forked from open-policy-agent/opa
/
bindings.go
386 lines (336 loc) · 7.94 KB
/
bindings.go
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// Copyright 2017 The OPA Authors. All rights reserved.
// Use of this source code is governed by an Apache2
// license that can be found in the LICENSE file.
package topdown
import (
"fmt"
"strings"
"github.com/open-policy-agent/opa/ast"
)
type undo struct {
k *ast.Term
u *bindings
next *undo
}
func (u *undo) Undo() {
if u == nil {
// Allow call on zero value of Undo for ease-of-use.
return
}
if u.u == nil {
// Call on empty unifier undos a no-op unify operation.
return
}
u.u.delete(u.k)
u.next.Undo()
}
type bindings struct {
id uint64
values bindingsArrayHashmap
instr *Instrumentation
}
func newBindings(id uint64, instr *Instrumentation) *bindings {
values := newBindingsArrayHashmap()
return &bindings{id, values, instr}
}
func (u *bindings) Iter(caller *bindings, iter func(*ast.Term, *ast.Term) error) error {
var err error
u.values.Iter(func(k *ast.Term, v value) bool {
if err != nil {
return true
}
err = iter(k, u.PlugNamespaced(k, caller))
return false
})
return err
}
func (u *bindings) Namespace(x ast.Node, caller *bindings) {
ast.Walk(namespacingVisitor{
b: u,
caller: caller,
}, x)
}
func (u *bindings) Plug(a *ast.Term) *ast.Term {
return u.PlugNamespaced(a, nil)
}
func (u *bindings) PlugNamespaced(a *ast.Term, caller *bindings) *ast.Term {
if u != nil {
u.instr.startTimer(evalOpPlug)
t := u.plugNamespaced(a, caller)
u.instr.stopTimer(evalOpPlug)
return t
}
return u.plugNamespaced(a, caller)
}
func (u *bindings) plugNamespaced(a *ast.Term, caller *bindings) *ast.Term {
switch v := a.Value.(type) {
case ast.Var:
b, next := u.apply(a)
if a != b || u != next {
return next.plugNamespaced(b, caller)
}
return u.namespaceVar(b, caller)
case ast.Array:
cpy := *a
arr := make(ast.Array, len(v))
for i := 0; i < len(arr); i++ {
arr[i] = u.plugNamespaced(v[i], caller)
}
cpy.Value = arr
return &cpy
case ast.Object:
if a.IsGround() {
return a
}
cpy := *a
cpy.Value, _ = v.Map(func(k, v *ast.Term) (*ast.Term, *ast.Term, error) {
return u.plugNamespaced(k, caller), u.plugNamespaced(v, caller), nil
})
return &cpy
case ast.Set:
cpy := *a
cpy.Value, _ = v.Map(func(x *ast.Term) (*ast.Term, error) {
return u.plugNamespaced(x, caller), nil
})
return &cpy
case ast.Ref:
cpy := *a
ref := make(ast.Ref, len(v))
for i := 0; i < len(ref); i++ {
ref[i] = u.plugNamespaced(v[i], caller)
}
cpy.Value = ref
return &cpy
}
return a
}
func (u *bindings) bind(a *ast.Term, b *ast.Term, other *bindings) *undo {
u.values.Put(a, value{
u: other,
v: b,
})
return &undo{a, u, nil}
}
func (u *bindings) apply(a *ast.Term) (*ast.Term, *bindings) {
// Early exit for non-var terms. Only vars are bound in the binding list,
// so the lookup below will always fail for non-var terms. In some cases,
// the lookup may be expensive as it has to hash the term (which for large
// inputs can be costly.)
_, ok := a.Value.(ast.Var)
if !ok {
return a, u
}
val, ok := u.get(a)
if !ok {
return a, u
}
return val.u.apply(val.v)
}
func (u *bindings) delete(v *ast.Term) {
u.values.Delete(v)
}
func (u *bindings) get(v *ast.Term) (value, bool) {
if u == nil {
return value{}, false
}
return u.values.Get(v)
}
func (u *bindings) String() string {
if u == nil {
return "()"
}
var buf []string
u.values.Iter(func(a *ast.Term, b value) bool {
buf = append(buf, fmt.Sprintf("%v: %v", a, b))
return false
})
return fmt.Sprintf("({%v}, %v)", strings.Join(buf, ", "), u.id)
}
func (u *bindings) namespaceVar(v *ast.Term, caller *bindings) *ast.Term {
name, ok := v.Value.(ast.Var)
if !ok {
panic("illegal value")
}
if caller != nil && caller != u {
// Root documents (i.e., data, input) should never be namespaced because they
// are globally unique.
