63 lines
1.5 KiB
Nim
63 lines
1.5 KiB
Nim
## ewasm “WRC20” token contract coding challenge
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## https://gist.github.com/axic/16158c5c88fbc7b1d09dfa8c658bc363
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import ../eth_contracts, stint
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proc do_balance() =
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if getCallDataSize() != 24:
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revert(nil, 0)
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var address: array[20, byte]
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callDataCopy(address, 4)
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var balance: array[32, byte]
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storageLoad(address, addr balance)
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ret(addr balance, sizeof(balance).int32)
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proc do_transfer() =
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if getCallDataSize() != 32:
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revert(nil, 0)
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var sender: array[20, byte]
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getCaller(addr sender)
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var recipient: array[20, byte]
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callDataCopy(recipient, 4)
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var value: uint64
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callDataCopy(value, 24)
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var senderBalance: array[32, byte]
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storageLoad(sender, addr senderBalance)
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var recipientBalance: array[32, byte]
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storageLoad(recipient, addr recipientBalance)
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var sb = readUintBE[256](senderBalance)
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var rb = readUintBE[256](recipientBalance)
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let v = value.u256
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block:
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# This is a quick stub to avoid using stint for now. Works only with
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# single byte values.
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if sb < v:
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revert(nil, 0)
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sb -= v
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rb += v
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senderBalance = sb.toByteArrayBE()
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recipientBalance = rb.toByteArrayBE()
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storageStore(sender, addr senderBalance)
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storageStore(recipient, addr recipientBalance)
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proc main() {.exportwasm.} =
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if getCallDataSize() < 4:
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revert(nil, 0)
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var selector: uint32
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callDataCopy(selector, 0)
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case selector
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of 0x9993021a'u32:
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do_balance()
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of 0x5d359fbd'u32:
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do_transfer()
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else:
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revert(nil, 0)
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