github.com/jeffallen/go-ethereum@v1.1.4-0.20150910155051-571d3236c49c/core/vm/context.go (about)

     1  // Copyright 2014 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package vm
    18  
    19  import (
    20  	"math/big"
    21  
    22  	"github.com/ethereum/go-ethereum/common"
    23  )
    24  
    25  type ContextRef interface {
    26  	ReturnGas(*big.Int, *big.Int)
    27  	Address() common.Address
    28  	SetCode([]byte)
    29  }
    30  
    31  type Context struct {
    32  	caller ContextRef
    33  	self   ContextRef
    34  
    35  	jumpdests destinations // result of JUMPDEST analysis.
    36  
    37  	Code     []byte
    38  	Input    []byte
    39  	CodeAddr *common.Address
    40  
    41  	value, Gas, UsedGas, Price *big.Int
    42  
    43  	Args []byte
    44  }
    45  
    46  // Create a new context for the given data items.
    47  func NewContext(caller ContextRef, object ContextRef, value, gas, price *big.Int) *Context {
    48  	c := &Context{caller: caller, self: object, Args: nil}
    49  
    50  	if parent, ok := caller.(*Context); ok {
    51  		// Reuse JUMPDEST analysis from parent context if available.
    52  		c.jumpdests = parent.jumpdests
    53  	} else {
    54  		c.jumpdests = make(destinations)
    55  	}
    56  
    57  	// Gas should be a pointer so it can safely be reduced through the run
    58  	// This pointer will be off the state transition
    59  	c.Gas = gas //new(big.Int).Set(gas)
    60  	c.value = new(big.Int).Set(value)
    61  	// In most cases price and value are pointers to transaction objects
    62  	// and we don't want the transaction's values to change.
    63  	c.Price = new(big.Int).Set(price)
    64  	c.UsedGas = new(big.Int)
    65  
    66  	return c
    67  }
    68  
    69  func (c *Context) GetOp(n uint64) OpCode {
    70  	return OpCode(c.GetByte(n))
    71  }
    72  
    73  func (c *Context) GetByte(n uint64) byte {
    74  	if n < uint64(len(c.Code)) {
    75  		return c.Code[n]
    76  	}
    77  
    78  	return 0
    79  }
    80  
    81  func (c *Context) Return(ret []byte) []byte {
    82  	// Return the remaining gas to the caller
    83  	c.caller.ReturnGas(c.Gas, c.Price)
    84  
    85  	return ret
    86  }
    87  
    88  /*
    89   * Gas functions
    90   */
    91  func (c *Context) UseGas(gas *big.Int) (ok bool) {
    92  	ok = UseGas(c.Gas, gas)
    93  	if ok {
    94  		c.UsedGas.Add(c.UsedGas, gas)
    95  	}
    96  	return
    97  }
    98  
    99  // Implement the caller interface
   100  func (c *Context) ReturnGas(gas, price *big.Int) {
   101  	// Return the gas to the context
   102  	c.Gas.Add(c.Gas, gas)
   103  	c.UsedGas.Sub(c.UsedGas, gas)
   104  }
   105  
   106  /*
   107   * Set / Get
   108   */
   109  func (c *Context) Address() common.Address {
   110  	return c.self.Address()
   111  }
   112  
   113  func (self *Context) SetCode(code []byte) {
   114  	self.Code = code
   115  }
   116  
   117  func (self *Context) SetCallCode(addr *common.Address, code []byte) {
   118  	self.Code = code
   119  	self.CodeAddr = addr
   120  }