Implemented (but not tested) cursor.RuneReader
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@ -25,6 +25,9 @@ type Cursor[Datum any] interface {
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// Pos returns the Cursor's position within the source.
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Pos() uint64
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// At returns a new cursor at the position pos.
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At(pos uint64) Cursor[Datum]
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}
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type SliceCursor[Datum any] struct {
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@ -56,6 +59,11 @@ func (sc SliceCursor[Datum]) Pos() uint64 {
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return sc.offset
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}
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func (sc SliceCursor[Datum]) At(pos uint64) Cursor[Datum] {
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sc.offset = pos
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return sc
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}
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type ReaderAtCursor struct {
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r io.ReaderAt
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pos uint64
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@ -77,6 +85,11 @@ func (rac ReaderAtCursor) Pos() uint64 {
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return rac.pos
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}
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func (rac ReaderAtCursor) At(pos uint64) Cursor[byte] {
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rac.pos = pos
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return rac
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}
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// StringCursor is identical to SliceCursor[byte], but uses a string as its data source.
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// The advantage is that creating a StringCursor does not require copying the source
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// string into a []byte.
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@ -105,3 +118,8 @@ func (sc StringCursor) Read(dst []byte) (n uint64, next Cursor[byte], err error)
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func (sc StringCursor) Pos() uint64 {
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return sc.offset
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}
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func (sc StringCursor) At(pos uint64) Cursor[byte] {
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sc.offset = pos
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return sc
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}
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@ -73,6 +73,7 @@ func testCursor[C cursor.Cursor[byte]](t *testing.T, makeCursor func([]byte) C)
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test.ErrorIs(t, err, io.EOF)
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test.EqOp(t, len(data), int(n))
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}))
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t.Run("At", Todo)
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}
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func TestSliceCursor(t *testing.T) {
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@ -1,6 +1,11 @@
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package cursor
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import "io"
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import (
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"errors"
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"fmt"
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"io"
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"unicode/utf8"
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)
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// BufferedReaderAt uses a buffer to supplement an io.Reader
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// with limited backward seeking.
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@ -31,12 +36,20 @@ func NewRuneReader(c Cursor[byte]) *RuneReader {
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return &RuneReader{cursor: c}
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}
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func (r *RuneReader) Read(dst []byte) (int, error) {
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n, c, err := r.cursor.Read(dst)
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r.cursor = c
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return int(n), err
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func (rr *RuneReader) ReadRune() (r rune, size int, err error) {
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var b [4]byte
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s := b[:]
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n, next, err := rr.cursor.Read(s)
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if err != nil && !errors.Is(err, io.EOF) {
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rr.cursor = next
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return 0, 0, fmt.Errorf("ReadRune: %w", err)
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}
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s = s[:n]
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r, size = utf8.DecodeRune(s)
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rr.cursor = rr.cursor.At(rr.cursor.Pos() + uint64(size))
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return r, size, err
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}
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func (r *RuneReader) Cursor() Cursor[byte] {
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return r.cursor
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func (rr *RuneReader) Cursor() Cursor[byte] {
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return rr.cursor
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}
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