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// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// prestateTracer outputs sufficient information to create a local execution of
// the transaction from a custom assembled genesis block.
{
// prestate is the genesis that we're building.
prestate: null,
// lookupAccount injects the specified account into the prestate object.
lookupAccount: function(addr, db){
var acc = toHex(addr);
if (this.prestate[acc] === undefined) {
this.prestate[acc] = {
balance: '0x' + db.getBalance(addr).toString(16),
nonce: db.getNonce(addr),
code: toHex(db.getCode(addr)),
storage: {}
};
}
},
// lookupStorage injects the specified storage entry of the given account into
// the prestate object.
lookupStorage: function(addr, key, db){
var acc = toHex(addr);
var idx = toHex(key);
if (this.prestate[acc].storage[idx] === undefined) {
var val = toHex(db.getState(addr, key));
if (val != "0x0000000000000000000000000000000000000000000000000000000000000000") {
this.prestate[acc].storage[idx] = toHex(db.getState(addr, key));
}
}
},
// result is invoked when all the opcodes have been iterated over and returns
// the final result of the tracing.
result: function(ctx, db) {
// At this point, we need to deduct the 'value' from the
// outer transaction, and move it back to the origin
this.lookupAccount(ctx.from, db);
var fromBal = bigInt(this.prestate[toHex(ctx.from)].balance.slice(2), 16);
var toBal = bigInt(this.prestate[toHex(ctx.to)].balance.slice(2), 16);
this.prestate[toHex(ctx.to)].balance = '0x'+toBal.subtract(ctx.value).toString(16);
this.prestate[toHex(ctx.from)].balance = '0x'+fromBal.add(ctx.value).toString(16);
// Decrement the caller's nonce, and remove empty create targets
this.prestate[toHex(ctx.from)].nonce--;
if (ctx.type == 'CREATE') {
// We can blibdly delete the contract prestate, as any existing state would
// have caused the transaction to be rejected as invalid in the first place.
delete this.prestate[toHex(ctx.to)];
}
// Return the assembled allocations (prestate)
return this.prestate;
},
// step is invoked for every opcode that the VM executes.
step: function(log, db) {
// Add the current account if we just started tracing
if (this.prestate === null){
this.prestate = {};
// Balance will potentially be wrong here, since this will include the value
// sent along with the message. We fix that in 'result()'.
this.lookupAccount(log.contract.getAddress(), db);
}
// Whenever new state is accessed, add it to the prestate
switch (log.op.toString()) {
case "EXTCODECOPY": case "EXTCODESIZE": case "BALANCE":
this.lookupAccount(toAddress(log.stack.peek(0).toString(16)), db);
break;
case "CREATE":
var from = log.contract.getAddress();
this.lookupAccount(toContract(from, db.getNonce(from)), db);
break;
case "CALL": case "CALLCODE": case "DELEGATECALL": case "STATICCALL":
this.lookupAccount(toAddress(log.stack.peek(1).toString(16)), db);
break;
case 'SSTORE':case 'SLOAD':
this.lookupStorage(log.contract.getAddress(), toWord(log.stack.peek(0).toString(16)), db);
break;
}
},
// fault is invoked when the actual execution of an opcode fails.
fault: function(log, db) {}
}
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