257 lines
7.4 KiB
Nim
257 lines
7.4 KiB
Nim
# beacon_chain
|
|
# Copyright (c) 2018 Status Research & Development GmbH
|
|
# Licensed and distributed under either of
|
|
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
|
|
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
|
|
# at your option. This file may not be copied, modified, or distributed except according to those terms.
|
|
|
|
{.push raises: [Defect].}
|
|
|
|
import
|
|
stew/[bitops2, ptrops]
|
|
|
|
type
|
|
Bytes = seq[byte]
|
|
|
|
BitSeq* = distinct Bytes
|
|
## The current design of BitSeq tries to follow precisely
|
|
## the bitwise representation of the SSZ bitlists.
|
|
## This is a relatively compact representation, but as
|
|
## evident from the code below, many of the operations
|
|
## are not trivial.
|
|
|
|
BitArray*[bits: static int] = object
|
|
bytes*: array[(bits + 7) div 8, byte]
|
|
|
|
func bitsLen*(bytes: openarray[byte]): int =
|
|
let
|
|
bytesCount = bytes.len
|
|
lastByte = bytes[bytesCount - 1]
|
|
markerPos = log2trunc(lastByte)
|
|
|
|
bytesCount * 8 - (8 - markerPos)
|
|
|
|
template len*(s: BitSeq): int =
|
|
bitsLen(Bytes s)
|
|
|
|
template len*(a: BitArray): int =
|
|
a.bits
|
|
|
|
func add*(s: var BitSeq, value: bool) =
|
|
let
|
|
lastBytePos = s.Bytes.len - 1
|
|
lastByte = s.Bytes[lastBytePos]
|
|
|
|
if (lastByte and byte(128)) == 0:
|
|
# There is at least one leading zero, so we have enough
|
|
# room to store the new bit
|
|
let markerPos = log2trunc(lastByte)
|
|
s.Bytes[lastBytePos].changeBit markerPos, value
|
|
s.Bytes[lastBytePos].setBit markerPos + 1
|
|
else:
|
|
s.Bytes[lastBytePos].changeBit 7, value
|
|
s.Bytes.add byte(1)
|
|
|
|
func loadLEBytes(WordType: type, bytes: openarray[byte]): WordType =
|
|
# TODO: this is a temporary proc until the endians API is improved
|
|
var shift = 0
|
|
for b in bytes:
|
|
result = result or (WordType(b) shl shift)
|
|
shift += 8
|
|
|
|
func storeLEBytes(value: SomeUnsignedInt, dst: var openarray[byte]) =
|
|
doAssert dst.len <= sizeof(value)
|
|
when system.cpuEndian == bigEndian:
|
|
var shift = 0
|
|
for i in 0 ..< dst.len:
|
|
result[i] = byte((v shr shift) and 0xff)
|
|
shift += 8
|
|
else:
|
|
copyMem(addr dst[0], unsafeAddr value, dst.len)
|
|
|
|
template loopOverWords(lhs, rhs: BitSeq,
|
|
lhsIsVar, rhsIsVar: static bool,
|
|
WordType: type,
|
|
lhsBits, rhsBits, body: untyped) =
|
|
const hasRhs = astToStr(lhs) != astToStr(rhs)
|
|
|
|
let bytesCount = len Bytes(lhs)
|
|
when hasRhs: doAssert len(Bytes(rhs)) == bytesCount
|
|
|
|
var fullWordsCount = bytesCount div sizeof(WordType)
|
|
let lastWordSize = bytesCount mod sizeof(WordType)
|
|
|
|
block:
|
|
var lhsWord: WordType
|
|
when hasRhs:
|
|
var rhsWord: WordType
|
|
var firstByteOfLastWord, lastByteOfLastWord: int
|
|
|
|
# TODO: Returing a `var` value from an iterator is always safe due to
|
|
# the way inlining works, but currently the compiler reports an error
|
|
# when a local variable escapes. We have to cheat it with this location
|
|
# obfuscation through pointers:
|
|
template lhsBits: auto = (addr(lhsWord))[]
|
|
|
|
when hasRhs:
|
|
template rhsBits: auto = (addr(rhsWord))[]
|
|
|
|
template lastWordBytes(bitseq): auto =
|
|
Bytes(bitseq).toOpenArray(firstByteOfLastWord, lastByteOfLastWord)
|
|
|
|
template initLastWords =
|
|
lhsWord = loadLEBytes(WordType, lastWordBytes(lhs))
|
|
when hasRhs: rhsWord = loadLEBytes(WordType, lastWordBytes(rhs))
|
|
|
|
if lastWordSize == 0:
|
|
firstByteOfLastWord = bytesCount - sizeof(WordType)
|
|
lastByteOfLastWord = bytesCount - 1
|
|
dec fullWordsCount
|
|
else:
|
|
firstByteOfLastWord = bytesCount - lastWordSize
|
|
lastByteOfLastWord = bytesCount - 1
|
|
|
|
initLastWords()
|
|
let markerPos = log2trunc(lhsWord)
|
|
when hasRhs: doAssert log2trunc(rhsWord) == markerPos
|
|
|
|
lhsWord.clearBit markerPos
|
|
when hasRhs: rhsWord.clearBit markerPos
|
|
|
|
body
|
|
|
|
when lhsIsVar or rhsIsVar:
