93 lines
3.0 KiB
Python
93 lines
3.0 KiB
Python
"""
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Copyright (c) 2021 Alex Forencich
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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"""
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class BuddyAllocator:
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def __init__(self, size, min_alloc=1):
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self.size = size
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self.min_alloc = min_alloc
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self.free_lists = [[] for x in range((self.size-1).bit_length())]
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self.free_lists.append([0])
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self.allocations = {}
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def alloc(self, size):
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if size < 1 or size > self.size:
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raise ValueError("size out of range")
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size = max(size, self.min_alloc)
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bucket = (size-1).bit_length()
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orig_bucket = bucket
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while bucket < len(self.free_lists):
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if not self.free_lists[bucket]:
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# find free block
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bucket += 1
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continue
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while bucket > orig_bucket:
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# split block
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block = self.free_lists[bucket].pop(0)
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bucket -= 1
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self.free_lists[bucket].append(block)
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self.free_lists[bucket].append(block+2**bucket)
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if self.free_lists[bucket]:
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# allocate
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block = self.free_lists[bucket].pop(0)
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self.allocations[block] = bucket
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return block
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break
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raise Exception("out of memory")
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def free(self, addr):
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if addr not in self.allocations:
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raise ValueError("unknown allocation")
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bucket = self.allocations.pop(addr)
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while bucket < len(self.free_lists):
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size = 2**bucket
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# find buddy
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if (addr // size) % 2:
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buddy = addr - size
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else:
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buddy = addr + size
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if buddy in self.free_lists[bucket]:
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# buddy is free, merge
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self.free_lists[bucket].remove(buddy)
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addr = min(addr, buddy)
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bucket += 1
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else:
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# buddy is not free, so add to free list
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self.free_lists[bucket].append(addr)
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return
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raise Exception("failed to free memory")
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