diff --git a/internal/ring.go b/internal/ring.go
new file mode 100644
index 0000000..12c0f8c
--- /dev/null
+++ b/internal/ring.go
@@ -0,0 +1,209 @@
+package internal
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"math"
+	"unsafe"
+)
+
+var errRingBufferFull = errors.New("tseq/ring: buffer full")
+
+// NewRing returns a new ring buffer ready for use.
+func NewRing(buf []byte) *Ring {
+	return &Ring{buf: buf}
+}
+
+// Ring implements basic Ring buffer functionality.
+type Ring struct {
+	buf []byte
+	off int
+	end int
+}
+
+// WriteString is a wrapper around [Ring.Write] that avoids allocation of converting byte slice to string.
+func (r *Ring) WriteString(s string) (int, error) {
+	return r.Write(unsafe.Slice(unsafe.StringData(s), len(s)))
+}
+
+// Write appends data to the ring buffer that can then be read back in order with [Ring.Read] methods. An error is returned if length of data too large for buffer.
+func (r *Ring) Write(b []byte) (int, error) {
+	free := r.Free()
+	if len(b) > free {
+		return 0, errRingBufferFull
+	}
+	midFree := r.midFree()
+	if midFree > 0 {
+		// start     end       off    len(buf)
+		//   |  used  |  mfree  |  used  |
+		n := copy(r.buf[r.end:r.off], b)
+		r.end += n
+		return n, nil
+	}
+	// start       off       end      len(buf)
+	//   |  sfree   |  used   |  efree   |
+	n := copy(r.buf[r.end:], b)
+	r.end += n
+	if n < len(b) {
+		n2 := copy(r.buf, b[n:])
+		r.end = n2
+		n += n2
+	}
+	return n, nil
+}
+
+// ReadDiscard is a performance auxiliary method that performs a dummy read or no-op read
+// for advancing the read pointer n bytes without actually copying data.
+// This method panics if amount of bytes is more than buffered (see [Ring.Buffered]).
+func (r *Ring) ReadDiscard(n int) {
+	if n < 0 {
+		panic("negative discard amount")
+	}
+	buffered := r.Buffered()
+	switch {
+	case n > buffered:
+		panic("discard exceeds length")
+	case n == buffered:
+		r.Reset()
+	case n+r.off > len(r.buf):
+		r.off = n - (len(r.buf) - r.off)
+	default:
+		r.off += n
+	}
+}
+
+// ReadAt reads data at an offset from start of readable data but does not advance read pointer. [io.EOF] returned when no data available.
+func (r *Ring) ReadAt(p []byte, off64 int64) (int, error) {
+	if math.MaxInt != math.MaxInt64 && off64+int64(len(p)) > math.MaxInt32 {
+		return 0, errors.New("offset too large (32 bit overflow)") // Check only compiles for 32-bit platforms.
+	}
+	off := int(off64)
+	if off+len(p) > r.Buffered() {
+		return 0, io.ErrUnexpectedEOF
+	}
+	r2 := *r
+	r2.off = (r2.off + off) % (r.Size())
+	return r2.ReadPeek(p)
+}
+
+// ReadPeek reads up to len(b) bytes from the ring buffer but does not advance the read pointer. [io.EOF] returned when no data available.
+func (r *Ring) ReadPeek(b []byte) (int, error) {
+	n, _, err := r.read(b)
+	return n, err
+}
+
+// Read reads up to len(b) bytes from the ring buffer and advances the read pointer. [io.EOF] returned when no data available.
+func (r *Ring) Read(b []byte) (int, error) {
+	n, newOff, err := r.read(b)
+	if err != nil {
+		return n, err
+	}
+	r.off = newOff
+	r.onReadEnd()
+	return n, nil
+}
+
+func (r *Ring) read(b []byte) (n, newOff int, err error) {
+	newOff = r.off
+	if r.Buffered() == 0 {
+		return 0, newOff, io.EOF
+	}
+	if r.end > r.off {
+		// start       off       end      len(buf)
+		//   |  sfree   |  used   |  efree   |
+		n = copy(b, r.buf[r.off:r.end])
+		newOff += n
+		return n, newOff, nil
+	}
+	// start     end       off     len(buf)
+	//   |  used  |  mfree  |  used  |
+	n = copy(b, r.buf[r.off:])
+	newOff += n
+	if n < len(b) {
+		n2 := copy(b[n:], r.buf[:r.end])
+		newOff = n2
+		n += n2
+	}
+	return n, newOff, nil
+}
+
+// Reset flushes all data from ring buffer so that no data can be further read.
