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Ethereum Environment Interface (EEI) Specification

The Ethereum Environment Interface exposes the core Ethereum API to the ewasm environment. The Ethereum module will be implemented in the Ethereum client's native language. All parameters and returns are restricted to 32 or 64 bit integers. Floats are disallowed.

Data types

We define the following Ethereum data types:

  • bytes: an array of bytes with unrestricted length
  • bytes32: an array of 32 bytes
  • address: an array of 20 bytes
  • u128: a 128 bit number, represented as a 16 bytes long little endian unsigned integer in memory
  • u256: a 256 bit number, represented as a 32 bytes long little endian unsigned integer in memory

We also define the following WebAssembly data types:

  • i32: same as i32 in WebAssembly
  • i32ptr: same as i32 in WebAssembly, but treated as a pointer to a WebAssembly memory offset
  • i64: same as i64 in WebAssembly

API

useGas

Subtracts an amount to the gas counter

Parameters

  • amount i64 the amount to subtract to the gas counter

Returns

nothing

getAddress

Gets address of currently executing account and stores it in memory at the given offset.

Parameters

  • resultOffset i32ptr the memory offset at which the address is to be stored (address)

Returns

nothing

Trap conditions

  • store to memory at resultOffset results in out of bounds access.

getExternalBalance

Gets balance of the given account and loads it into memory at the given offset.

Parameters

  • addressOffset i32ptr the memory offset to load the address from (address)
  • resultOffset i32ptr the memory offset to load the balance into (u128)

Returns

nothing

Trap conditions

  • load from memory at addressOffset results in out of bounds access,
  • store to memory at resultOffset results in out of bounds access.

getBlockHash

Gets the hash of one of the 256 most recent complete blocks.

Parameters

  • number i64 which block to load
  • resultOffset i32ptr the memory offset to load the hash into (bytes32)

Returns

result i32 Returns 0 on success and 1 on failure

Note: in case of failure, the output memory pointed by resultOffset is unchanged.

Trap conditions

  • store to memory at resultOffset results in out of bounds access (also checked on failure).

call

Sends a message with arbitrary data to a given address path

Parameters

  • gas i64 the gas limit
  • addressOffset i32ptr the memory offset to load the address from (address)
  • valueOffset i32ptr the memory offset to load the value from (u128)
  • dataOffset i32ptr the memory offset to load data from (bytes)
  • dataLength i32 the length of data

Returns

result i32 Returns 0 on success, 1 on failure and 2 on revert

Trap conditions

  • load address from memory at addressOffset results in out of bounds access,
  • load u128 from memory at valueOffset results in out of bounds access,
  • load dataLength number of bytes from memory at dataOffset results in out of bounds access.

callDataCopy

Copies the input data in current environment to memory. This pertains to the input data passed with the message call instruction or transaction.

Parameters

  • resultOffset i32ptr the memory offset to load data into (bytes)
  • dataOffset i32 the offset in the input data
  • length i32 the length of data to copy

Returns

nothing

Trap conditions

  • load length number of bytes from input data buffer at dataOffset results in out of bounds access,
  • store length number of bytes to memory at resultOffset results in out of bounds access.

getCallDataSize

Get size of input data in current environment. This pertains to the input data passed with the message call instruction or transaction.

Parameters

none

Returns

callDataSize i32

callCode

Message-call into this account with an alternative account's code.

Parameters

  • gas i64 the gas limit
  • addressOffset i32ptr the memory offset to load the address from (address)
  • valueOffset i32ptr the memory offset to load the value from (u128)
  • dataOffset i32ptr the memory offset to load data from (bytes)
  • dataLength i32 the length of data

Returns

result i32 Returns 0 on success, 1 on failure and 2 on revert

Trap conditions

  • load address from memory at addressOffset results in out of bounds access,
  • load u128 from memory at valueOffset results in out of bounds access,
  • load dataLength number of bytes from memory at dataOffset results in out of bounds access.

callDelegate

Message-call into this account with an alternative account’s code, but persisting the current values for sender and value.

