windows-server-2003/base/crts/crtw32/heap/align.c

/***
*align.c - Aligned allocation, reallocation or freeing of memory in the heap
*
*       Copyright (c) 1989-2001, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       Defines the _aligned_malloc(),
*                   _aligned_realloc(),
*                   _aligned_offset_malloc(),
*                   _aligned_offset_realloc() and
*                   _aligned_free() functions.
*
*Revision History:
*       11-05-99  GB    Module created.
*       01-04-00  GB    renamed the routines.
*                       _aligned_routine -> _aligned_routine_base
*       01-19-00  GB    Fixed _alingned_realloc and _aligned_offset_realloc
*                       to move the memblock while realloc.
*       03-20-00  GB    Rewrite _aligned_malloc and _aligned_realloc making
*                       use of their offset counterparts with offset=0
*       06-21-00  GB    Changed _aligned_realloc so as to mimic realloc.
* 
*******************************************************************************/

#include <dbgint.h>
#include <crtdbg.h>
#include <errno.h>
#include <string.h>
#include <malloc.h>
#include <stddef.h>
#include <stdlib.h>
#define IS_2_POW_N(X)   (((X)&(X-1)) == 0)
#define PTR_SZ          sizeof(void *)
/***
* 
* |1|___6___|2|3|4|_________5__________|_6_|
*
* 1 -> Pointer to start of the block allocated by malloc.
* 2 -> Value of 1.
* 3 -> Gap used to get 1 aligned on sizeof(void *).
* 4 -> Pointer to the start of data block.
* 4+5 -> Data block.
* 6 -> Wasted memory at rear of data block.
* 6 -> Wasted memory.
*
*******************************************************************************/

/***
* void *_aligned_malloc_base(size_t size, size_t alignment)
*       - Get a block of aligned memory from the heap.
*
* Purpose:
*       Allocate of block of aligned memory aligned on the alignment of at least
*       size bytes from the heap and return a pointer to it.
*
* Entry:
*       size_t size - size of block requested
*       size_t alignment - alignment of memory
*
* Exit:
*       Sucess: Pointer to memory block
*       Faliure: Null
*******************************************************************************/

void * __cdecl _aligned_malloc_base(
    size_t size,
    size_t alignment
    )
{
    return _aligned_offset_malloc_base(size, alignment, 0);
}
/***
* void *_aligned_offset_malloc_base(size_t size, size_t alignment, int offset)
*       - Get a block of memory from the heap.
*
* Purpose:
*       Allocate a block of memory which is shifted by offset from alignment of
*       at least size bytes from the heap and return a pointer to it.
*
* Entry:
*       size_t size - size of block of memory
*       size_t alignment - alignment of memory
*       size_t offset - offset of memory from the alignment
*
* Exit:
*       Sucess: Pointer to memory block
*       Faliure: Null
*
*******************************************************************************/


void * __cdecl _aligned_offset_malloc_base(
    size_t size,
    size_t align,
    size_t offset
    )
{
    uintptr_t ptr, retptr, gap;

    if (!IS_2_POW_N(align))
    {
        errno = EINVAL;
        return NULL;
    }
    if ( offset >= size && offset != 0)
    {
        errno = EINVAL;
        return NULL;
    }
    
    align = (align > PTR_SZ ? align : PTR_SZ) -1;
    
    /* gap = number of bytes needed to round up offset to align with PTR_SZ*/
    gap = (0 - offset)&(PTR_SZ -1);

    if ( (ptr =(uintptr_t)malloc(PTR_SZ +gap +align +size)) == (uintptr_t)NULL)
        return NULL;

    retptr =((ptr +PTR_SZ +gap +align +offset)&~align)- offset;
    ((uintptr_t *)(retptr - gap))[-1] = ptr;
    
    return (void *)retptr;
}

/***
* 
* void *_aligned_realloc_base(void * memblock, size_t size, size_t alignment)
*       - Reallocate a block of aligned memory from the heap.
*
* Purpose:
*       Reallocates of block of aligned memory aligned on the alignment of at
*       least size bytes from the heap and return a pointer to it. Size can be
*       either greater or less than the original size of the block.
*       The reallocation may result in moving the block as well as changing the
*       size.
*
* Entry:
*       void *memblock - pointer to block in the heap previously allocated by
*               call to _aligned_malloc(), _aligned_offset_malloc(),
*               _aligned_realloc() or _aligned_offset_realloc().
*       size_t size - size of block requested
*       size_t alignment - alignment of memory
*
* Exit:
*       Sucess: Pointer to re-allocated memory block
*       Faliure: Null
*
*******************************************************************************/

void * __cdecl _aligned_realloc_base(
    void *memblock,
    size_t size,
    size_t alignment
    )
{
    return _aligned_offset_realloc_base(memblock, size, alignment, 0);
}