+func (r *Ring) Reset() {
+	r.off = 0
+	r.end = 0
+}
+
+// Size returns the capacity of the ring buffer.
+func (r *Ring) Size() int {
+	return len(r.buf)
+}
+
+// Buffered returns amount of bytes ready to read from ring buffer. Always less than [ring.Size].
+func (r *Ring) Buffered() int {
+	return r.Size() - r.Free()
+}
+
+// Free returns amount of bytes that can be read into ring buffer before reaching maximum capacity given by [ring.Size]. Always less than [ring.Size].
+func (r *Ring) Free() int {
+	if r.off == 0 {
+		return len(r.buf) - r.end
+	}
+
+	if r.off < r.end {
+		// start       off       end      len(buf)
+		//   |  sfree   |  used   |  efree   |
+		startFree := r.off
+		endFree := len(r.buf) - r.end
+		return startFree + endFree
+	}
+	// start     end       off     len(buf)
+	//   |  used  |  mfree  |  used  |
+	return r.off - r.end
+}
+
+func (r *Ring) midFree() int {
+	if r.end >= r.off {
+		return 0
+	}
+	return r.off - r.end
+}
+
+// onReadEnd does some cleanup of [ring.off] and [ring.end] fields if possible for contiguous read performance benefits.
+func (r *Ring) onReadEnd() {
+	if r.end == len(r.buf) {
+		r.end = 0 // Wrap around.
+	}
+	if r.off == len(r.buf) {
+		r.off = 0 // Wrap around.
+	}
+	if r.off == r.end {
+		r.Reset() // We read everything, reset.
+	}
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func (r *Ring) string() string {
+	var b bytes.Buffer
+	r2 := *r
+	b.ReadFrom(&r2)
+	return b.String()
+}
+
+func (r *Ring) _string(off int64) string {
+	s := r.string()
+	return s[off:]
+}
diff --git a/internal/ring_test.go b/internal/ring_test.go
new file mode 100644
index 0000000..e468a18
--- /dev/null
+++ b/internal/ring_test.go
@@ -0,0 +1,317 @@
+package internal
+
+import (
+	"bytes"
+	"io"
+	"math/rand"
+	"testing"
+)
+
+func TestRing(t *testing.T) {
+	rng := rand.New(rand.NewSource(0))
+	const bufSize = 10
+	r := &Ring{
+		buf: make([]byte, bufSize),
+	}
+	const data = "hello"
+	_, err := r.WriteString(data)
+	if err != nil {
+		t.Error(err)
+	}
+	// Case where data is contiguous and at start of buffer.
+	var buf [bufSize]byte
+	n, err := fragmentReadInto(r, buf[:])
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(buf[:n]) != data {
+		t.Fatalf("got %q; want %q", buf[:n], data)
+	}
+
+	// Case where data overwrites end of buffer.
+	const overdata = "hello world"
+	n, err = r.Write([]byte(overdata))
+	if err == nil || n > 0 {
+		t.Fatal(err, n)
+	}
+
+	// Set Random data in ring buffer and read it back.
+	for i := 0; i < 32; i++ {
+		n := rng.Intn(bufSize)
+		copy(buf[:], overdata[:n])
+		offset := rng.Intn(bufSize - 1)
+		setRingData(t, r, offset, buf[:n])
+
+		// Case where data wraps around end of buffer.
+		n, err = r.Read(buf[:])
+		if err != nil {
+			break
+		}
+		if string(buf[:n]) != overdata[:n] {
+			t.Error("got", buf[:n], "want", overdata[:n])
+		}
+	}
+
+	// Set random data and write some more and read it back.
+	for i := 0; i < 32; i++ {
+		nfirst := rng.Intn(bufSize) / 2
+		nsecond := rng.Intn(bufSize) / 2
+		if nfirst+nsecond > bufSize {
+			nfirst = bufSize - nsecond
+		}
+		offset := rng.Intn(bufSize - 1)
+
+		copy(buf[:], overdata[:nfirst])
+		setRingData(t, r, offset, buf[:nfirst])
+		// println("test", r.end, r.off, offset, r)
+		ngot, err := r.WriteString(overdata[nfirst : nfirst+nsecond])
+		if err != nil {
+			t.Fatal(err)
+		}
+		if ngot != nsecond {
+			t.Errorf("%d did not write data correctly: got %d; want %d", i, ngot, nsecond)
+		}
+		buf = [bufSize]byte{}
+		// Case where data wraps around end of buffer.
