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nuttx/mm/mm_gran/mm_granalloc.c

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/****************************************************************************
* mm/mm_gran/mm_granalloc.c
*
* Copyright (C) 2012 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* 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
* COPYRIGHT OWNER 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <assert.h>
#include <nuttx/mm/gran.h>
#include "mm_gran/mm_gran.h"
#ifdef CONFIG_GRAN
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: gran_common_alloc
*
* Description:
* Allocate memory from the granule heap.
*
* Input Parameters:
* priv - The granule heap state structure.
* size - The size of the memory region to allocate.
*
* Returned Value:
* On success, a non-NULL pointer to the allocated memory is returned.
*
****************************************************************************/
static inline FAR void *gran_common_alloc(FAR struct gran_s *priv, size_t size)
{
unsigned int ngranules;
size_t tmpmask;
uintptr_t alloc;
uint32_t curr;
uint32_t next;
uint32_t mask;
int granidx;
int gatidx;
int bitidx;
int shift;
DEBUGASSERT(priv && size <= 32 * (1 << priv->log2gran));
if (priv && size > 0)
{
/* Get exclusive access to the GAT */
gran_enter_critical(priv);
/* How many contiguous granules we we need to find? */
tmpmask = (1 << priv->log2gran) - 1;
ngranules = (size + tmpmask) >> priv->log2gran;
/* Then create mask for that number of granules */
DEBUGASSERT(ngranules <= 32);
mask = 0xffffffff >> (32 - ngranules);
/* Now search the granule allocation table for that number of contiguous */
alloc = priv->heapstart;
for (granidx = 0; granidx < priv->ngranules; granidx += 32)
{
/* Get the GAT index associated with the granule table entry */
gatidx = granidx >> 5;
curr = priv->gat[gatidx];
/* Handle the case where there are no free granules in the entry */
if (curr == 0xffffffff)
{
alloc += (32 << priv->log2gran);
continue;
}
/* Get the next entry from the GAT to support a 64 bit shift */
if (granidx < priv->ngranules)
{
next = priv->gat[gatidx + 1];
}
/* Use all ones when are at the last entry in the GAT (meaning
* nothing can be allocated.
*/
else
{
next = 0xffffffff;
}
/* Search through the allocations in the 'curr' GAT entry
* to see if we can satisfy the allocation starting in that
* entry.
*
* This loop continues until either all of the bits have been
* examined (bitidx >= 32), or until there are insufficient
* granules left to satisfy the allocation.
*/
for (bitidx = 0;
bitidx < 32 && (granidx + bitidx + ngranules) <= priv->ngranules;
)
{
/* Break out if there are no further free bits in 'curr'.
* All of the zero bits might have gotten shifted out.
*/
if (curr == 0xffffffff)
{
break;
}
/* Check for the first zero bit in the lower or upper 16-bits.
* From the test above, we know that at least one of the 32-
* bits in 'curr' is zero.
*/
else if ((curr & 0x0000ffff) == 0x0000ffff)
{
/* Not in the lower 16 bits. The first free bit must be
* in the upper 16 bits.
*/
shift = 16;
}
/* We know that the first free bit is now within the lower 16
* bits of 'curr'. Is it in the upper or lower byte?
*/
else if ((curr & 0x0000ff) == 0x000000ff)
{
/* Not in the lower 8 bits. The first free bit must be in
* the upper 8 bits.
*/
shift = 8;
}
/* We know that the first free bit is now within the lower 4
* bits of 'curr'. Is it in the upper or lower nibble?
*/
else if ((curr & 0x00000f) == 0x0000000f)
{
/* Not in the lower 4 bits. The first free bit must be in
* the upper 4 bits.
*/
shift = 4;
}
/* We know that the first free bit is now within the lower 4 bits
* of 'curr'. Is it in the upper or lower pair?
*/
else if ((curr & 0x000003) == 0x00000003)
{
/* Not in the lower 2 bits. The first free bit must be in
* the upper 2 bits.
*/
shift = 2;
}
/* We know that the first free bit is now within the lower 4 bits
* of 'curr'. Check if we have the allocation at this bit position.
*/
else if ((curr & mask) == 0)
{
/* Yes.. mark these granules allocated */
gran_mark_allocated(priv, alloc, ngranules);
/* And return the allocation address */
gran_leave_critical(priv);
return (FAR void *)alloc;
}
/* The free allocation does not start at this position */
else
{
shift = 1;
}
/* Set up for the next time through the loop. Perform a 64
* bit shift to move to the next gran position andi ncrement
* to the next candidate allocation address.
*/
alloc += (shift << priv->log2gran);
curr = (curr >> shift) | (next << (32 - shift));
next >>= shift;
bitidx += shift;
}
}
gran_leave_critical(priv);
}
return NULL;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: gran_alloc
*
* Description:
* Allocate memory from the granule heap.
*
* NOTE: The current implementation also restricts the maximum allocation
* size to 32 granules. That restriction could be eliminated with some
* additional coding effort.
*
* Input Parameters:
* handle - The handle previously returned by gran_initialize
* size - The size of the memory region to allocate.
*
* Returned Value:
* On success, either a non-NULL pointer to the allocated memory (if
* CONFIG_GRAN_SINGLE) or zero (if !CONFIG_GRAN_SINGLE) is returned.
*
****************************************************************************/
#ifdef CONFIG_GRAN_SINGLE
FAR void *gran_alloc(size_t size)
{
return gran_common_alloc(g_graninfo, size);
}
#else
FAR void *gran_alloc(GRAN_HANDLE handle, size_t size)
{
return gran_common_alloc((FAR struct gran_s *)handle, size);
}
#endif
#endif /* CONFIG_GRAN */
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