64 lines
2.0 KiB
Nim
64 lines
2.0 KiB
Nim
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import
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stew/objects, stew/ranges/ptr_arith,
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./types, ./bytes_reader
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type
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MemRange = object
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startAddr: ptr byte
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length: int
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SszNavigator*[T] = object
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m: MemRange
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func sszMount*(data: openarray[byte], T: type): SszNavigator[T] =
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let startAddr = unsafeAddr data[0]
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SszNavigator[T](m: MemRange(startAddr: startAddr, length: data.len))
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template checkBounds(m: MemRange, offset: int) =
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if offset > m.length:
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raise newException(MalformedSszError, "Malformed SSZ")
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template toOpenArray(m: MemRange): auto =
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makeOpenArray(m.startAddr, m.length)
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func navigateToField[T](n: SszNavigator[T],
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fieldName: static string,
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FieldType: type): SszNavigator[FieldType] =
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mixin toSszType
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type SszFieldType = type toSszType(default FieldType)
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const boundingOffsets = getFieldBoundingOffsets(T, fieldName)
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checkBounds(n.m, boundingOffsets[1])
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when isFixedSize(SszFieldType):
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SszNavigator[FieldType](m: MemRange(
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startAddr: shift(n.m.startAddr, boundingOffsets[0]),
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length: boundingOffsets[1] - boundingOffsets[0]))
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else:
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template readOffset(offset): int =
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int fromSszBytes(uint32, makeOpenArray(shift(n.m.startAddr, offset),
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sizeof(uint32)))
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let
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startOffset = readOffset boundingOffsets[0]
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endOffset = when boundingOffsets[1] == -1: n.m.length
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else: readOffset boundingOffsets[1]
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if endOffset < startOffset or endOffset > n.m.length:
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raise newException(MalformedSszError, "Incorrect offset values")
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SszNavigator[FieldType](m: MemRange(
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startAddr: shift(n.m.startAddr, startOffset),
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length: endOffset - startOffset))
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template `.`*[T](n: SszNavigator[T], field: untyped): auto =
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type RecType = T
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type FieldType = type(default(RecType).field)
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navigateToField(n, astToStr(field), FieldType)
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func `[]`*[T](n: SszNavigator[T]): T =
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readSszValue(toOpenArray(n.m), T)
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converter derefNavigator*[T](n: SszNavigator[T]): T =
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n[]
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