+		n, err = r.Read(buf[:])
+		if err != nil {
+			break
+		}
+
+		if n != nfirst+nsecond {
+			t.Errorf("got %d; want %d (%d+%d)", n, nfirst+nsecond, nfirst, nsecond)
+		}
+		if string(buf[:n]) != overdata[:n] {
+			t.Errorf("got %q; want %q", buf[:n], overdata[:n])
+		}
+	}
+
+	var readback [bufSize]byte
+	var zeros [bufSize]byte
+
+	// Set random data and write some more and read it back with ReadAt and ReadPeek and ReadDiscard.
+	for i := 0; i < 32; i++ {
+		nfirst := rng.Intn(len(data))/2 + 1 // write garbage data first.
+		nsecond := rng.Intn(len(data))/2 + 1
+		if nfirst+nsecond > bufSize {
+			nfirst = bufSize - nsecond
+		}
+		r.Reset()
+
+		randOff := rng.Intn(bufSize)
+		content := append([]byte{}, zeros[:nfirst]...)
+		content = append(content, data[:nsecond]...)
+		setRingData(t, r, randOff, content)
+		// Two-tap ReadPeek to make sure pointer not advanced.
+		for i := 0; i < 2; i++ {
+			n, err = r.ReadPeek(readback[:])
+			if err != nil && err != io.EOF {
+				t.Fatal("read failed", err)
+			} else if n != nfirst+nsecond {
+				t.Errorf("want!=got bytes read %d, %d", nfirst+nsecond, n)
+			} else if !bytes.Equal(readback[:nfirst], zeros[:nfirst]) {
+				t.Error("first section not match")
+			} else if !bytes.Equal(readback[nfirst:nfirst+nsecond], []byte(data[:nsecond])) {
+				t.Error("second section not match")
+			}
+		}
+
+		// Two-tap ReadAt to make sure pointer not advanced.
+		for i := 0; i < 2; i++ {
+			off := rng.Intn(nfirst + nsecond)
+			n, err = r.ReadAt(readback[:nfirst+nsecond-off], int64(off))
+
+			readat := readback[:n]
+			first := zeros[min(off, nfirst):nfirst]
+			secondOff := max(0, off-nfirst)
+			second := []byte(data[secondOff:nsecond])
+			gotSecond := readat[len(first):]
+			if err != nil && err != io.EOF {
+				t.Fatal("read failed", off, err)
+			} else if n != nfirst+nsecond-off {
+				t.Errorf("want!=got bytes read %d, %d", nfirst+nsecond-off, n)
+			} else if len(first) > 0 && !bytes.Equal(readat[:nfirst-off], first) {
+				t.Error("first section not match")
+			} else if len(second) > 0 && !bytes.Equal(gotSecond, second) {
+				t.Errorf("second section not match got=%q want=%q", gotSecond, second)
+			}
+		}
+
+		// ReadDiscard test.
+
+		discard := rng.Intn(nfirst+nsecond) + 1
+		r.ReadDiscard(discard)
+		n, err := r.Read(readback[:])
+		if err != nil && err != io.EOF {
+			t.Fatal(err)
+		}
+		wantN := nfirst + nsecond - discard
+		if wantN != n {
+			t.Errorf("Want %d bytes read, got %d", wantN, n)
+		}
+		if !bytes.Equal(readback[:n], content[discard:]) {
+			t.Errorf("want data read %q, got %q", content[discard:], readback[:n])
+		}
+	}
+
+	_ = r._string(0)
+}
+
+func TestRing2(t *testing.T) {
+	const maxsize = 6
+	const ntests = 800
+	rng := rand.New(rand.NewSource(0))
+	data := make([]byte, maxsize)
+	ringbuf := make([]byte, maxsize)
+	auxbuf := make([]byte, maxsize)
+	rng.Read(data)
+	// TODO(soypat): This test fails for greater ntests.
+	// It was not fixed because of a compiler bug: https://github.com/golang/go/issues/64854
+	// and since the benefits of the changes in this PR are already much better than what we previously had.
+	for i := 0; i < ntests; i++ {
+		dsize := max(rng.Intn(len(data)), 1)
+		if !testRing1_loopback(t, rng, ringbuf, data[:dsize], auxbuf) {
+			t.Fatalf("failed test %d", i)
+		}
+	}
+}
+
+func TestRing_findcrash(t *testing.T) {
+	const maxsize = 33
+	const ntests = 800000
+	r := Ring{
+		buf: make([]byte, maxsize*6),
+	}
+	rng := rand.New(rand.NewSource(0))
+	data := make([]byte, maxsize)
+
+	for i := 0; i < ntests; i++ {
+		free := r.Free()
+		if free < 0 {
+			t.Fatal("free < 0")
+		}
+		if rng.Intn(2) == 0 {
+			l := max(rng.Intn(len(data)), 1)
+			if l > free {
+				continue // Buffer full.
