nimbus-eth2/beacon_chain/ssz/bytes_reader.nim

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{.push raises: [Defect].}
{.pragma: raisesssz, raises: [Defect, MalformedSszError, SszSizeMismatchError].}
import
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typetraits, options,
stew/[bitseqs, bitops2, endians2, objects, bitseqs], serialization/testing/tracing,
../spec/[digest, datatypes], ./types
template raiseIncorrectSize(T: type) =
const typeName = name(T)
raise newException(MalformedSszError,
"SSZ " & typeName & " input of incorrect size")
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template setOutputSize[R, T](a: var array[R, T], length: int) =
if length != a.len:
raiseIncorrectSize a.type
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proc setOutputSize(list: var List, length: int) {.raisesssz.} =
if int64(length) > list.maxLen:
raise newException(MalformedSszError, "SSZ list maximum size exceeded")
list.setLen length
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# fromSszBytes copies the wire representation to a Nim variable,
# assuming there's enough data in the buffer
func fromSszBytes*(T: type UintN, data: openarray[byte]): T {.raisesssz.} =
## Convert directly to bytes the size of the int. (e.g. ``uint16 = 2 bytes``)
## All integers are serialized as **little endian**.
if data.len != sizeof(result):
raiseIncorrectSize T
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T.fromBytesLE(data)
func fromSszBytes*(T: type bool, data: openarray[byte]): T {.raisesssz.} =
# Strict: only allow 0 or 1
if data.len != 1 or byte(data[0]) > byte(1):
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raise newException(MalformedSszError, "invalid boolean value")
data[0] == 1
func fromSszBytes*(T: type Eth2Digest, data: openarray[byte]): T {.raisesssz.} =
if data.len != sizeof(result.data):
raiseIncorrectSize T
copyMem(result.data.addr, unsafeAddr data[0], sizeof(result.data))
template fromSszBytes*(T: type Slot, bytes: openarray[byte]): Slot =
Slot fromSszBytes(uint64, bytes)
template fromSszBytes*(T: type Epoch, bytes: openarray[byte]): Epoch =
Epoch fromSszBytes(uint64, bytes)
func fromSszBytes*(T: type ForkDigest, bytes: openarray[byte]): T {.raisesssz.} =
if bytes.len != sizeof(result):
raiseIncorrectSize T
copyMem(result.addr, unsafeAddr bytes[0], sizeof(result))
func fromSszBytes*(T: type Version, bytes: openarray[byte]): T {.raisesssz.} =
if bytes.len != sizeof(result):
raiseIncorrectSize T
copyMem(result.addr, unsafeAddr bytes[0], sizeof(result))
template fromSszBytes*(T: type enum, bytes: openarray[byte]): auto =
T fromSszBytes(uint64, bytes)
template fromSszBytes*(T: type BitSeq, bytes: openarray[byte]): auto =
BitSeq @bytes
proc `[]`[T, U, V](s: openArray[T], x: HSlice[U, V]) {.error:
"Please don't use openarray's [] as it allocates a result sequence".}
template checkForForbiddenBits(ResulType: type,
input: openarray[byte],
expectedBits: static int) =
## This checks if the input contains any bits set above the maximum
## sized allowed. We only need to check the last byte to verify this:
const bitsInLastByte = (expectedBits mod 8)
when bitsInLastByte != 0:
# As an example, if there are 3 bits expected in the last byte,
# we calculate a bitmask equal to 11111000. If the input has any
# raised bits in range of the bitmask, this would be a violation
# of the size of the BitArray:
const forbiddenBitsMask = byte(byte(0xff) shl bitsInLastByte)
if (input[^1] and forbiddenBitsMask) != 0:
raiseIncorrectSize ResulType
func readSszValue*[T](input: openarray[byte], val: var T) {.raisesssz.} =
mixin fromSszBytes, toSszType
template readOffsetUnchecked(n: int): int {.used.}=
int fromSszBytes(uint32, input.toOpenArray(n, n + offsetSize - 1))
template readOffset(n: int): int {.used.} =
let offset = readOffsetUnchecked(n)
if offset > input.len:
raise newException(MalformedSszError, "SSZ list element offset points past the end of the input")
offset
#when result is List:
# result.setOutputSize input.len
# readOpenArray(toSeq result, input)
#elif result is array:
# result.checkOutputSize input.len
# readOpenArray(result, input)
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when val is BitList:
if input.len == 0:
raise newException(MalformedSszError, "Invalid empty SSZ BitList value")
# Since our BitLists have an in-memory representation that precisely
# matches their SSZ encoding, we can deserialize them as regular Lists:
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const maxExpectedSize = (val.maxLen div 8) + 1
type MatchingListType = List[byte, maxExpectedSize]
when false:
# TODO: Nim doesn't like this simple type coercion,
# we'll rely on `cast` for now (see below)
readSszValue(input, MatchingListType val)
else:
static:
# As a sanity check, we verify that the coercion is accepted by the compiler:
doAssert MatchingListType(val) is MatchingListType
readSszValue(input, cast[ptr MatchingListType](addr val)[])
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let resultBytesCount = len bytes(val)
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if bytes(val)[resultBytesCount - 1] == 0:
raise newException(MalformedSszError, "SSZ BitList is not properly terminated")
if resultBytesCount == maxExpectedSize:
checkForForbiddenBits(T, input, val.maxLen + 1)
elif val is HashList:
readSszValue(input, val.data)
val.hashes.setLen(0)
val.growHashes()
elif val is HashArray:
readSszValue(input, val.data)
for h in val.hashes.mitems():
clearCache(h)
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elif val is List|array:
type E = type val[0]
when E is byte:
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val.setOutputSize input.len
if input.len > 0:
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copyMem(addr val[0], unsafeAddr input[0], input.len)
elif isFixedSize(E):
const elemSize = fixedPortionSize(E)
if input.len mod elemSize != 0:
var ex = new SszSizeMismatchError
ex.deserializedType = cstring typetraits.name(T)
ex.actualSszSize = input.len
ex.elementSize = elemSize
raise ex
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val.setOutputSize input.len div elemSize
trs "READING LIST WITH LEN ", val.len
for i in 0 ..< val.len:
trs "TRYING TO READ LIST ELEM ", i
let offset = i * elemSize
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readSszValue(input.toOpenArray(offset, offset + elemSize - 1), val[i])
trs "LIST READING COMPLETE"
else:
if input.len == 0:
