91 lines
2.2 KiB
Nim
91 lines
2.2 KiB
Nim
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import
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strformat, strutils, sequtils, sets,
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../logging, ../constants, ../opcode_values
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# I don't see why would we wrap our in memory stream in something like BytesIO
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type
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CodeStream* = ref object
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bytes: seq[byte]
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depthProcessed: int
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invalidPositions: HashSet[int]
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pc*: int
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logger: Logger
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proc `$`*(b: byte): string =
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$(b.int)
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proc newCodeStream*(codeBytes: cstring): CodeStream =
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new(result)
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result.bytes = codeBytes.mapIt(it.byte)
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result.pc = 0
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result.invalidPositions = initSet[int]()
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result.depthProcessed = 0
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result.logger = logging.getLogger("evm.vm.CodeStream")
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proc read*(c: var CodeStream, size: int): seq[byte] =
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result = c.bytes[c.pc .. c.pc + size - 1]
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c.pc += size
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proc len*(c: CodeStream): int =
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len(c.bytes)
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proc next*(c: var CodeStream): byte =
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var nextOpcode = c.read(1)
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if nextOpcode[0] != 0x0.byte:
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return nextOpcode[0]
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else:
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return opcode_values.STOP
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iterator items*(c: var CodeStream): byte =
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var nextOpcode = c.next()
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while nextOpcode != opcode_values.STOP:
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yield nextOpcode
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nextOpcode = c.next()
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proc `[]`*(c: CodeStream, offset: int): byte =
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c.bytes[offset]
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proc peek*(c: var CodeStream): byte =
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var currentPc = c.pc
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result = c.next()
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c.pc = currentPc
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proc updatePc*(c: var CodeStream, value: int) =
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c.pc = min(value, len(c))
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template seek*(c: var CodeStream, pc: int, handler: untyped): untyped =
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var anchorPc = pc
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`c`.pc = pc
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try:
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var c = `c` {.inject.}
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`handler`
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finally:
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`c`.pc = anchorPc
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proc isValidOpcode*(c: var CodeStream, position: int): bool =
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if position >= len(c):
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return false
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if position in c.invalidPositions:
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return false
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if position <= c.depthProcessed:
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return true
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else:
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var i = c.depthProcessed
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while i <= position:
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var opcode = c[i]
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if opcode >= opcode_values.PUSH1 and opcode <= opcode_values.PUSH32:
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var leftBound = (i + 1)
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var rightBound = leftBound + (opcode.int - 95)
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for z in leftBound ..< rightBound:
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c.invalidPositions.incl(z)
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i = rightBound
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else:
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c.depthProcessed = i
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i += 1
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if position in c.invalidPositions:
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return false
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else:
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return true
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