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- /****************************************************************************
- * mm/mm_gran/mm_granalloc.c
- *
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership. The
- * ASF licenses this file to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance with the
- * License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
- * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
- * License for the specific language governing permissions and limitations
- * under the License.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.h>
- #include <assert.h>
- #include <nuttx/mm/gran.h>
- #include "mm_gran/mm_gran.h"
- #ifdef CONFIG_GRAN
- /****************************************************************************
- * 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, a non-NULL pointer to the allocated memory is returned;
- * NULL is returned on failure.
- *
- ****************************************************************************/
- FAR void *gran_alloc(GRAN_HANDLE handle, size_t size)
- {
- FAR struct gran_s *priv = (FAR struct gran_s *)handle;
- 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;
- int ret;
- DEBUGASSERT(priv != NULL && size <= 32 * (1 << priv->log2gran));
- if (priv != NULL && size > 0)
- {
- /* Get exclusive access to the GAT */
- ret = gran_enter_critical(priv);
- if (ret < 0)
- {
- return NULL;
- }
- /* 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 */
- 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)
- {
- 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.
- */
- alloc = priv->heapstart + (granidx << priv->log2gran);
- 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 and increment
- * 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;
- }
- #endif /* CONFIG_GRAN */
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