nimbus-eth2/beacon_chain/ssz/ssz_serialization.nim

239 lines
7.8 KiB
Nim

# beacon_chain
# Copyright (c) 2018-2020 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.
# TODO Cannot override push, even though the function is annotated
# nimbus-eth2/beacon_chain/ssz.nim(212, 18) Error: can raise an unlisted exception: IOError
# {.push raises: [Defect].}
{.pragma: raisesssz, raises: [Defect, MalformedSszError, SszSizeMismatchError].}
## SSZ serialization for core SSZ types, as specified in:
# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/ssz/simple-serialize.md#serialization
import
std/[typetraits, options],
stew/[bitops2, endians2, leb128, objects],
serialization, serialization/testing/tracing,
../spec/[digest, datatypes],
./bytes_reader, ./bitseqs, ./types, ./spec_types
export
serialization, types, bitseqs
type
SszReader* = object
stream: InputStream
updateRoot: bool
SszWriter* = object
stream: OutputStream
SizePrefixed*[T] = distinct T
SszMaxSizeExceeded* = object of SerializationError
VarSizedWriterCtx = object
fixedParts: WriteCursor
offset: int
FixedSizedWriterCtx = object
serializationFormat SSZ,
Reader = SszReader,
Writer = SszWriter,
PreferedOutput = seq[byte]
template sizePrefixed*[TT](x: TT): untyped =
type T = TT
SizePrefixed[T](x)
proc init*(T: type SszReader,
stream: InputStream,
updateRoot: bool = true): T {.raises: [Defect].} =
T(stream: stream, updateRoot: updateRoot)
proc writeFixedSized(s: var (OutputStream|WriteCursor), x: auto) {.raises: [Defect, IOError].} =
mixin toSszType
when x is byte:
s.write x
elif x is bool:
s.write byte(ord(x))
elif x is UintN:
when cpuEndian == bigEndian:
s.write toBytesLE(x)
else:
s.writeMemCopy x
elif x is array:
when x[0] is byte:
trs "APPENDING FIXED SIZE BYTES", x
s.write x
else:
for elem in x:
trs "WRITING FIXED SIZE ARRAY ELEMENT"
s.writeFixedSized toSszType(elem)
elif x is tuple|object:
enumInstanceSerializedFields(x, fieldName, field):
trs "WRITING FIXED SIZE FIELD", fieldName
s.writeFixedSized toSszType(field)
else:
unsupported x.type
template writeOffset(cursor: var WriteCursor, offset: int) =
write cursor, toBytesLE(uint32 offset)
template supports*(_: type SSZ, T: type): bool =
mixin toSszType
anonConst compiles(fixedPortionSize toSszType(declval T))
func init*(T: type SszWriter, stream: OutputStream): T {.raises: [Defect].} =
result.stream = stream
proc writeVarSizeType(w: var SszWriter, value: auto) {.gcsafe.}
proc beginRecord*(w: var SszWriter, TT: type): auto {.raises: [Defect].} =
type T = TT
when isFixedSize(T):
FixedSizedWriterCtx()
else:
const offset = when T is array|HashArray: len(T) * offsetSize
else: fixedPortionSize(T)
VarSizedWriterCtx(offset: offset,
fixedParts: w.stream.delayFixedSizeWrite(offset))
template writeField*(w: var SszWriter,
ctx: var auto,
fieldName: string,
field: auto) =
mixin toSszType
when ctx is FixedSizedWriterCtx:
writeFixedSized(w.stream, toSszType(field))
else:
type FieldType = type toSszType(field)
when isFixedSize(FieldType):
writeFixedSized(ctx.fixedParts, toSszType(field))
else:
trs "WRITING OFFSET ", ctx.offset, " FOR ", fieldName
writeOffset(ctx.fixedParts, ctx.offset)
let initPos = w.stream.pos
trs "WRITING VAR SIZE VALUE OF TYPE ", name(FieldType)
when FieldType is BitList:
trs "BIT SEQ ", bytes(field)
writeVarSizeType(w, toSszType(field))
ctx.offset += w.stream.pos - initPos
template endRecord*(w: var SszWriter, ctx: var auto) =
when ctx is VarSizedWriterCtx:
finalize ctx.fixedParts
proc writeSeq[T](w: var SszWriter, value: seq[T])
