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Add C-API example
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mratsim
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155
examples/capi.nim
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155
examples/capi.nim
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import ../src/evmjit, examplevm, strutils
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proc balance(context: ptr evm_context,
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address: ptr evm_address): evm_uint256be =
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result.bytes[0..3] = [1.uint8, 2, 3, 4]
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proc address(context: ptr evm_context): evm_address =
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result.bytes[0..3] = [1.uint8, 2, 3, 4]
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proc `$`(address: evm_address):string =
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result = ""
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for i in address.bytes:
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result.add($i)
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proc account_exists(context: ptr evm_context, address: ptr evm_address): cint {.cdecl.}=
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echo "EVM-C: EXISTS @"
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echo address[]
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echo "\n"
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return 0
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proc get_storage(result: ptr evm_uint256be,
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context: ptr evm_context,
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address: ptr evm_address,
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key: ptr evm_uint256be) {.cdecl.}=
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echo "EVM-C: SLOAD @"
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echo address[]
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echo "\n"
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proc set_storage(context: ptr evm_context,
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address: ptr evm_address,
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key: ptr evm_uint256be,
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value: ptr evm_uint256be) {.cdecl.}=
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echo "EVM-C: SSTORE @"
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echo address[]
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echo "\n"
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proc get_balance(result: ptr evm_uint256be,
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context: ptr evm_context,
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address: ptr evm_address) {.cdecl.}=
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echo "EVM-C: BALANCE @"
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echo address[]
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echo "\n"
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result[] = balance(context, address)
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proc get_code(code: ptr ptr uint8,
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context: ptr evm_context,
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address: ptr evm_address): csize {.cdecl.}=
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echo "EVM-C: CODE @"
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echo address[]
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echo "\n"
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return 0
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proc selfdestruct(context: ptr evm_context,
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address: ptr evm_address,
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beneficiary: ptr evm_address) {.cdecl.}=
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echo "EVM-C: SELFDESTRUCT"
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echo address[]
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echo " -> "
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echo beneficiary[]
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echo "\n"
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proc call(result: ptr evm_result,
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context: ptr evm_context,
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msg: ptr evm_message) {.cdecl.}=
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echo "EVM-C: CALL (depth: %1)\n" % $msg.depth
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result.status_code = EVM_FAILURE
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proc get_tx_context(result: ptr evm_tx_context, context: ptr evm_context) {.cdecl.}=
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discard
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proc get_block_hash(result: ptr evm_uint256be, context: ptr evm_context, number: int64) {.cdecl.}=
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discard
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# EVM log callback
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# Note: the evm_log name is used to avoid conflict with `log()`C function.
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proc evm_log(context: ptr evm_context,
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address: ptr evm_address,
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data: ptr uint8,
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data_size: csize,
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topics: ptr evm_uint256be,
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topics_count: csize) {.cdecl.}=
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echo "EVM-C: LOG%1\n" % $topics_count
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const ctx_fn_table = evm_context_fn_table(
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account_exists: account_exists,
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get_storage: get_storage,
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set_storage: set_storage,
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get_balance: get_balance,
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get_code: get_code,
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selfdestruct: selfdestruct,
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call: call,
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get_tx_context: get_tx_context,
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get_block_hash: get_block_hash,
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emit_log: evm_log
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)
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# Example of how the API is supposed to be used
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proc main() =
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let jit = examplevm_create()
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if jit.abi_version != EVM_ABI_VERSION:
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raise newException(LibraryError, "Incompatible ABI version")
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let
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# code: cstring = "Place some EVM bytecode here"
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code: cstring = "600160005401600055"
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code_size = code.len
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input: cstring = "Hello World!"
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gas: int64 = 200000
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var
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code_hash: evm_uint256be
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value: evm_uint256be
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address: evm_address
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code_hash.bytes[0..2] = [1.uint8, 2, 3]
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value.bytes[0..1] = [1.uint8, 0]
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address.bytes[0..2] = [1.uint8, 2, 3]
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var fn_table: ref evm_context_fn_table # Note fn_table will be garbage collected at the end of main function
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# as we will always use it as ptr and not ref
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new fn_table
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fn_table[] = ctx_fn_table
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var ctx = evm_context(fn_table: cast[ptr evm_context_fn_table](fn_table))
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var msg = evm_message(
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destination: address, sender: address, value: value, input_data: cast[ptr uint8](input),
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input_size: sizeof(input), code_hash: code_hash, gas: gas, depth:0
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)
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var result = jit.execute(jit, addr ctx, EVM_HOMESTEAD, addr msg, cast[ptr uint8](code), code_size)
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echo "Execution result:\n"
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if result.status_code != EVM_SUCCESS:
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echo " EVM execution failure: ", $result.status_code
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else:
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echo " Gas used: ", $(gas - result.gas_left)
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echo " Gas left: ", $result.gas_left
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echo " Output size: ", $(gas - result.gas_left)
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echo "\n Output: "
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var output = ""
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for i in 0 ..< result.output_size:
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output.add cast[char](cast[ptr UncheckedArray[uint8]](result.output_data)[i])
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echo output
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if not result.release.isNil:
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result.release(addr result)
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jit.destroy(jit)
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main()
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107
examples/examplevm.nim
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107
examples/examplevm.nim
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# Port of https://github.com/ethereum/evmjit/blob/develop/examples/examplevm.c
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# to Nim language
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import ../src/evmjit, strutils
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proc c_malloc(size: csize): pointer {.
