nimbus-eth1/nimbus/vm2/code_stream.nim

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# Nimbus
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed except according to those terms.
import
chronicles, strformat, strutils, sequtils, parseutils, sets, macros,
eth/common,
./interpreter/op_codes
logScope:
topics = "vm code_stream"
type
CodeStream* = ref object
bytes*: seq[byte]
depthProcessed: int
invalidPositions: HashSet[int]
pc*: int
cached: seq[(int, Op, string)]
proc `$`*(b: byte): string =
$(b.int)
proc newCodeStream*(codeBytes: seq[byte]): CodeStream =
new(result)
shallowCopy(result.bytes, codeBytes)
result.pc = 0
result.invalidPositions = initHashSet[int]()
result.depthProcessed = 0
result.cached = @[]
proc newCodeStream*(codeBytes: string): CodeStream =
newCodeStream(codeBytes.mapIt(it.byte))
proc newCodeStreamFromUnescaped*(code: string): CodeStream =
# from 0xunescaped
var codeBytes: seq[byte] = @[]
for z, c in code[2..^1]:
if z mod 2 == 1:
var value: int
discard parseHex(&"0x{code[z+1..z+2]}", value)
codeBytes.add(value.byte)
newCodeStream(codeBytes)
proc read*(c: var CodeStream, size: int): seq[byte] =
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# TODO: use openArray[bytes]
if c.pc + size - 1 < c.bytes.len:
result = c.bytes[c.pc .. c.pc + size - 1]
c.pc += size
else:
result = @[]
c.pc = c.bytes.len
proc readVmWord*(c: var CodeStream, n: int): UInt256 =
## Reads `n` bytes from the code stream and pads
## the remaining bytes with zeros.
let result_bytes = cast[ptr array[32, byte]](addr result)
let last = min(c.pc + n, c.bytes.len)
let toWrite = last - c.pc
for i in 0 ..< toWrite : result_bytes[i] = c.bytes[last - i - 1]
c.pc = last
proc len*(c: CodeStream): int =
len(c.bytes)
proc next*(c: var CodeStream): Op =
if c.pc != c.bytes.len:
result = Op(c.bytes[c.pc])
inc c.pc
else:
result = Stop
iterator items*(c: var CodeStream): Op =
var nextOpcode = c.next()
while nextOpcode != Op.STOP:
yield nextOpcode
nextOpcode = c.next()
proc `[]`*(c: CodeStream, offset: int): Op =
Op(c.bytes[offset])
proc peek*(c: var CodeStream): Op =
if c.pc < c.bytes.len:
result = Op(c.bytes[c.pc])
else:
result = Stop
proc updatePc*(c: var CodeStream, value: int) =
c.pc = min(value, len(c))
when false:
template seek*(cs: var CodeStream, pc: int, handler: untyped): untyped =
var anchorPc = cs.pc
cs.pc = pc
try:
var c {.inject.} = cs
handler
finally:
cs.pc = anchorPc
proc isValidOpcode*(c: CodeStream, position: int): bool =
if position >= len(c):
return false
if position in c.invalidPositions:
return false
if position <= c.depthProcessed:
return true
else:
var i = c.depthProcessed
while i <= position:
var opcode = Op(c[i])
if opcode >= Op.PUSH1 and opcode <= Op.PUSH32:
var leftBound = (i + 1)
var rightBound = leftBound + (opcode.int - 95)
for z in leftBound ..< rightBound:
c.invalidPositions.incl(z)
i = rightBound
else:
c.depthProcessed = i
i += 1
if position in c.invalidPositions:
return false
else:
return true
proc decompile*(original: var CodeStream): seq[(int, Op, string)] =
# behave as https://etherscan.io/opcode-tool
# TODO
if original.cached.len > 0:
return original.cached
result = @[]
var c = newCodeStream(original.bytes)
while true:
var op = c.next
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if op >= Push1 and op <= Push32:
let bytes = c.read(op.int - 95)
result.add((c.pc - 1, op, "0x" & bytes.mapIt($(it.BiggestInt.toHex(2))).join("")))
elif op != Op.Stop:
result.add((c.pc - 1, op, ""))
else:
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result.add((-1, Op.Stop, ""))
break
original.cached = result
proc displayDecompiled*(c: CodeStream) =
var copy = c
let opcodes = copy.decompile()
for op in opcodes:
echo op[0], " ", op[1], " ", op[2]
proc hasSStore*(c: var CodeStream): bool =
let opcodes = c.decompile()
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result = opcodes.anyIt(it[1] == Sstore)
proc atEnd*(c: CodeStream): bool =
result = c.pc >= c.bytes.len