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package cty
import (
"fmt"
"hash/crc64"
"github.com/zclconf/go-cty/cty/set"
)
// PathSet represents a set of Path objects. This can be used, for example,
// to talk about a subset of paths within a value that meet some criteria,
// without directly modifying the values at those paths.
type PathSet struct {
set set.Set
}
// NewPathSet creates and returns a PathSet, with initial contents optionally
// set by the given arguments.
func NewPathSet(paths ...Path) PathSet {
ret := PathSet{
set: set.NewSet(pathSetRules{}),
}
for _, path := range paths {
ret.Add(path)
}
return ret
}
// Add inserts a single given path into the set.
//
// Paths are immutable after construction by convention. It is particularly
// important not to mutate a path after it has been placed into a PathSet.
// If a Path is mutated while in a set, behavior is undefined.
func (s PathSet) Add(path Path) {
s.set.Add(path)
}
// AddAllSteps is like Add but it also adds all of the steps leading to
// the given path.
//
// For example, if given a path representing "foo.bar", it will add both
// "foo" and "bar".
func (s PathSet) AddAllSteps(path Path) {
for i := 1; i <= len(path); i++ {
s.Add(path[:i])
}
}
// Has returns true if the given path is in the receiving set.
func (s PathSet) Has(path Path) bool {
return s.set.Has(path)
}
// List makes and returns a slice of all of the paths in the receiving set,
// in an undefined but consistent order.
func (s PathSet) List() []Path {
if s.Empty() {
return nil
}
ret := make([]Path, 0, s.set.Length())
for it := s.set.Iterator(); it.Next(); {
ret = append(ret, it.Value().(Path))
}
return ret
}
// Remove modifies the receving set to no longer include the given path.
// If the given path was already absent, this is a no-op.
func (s PathSet) Remove(path Path) {
s.set.Remove(path)
}
// Empty returns true if the length of the receiving set is zero.
func (s PathSet) Empty() bool {
return s.set.Length() == 0
}
// Union returns a new set whose contents are the union of the receiver and
// the given other set.
func (s PathSet) Union(other PathSet) PathSet {
return PathSet{
set: s.set.Union(other.set),
}
}
// Intersection returns a new set whose contents are the intersection of the
// receiver and the given other set.
func (s PathSet) Intersection(other PathSet) PathSet {
return PathSet{
set: s.set.Intersection(other.set),
}
}
// Subtract returns a new set whose contents are those from the receiver with
// any elements of the other given set subtracted.
func (s PathSet) Subtract(other PathSet) PathSet {
return PathSet{
set: s.set.Subtract(other.set),
}
}
// SymmetricDifference returns a new set whose contents are the symmetric
// difference of the receiver and the given other set.
func (s PathSet) SymmetricDifference(other PathSet) PathSet {
return PathSet{
set: s.set.SymmetricDifference(other.set),
}
}
// Equal returns true if and only if both the receiver and the given other
// set contain exactly the same paths.
func (s PathSet) Equal(other PathSet) bool {
if s.set.Length() != other.set.Length() {
return false
}
// Now we know the lengths are the same we only need to test in one
// direction whether everything in one is in the other.
for it := s.set.Iterator(); it.Next(); {
if !other.set.Has(it.Value()) {
return false
}
}
return true
}
var crc64Table = crc64.MakeTable(crc64.ISO)
var indexStepPlaceholder = []byte("#")
// pathSetRules is an implementation of set.Rules from the set package,
// used internally within PathSet.
type pathSetRules struct {
}
func (r pathSetRules) Hash(v interface{}) int {
path := v.(Path)
hash := crc64.New(crc64Table)
for _, rawStep := range path {
switch step := rawStep.(type) {
case GetAttrStep:
// (this creates some garbage converting the string name to a
// []byte, but that's okay since cty is not designed to be
// used in tight loops under memory pressure.)
hash.Write([]byte(step.Name))
default:
// For any other step type we just append a predefined value,
// which means that e.g. all indexes into a given collection will
// hash to the same value but we assume that collections are
// small and thus this won't hurt too much.
hash.Write(indexStepPlaceholder)
}
}
// We discard half of the hash on 32-bit platforms; collisions just make
// our lookups take marginally longer, so not a big deal.
return int(hash.Sum64())
}
func (r pathSetRules) Equivalent(a, b interface{}) bool {
aPath := a.(Path)
bPath := b.(Path)
if len(aPath) != len(bPath) {
return false
}
for i := range aPath {
switch aStep := aPath[i].(type) {
case GetAttrStep:
bStep, ok := bPath[i].(GetAttrStep)
if !ok {
return false
}
if aStep.Name != bStep.Name {
return false
}
case IndexStep:
bStep, ok := bPath[i].(IndexStep)
if !ok {
return false
}
eq := aStep.Key.Equals(bStep.Key)
if !eq.IsKnown() || eq.False() {
return false
}
default:
// Should never happen, since we document PathStep as a closed type.
panic(fmt.Errorf("unsupported step type %T", aStep))
}
}
return true
}
|