/***
* 
* void *_aligned_offset_realloc_base (void * memblock, size_t size,
*                                     size_t alignment, int offset)
*       - Reallocate a block of memory from the heap.
*
* Purpose:
*       Reallocates a block of memory which is shifted by offset from
*       alignment of at least size bytes from the heap and return a pointer
*       to it. Size can be either greater or less than the original size of the
*       block.
*
* Entry:
*       void *memblock - pointer to block in the heap previously allocated by
*               call to _aligned_malloc(), _aligned_offset_malloc(),
*               _aligned_realloc() or _aligned_offset_realloc().
*       size_t size - size of block of memory
*       size_t alignment - alignment of memory
*       size_t offset - offset of memory from the alignment
*
* Exit:
*       Sucess: Pointer to the re-allocated memory block
*       Faliure: Null
*
*******************************************************************************/

void * __cdecl _aligned_offset_realloc_base(
    void *memblock,
    size_t size,
    size_t align,
    size_t offset
    )
{
    uintptr_t ptr, retptr, gap, stptr, diff;
    uintptr_t movsz, reqsz;
    int bFree = 0;

    if (memblock == NULL)
    {
        return _aligned_offset_malloc_base(size, align, offset);
    }
    if ( size == 0)
    {
        _aligned_free_base(memblock);
        return NULL;
    }
    if ( offset >= size && offset != 0)
    {
        errno = EINVAL;
        return NULL;
    }

    stptr = (uintptr_t)memblock;

    /* ptr points to the pointer to starting of the memory block */
    stptr = (stptr & ~(PTR_SZ -1)) - PTR_SZ;

    /* ptr is the pointer to the start of memory block*/
    stptr = *((uintptr_t *)stptr);

    if (!IS_2_POW_N(align))
    {
        errno = EINVAL;
        return NULL;
    }

    align = (align > PTR_SZ ? align : PTR_SZ) -1;
    /* gap = number of bytes needed to round up offset to align with PTR_SZ*/
    gap = (0 -offset)&(PTR_SZ -1);

    diff = (uintptr_t)memblock - stptr;
    /* Mov size is min of the size of data available and sizw requested.
     */
    movsz = _msize((void *)stptr) - ((uintptr_t)memblock - stptr);
    movsz = movsz > size? size: movsz;
    reqsz = PTR_SZ +gap +align +size;

    /* First check if we can expand(reducing or expanding using expand) data 
     * safely, ie no data is lost. eg, reducing alignment and keeping size
     * same might result in loss of data at the tail of data block while
     * expanding.
     *
     * If no, use malloc to allocate the new data and move data.
     *
     * If yes, expand and then check if we need to move the data.
     */
    if ((stptr +align +PTR_SZ +gap)<(uintptr_t)memblock)
    {
        if ((ptr = (uintptr_t)malloc(reqsz)) == (uintptr_t) NULL)
            return NULL;
        bFree = 1;
    }
    else
    {
        if ((ptr = (uintptr_t)_expand((void *)stptr, reqsz)) == (uintptr_t)NULL)
        {
            if ((ptr = (uintptr_t)malloc(reqsz)) == (uintptr_t) NULL)
                return NULL;
            bFree = 1;
        }
        else
            stptr = ptr;
    }


    if ( ptr == ((uintptr_t)memblock - diff)
         && !( ((size_t)memblock + gap +offset) & ~(align) ))
    {
        return memblock;
    }

    retptr =((ptr +PTR_SZ +gap +align +offset)&~align)- offset;
    memmove((void *)retptr, (void *)(stptr + diff), movsz);
    if ( bFree)
        free ((void *)stptr);
    
    ((uintptr_t *)(retptr - gap))[-1] = ptr;
    return (void *)retptr;
}


/***
*
* void *_aligned_free_base(void *memblock)
*       - Free the memory which was allocated using _aligned_malloc or
*       _aligned_offset_memory
*
* Purpose:
*       Frees the algned memory block which was allocated using _aligned_malloc
*       or _aligned_memory.
*
* Entry:
*       void * memblock - pointer to the block of memory
*
*******************************************************************************/


void  __cdecl _aligned_free_base(void *memblock)
{
    uintptr_t ptr;

    if (memblock == NULL)
        return;

    ptr = (uintptr_t)memblock;

    /* ptr points to the pointer to starting of the memory block */
    ptr = (ptr & ~(PTR_SZ -1)) - PTR_SZ;

    /* ptr is the pointer to the start of memory block*/
    ptr = *((uintptr_t *)ptr);
    free((void *)ptr);
}