mirror of
https://github.com/DrBeef/Raze.git
synced 2024-11-16 17:31:27 +00:00
276 lines
7.7 KiB
Lua
276 lines
7.7 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 math = require "math"
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local ffi = require "ffi"
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local assert = assert
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local error = error
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local type = type
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local tostring = tostring
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module(...)
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ffi.cdef[[
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struct bitar { const double maxbidx, maxidx; const intptr_t arptr; }
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]]
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local bitar_ct = ffi.typeof("struct bitar")
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local ptr_to_int = ffi.typeof("int32_t *")
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local anchor = {}
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-- population count of a nibble
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local nibpop = ffi.new("double [?]", 16,
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{ 0, 1, 1, 2, 1, 2, 2, 3,
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1, 2, 2, 3, 2, 3, 3, 4 })
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-- ...and of a byte
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local bytepop = ffi.new("double [?]", 256)
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for i=0,255 do
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bytepop[i] = nibpop[bit.band(i, 15)] + nibpop[bit.rshift(i, 4)]
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end
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nibpop = nil
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local function bitar_from_intar(maxbidx, maxidx, ar)
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-- We need to have the int32_t[?] array be reachable so that it will not be
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-- garbage collected
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local ar_intptr = ffi.cast("intptr_t", ar)
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anchor[tostring(ar_intptr)] = ar
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-- Leaving the (potential) high trailing bits at 0 lets us not worry
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-- about them in the population count calculation (__len metamethod).
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-- Also, this is correct for maxbidx%32 == 0, since BitOp's shifts
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-- mask the 5 lower bits of the counts.
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local numremain = bit.band(maxbidx+1, 31)
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ar[maxidx] = bit.band(ar[maxidx], bit.rshift(-1, 32-numremain))
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return bitar_ct(maxbidx, maxidx, ar_intptr)
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end
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local function setop_common_rel(s1, s2)
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if (s1.maxbidx ~= s2.maxbidx) then
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error("bad arguments to bit array set op: must be of same length", 4)
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end
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local ar1 = ffi.cast(ptr_to_int, s1.arptr)
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local ar2 = ffi.cast(ptr_to_int, s2.arptr)
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return ar1, ar2
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end
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local function setop_common(s1, s2)
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if (not ffi.istype(bitar_ct, s1) or not ffi.istype(bitar_ct, s2)) then
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error("bad arguments to bit array set op: both must be 'bitar' types", 3)
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end
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local ar1, ar2 = setop_common_rel(s1, s2)
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local ar = ffi.new("int32_t [?]", s1.maxidx+1)
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return ar, ar1, ar2
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end
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local mt = {
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--- Operational methods
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__add = function(s1, s2) -- set union
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local ar, ar1, ar2 = setop_common(s1, s2)
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for i=0,s1.maxidx do
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ar[i] = bit.bor(ar1[i], ar2[i])
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end
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return bitar_from_intar(s1.maxbidx, s1.maxidx, ar)
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end,
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__mul = function(s1, s2) -- set intersection
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local ar, ar1, ar2 = setop_common(s1, s2)
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for i=0,s1.maxidx do
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ar[i] = bit.band(ar1[i], ar2[i])
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end
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return bitar_from_intar(s1.maxbidx, s1.maxidx, ar)
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end,
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__sub = function(s1, s2) -- set difference
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local ar, ar1, ar2 = setop_common(s1, s2)
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for i=0,s1.maxidx do
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ar[i] = bit.band(ar1[i], bit.bnot(ar2[i]))
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end
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return bitar_from_intar(s1.maxbidx, s1.maxidx, ar)
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end,
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__unm = function(s) -- bitwise NOT
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local newar = ffi.new("int32_t [?]", s.maxidx+1)
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local oldar = ffi.cast(ptr_to_int, s.arptr)
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for i=0,s.maxidx do
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newar[i] = bit.bnot(oldar[i])
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end
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return bitar_from_intar(s.maxbidx, s.maxidx, newar)
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end,
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--- Additional operations
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__index = {
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-- Is bit i set?
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isset = function(s, i)
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if (not (i >= 0 and i<=s.maxbidx)) then
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error("bad bit index for isset: must be in [0.."..s.maxbidx.."]", 2)
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end
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s = ffi.cast(ptr_to_int, s.arptr)
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return (bit.band(s[bit.rshift(i, 5)], bit.lshift(1, i)) ~= 0)
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end,
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-- Clear bit i.
