Update go.mod

errors.go

@@ -6,5 +6,6 @@ import (
 
 var (
 	ErrNothingToUnread = adverr.NewErrTmpl("ErrNothingToUnread", "Unreading failed because there wasn't any Read yet")
+	ErrPopFailed       = adverr.NewErrTmpl("ErrPopFailed", "stack cannot be popped. It was never pushed")
 	ErrNoMoreValues    = adverr.NewErrTmpl("ErrNoMoreValues", "source does not have any more values")
 )

go.mod

@@ -1,8 +1,11 @@
-module git.milar.in/milarin/anyreader
+module git.tordarus.net/tordarus/anyreader
 
 go 1.20
 
 require (
-	git.milar.in/milarin/adverr v1.1.0
-	git.milar.in/milarin/ds v0.0.2
+	git.tordarus.net/tordarus/adverr v1.1.0
+	git.tordarus.net/tordarus/ds v0.0.2
+	git.tordarus.net/tordarus/slices v0.0.8
 )
+
+require git.tordarus.net/tordarus/gmath v0.0.3 // indirect

go.sum

@@ -2,3 +2,7 @@ git.milar.in/milarin/adverr v1.1.0 h1:jD9WnOvs40lfMhvqQ7cllOaRJNBMWr1f07/s9jAadp
 git.milar.in/milarin/adverr v1.1.0/go.mod h1:joU9sBb7ySyNv4SpTXB0Z4o1mjXsArBw4N27wjgzj9E=
 git.milar.in/milarin/ds v0.0.2 h1:vCA3mDxZUNfvHpzrdz7SeBUKiPn74NTopo915IUG7I0=
 git.milar.in/milarin/ds v0.0.2/go.mod h1:HJK7QERcRvV9j7xzEocrKUtW+1q4JB1Ly4Bj54chfwI=
+git.milar.in/milarin/gmath v0.0.3 h1:ii6rKNItS55O/wtIFhD1cTN2BMwDZjTBmiOocKURvxM=
+git.milar.in/milarin/gmath v0.0.3/go.mod h1:HDLftG5RLpiNGKiIWh+O2G1PYkNzyLDADO8Cd/1abiE=
+git.milar.in/milarin/slices v0.0.8 h1:qN9TE3tkArdTixMKSnwvNPcApwAjxpLVwA5a9k1rm2s=
+git.milar.in/milarin/slices v0.0.8/go.mod h1:qMhdtMnfWswc1rHpwgNw33lB84aNEkdBn5BDiYA+G3k=

reader.go

@@ -1,10 +1,15 @@
 package anyreader
 
-import "git.milar.in/milarin/ds"
+import (
+	"git.milar.in/milarin/ds"
+	"git.milar.in/milarin/slices"
+)
 
 type Reader[T any] struct {
-	buf ds.Stack[T]
-	src func() (T, error)
+	buf     ds.Stack[T]
+	indices ds.Stack[uint64]
+	index   uint64
+	src     func() (T, error)
 }
 
 func NewReaderFromSlice[T any](s []T) *Reader[T] {
@@ -17,8 +22,10 @@ func NewReaderFromFunc[T any](src func() T) *Reader[T] {
 
 func NewReaderFromErrorFunc[T any](src func() (T, error)) *Reader[T] {
 	return &Reader[T]{
-		src: src,
-		buf: ds.NewArrayStack[T](),
+		src:     src,
+		buf:     ds.NewArrayStack[T](),
+		index:   0,
+		indices: ds.NewArrayStack[uint64](),
 	}
 }
 
@@ -26,6 +33,7 @@ func (r *Reader[T]) Read() (T, error) {
 	v, err := r.src()
 	if err == nil {
 		r.buf.Push(v)
+		r.index++
 	}
 	return v, err
 }
@@ -36,6 +44,7 @@ func (r *Reader[T]) Unread() error {
 	}
 
 	v := r.buf.Pop()
+	r.index--
 
 	returned := false
 	oldSrc := r.src
@@ -114,6 +123,44 @@ func (r *Reader[T]) Expect(f ...func(T) bool) (bool, error) {
 	return findFirstTrue(value, f), nil
 }
 
