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 }