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set0 = function(s, i)
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if (not (i >= 0 and i<=s.maxbidx)) then
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error("bad bit index for set0: must be in [0.."..s.maxbidx.."]", 2)
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end
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s = ffi.cast(ptr_to_int, s.arptr)
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local jx = bit.rshift(i, 5)
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s[jx] = bit.band(s[jx], bit.rol(0xfffffffe, i))
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end,
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-- Set bit i.
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set1 = function(s, i)
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if (not (i >= 0 and i<=s.maxbidx)) then
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error("bad bit index for set1: must be in [0.."..s.maxbidx.."]", 2)
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end
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s = ffi.cast(ptr_to_int, s.arptr)
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local jx = bit.rshift(i, 5)
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s[jx] = bit.bor(s[jx], bit.rol(0x00000001, i))
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end
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},
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--- Relational methods
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__eq = function(s1, s2) -- set identity
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local ar1, ar2 = setop_common_rel(s1, s2)
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for i=0,s1.maxidx do
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if (bit.bxor(ar1[i], ar2[i]) ~= 0) then
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return false
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end
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end
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return true
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end,
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__le = function(s1, s2)
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local ar1, ar2 = setop_common_rel(s1, s2)
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for i=0,s1.maxidx do
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if (bit.band(ar1[i], bit.bnot(ar2[i])) ~= 0) then
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return false
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end
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end
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return true
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end,
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__lt = function(s1, s2)
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return s1 <= s2 and not (s2 == s1)
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end,
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-- The length operator gets the population count of the bit array, i.e. the
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-- number of set bits.
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__len = function(s)
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local ar = ffi.cast(ptr_to_int, s.arptr)
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local popcnt = 0
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for i=0,s.maxidx do
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popcnt = popcnt + bytepop[bit.band(ar[i], 255)] +
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bytepop[bit.band(bit.rshift(ar[i], 8), 255)] +
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bytepop[bit.band(bit.rshift(ar[i], 16), 255)] +
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bytepop[bit.rshift(ar[i], 24)]
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end
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return popcnt
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end,
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-- serialization
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__tostring = function(s)
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local size=s.maxidx+1
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local ar = ffi.cast(ptr_to_int, s.arptr)
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local hdr = "bitar.new("..s.maxbidx..", '"
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local ofs = #hdr
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local totalstrlen = ofs+8*size+2
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local str = ffi.new("char [?]", totalstrlen)
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ffi.copy(str, hdr, ofs)
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for i=0,s.maxidx do
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-- 'a' is ASCII 97
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for nib=0,7 do
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str[ofs + 8*i + nib] = 97 + bit.band(bit.rshift(ar[i], 4*nib), 0x0000000f)
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end
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end
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ffi.copy(str+totalstrlen-2, "')", 2)
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return ffi.string(str, totalstrlen)
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end,
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-- On garbage collection of the bitar, clear the array's anchor so that it
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-- can be collected too.
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__gc = function(s)
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anchor[tostring(s.arptr)] = nil
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end,
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}
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local bitar = ffi.metatype("struct bitar", mt)
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-- Create new bit array.
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function new(maxbidx, initval)
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if (type(maxbidx) ~= "number" or not (maxbidx >= 0 and maxbidx <= (2^31)-2)) then
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error("bad argument #1 to bitar.new (must be a number in [0..(2^31)-2])", 2)
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end
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if (math.floor(maxbidx) ~= maxbidx) then
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error("bad argument #1 to bitar.new (must be an integral number)")
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end
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if (type(initval)=="string") then
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-- string containing hex digits (a..p) given, for INTERNAL use
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local lstr = initval
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local numnibs = #lstr
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assert(numnibs%8 == 0)
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local size = numnibs/8
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local maxidx = size-1
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local ar = ffi.new("int32_t [?]", size)
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local str = ffi.new("char [?]", numnibs)
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ffi.copy(str, lstr, numnibs)
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for i=0,maxidx do
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ar[i] = 0
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for nib=0,7 do
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local hexdig = str[8*i + nib]
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assert(hexdig >= 97 and hexdig < 97+16)
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ar[i] = bit.bor(ar[i], bit.lshift(hexdig-97, 4*nib))
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end
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end
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return bitar_from_intar(maxbidx, maxidx, ar)
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else
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-- User-requested bitar creation.
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if (initval ~= 0 and initval ~= 1) then
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error("bad argument #2 to bitar.new (must be either 0 or 1)", 2)
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end
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local maxidx = math.floor(maxbidx/32)
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local size = maxidx+1
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local ar = ffi.new("int32_t [?]", size)
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if (initval==1) then
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ffi.fill(ar, size*4, -1)
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end
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return bitar_from_intar(maxbidx, maxidx, ar)
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end
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end
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