+			}
+			n, err := r.Write(data[:l])
+			expectFree := free - n
+			free = r.Free()
+			if n != l {
+				t.Fatal(i, "write failed", n, l, err)
+			} else if expectFree != free {
+				t.Fatal(i, "free not updated correctly", expectFree, free)
+			}
+		}
+		buffered := r.Buffered()
+		if buffered < 0 {
+			t.Fatal("buffered < 0")
+		}
+		if rng.Intn(2) == 0 {
+			l := max(rng.Intn(len(data)), 1)
+			n, err := r.Read(data[:l])
+			expectRead := min(buffered, l)
+			expectBuffered := buffered - n
+			buffered = r.Buffered()
+			if n != expectRead {
+				t.Fatal(i, "read failed", n, l, expectRead, err)
+			} else if buffered != expectBuffered {
+				t.Fatal(i, "buffered not updated correctly", expectBuffered, buffered)
+			}
+		}
+	}
+}
+
+func testRing1_loopback(t *testing.T, rng *rand.Rand, ringbuf, data, auxbuf []byte) bool {
+	if len(data) > len(ringbuf) || len(data) > len(auxbuf) {
+		panic("invalid ringbuf or data")
+	}
+	dsize := len(data)
+	var r Ring
+	r.buf = ringbuf
+
+	nfirst := rng.Intn(dsize) / 2
+	nsecond := rng.Intn(dsize) / 2
+	if nfirst == 0 || nsecond == 0 {
+		return true
+	}
+	offset := rng.Intn(dsize - 1)
+
+	setRingData(t, &r, offset, data[:nfirst])
+	ngot, err := r.Write(data[nfirst : nfirst+nsecond])
+	if err != nil {
+		t.Error(err)
+		return false
+	}
+	if ngot != nsecond {
+		t.Errorf("did not write data correctly: got %d; want %d", ngot, nsecond)
+	}
+	// Case where data wraps around end of buffer.
+	n, err := r.Read(auxbuf[:])
+	if err != nil {
+		t.Error(err)
+		return false
+	}
+
+	if n != nfirst+nsecond {
+		t.Errorf("got %d; want %d (%d+%d)", n, nfirst+nsecond, nfirst, nsecond)
+	}
+	if !bytes.Equal(auxbuf[:n], data[:n]) {
+		t.Errorf("got %q; want %q", auxbuf[:n], data[:n])
+	}
+	return !t.Failed()
+}
+
+func fragmentReadInto(r io.Reader, buf []byte) (n int, _ error) {
+	maxSize := len(buf) / 4
+	for {
+		ntop := min(n+rand.Intn(maxSize)+1, len(buf))
+		ngot, err := r.Read(buf[n:ntop])
+		n += ngot
+		if err != nil {
+			if err == io.EOF {
+				return n, nil
+			}
+			return n, err
+		}
+		if n == len(buf) {
+			return n, nil
+		}
+	}
+}
+
+func setRingData(t *testing.T, r *Ring, offset int, data []byte) {
+	t.Helper()
+	if len(data) > len(r.buf) {
+		panic("data too large")
+	}
+	n := copy(r.buf[offset:], data)
+	r.end = offset + n
+	if len(data)+offset > len(r.buf) {
+		// End of buffer not enough to hold data, wrap around.
+		n = copy(r.buf, data[n:])
+		r.end = n
+	}
+	r.off = offset
+	r.onReadEnd()
+	// println("buf:", len(r.buf), "end:", r.end, "off:", r.off, offset, "data:", len(data))
+	free := r.Free()
+	wantFree := len(r.buf) - len(data)
+	if free != wantFree {
+		t.Fatalf("free got %d; want %d", free, wantFree)
+	}
+	buffered := r.Buffered()
+	wantBuffered := len(data)
+	if buffered != wantBuffered {
+		t.Fatalf("buffered got %d; want %d", buffered, wantBuffered)
+	}
+	end := r.end
+	off := r.off
+	sdata := r.string()
+	if sdata != string(data) {
+		t.Fatalf("data got %q; want %q", sdata, data)
+	}
+	r.end = end
+	r.off = off
+}