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|
package stack
import (
"jinx/pkg/lang/vm/mem"
"jinx/pkg/lang/vm/value"
)
type Stack interface {
Push(value value.Value)
Pop() (value.Value, error)
Get(index int) (value.Value, error)
Set(index int, value value.Value) error
Local(offset int) (value.Value, error)
Top() (value.Value, error)
Len() int
IsEmpty() bool
PushCall(newPc, returnPc int, env mem.Ptr) error
PopCall() (int, error)
ShiftTopCallBase(by int) error
CurrentCallEnv() mem.Ptr
CallDepth() int
ReachedBaseOfCall() bool
LocalToStackIndex(local int) int
}
type stackImpl struct {
data []value.Value
calls []callFrame
}
func New() Stack {
data := make([]value.Value, 0, 64)
calls := make([]callFrame, 0, 8)
calls = append(calls, callFrame{
pc: 0,
returnPc: 0,
base: 0,
})
return &stackImpl{
data: data,
calls: calls,
}
}
func (stack *stackImpl) Push(value value.Value) {
stack.data = append(stack.data, value)
}
func (stack *stackImpl) Pop() (value.Value, error) {
if stack.IsEmpty() || stack.ReachedBaseOfCall() {
return value.Value{}, ErrStackUnderflow
}
v, err := stack.Top()
if err != nil {
return value.Value{}, err
}
stack.data = stack.data[:stack.Len()-1]
return v, nil
}
func (stack *stackImpl) Get(index int) (value.Value, error) {
if index < 0 || index >= stack.Len() {
return value.Value{}, ErrStackIndexOutOfBounds{Index: index, Len: stack.Len()}
}
return stack.data[index], nil
}
func (stack *stackImpl) Set(index int, value value.Value) error {
if index < 0 || index >= stack.Len() {
return ErrStackIndexOutOfBounds{Index: index, Len: stack.Len()}
}
stack.data[index] = value
return nil
}
func (stack *stackImpl) Local(offset int) (value.Value, error) {
if stack.ReachedBaseOfCall() {
return value.Value{}, ErrStackUnderflow
}
return stack.Get(stack.LocalToStackIndex(offset))
}
func (stack *stackImpl) Top() (value.Value, error) {
if stack.IsEmpty() || stack.ReachedBaseOfCall() {
return value.Value{}, ErrStackUnderflow
}
return stack.data[stack.Len()-1], nil
}
func (stack *stackImpl) Len() int {
return len(stack.data)
}
func (stack *stackImpl) IsEmpty() bool {
return len(stack.data) == 0
}
func (stack *stackImpl) PushCall(newPc, returnPc int, env mem.Ptr) error {
if stack.CallDepth() == 1000 {
return ErrReachedMaxCallDepth
}
stack.calls = append(stack.calls, callFrame{
pc: newPc,
returnPc: returnPc,
base: stack.Len(),
env: env,
})
return nil
}
func (stack *stackImpl) PopCall() (int, error) {
if stack.CallDepth() == 0 {
return 0, ErrReachedRootCallFrame
}
call := stack.topCall()
stack.calls = stack.calls[:stack.CallDepth()-1]
return call.returnPc, nil
}
func (stack *stackImpl) ShiftTopCallBase(by int) error {
call := stack.topCall()
newBase := call.base - by
if newBase < 0 {
return ErrCallBaseCantBeNegative
}
call.base = newBase
return nil
}
func (stack *stackImpl) CurrentCallEnv() mem.Ptr {
if stack.CallDepth() == 0 || stack.topCall().env.IsNull() {
return mem.NullPtr
}
return stack.topCall().env
}
func (stack *stackImpl) CallDepth() int {
return len(stack.calls)
}
func (stack *stackImpl) ReachedBaseOfCall() bool {
return stack.topCall().base == stack.Len()
}
func (stack *stackImpl) LocalToStackIndex(local int) int {
if stack.CallDepth() == 0 {
return local
}
return stack.topCall().base + local
}
func (stack *stackImpl) topCall() *callFrame {
return &stack.calls[len(stack.calls)-1]
}
type callFrame struct {
pc int // Beginning of the called function.
returnPc int // Where to return to after the called function returns.
base int // Base of the local variables on the data stack.
env mem.Ptr // Environment of the called function.
}
|