if !ast.RootDocumentNames.Contains(v) {
return ast.NewTerm(ast.Var(string(name) + fmt.Sprint(u.id)))
}
}
return v
}
type value struct {
u *bindings
v *ast.Term
}
func (v value) String() string {
return fmt.Sprintf("(%v, %d)", v.v, v.u.id)
}
func (v value) equal(other *value) bool {
if v.u == other.u {
return v.v.Equal(other.v)
}
return false
}
type namespacingVisitor struct {
b *bindings
caller *bindings
}
func (vis namespacingVisitor) Visit(x interface{}) ast.Visitor {
switch x := x.(type) {
case *ast.ArrayComprehension:
x.Term = vis.namespaceTerm(x.Term)
ast.Walk(vis, x.Body)
return nil
case *ast.SetComprehension:
x.Term = vis.namespaceTerm(x.Term)
ast.Walk(vis, x.Body)
return nil
case *ast.ObjectComprehension:
x.Key = vis.namespaceTerm(x.Key)
x.Value = vis.namespaceTerm(x.Value)
ast.Walk(vis, x.Body)
return nil
case *ast.Expr:
switch terms := x.Terms.(type) {
case []*ast.Term:
for i := 1; i < len(terms); i++ {
terms[i] = vis.namespaceTerm(terms[i])
}
case *ast.Term:
x.Terms = vis.namespaceTerm(terms)
}
for _, w := range x.With {
w.Target = vis.namespaceTerm(w.Target)
w.Value = vis.namespaceTerm(w.Value)
}
}
return vis
}
func (vis namespacingVisitor) namespaceTerm(a *ast.Term) *ast.Term {
switch v := a.Value.(type) {
case ast.Var:
return vis.b.namespaceVar(a, vis.caller)
case ast.Array:
cpy := *a
arr := make(ast.Array, len(v))
for i := 0; i < len(arr); i++ {
arr[i] = vis.namespaceTerm(v[i])
}
cpy.Value = arr
return &cpy
case ast.Object:
if a.IsGround() {
return a
}
cpy := *a
cpy.Value, _ = v.Map(func(k, v *ast.Term) (*ast.Term, *ast.Term, error) {
return vis.namespaceTerm(k), vis.namespaceTerm(v), nil
})
return &cpy
case ast.Set:
cpy := *a
cpy.Value, _ = v.Map(func(x *ast.Term) (*ast.Term, error) {
return vis.namespaceTerm(x), nil
})
return &cpy
case ast.Ref:
cpy := *a
ref := make(ast.Ref, len(v))
for i := 0; i < len(ref); i++ {
ref[i] = vis.namespaceTerm(v[i])
}
cpy.Value = ref
return &cpy
}
return a
}
const maxLinearScan = 16
// bindingsArrayHashMap uses an array with linear scan instead of a hash map for smaller # of entries. Hash maps start to show off their performance advantage only after 16 keys.
type bindingsArrayHashmap struct {
n int // Entries in the array.
a *[maxLinearScan]bindingArrayKeyValue
m map[ast.Var]bindingArrayKeyValue
}
type bindingArrayKeyValue struct {
key *ast.Term
value value
}
func newBindingsArrayHashmap() bindingsArrayHashmap {
return bindingsArrayHashmap{}
}
func (b *bindingsArrayHashmap) Put(key *ast.Term, value value) {
if b.m == nil {
if b.a == nil {
b.a = new([maxLinearScan]bindingArrayKeyValue)
} else if i := b.find(key); i >= 0 {
(*b.a)[i].value = value
return
}
if b.n < maxLinearScan {
(*b.a)[b.n] = bindingArrayKeyValue{key, value}
b.n++
return
}
// Array is full, revert to using the hash map instead.
b.m = make(map[ast.Var]bindingArrayKeyValue, maxLinearScan+1)
for _, kv := range *b.a {
b.m[kv.key.Value.(ast.Var)] = bindingArrayKeyValue{kv.key, kv.value}
}
b.m[key.Value.(ast.Var)] = bindingArrayKeyValue{key, value}
b.n = 0
return
}
b.m[key.Value.(ast.Var)] = bindingArrayKeyValue{key, value}
}
func (b *bindingsArrayHashmap) Get(key *ast.Term) (value, bool) {
if b.m == nil {
if i := b.find(key); i >= 0 {
return (*b.a)[i].value, true
}
return value{}, false
}
v, ok := b.m[key.Value.(ast.Var)]
if ok {
return v.value, true
}
return value{}, false
}
func (b *bindingsArrayHashmap) Delete(key *ast.Term) {
if b.m == nil {
if i := b.find(key); i >= 0 {
n := b.n - 1
if i < n {
(*b.a)[i] = (*b.a)[n]
}
b.n = n
}
return
}
delete(b.m, key.Value.(ast.Var))
}
func (b *bindingsArrayHashmap) Iter(f func(k *ast.Term, v value) bool) {
if b.m == nil {
for i := 0; i < b.n; i++ {
if f((*b.a)[i].key, (*b.a)[i].value) {
return
}
}
return
}
for _, v := range b.m {
if f(v.key, v.value) {
return
}
}
}
func (b *bindingsArrayHashmap) find(key *ast.Term) int {
v := key.Value.(ast.Var)
for i := 0; i < b.n; i++ {
if (*b.a)[i].key.Value.(ast.Var) == v {
return i
}
}
return -1
}