chore: create buftest package

pkg/btree/bptree_test.go

@@ -4,6 +4,8 @@ import (
 	"encoding/binary"
 	"math/rand"
 	"testing"
+
+	"github.com/kevmo314/appendable/pkg/buftest"
 )
 
 type testMetaPage struct {
@@ -21,7 +23,7 @@ func (m *testMetaPage) Root() (MemoryPointer, error) {
 
 func TestBPTree(t *testing.T) {
 	t.Run("empty tree", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -38,7 +40,7 @@ func TestBPTree(t *testing.T) {
 	})
 
 	t.Run("insert creates a root", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -60,7 +62,7 @@ func TestBPTree(t *testing.T) {
 	})
 
 	t.Run("insert into root", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -95,7 +97,7 @@ func TestBPTree(t *testing.T) {
 	})
 
 	t.Run("split root", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -156,7 +158,7 @@ func TestBPTree(t *testing.T) {
 	})
 
 	t.Run("split intermediate", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -180,7 +182,7 @@ func TestBPTree(t *testing.T) {
 	})
 
 	t.Run("insertion test", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -210,7 +212,7 @@ func TestBPTree(t *testing.T) {
 	})
 
 	t.Run("random insertion test", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -246,7 +248,7 @@ func TestBPTree(t *testing.T) {
 	})
 
 	// t.Run("bulk insert", func(t *testing.T) {
-	// 	b := newSeekableBuffer()
+	// 	b := buftest.NewSeekableBuffer()
 	// 	tree :=NewBPTree(b, 2)
 	// 	if err != nil {
 	// 		t.Fatal(err)

pkg/btree/multi_test.go

@@ -3,11 +3,13 @@ package btree
 import (
 	"reflect"
 	"testing"
+
+	"github.com/kevmo314/appendable/pkg/buftest"
 )
 
 func TestMultiBPTree(t *testing.T) {
 	t.Run("empty tree", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -23,7 +25,7 @@ func TestMultiBPTree(t *testing.T) {
 	})
 
 	t.Run("reset tree", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -46,7 +48,7 @@ func TestMultiBPTree(t *testing.T) {
 	})
 
 	t.Run("insert a second page", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -85,7 +87,7 @@ func TestMultiBPTree(t *testing.T) {
 	})
 
 	t.Run("duplicate next pointer", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -108,7 +110,7 @@ func TestMultiBPTree(t *testing.T) {
 	})
 
 	t.Run("starts with empty metadata", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)
@@ -127,7 +129,7 @@ func TestMultiBPTree(t *testing.T) {
 	})
 
 	t.Run("storing metadata works", func(t *testing.T) {
-		b := newSeekableBuffer()
+		b := buftest.NewSeekableBuffer()
 		p, err := NewPageFile(b)
 		if err != nil {
 			t.Fatal(err)

pkg/btree/pagefile_test.go

@@ -3,11 +3,13 @@ package btree
 import (
 	"io"
 	"testing"
+
+	"github.com/kevmo314/appendable/pkg/buftest"
 )
 
 func TestPageFile(t *testing.T) {
 	t.Run("allocates first page", func(t *testing.T) {
-		buf := newSeekableBuffer()
+		buf := buftest.NewSeekableBuffer()
 		pf, err := NewPageFile(buf)
 		if err != nil {
 			t.Fatal(err)
@@ -22,7 +24,7 @@ func TestPageFile(t *testing.T) {
 	})
 
 	t.Run("page size reuses page without allocation", func(t *testing.T) {
-		buf := newSeekableBuffer()
+		buf := buftest.NewSeekableBuffer()
 		pf, err := NewPageFile(buf)
 		if err != nil {
 			t.Fatal(err)
@@ -45,7 +47,7 @@ func TestPageFile(t *testing.T) {
 	})
 
 	t.Run("page size allocates second page", func(t *testing.T) {
-		buf := newSeekableBuffer()
+		buf := buftest.NewSeekableBuffer()
 		pf, err := NewPageFile(buf)
 		if err != nil {
 			t.Fatal(err)
@@ -71,7 +73,7 @@ func TestPageFile(t *testing.T) {
 	})
 
 	t.Run("new page seeks to page", func(t *testing.T) {
-		buf := newSeekableBuffer()
+		buf := buftest.NewSeekableBuffer()
 		pf, err := NewPageFile(buf)
 		if err != nil {
 			t.Fatal(err)
@@ -90,7 +92,7 @@ func TestPageFile(t *testing.T) {
 	})
 
 	t.Run("free page reuses page", func(t *testing.T) {
-		buf := newSeekableBuffer()
+		buf := buftest.NewSeekableBuffer()
 		pf, err := NewPageFile(buf)
 		if err != nil {
 			t.Fatal(err)

pkg/buftest/buffer.go

@@ -0,0 +1,91 @@
+package buftest
+
+import "io"
+
+// SeekableBuffer is a buffer that can be seeked into.
+// this replicates the behavior of a file on disk without having to write to disk
+// which is useful for testing.
+type SeekableBuffer struct {
+	buf []byte
+	pos int
+}
+
+func NewSeekableBuffer() *SeekableBuffer {
+	return &SeekableBuffer{}
+}
+
+func (b *SeekableBuffer) Write(p []byte) (int, error) {
+	n := copy(b.buf[b.pos:], p)
+	if n < len(p) {
+		b.buf = append(b.buf, p[n:]...)
+	}
+	b.pos += len(p)
+	return len(p), nil
+}
+
+func (b *SeekableBuffer) Seek(offset int64, whence int) (int64, error) {
+	switch whence {
+	case io.SeekStart:
+		b.pos = int(offset)
+	case io.SeekCurrent:
+		b.pos += int(offset)
+	case io.SeekEnd:
+		b.pos = len(b.buf) + int(offset)
+	}
+	if b.pos < 0 {
+		b.pos = 0
+	}
+	if b.pos > len(b.buf) {
+		b.pos = len(b.buf)
+	}
+	return int64(b.pos), nil
+}
+
+func (b *SeekableBuffer) Read(p []byte) (int, error) {
+	if b.pos >= len(b.buf) {
+		return 0, io.EOF
+	}
+	n := copy(p, b.buf[b.pos:])
+	b.pos += n
+	return n, nil
+}
+
+func (b *SeekableBuffer) Truncate(size int64) error {
+	if size < 0 {
+		return io.ErrShortBuffer
+	}
+	if size > int64(len(b.buf)) {
+		return io.ErrShortWrite
+	}
+	b.buf = b.buf[:size]
+	return nil
+}
+
+func (b *SeekableBuffer) WriteAt(p []byte, off int64) (int, error) {
+	if off < 0 {
+		return 0, io.ErrShortBuffer
+	}
+	if off > int64(len(b.buf)) {
+		return 0, io.ErrShortWrite
+	}
+	n := copy(b.buf[off:], p)
+	if n < len(p) {
+		b.buf = append(b.buf, p[n:]...)
+	}
+	return len(p), nil
+}
+
+func (b *SeekableBuffer) ReadAt(p []byte, off int64) (int, error) {
+	if off < 0 {
+		return 0, io.ErrShortBuffer
+	}
+	if off > int64(len(b.buf)) {
+		return 0, io.EOF
+	}
+	n := copy(p, b.buf[off:])
+	return n, nil
+}
+
+var _ io.ReadWriteSeeker = &SeekableBuffer{}
+var _ io.ReaderAt = &SeekableBuffer{}
+var _ io.WriterAt = &SeekableBuffer{}