98 lines
3.5 KiB
Go
98 lines
3.5 KiB
Go
// Copyright 2016 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package core
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import (
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"math/big"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/consensus"
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"github.com/ethereum/go-ethereum/core/types"
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"github.com/ethereum/go-ethereum/core/vm"
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)
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// ChainContext supports retrieving headers and consensus parameters from the
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// current blockchain to be used during transaction processing.
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type ChainContext interface {
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// Engine retrieves the chain's consensus engine.
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Engine() consensus.Engine
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// GetHeader returns the hash corresponding to their hash.
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GetHeader(common.Hash, uint64) *types.Header
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}
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// NewEVMContext creates a new context for use in the EVM.
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func NewEVMContext(msg Message, header *types.Header, chain ChainContext, author *common.Address) vm.Context {
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// If we don't have an explicit author (i.e. not mining), extract from the header
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var beneficiary common.Address
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if author == nil {
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beneficiary, _ = chain.Engine().Author(header) // Ignore error, we're past header validation
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} else {
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beneficiary = *author
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}
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return vm.Context{
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CanTransfer: CanTransfer,
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Transfer: Transfer,
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GetHash: GetHashFn(header, chain),
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Origin: msg.From(),
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Coinbase: beneficiary,
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BlockNumber: new(big.Int).Set(header.Number),
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Time: new(big.Int).Set(header.Time),
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Difficulty: new(big.Int).Set(header.Difficulty),
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GasLimit: header.GasLimit,
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GasPrice: new(big.Int).Set(msg.GasPrice()),
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}
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}
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// GetHashFn returns a GetHashFunc which retrieves header hashes by number
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func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash {
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var cache map[uint64]common.Hash
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return func(n uint64) common.Hash {
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// If there's no hash cache yet, make one
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if cache == nil {
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cache = map[uint64]common.Hash{
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ref.Number.Uint64() - 1: ref.ParentHash,
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}
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}
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// Try to fulfill the request from the cache
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if hash, ok := cache[n]; ok {
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return hash
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}
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// Not cached, iterate the blocks and cache the hashes
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for header := chain.GetHeader(ref.ParentHash, ref.Number.Uint64()-1); header != nil; header = chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) {
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cache[header.Number.Uint64()-1] = header.ParentHash
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if n == header.Number.Uint64()-1 {
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return header.ParentHash
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}
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}
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return common.Hash{}
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}
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}
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// CanTransfer checks wether there are enough funds in the address' account to make a transfer.
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// This does not take the necessary gas in to account to make the transfer valid.
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func CanTransfer(db vm.StateDB, addr common.Address, amount *big.Int) bool {
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return db.GetBalance(addr).Cmp(amount) >= 0
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}
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// Transfer subtracts amount from sender and adds amount to recipient using the given Db
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func Transfer(db vm.StateDB, sender, recipient common.Address, amount *big.Int) {
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db.SubBalance(sender, amount)
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db.AddBalance(recipient, amount)
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}
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