{.raises: [Defect, IOError].} =
# Please note that `writeSeq` exists in order to reduce the code bloat
# produced from generic instantiations of the unique `List[N, T]` types.
when isFixedSize(T):
trs "WRITING LIST WITH FIXED SIZE ELEMENTS"
for elem in value:
w.stream.writeFixedSized toSszType(elem)
trs "DONE"
else:
trs "WRITING LIST WITH VAR SIZE ELEMENTS"
var offset = value.len * offsetSize
var cursor = w.stream.delayFixedSizeWrite offset
for elem in value:
cursor.writeFixedSized uint32(offset)
let initPos = w.stream.pos
w.writeVarSizeType toSszType(elem)
offset += w.stream.pos - initPos
finalize cursor
trs "DONE"
proc writeVarSizeType(w: var SszWriter, value: auto) {.raises: [Defect, IOError].} =
trs "STARTING VAR SIZE TYPE"
when value is HashArray|HashList:
writeVarSizeType(w, value.data)
elif value is List:
# We reduce code bloat by forwarding all `List` types to a general `seq[T]` proc.
writeSeq(w, asSeq value)
elif value is BitList:
# ATTENTION! We can reuse `writeSeq` only as long as our BitList type is implemented
# to internally match the binary representation of SSZ BitLists in memory.
writeSeq(w, bytes value)
elif value is object|tuple|array:
trs "WRITING OBJECT OR ARRAY"
var ctx = beginRecord(w, type value)
enumerateSubFields(value, field):
writeField w, ctx, astToStr(field), field
endRecord w, ctx
else:
unsupported type(value)
proc writeValue*(w: var SszWriter, x: auto) {.gcsafe, raises: [Defect, IOError].} =
mixin toSszType
type T = type toSszType(x)
when isFixedSize(T):
w.stream.writeFixedSized toSszType(x)
else:
w.writeVarSizeType toSszType(x)
func sszSize*(value: auto): int {.gcsafe, raises: [Defect].}
func sszSizeForVarSizeList[T](value: openArray[T]): int =
result = len(value) * offsetSize
for elem in value:
result += sszSize(toSszType elem)
func sszSize*(value: auto): int {.gcsafe, raises: [Defect].} =
mixin toSszType
type T = type toSszType(value)
when isFixedSize(T):
anonConst fixedPortionSize(T)
elif T is array|List|HashList|HashArray:
type E = ElemType(T)
when isFixedSize(E):
len(value) * anonConst(fixedPortionSize(E))
elif T is HashArray:
sszSizeForVarSizeList(value.data)
elif T is array:
sszSizeForVarSizeList(value)
else:
sszSizeForVarSizeList(asSeq value)
elif T is BitList:
return len(bytes(value))
elif T is object|tuple:
result = anonConst fixedPortionSize(T)
enumInstanceSerializedFields(value, _{.used.}, field):
type FieldType = type toSszType(field)
when not isFixedSize(FieldType):
result += sszSize(toSszType field)
else:
unsupported T
proc writeValue*[T](w: var SszWriter, x: SizePrefixed[T]) {.raises: [Defect, IOError].} =
var cursor = w.stream.delayVarSizeWrite(Leb128.maxLen(uint64))
let initPos = w.stream.pos
w.writeValue T(x)
let length = toBytes(uint64(w.stream.pos - initPos), Leb128)
cursor.finalWrite length.toOpenArray()
proc readValue*[T](r: var SszReader, val: var T) {.raises: [Defect, MalformedSszError, SszSizeMismatchError, IOError].} =
when isFixedSize(T):
const minimalSize = fixedPortionSize(T)
if r.stream.readable(minimalSize):
readSszValue(r.stream.read(minimalSize), val, r.updateRoot)
else:
raise newException(MalformedSszError, "SSZ input of insufficient size")
else:
# TODO(zah) Read the fixed portion first and precisely measure the
# size of the dynamic portion to consume the right number of bytes.
readSszValue(r.stream.read(r.stream.len.get), val, r.updateRoot)