Parameters

  • gas i64 the gas limit
  • addressOffset i32ptr the memory offset to load the address from (address)
  • dataOffset i32ptr the memory offset to load data from (bytes)
  • dataLength i32 the length of data

Returns

result i32 Returns 0 on success, 1 on failure and 2 on revert

Trap conditions

  • load address from memory at addressOffset results in out of bounds access,
  • load dataLength number of bytes from memory at dataOffset results in out of bounds access.

callStatic

Sends a message with arbitrary data to a given address path, but disallow state modifications. This includes log, create, selfdestruct and call with a non-zero value.

Parameters

  • gas i64 the gas limit
  • addressOffset i32ptr the memory offset to load the address from (address)
  • dataOffset i32ptr the memory offset to load data from (bytes)
  • dataLength i32 the length of data

Returns

result i32 Returns 0 on success, 1 on failure and 2 on revert

Trap conditions

  • load address from memory at addressOffset results in out of bounds access,
  • load dataLength number of bytes from memory at dataOffset results in out of bounds access.

storageStore

Store 256-bit a value in memory to persistent storage

Parameters

  • pathOffset i32ptr the memory offset to load the path from (bytes32)
  • valueOffset i32ptr the memory offset to load the value from (bytes32)

Returns

nothing

Trap conditions

  • load bytes32 from memory at pathOffset results in out of bounds access,
  • load bytes32 from memory at valueOffset results in out of bounds access.

storageLoad

Loads a 256-bit a value to memory from persistent storage

Parameters

  • pathOffset i32ptr the memory offset to load the path from (bytes32)
  • resultOffset i32ptr the memory offset to store the result at (bytes32)

Returns

nothing

Trap conditions

  • load bytes32 from memory at pathOffset results in out of bounds access,
  • store bytes32 to memory at resultOffset results in out of bounds access.

getCaller

Gets caller address and loads it into memory at the given offset. This is the address of the account that is directly responsible for this execution.

Parameters

  • resultOffset i32ptr the memory offset to load the address into (address)

Returns

nothing

Trap conditions

  • store address to memory at resultOffset results in out of bounds access.

getCallValue

Gets the deposited value by the instruction/transaction responsible for this execution and loads it into memory at the given location.

Parameters

  • resultOffset i32ptr the memory offset to load the value into (u128)

Returns

nothing

Trap conditions

  • store u128 to memory at resultOffset results in out of bounds access.

codeCopy

Copies the code running in current environment to memory.

Parameters

  • resultOffset i32ptr the memory offset to load the result into (bytes)
  • codeOffset i32 the offset within the code
  • length i32 the length of code to copy

Returns

nothing

Trap conditions

  • load length number of bytes from the current code buffer at codeOffset results in out of bounds access,
  • store length number of bytes to memory at resultOffset results in out of bounds access.

getCodeSize

Gets the size of code running in current environment.

Parameters

none

Returns

codeSize i32

getBlockCoinbase

Gets the block’s beneficiary address and loads into memory.

Parameters

  • resultOffset i32ptr the memory offset to load the coinbase address into (address)

Returns

nothing

Trap conditions

  • store address to memory at resultOffset results in out of bounds access.

create

Creates a new contract with a given value.

Parameters

  • valueOffset i32ptr the memory offset to load the value from (u128)
  • dataOffset i32ptr the memory offset to load the code for the new contract from (bytes)
  • dataLength i32 the data length
  • resultOffset i32ptr the memory offset to write the new contract address to (address)

Note: create will clear the return buffer in case of success or may fill it with data coming from revert.

Returns

result i32 Returns 0 on success, 1 on failure and 2 on revert

Trap conditions

  • load u128 from memory at valueOffset results in out of bounds access,
  • load dataLength number of bytes from memory at dataOffset results in out of bounds access.
  • store address to memory at resultOffset results in out of bounds access.

getBlockDifficulty

Get the block’s difficulty.

Parameters

  • resultOffset i32ptr the memory offset to load the difficulty into (u256)

Returns

nothing

Trap conditions

  • store u256 to memory at resultOffset results in out of bounds access.

externalCodeCopy

Copies the code of an account to memory.