# This is an empty list.
# The default initialization of the return value is fine.
return
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elif input.len < offsetSize:
raise newException(MalformedSszError, "SSZ input of insufficient size")
var offset = readOffset 0
trs "GOT OFFSET ", offset
let resultLen = offset div offsetSize
trs "LEN ", resultLen
if resultLen == 0:
# If there are too many elements, other constraints detect problems
# (not monotonically increasing, past end of input, or last element
# not matching up with its nextOffset properly)
raise newException(MalformedSszError, "SSZ list incorrectly encoded of zero length")
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val.setOutputSize resultLen
for i in 1 ..< resultLen:
let nextOffset = readOffset(i * offsetSize)
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if nextOffset <= offset:
raise newException(MalformedSszError, "SSZ list element offsets are not monotonically increasing")
else:
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readSszValue(input.toOpenArray(offset, nextOffset - 1), val[i - 1])
offset = nextOffset
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readSszValue(input.toOpenArray(offset, input.len - 1), val[resultLen - 1])
# TODO: Should be possible to remove BitArray from here
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elif val is UintN|bool|enum:
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trs "READING BASIC TYPE ", typetraits.name(T), " input=", input.len
val = fromSszBytes(T, input)
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trs "RESULT WAS ", repr(val)
elif val is BitArray:
if sizeof(val) != input.len:
raiseIncorrectSize(T)
checkForForbiddenBits(T, input, val.bits)
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copyMem(addr val.bytes[0], unsafeAddr input[0], input.len)
elif val is object|tuple:
const minimallyExpectedSize = fixedPortionSize(T)
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if input.len < minimallyExpectedSize:
raise newException(MalformedSszError, "SSZ input of insufficient size")
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enumInstanceSerializedFields(val, fieldName, field):
const boundingOffsets = getFieldBoundingOffsets(T, fieldName)
trs "BOUNDING OFFSET FOR FIELD ", fieldName, " = ", boundingOffsets
# type FieldType = type field # buggy
# For some reason, Nim gets confused about the alias here. This could be a
# generics caching issue caused by the use of distinct types. Such an
# issue is very scary in general.
# The bug can be seen with the two List[uint64, N] types that exist in
# the spec, with different N.
type SszType = type toSszType(declval type(field))
when isFixedSize(SszType):
const
startOffset = boundingOffsets[0]
endOffset = boundingOffsets[1]
trs "FIXED FIELD ", startOffset, "-", endOffset
else:
let
startOffset = readOffsetUnchecked(boundingOffsets[0])
endOffset = if boundingOffsets[1] == -1: input.len
else: readOffsetUnchecked(boundingOffsets[1])
when boundingOffsets.isFirstOffset:
if startOffset != minimallyExpectedSize:
raise newException(MalformedSszError, "SSZ object dynamic portion starts at invalid offset")
trs "VAR FIELD ", startOffset, "-", endOffset
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if startOffset > endOffset:
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raise newException(MalformedSszError, "SSZ field offsets are not monotonically increasing")
elif endOffset > input.len:
raise newException(MalformedSszError, "SSZ field offset points past the end of the input")
elif startOffset < minimallyExpectedSize:
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raise newException(MalformedSszError, "SSZ field offset points outside bounding offsets")
# TODO The extra type escaping here is a work-around for a Nim issue:
when type(field) is type(SszType):
trs "READING NATIVE ", fieldName, ": ", name(SszType)
# TODO passing in `FieldType` instead of `type(field)` triggers a
# bug in the compiler
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readSszValue(
input.toOpenArray(startOffset, endOffset - 1),
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field)
trs "READING COMPLETE ", fieldName
else:
trs "READING FOREIGN ", fieldName, ": ", name(SszType)
field = fromSszBytes(
type(field),
input.toOpenArray(startOffset, endOffset - 1))
else:
unsupported T