/**************************************************************************** * 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 #include #include #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 */