Parameters

  • addressOffset i32ptr the memory offset to load the address from (address)
  • resultOffset i32ptr the memory offset to load the result into (bytes)
  • codeOffset i32 the offset within the code
  • length i32 the length of code to copy

Returns

nothing

Trap conditions

  • load address from memory at addressOffset results in out of bounds access,
  • load length number of bytes from the account code buffer at codeOffset results in out of bounds access,
  • store length number of bytes to memory at resultOffset results in out of bounds access.

getExternalCodeSize

Get size of an account’s code.

Parameters

  • addressOffset i32ptr the memory offset to load the address from (address)

Returns

extCodeSize i32

Trap conditions

  • load address from memory at addressOffset results in out of bounds access.

getGasLeft

Returns the current gasCounter

Parameters

none

Returns

gasLeft i64

getBlockGasLimit

Get the block’s gas limit.

Parameters

none

Returns

blockGasLimit i64

getTxGasPrice

Gets price of gas in current environment.

Parameters

  • resultOffset i32ptr the memory offset to write the value to (u128)

Returns

nothing

Trap conditions

  • store u128 to memory at resultOffset results in out of bounds access.

log

Creates a new log in the current environment

Parameters

  • dataOffset i32ptr the memory offset to load data from (bytes)
  • dataLength i32 the data length
  • numberOfTopics i32 the number of topics following (0 to 4)
  • topic1 i32ptr the memory offset to load topic1 from (bytes32)
  • topic2 i32ptr the memory offset to load topic2 from (bytes32)
  • topic3 i32ptr the memory offset to load topic3 from (bytes32)
  • topic4 i32ptr the memory offset to load topic4 from (bytes32)

Returns

nothing

Trap conditions

  • load dataLength number of bytes from memory at dataOffset results in out of bounds access,
  • numberOfTopics is greater than 4,
  • load bytes32 from memory at topic1 results in out of bounds access,
  • load bytes32 from memory at topic2 results in out of bounds access,
  • load bytes32 from memory at topic3 results in out of bounds access,
  • load bytes32 from memory at topic4 results in out of bounds access.

getBlockNumber

Get the block’s number.

Parameters

none

Returns

blockNumber i64

getTxOrigin

Gets the execution's origination address and loads it into memory at the given offset. This is the sender of original transaction; it is never an account with non-empty associated code.

Parameters

  • resultOffset i32ptr the memory offset to load the origin address from (address)

Returns

nothing

Trap conditions

  • store address to memory at resultOffset results in out of bounds access.

finish

Set the returning output data for the execution. This will halt the execution immediately.

Parameters

  • dataOffset i32ptr the memory offset of the output data (bytes)
  • dataLength i32 the length of the output data

Returns

doesn't return

Trap conditions

  • load dataLength number of bytes from memory at dataOffset results in out of bounds access.

revert

Set the returning output data for the execution. This will halt the execution immediately and set the execution result to "reverted".

Parameters

  • dataOffset i32ptr the memory offset of the output data (bytes)
  • dataLength i32 the length of the output data

Returns

doesn't return

Trap conditions

  • load dataLength number of bytes from memory at dataOffset results in out of bounds access.

getReturnDataSize

Get size of current return data buffer to memory. This contains the return data from the last executed call, callCode, callDelegate, callStatic or create.

Note: create only fills the return data buffer in case of a failure.

Parameters

none

Returns

dataSize i32

returnDataCopy

Copies the current return data buffer to memory. This contains the return data from last executed call, callCode, callDelegate, callStatic or create.

Note: create only fills the return data buffer in case of a failure.

Parameters

  • resultOffset i32ptr the memory offset to load data into (bytes)
  • dataOffset i32 the offset in the return data
  • length i32 the length of data to copy

Returns

nothing

Trap conditions

  • load length number of bytes from input data buffer at dataOffset results in out of bounds access,
  • store length number of bytes to memory at resultOffset results in out of bounds access.

selfDestruct

Mark account for later deletion and give the remaining balance to the specified beneficiary address. This will cause a trap and the execution will be aborted immediately.

Parameters

  • addressOffset i32ptr the memory offset to load the address from (address)

Returns

doesn't return

Trap conditions

  • load address from memory at addressOffset results in out of bounds access.

getBlockTimestamp

Get the block’s timestamp.

Parameters

none

Returns

blockTimestamp i64