|
|
let
|
|
markerBit = uint(1 shl markerPos)
|
|
mask = markerBit - 1'u
|
|
|
|
when lhsIsVar:
|
|
let lhsEndResult = (lhsWord and mask) or markerBit
|
|
storeLEBytes(lhsEndResult, lastWordBytes(lhs))
|
|
|
|
when rhsIsVar:
|
|
let rhsEndResult = (rhsWord and mask) or markerBit
|
|
storeLEBytes(rhsEndResult, lastWordBytes(rhs))
|
|
|
|
var lhsCurrAddr = cast[ptr WordType](unsafeAddr Bytes(lhs)[0])
|
|
let lhsEndAddr = offset(lhsCurrAddr, fullWordsCount)
|
|
when hasRhs:
|
|
var rhsCurrAddr = cast[ptr WordType](unsafeAddr Bytes(rhs)[0])
|
|
|
|
while lhsCurrAddr < lhsEndAddr:
|
|
template lhsBits: auto = lhsCurrAddr[]
|
|
when hasRhs:
|
|
template rhsBits: auto = rhsCurrAddr[]
|
|
|
|
body
|
|
|
|
lhsCurrAddr = offset(lhsCurrAddr, 1)
|
|
when hasRhs: rhsCurrAddr = offset(rhsCurrAddr, 1)
|
|
|
|
iterator words*(x: var BitSeq): var uint =
|
|
loopOverWords(x, x, true, false, uint, word, wordB):
|
|
yield word
|
|
|
|
iterator words*(x: BitSeq): uint =
|
|
loopOverWords(x, x, false, false, uint, word, word):
|
|
yield word
|
|
|
|
iterator words*(a, b: BitSeq): (uint, uint) =
|
|
loopOverWords(a, b, false, false, uint, wordA, wordB):
|
|
yield (wordA, wordB)
|
|
|
|
iterator words*(a: var BitSeq, b: BitSeq): (var uint, uint) =
|
|
loopOverWords(a, b, true, false, uint, wordA, wordB):
|
|
yield (wordA, wordB)
|
|
|
|
iterator words*(a, b: var BitSeq): (var uint, var uint) =
|
|
loopOverWords(a, b, true, true, uint, wordA, wordB):
|
|
yield (wordA, wordB)
|
|
|
|
func `[]`*(s: BitSeq, pos: Natural): bool {.inline.} =
|
|
doAssert pos < s.len
|
|
s.Bytes.getBit pos
|
|
|
|
func `[]=`*(s: var BitSeq, pos: Natural, value: bool) {.inline.} =
|
|
doAssert pos < s.len
|
|
s.Bytes.changeBit pos, value
|
|
|
|
func setBit*(s: var BitSeq, pos: Natural) {.inline.} =
|
|
doAssert pos < s.len
|
|
setBit s.Bytes, pos
|
|
|
|
func clearBit*(s: var BitSeq, pos: Natural) {.inline.} =
|
|
doAssert pos < s.len
|
|
clearBit s.Bytes, pos
|
|
|
|
func init*(T: type BitSeq, len: int): T =
|
|
result = BitSeq newSeq[byte](1 + len div 8)
|
|
Bytes(result).setBit len
|
|
|
|
func init*(T: type BitArray): T =
|
|
# The default zero-initializatio is fine
|
|
discard
|
|
|
|
template `[]`*(a: BitArray, pos: Natural): bool =
|
|
getBit a.bytes, pos
|
|
|
|
template `[]=`*(a: var BitArray, pos: Natural, value: bool) =
|
|
changeBit a.bytes, pos, value
|
|
|
|
template setBit*(a: var BitArray, pos: Natural) =
|
|
setBit a.bytes, pos
|
|
|
|
template clearBit*(a: var BitArray, pos: Natural) =
|
|
clearBit a.bytes, pos
|
|
|
|
# TODO: Submit this to the standard library as `cmp`
|
|
# At the moment, it doesn't work quite well because Nim selects
|
|
# the generic cmp[T] from the system module instead of choosing
|
|
# the openarray overload
|
|
func compareArrays[T](a, b: openarray[T]): int =
|
|
result = cmp(a.len, b.len)
|
|
if result != 0: return
|
|
|
|
for i in 0 ..< a.len:
|
|
result = cmp(a[i], b[i])
|
|
if result != 0: return
|
|
|
|
template cmp*(a, b: BitSeq): int =
|
|
compareArrays(Bytes a, Bytes b)
|
|
|
|
template `==`*(a, b: BitSeq): bool =
|
|
cmp(a, b) == 0
|
|
|
|
func `$`*(a: BitSeq): string =
|
|
let length = a.len
|
|
result = newStringOfCap(2 + length)
|
|
result.add "0b"
|
|
for i in countdown(length - 1, 0):
|
|
result.add if a[i]: '1' else: '0'
|
|
|
|
func combine*(tgt: var BitSeq, src: BitSeq) =
|
|
doAssert tgt.len == src.len
|
|
for tgtWord, srcWord in words(tgt, src):
|
|
tgtWord = tgtWord or srcWord
|
|
|
|
func overlaps*(a, b: BitSeq): bool =
|
|
for wa, wb in words(a, b):
|
|
if (wa and wb) != 0:
|
|
return true
|
|
|
|
func isSubsetOf*(a, b: BitSeq): bool =
|
|
let alen = a.len
|
|
doAssert b.len == alen
|
|
for i in 0 ..< alen:
|
|
if a[i] and not b[i]:
|
|
return false
|
|
true
|
|
|
|
proc isZeros*(x: BitSeq): bool =
|
|
for w in words(x):
|
|
if w != 0: return false
|
|
return true
|
|
|
|
template bytes*(x: BitSeq): untyped =
|
|
seq[byte](x)
|