to link to the
// Avisynth C interface with independent modules that communicate with
// the Avisynth C interface solely through the interfaces defined in
// avisynth_c.h, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting combined work
// under terms of your choice, provided that every copy of the
// combined work is accompanied by a complete copy of the source code
// of the Avisynth C interface and Avisynth itself (with the version
// used to produce the combined work), being distributed under the
// terms of the GNU General Public License plus this exception. An
// independent module is a module which is not derived from or based
// on Avisynth C Interface, such as 3rd-party filters, import and
// export plugins, or graphical user interfaces.
#ifndef AVS_ALIGNMENT_H
#define AVS_ALIGNMENT_H
// Functions and macros to help work with alignment requirements.
// Tells if a number is a power of two.
#define IS_POWER2(n) ((n) && !((n) & ((n) - 1)))
// Tells if the pointer "ptr" is aligned to "align" bytes.
#define IS_PTR_ALIGNED(ptr, align) (((uintptr_t)ptr & ((uintptr_t)(align-1))) == 0)
// Rounds up the number "n" to the next greater multiple of "align"
#define ALIGN_NUMBER(n, align) (((n) + (align)-1) & (~((align)-1)))
// Rounds up the pointer address "ptr" to the next greater multiple of "align"
#define ALIGN_POINTER(ptr, align) (((uintptr_t)(ptr) + (align)-1) & (~(uintptr_t)((align)-1)))
#ifdef __cplusplus
#include <cassert>
#include <cstdlib>
template<typename T>
static bool IsPtrAligned(T* ptr, size_t align)
{
assert(IS_POWER2(align));
return (bool)IS_PTR_ALIGNED(ptr, align);
}
template<typename T>
static T AlignNumber(T n, T align)
{
assert(IS_POWER2(align));
return ALIGN_NUMBER(n, align);
}
template<typename T>
static T* AlignPointer(T* ptr, size_t align)
{
assert(IS_POWER2(align));
return (T*)ALIGN_POINTER(ptr, align);
}
extern "C"
{
#else
#include <stdlib.h>
#endif // __cplusplus
// Returns a new buffer that is at least the size "nbytes".
// The buffer will be aligned to "align" bytes.
// Returns NULL on error. On successful allocation,
// the returned buffer must be freed using "avs_free".
inline void* avs_malloc(size_t nbytes, size_t align)
{
if (!IS_POWER2(align))
return NULL;
size_t offset = sizeof(void*) + align - 1;
void *orig = malloc(nbytes + offset);
if (orig == NULL)
return NULL;
void **aligned = (void**)(((uintptr_t)orig + (uintptr_t)offset) & (~(uintptr_t)(align-1)));
aligned[-1] = orig;
return aligned;
}
// Buffers allocated using "avs_malloc" must be freed
// using "avs_free" instead of "free".
inline void avs_free(void *ptr)
{
// Mirroring free()'s semantic requires us to accept NULLs
if (ptr == NULL)
return;
free(((void**)ptr)[-1]);
}
#ifdef __cplusplus
} // extern "C"
// The point of these undef's is to force using the template functions
// if we are in C++ mode. For C, the user can rely only on the macros.
#undef IS_PTR_ALIGNED
#undef ALIGN_NUMBER
#undef ALIGN_POINTER
#endif // __cplusplus
#endif //AVS_ALIGNMENT_H