132 lines
3.4 KiB
Nim
132 lines
3.4 KiB
Nim
import
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../bitops2, typedranges
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type
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BitRange* = object
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data: MutByteRange
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start: int
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mLen: int
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template `@`(s, idx: untyped): untyped =
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(when idx is BackwardsIndex: s.len - int(idx) else: int(idx))
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proc bits*(a: MutByteRange, start, len: int): BitRange =
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doAssert start <= len
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doAssert len <= 8 * a.len
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result.data = a
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result.start = start
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result.mLen = len
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template bits*(a: var seq[byte], start, len: int): BitRange =
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bits(a.toRange, start, len)
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template bits*(a: MutByteRange): BitRange =
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bits(a, 0, a.len * 8)
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template bits*(a: var seq[byte]): BitRange =
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bits(a.toRange, 0, a.len * 8)
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template bits*(a: MutByteRange, len: int): BitRange =
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bits(a, 0, len)
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template bits*(a: var seq[byte], len: int): BitRange =
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bits(a.toRange, 0, len)
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template bits*(bytes: MutByteRange, slice: HSlice): BitRange =
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bits(bytes, bytes @ slice.a, bytes @ slice.b)
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template bits*(x: BitRange): BitRange = x
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proc len*(r: BitRange): int {.inline.} = r.mLen
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iterator enumerateBits(x: BitRange): (int, bool) =
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var p = x.start
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var i = 0
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let e = x.len
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while i != e:
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yield (i, getBitBE(x.data.toOpenArray, p))
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inc p
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inc i
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iterator items*(x: BitRange): bool =
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for _, v in enumerateBits(x): yield v
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iterator pairs*(x: BitRange): (int, bool) =
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for i, v in enumerateBits(x): yield (i, v)
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proc `[]`*(x: BitRange, idx: int): bool {.inline.} =
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doAssert idx < x.len
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let p = x.start + idx
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result = getBitBE(x.data.toOpenArray, p)
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proc sliceNormalized(x: BitRange, ibegin, iend: int): BitRange =
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doAssert ibegin >= 0 and
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ibegin < x.len and
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iend < x.len and
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iend + 1 >= ibegin # the +1 here allows the result to be
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# an empty range
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result.data = x.data
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result.start = x.start + ibegin
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result.mLen = iend - ibegin + 1
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proc `[]`*(r: BitRange, s: HSlice): BitRange {.inline.} =
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sliceNormalized(r, r @ s.a, r @ s.b)
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proc `==`*(a, b: BitRange): bool =
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if a.len != b.len: return false
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for i in 0 ..< a.len:
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if a[i] != b[i]: return false
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true
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proc `[]=`*(r: var BitRange, idx: Natural, val: bool) {.inline.} =
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doAssert idx < r.len
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let absIdx = r.start + idx
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changeBitBE(r.data.toOpenArray, absIdx, val)
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proc pushFront*(x: var BitRange, val: bool) =
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doAssert x.start > 0
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dec x.start
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x[0] = val
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inc x.mLen
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template neededBytes(nBits: int): int =
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(nBits shr 3) + ord((nBits and 0b111) != 0)
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static:
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doAssert neededBytes(2) == 1
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doAssert neededBytes(8) == 1
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doAssert neededBytes(9) == 2
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proc `&`*(a, b: BitRange): BitRange =
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let totalLen = a.len + b.len
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var bytes = newSeq[byte](totalLen.neededBytes)
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result = bits(bytes, 0, totalLen)
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for i in 0 ..< a.len: result.data.toOpenArray.changeBitBE(i, a[i])
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for i in 0 ..< b.len: result.data.toOpenArray.changeBitBE(i + a.len, b[i])
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proc `$`*(r: BitRange): string =
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result = newStringOfCap(r.len)
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for bit in r:
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result.add(if bit: '1' else: '0')
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proc fromBits*(T: type, r: BitRange, offset, num: Natural): T =
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doAssert(num <= sizeof(T) * 8)
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# XXX: Nim has a bug that a typedesc parameter cannot be used
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# in a type coercion, so we must define an alias here:
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type TT = T
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for i in 0 ..< num:
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result = (result shl 1) or TT(r[offset + i])
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proc parse*(T: type BitRange, s: string): BitRange =
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var bytes = newSeq[byte](s.len.neededBytes)
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for i, c in s:
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case c
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of '0': discard
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of '1': setBitBE(bytes, i)
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else: doAssert false
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result = bits(bytes, 0, s.len)
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