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importc: "malloc", header: "<stdlib.h>".}
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proc c_calloc(num, size: csize): pointer {.
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importc: "calloc", header: "<stdlib.h>".}
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proc c_free(p: pointer) {.
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importc: "free", header: "<stdlib.h>".}
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type ExampleVM = object
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instance: evm_instance
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verbose: bool
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proc evm_destroy(evm: ptr evm_instance) {.cdecl.}=
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c_free evm
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# Example options
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proc evm_set_option(instance: ptr evm_instance, name: cstring, value: cstring): cint {.cdecl.}=
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var vm = ExampleVM(instance: instance[])
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if name == "verbose":
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vm.verbose = ($name).parseBool
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# Note: we don't return 1 if not a number or in int range as Nim will throw an exception instead
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return 0
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proc evm_release_result(r: ptr evm_result) {.cdecl.}=
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r[] = evm_result() # Create a new empty evm_result
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proc free_result_output_data(r: ptr evm_result) {.cdecl.}=
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c_free r.output_data
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proc execute(instance: ptr evm_instance; context: ptr evm_context;
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rev: evm_revision; msg: ptr evm_message; code: ptr uint8;
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code_size: csize): evm_result {.cdecl.}=
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if code_size == 0:
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# In case of empty code return a fancy error message
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let error: cstring = if rev == EVM_BYZANTIUM: "Welcome to Byzantium"
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else: "Hello Ethereum"
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result.output_data = cast[ptr uint8](error)
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result.output_size = error.len
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result.status_code = EVM_FAILURE
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result.release = nil # We don't need to release the constant messages
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return
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let vm: ptr ExampleVM = cast[ptr ExampleVM](instance) # So much hacks in original code :/
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# Simulate executing by checking for some code patterns.
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# Solidity inline assemble is used in the examples instead of EVM bytecode.
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# Assembly: `{ mstore(0, address()) return(0, msize()) }`.
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const return_address = "30600052596000f3"
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# Assembly: `{ sstore(0, add(sload(0), 1)) }`
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const counter = "600160005401600055"
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echo "Debug: code_size = ", $code_size
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echo "Debug: return_address.len = ", $return_address.len
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echo "Debug: counter.len = ", $counter.len
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echo "Debug: $cast[cstring](code) == return_address - ", $($cast[cstring](code) == return_address)
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echo "Debug: $cast[cstring](code) == counter - ", $($cast[cstring](code) == counter)
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echo "\n"
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if code_size == return_address.len and $cast[cstring](code) == return_address:
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let address_size = sizeof(msg.destination)
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var output_data = cast[ptr uint8](c_malloc(address_size))
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if output_data == nil:
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result.status_code = EVM_INTERNAL_ERROR
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return
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copyMem(output_data, addr msg.destination, address_size)
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result.status_code = EVM_SUCCESS
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result.output_data = output_data
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result.output_size = address_size
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result.release = free_result_output_data
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return
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elif code_size == counter.len and $cast[cstring](code) == counter:
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var value: evm_uint256be
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var index = evm_uint256be() # Need var to have an address. Initialized to all 0 by default
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context.fn_table.get_storage(addr value, context, addr msg.destination, addr index)
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value.bytes[31] += 1
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context.fn_table.set_storage(context, addr msg.destination, addr index, addr value)
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result.status_code = EVM_SUCCESS
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return
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result.release = evm_release_result
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result.status_code = EVM_FAILURE
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result.gas_left = 0
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if vm.verbose:
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echo "Execution done.\n"
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proc examplevm_create*(): ptr evm_instance =
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var init = evm_instance(
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abi_version: EVM_ABI_VERSION,
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destroy: evm_destroy,
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execute: execute,
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set_option: evm_set_option
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)
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let vm = cast[ptr ExampleVM](c_calloc(1, sizeof(ExampleVM)))
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result = addr vm.instance
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copyMem(result, addr init, sizeof(init))
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