251 lines
7.6 KiB
C
251 lines
7.6 KiB
C
/****************************************************************************
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* mm/mm_gran/mm_granalloc.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <assert.h>
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#include <nuttx/mm/gran.h>
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#include "mm_gran/mm_gran.h"
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#ifdef CONFIG_GRAN
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: gran_alloc
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*
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* Description:
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* Allocate memory from the granule heap.
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*
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* NOTE: The current implementation also restricts the maximum allocation
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* size to 32 granules. That restriction could be eliminated with some
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* additional coding effort.
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*
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* Input Parameters:
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* handle - The handle previously returned by gran_initialize
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* size - The size of the memory region to allocate.
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*
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* Returned Value:
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* On success, a non-NULL pointer to the allocated memory is returned;
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* NULL is returned on failure.
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*
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****************************************************************************/
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FAR void *gran_alloc(GRAN_HANDLE handle, size_t size)
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{
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FAR struct gran_s *priv = (FAR struct gran_s *)handle;
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unsigned int ngranules;
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size_t tmpmask;
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uintptr_t alloc;
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uint32_t curr;
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uint32_t next;
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uint32_t mask;
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int granidx;
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int gatidx;
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int bitidx;
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int shift;
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int ret;
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DEBUGASSERT(priv != NULL && size <= 32 * (1 << priv->log2gran));
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if (priv != NULL && size > 0)
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{
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/* Get exclusive access to the GAT */
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ret = gran_enter_critical(priv);
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if (ret < 0)
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{
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return NULL;
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}
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/* How many contiguous granules we we need to find? */
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tmpmask = (1 << priv->log2gran) - 1;
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ngranules = (size + tmpmask) >> priv->log2gran;
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/* Then create mask for that number of granules */
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DEBUGASSERT(ngranules <= 32);
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mask = 0xffffffff >> (32 - ngranules);
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/* Now search the granule allocation table for that number
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* of contiguous
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*/
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for (granidx = 0; granidx < priv->ngranules; granidx += 32)
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{
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/* Get the GAT index associated with the granule table entry */
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gatidx = granidx >> 5;
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curr = priv->gat[gatidx];
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/* Handle the case where there are no free granules in the entry */
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if (curr == 0xffffffff)
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{
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continue;
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}
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/* Get the next entry from the GAT to support a 64 bit shift */
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if (granidx < priv->ngranules)
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{
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next = priv->gat[gatidx + 1];
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}
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/* Use all ones when are at the last entry in the GAT (meaning
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* nothing can be allocated.
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*/
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else
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{
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next = 0xffffffff;
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}
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/* Search through the allocations in the 'curr' GAT entry
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* to see if we can satisfy the allocation starting in that
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* entry.
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*
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* This loop continues until either all of the bits have been
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* examined (bitidx >= 32), or until there are insufficient
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* granules left to satisfy the allocation.
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*/
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alloc = priv->heapstart + (granidx << priv->log2gran);
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for (bitidx = 0;
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bitidx < 32 &&
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(granidx + bitidx + ngranules) <= priv->ngranules;
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)
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{
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/* Break out if there are no further free bits in 'curr'.
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* All of the zero bits might have gotten shifted out.
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*/
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if (curr == 0xffffffff)
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{
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break;
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}
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/* Check for the first zero bit in the lower or upper 16-bits.
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* From the test above, we know that at least one of the 32-
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* bits in 'curr' is zero.
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*/
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else if ((curr & 0x0000ffff) == 0x0000ffff)
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{
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/* Not in the lower 16 bits. The first free bit must be
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* in the upper 16 bits.
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*/
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shift = 16;
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}
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/* We know that the first free bit is now within the lower 16
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* bits of 'curr'. Is it in the upper or lower byte?
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*/
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else if ((curr & 0x0000ff) == 0x000000ff)
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{
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/* Not in the lower 8 bits. The first free bit must be in
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* the upper 8 bits.
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*/
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shift = 8;
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}
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/* We know that the first free bit is now within the lower 4
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* bits of 'curr'. Is it in the upper or lower nibble?
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*/
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else if ((curr & 0x00000f) == 0x0000000f)
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{
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/* Not in the lower 4 bits. The first free bit must be in
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* the upper 4 bits.
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*/
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shift = 4;
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}
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/* We know that the first free bit is now within the lower 4
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* bits of 'curr'. Is it in the upper or lower pair?
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*/
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else if ((curr & 0x000003) == 0x00000003)
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{
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/* Not in the lower 2 bits. The first free bit must be in
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* the upper 2 bits.
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*/
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shift = 2;
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}
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/* We know that the first free bit is now within the lower 4
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* bits of 'curr'. Check if we have the allocation at this
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* bit position.
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*/
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else if ((curr & mask) == 0)
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{
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/* Yes.. mark these granules allocated */
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gran_mark_allocated(priv, alloc, ngranules);
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/* And return the allocation address */
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gran_leave_critical(priv);
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return (FAR void *)alloc;
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}
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/* The free allocation does not start at this position */
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else
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{
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shift = 1;
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}
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/* Set up for the next time through the loop. Perform a 64
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* bit shift to move to the next gran position and increment
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* to the next candidate allocation address.
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*/
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alloc += (shift << priv->log2gran);
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curr = (curr >> shift) | (next << (32 - shift));
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next >>= shift;
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bitidx += shift;
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}
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}
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gran_leave_critical(priv);
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}
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return NULL;
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}
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#endif /* CONFIG_GRAN */
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