mirror of
https://github.com/DrBeef/Raze.git
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47 lines
1.1 KiB
Lua
47 lines
1.1 KiB
Lua
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-- "Bit array" module based on LuaJIT's BitOp.
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local bit = require "bit"
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local error = error
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local type = type
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module(...)
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-- Create new bit array.
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-- Returns a table p in which entries p[0] through p[floor((size+31)/32)]
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-- are set to an initialization value: 0 if 0 has been passed, -1 if 1
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-- has been passed.
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function new(size, initval)
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if (type(size) ~= "number" or size < 0) then
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error("bad argument #1 to newarray (must be a nonnegative number)", 2)
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end
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if (initval ~= 0 and initval ~= 1) then
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error("bad argument #2 to newarray (must be either 0 or 1)", 2)
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end
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local p = {}
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for i=0,(size+31)/32 do
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p[i] = -initval
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end
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return p
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end
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-- Is bit i set in bit array ar?
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function isset(ar, i)
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return bit.band(ar[bit.rshift(i, 5)], bit.lshift(1, i)) ~= 0
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end
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-- Set bit j in bit array ar.
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function set0(ar, j)
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local jx = bit.rshift(j, 5)
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ar[jx] = bit.band(ar[jx], bit.rol(0xfffffffe, j))
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end
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-- Clear bit j in bit array ar.
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function set1(ar, j)
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local jx = bit.rshift(j, 5)
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ar[jx] = bit.bor(ar[jx], bit.rol(0x00000001, j))
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end
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