-func (r *Reader[T]) Commit() {
-	r.buf.Clear()
+func (r *Reader[T]) Push() {
+	r.indices.Push(r.index)
+}
+
+func (r *Reader[T]) Pop() ([]T, error) {
+	if r.indices.Empty() {
+		return nil, ErrPopFailed.New()
+	}
+
+	lastIndex := r.indices.Pop()
+	currentIndex := r.index
+	if lastIndex < currentIndex {
+		values := make([]T, 0, int(currentIndex-lastIndex))
+		for i := 0; i < int(currentIndex-lastIndex); i++ {
+			err := r.Unread()
+			if err != nil {
+				return nil, err
+			}
+
+			value, err := r.Peek()
+			if err != nil {
+				return nil, err
+			}
+
+			values = append(values, value)
+		}
+		return slices.Reverse(values), nil
+	} else if lastIndex > currentIndex {
+		values := make([]T, 0, int(lastIndex-currentIndex))
+		for i := 0; i < int(lastIndex-currentIndex); i++ {
+			value, err := r.Read()
+			if err != nil {
+				return nil, err
+			}
+			values = append(values, value)
+		}
+		return values, nil
+	}
+
+	return []T{}, nil
 }

reader_test.go

@@ -8,6 +8,14 @@ import (
 func TestReader(t *testing.T) {
 	r := NewReaderFromSlice([]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10})
 	fmt.Println(r.Read())
-	r.Unread()
+	fmt.Println(r.Read())
+
+	r.Push()
+
+	fmt.Println(r.Unread())
+	fmt.Println(r.Unread())
+
+	fmt.Println(r.Pop())
+
 	fmt.Println(r.Read())
 }

safe_reader.go

@@ -0,0 +1,120 @@
+package anyreader
+
+import (
+	"git.milar.in/milarin/ds"
+	"git.milar.in/milarin/slices"
+)
+
+type SafeReader[T any] struct {
+	buf     ds.Stack[T]
+	indices ds.Stack[uint64]
+	index   uint64
+	src     func() T
+}
+
+func NewSafeReaderFromSlice[T any](s []T) *SafeReader[T] {
+	return NewSafeReaderFromFunc(sliceToSafeFunc(s))
+}
+
+func NewSafeReaderFromFunc[T any](src func() T) *SafeReader[T] {
+	return &SafeReader[T]{
+		src:     src,
+		buf:     ds.NewArrayStack[T](),
+		index:   0,
+		indices: ds.NewArrayStack[uint64](),
+	}
+}
+
+func (r *SafeReader[T]) Read() T {
+	v := r.src()
+	r.buf.Push(v)
+	r.index++
+	return v
+}
+
+func (r *SafeReader[T]) Unread() {
+	if r.buf.Empty() {
+		return
+	}
+
+	v := r.buf.Pop()
+	r.index--
+
+	returned := false
+	oldSrc := r.src
+	r.src = func() T {
+		if returned {
+			return oldSrc()
+		}
+
+		returned = true
+		return v
+	}
+}
+
+func (r *SafeReader[T]) UnreadN(n int) {
+	for i := 0; i < n; i++ {
+		r.Unread()
+	}
+}
+
+func (r *SafeReader[T]) Peek() T {
+	value := r.Read()
+	r.Unread()
+	return value
+}
+
+func (r *SafeReader[T]) ReadWhile(f ...func(T) bool) []T {
+	res := make([]T, 0, 10)
+	for value := r.Read(); findFirstTrue(value, f); value = r.Read() {
+		res = append(res, value)
+	}
+	return res
+}
+
+func (r *SafeReader[T]) ReadUntil(f ...func(T) bool) []T {
+	return r.ReadWhile(func(v T) bool { return !findFirstTrue(v, f) })
+}
+
+func (r *SafeReader[T]) SkipUntil(f ...func(T) bool) {
+	r.ReadUntil(f...)
+	r.Unread()
+}
+
+func (r *SafeReader[T]) SkipWhile(f ...func(T) bool) {
+	r.ReadWhile(f...)
+	r.Unread()
+}
+
+func (r *SafeReader[T]) Expect(f ...func(T) bool) bool {
+	return findFirstTrue(r.Read(), f)
+}
+
+func (r *SafeReader[T]) Push() {
+	r.indices.Push(r.index)
+}
+
+func (r *SafeReader[T]) Pop() []T {
+	if r.indices.Empty() {
+		return []T{}
+	}
+
+	lastIndex := r.indices.Pop()
+	currentIndex := r.index
+	if lastIndex < currentIndex {
+		values := make([]T, 0, int(currentIndex-lastIndex))
+		for i := 0; i < int(currentIndex-lastIndex); i++ {
+			r.Unread()
+			values = append(values, r.Peek())
+		}
+		return slices.Reverse(values)
+	} else if lastIndex > currentIndex {
+		values := make([]T, 0, int(lastIndex-currentIndex))
+		for i := 0; i < int(lastIndex-currentIndex); i++ {
+			values = append(values, r.Read())
+		}
+		return values
+	}
+
+	return []T{}
+}

utils.go

@@ -14,6 +14,20 @@ func sliceToFunc[T any](s []T) func() (T, error) {
 	}
 }
 
+func sliceToSafeFunc[T any](s []T) func() T {
+	i := 0
+	return func() T {
+		c := i
+
+		if c >= len(s) {
+			return *new(T)
+		}
+
+		i++
+		return s[c]
+	}
+}
+
 func findFirstTrue[T any](value T, functions []func(T) bool) bool {
 	for _, f := range functions {
 		if f(value) {