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-rw-r--r--core/vm/environment.go4
-rw-r--r--core/vm/vm.go48
2 files changed, 34 insertions, 18 deletions
diff --git a/core/vm/environment.go b/core/vm/environment.go
index 25bd2515e..e61676409 100644
--- a/core/vm/environment.go
+++ b/core/vm/environment.go
@@ -8,6 +8,8 @@ import (
"github.com/ethereum/go-ethereum/core/state"
)
+// Environment is is required by the virtual machine to get information from
+// it's own isolated environment. For an example see `core.VMEnv`
type Environment interface {
State() *state.StateDB
@@ -33,6 +35,8 @@ type Environment interface {
Create(me ContextRef, data []byte, gas, price, value *big.Int) ([]byte, error, ContextRef)
}
+// StructLog is emited to the Environment each cycle and lists information about the curent internal state
+// prior to the execution of the statement.
type StructLog struct {
Pc uint64
Op OpCode
diff --git a/core/vm/vm.go b/core/vm/vm.go
index e4f6e9268..bf8bbcdc2 100644
--- a/core/vm/vm.go
+++ b/core/vm/vm.go
@@ -10,6 +10,7 @@ import (
"github.com/ethereum/go-ethereum/params"
)
+// Vm implements VirtualMachine
type Vm struct {
env Environment
@@ -27,11 +28,13 @@ type Vm struct {
After func(*Context, error)
}
+// New returns a new Virtual Machine
func New(env Environment) *Vm {
return &Vm{env: env, debug: Debug, Recoverable: true}
}
-func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
+// Run loops and evaluates the contract's code with the given input data
+func (self *Vm) Run(context *Context, input []byte) (ret []byte, err error) {
self.env.SetDepth(self.env.Depth() + 1)
defer self.env.SetDepth(self.env.Depth() - 1)
@@ -59,7 +62,7 @@ func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
if context.CodeAddr != nil {
if p := Precompiled[context.CodeAddr.Str()]; p != nil {
- return self.RunPrecompiled(p, callData, context)
+ return self.RunPrecompiled(p, input, context)
}
}
@@ -69,13 +72,15 @@ func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
}
var (
- op OpCode
- codehash = crypto.Sha3Hash(code)
- mem = NewMemory()
- stack = newStack()
- pc = uint64(0)
- statedb = self.env.State()
-
+ op OpCode // current opcode
+ codehash = crypto.Sha3Hash(code) // codehash is used when doing jump dest caching
+ mem = NewMemory() // bound memory
+ stack = newStack() // local stack
+ pc = uint64(0) // program counter
+ statedb = self.env.State() // current state
+
+ // jump evaluates and checks whether the given jump destination is a valid one
+ // if valid move the `pc` otherwise return an error.
jump = func(from uint64, to *big.Int) error {
if !context.jumpdests.has(codehash, code, to) {
nop := context.GetOp(to.Uint64())
@@ -97,20 +102,22 @@ func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
self.log(pc, op, context.Gas, mem, stack, context)
+ // calculate the new memory size and gas price for the current executing opcode
newMemSize, gas, err := self.calculateGasAndSize(context, caller, op, statedb, mem, stack)
if err != nil {
return nil, err
}
+ // Use the calculated gas. When insufficient gas is present, use all gas and return an
+ // Out Of Gas error
if !context.UseGas(gas) {
-
tmp := new(big.Int).Set(context.Gas)
context.UseGas(context.Gas)
return context.Return(nil), OOG(gas, tmp)
}
-
+ // Resize the memory calculated previously
mem.Resize(newMemSize.Uint64())
switch op {
@@ -364,11 +371,11 @@ func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
stack.push(value)
case CALLDATALOAD:
- data := getData(callData, stack.pop(), common.Big32)
+ data := getData(input, stack.pop(), common.Big32)
stack.push(common.Bytes2Big(data))
case CALLDATASIZE:
- l := int64(len(callData))
+ l := int64(len(input))
stack.push(big.NewInt(l))
case CALLDATACOPY:
@@ -377,7 +384,7 @@ func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
cOff = stack.pop()
l = stack.pop()
)
- data := getData(callData, cOff, l)
+ data := getData(input, cOff, l)
mem.Set(mOff.Uint64(), l.Uint64(), data)
@@ -623,6 +630,8 @@ func (self *Vm) Run(context *Context, callData []byte) (ret []byte, err error) {
}
}
+// calculateGasAndSize calculates the required given the opcode and stack items calculates the new memorysize for
+// the operation. This does not reduce gas or resizes the memory.
func (self *Vm) calculateGasAndSize(context *Context, caller ContextRef, op OpCode, statedb *state.StateDB, mem *Memory, stack *Stack) (*big.Int, *big.Int, error) {
var (
gas = new(big.Int)
@@ -764,20 +773,22 @@ func (self *Vm) calculateGasAndSize(context *Context, caller ContextRef, op OpCo
return newMemSize, gas, nil
}
-func (self *Vm) RunPrecompiled(p *PrecompiledAccount, callData []byte, context *Context) (ret []byte, err error) {
- gas := p.Gas(len(callData))
+// RunPrecompile runs and evaluate the output of a precompiled contract defined in contracts.go
+func (self *Vm) RunPrecompiled(p *PrecompiledAccount, input []byte, context *Context) (ret []byte, err error) {
+ gas := p.Gas(len(input))
if context.UseGas(gas) {
- ret = p.Call(callData)
+ ret = p.Call(input)
return context.Return(ret), nil
} else {
-
tmp := new(big.Int).Set(context.Gas)
return nil, OOG(gas, tmp)
}
}
+// log emits a log event to the environment for each opcode encountered. This is not to be confused with the
+// LOG* opcode.
func (self *Vm) log(pc uint64, op OpCode, gas *big.Int, memory *Memory, stack *Stack, context *Context) {
if Debug {
mem := make([]byte, len(memory.Data()))
@@ -795,6 +806,7 @@ func (self *Vm) log(pc uint64, op OpCode, gas *big.Int, memory *Memory, stack *S
}
}
+// Environment returns the current workable state of the VM
func (self *Vm) Env() Environment {
return self.env
}