gcc.cpp

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/* Copyright (c) 2010 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include "precompiled.h"

#include "lib/sysdep/rtl.h"
#include "lib/bits.h"

// Linux glibc has posix_memalign and (obsolete) memalign
// Android libc has only memalign
// OS X and BSD probably do not have either.
#define HAVE_POSIX_MEMALIGN (OS_LINUX && !OS_ANDROID)
#define HAVE_MEMALIGN OS_LINUX

#if HAVE_POSIX_MEMALIGN

void* rtl_AllocateAligned(size_t size, size_t alignment)
{
    void *ptr;
    int ret = posix_memalign(&ptr, alignment, size);
    if (ret) {
        // TODO: report error?
        return NULL;
    }
    return ptr;
}

void rtl_FreeAligned(void* alignedPointer)
{
    free(alignedPointer);
}

#elif HAVE_MEMALIGN

void* rtl_AllocateAligned(size_t size, size_t alignment)
{
    return memalign(alignment, size);
}

void rtl_FreeAligned(void* alignedPointer)
{
    free(alignedPointer);
}

#else // Fallback aligned allocation using malloc

void* rtl_AllocateAligned(size_t size, size_t align)
{
    // This ensures we have enough extra space to store the original pointer,
    // and produce an aligned buffer, assuming the platform malloc ensures at
    // least sizeof(void*) alignment.
    if (align < 2*sizeof(void*))
        align = 2*sizeof(void*);
    
    void* const malloc_ptr = malloc(size + align);
    if (!malloc_ptr)
        return NULL;
    
    // Round malloc_ptr up to the next aligned address, leaving some unused
    // space before the pointer we'll return. The minimum alignment above
    // ensures we'll have at least sizeof(void*) extra space.
    void* const aligned_ptr =
        (void *)(round_down(uintptr_t(malloc_ptr), uintptr_t(align)) + align);

    // Just make sure we did the right thing with all the alignment hacks above.
    ENSURE(((void**)aligned_ptr) - 1 >= malloc_ptr);

    // Store the original pointer which will have to be sent to free().
    ((void **)aligned_ptr)[-1] = malloc_ptr;

    return aligned_ptr;
}

void rtl_FreeAligned(void* alignedPointer)
{
    if (alignedPointer)
        free(((void**)alignedPointer)[-1]);
}

#endif