nimbus-eth2/beacon_chain/ssz/bytes_reader.nim

161 lines
6.0 KiB
Nim

import
endians, typetraits, options,
stew/[objects, bitseqs], serialization/testing/tracing,
../spec/[digest, datatypes], ./types
template setLen[R, T](a: var array[R, T], length: int) =
if length != a.len:
raise newException(MalformedSszError, "SSZ input of insufficient size")
template assignNullValue(loc: untyped, T: type): auto =
when T is ref|ptr:
loc = nil
elif T is Option:
loc = T()
else:
raise newException(MalformedSszError, "SSZ list element of zero size")
# fromSszBytes copies the wire representation to a Nim variable,
# assuming there's enough data in the buffer
func fromSszBytes*(T: type SomeInteger, data: openarray[byte]): T =
## Convert directly to bytes the size of the int. (e.g. ``uint16 = 2 bytes``)
## All integers are serialized as **little endian**.
## TODO: Assumes data points to a sufficiently large buffer
doAssert data.len == sizeof(result)
# TODO: any better way to get a suitably aligned buffer in nim???
# see also: https://github.com/nim-lang/Nim/issues/9206
var tmp: uint64
var alignedBuf = cast[ptr byte](tmp.addr)
copyMem(alignedBuf, unsafeAddr data[0], result.sizeof)
when result.sizeof == 8: littleEndian64(result.addr, alignedBuf)
elif result.sizeof == 4: littleEndian32(result.addr, alignedBuf)
elif result.sizeof == 2: littleEndian16(result.addr, alignedBuf)
elif result.sizeof == 1: copyMem(result.addr, alignedBuf, sizeof(result))
else: {.fatal: "Unsupported type deserialization: " & $(type(result)).name.}
func fromSszBytes*(T: type bool, data: openarray[byte]): T =
# TODO: spec doesn't say what to do if the value is >1 - we'll use the C
# definition for now, but maybe this should be a parse error instead?
fromSszBytes(uint8, data) != 0
func fromSszBytes*(T: type Eth2Digest, data: openarray[byte]): T =
doAssert data.len == sizeof(result.data)
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)
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 fromSszBytes*[N](T: type BitList[N], bytes: openarray[byte]): auto =
BitList[N] @bytes
proc readSszValue*(input: openarray[byte], T: type): T =
mixin fromSszBytes, toSszType
type T {.used.}= type(result)
template readOffset(n: int): int {.used.}=
int fromSszBytes(uint32, input[n ..< n + offsetSize])
when useListType and result is List:
type ElemType = type result[0]
result = T readSszValue(input, seq[ElemType])
elif result is ptr|ref:
if input.len > 0:
new result
result[] = readSszValue(input, type(result[]))
elif result is Option:
if input.len > 0:
result = some readSszValue(input, result.T)
elif result is string|seq|openarray|array:
type ElemType = type result[0]
when ElemType is byte|char:
result.setLen input.len
if input.len > 0:
copyMem(addr result[0], unsafeAddr input[0], input.len)
elif isFixedSize(ElemType):
const elemSize = fixedPortionSize(ElemType)
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
result.setLen input.len div elemSize
trs "READING LIST WITH LEN ", result.len
for i in 0 ..< result.len:
trs "TRYING TO READ LIST ELEM ", i
let offset = i * elemSize
result[i] = readSszValue(input[offset ..< offset+elemSize], ElemType)
trs "LIST READING COMPLETE"
else:
if input.len == 0:
# This is an empty list.
# The default initialization of the return value is fine.
return
var offset = readOffset 0
trs "GOT OFFSET ", offset
let resultLen = offset div offsetSize
trs "LEN ", resultLen
result.setLen resultLen
for i in 1 ..< resultLen:
let nextOffset = readOffset(i * offsetSize)
if nextOffset == offset:
assignNullValue result[i - 1], ElemType
else:
result[i - 1] = readSszValue(input[offset ..< nextOffset], ElemType)
offset = nextOffset
result[resultLen - 1] = readSszValue(input[offset ..< input.len], ElemType)
elif result is object|tuple:
enumInstanceSerializedFields(result, fieldName, field):
const boundingOffsets = T.getFieldBoundingOffsets(fieldName)
trs "BOUNDING OFFSET FOR FIELD ", fieldName, " = ", boundingOffsets
type FieldType = type field
type SszType = type toSszType(default(FieldType))
when isFixedSize(SszType):
const
startOffset = boundingOffsets[0]
endOffset = boundingOffsets[1]
trs "FIXED FIELD ", startOffset, "-", endOffset
else:
let
startOffset = readOffset(boundingOffsets[0])
endOffset = if boundingOffsets[1] == -1: input.len
else: readOffset(boundingOffsets[1])
trs "VAR FIELD ", startOffset, "-", endOffset
# TODO The extra type escaping here is a work-around for a Nim issue:
when type(FieldType) is type(SszType):
trs "READING NATIVE ", fieldName, ": ", name(SszType)
field = readSszValue(input[startOffset ..< endOffset], SszType)
trs "READING COMPLETE ", fieldName
elif useListType and FieldType is List:
field = readSszValue(input[startOffset ..< endOffset], FieldType)
else:
trs "READING FOREIGN ", fieldName, ": ", name(SszType)
field = fromSszBytes(FieldType, input[startOffset ..< endOffset])
elif result is SomeInteger|bool|enum:
trs "READING BASIC TYPE ", type(result).name, " input=", input.len
result = fromSszBytes(type(result), input)
trs "RESULT WAS ", repr(result)
else:
unsupported T