Add zero-copy serialization APIs.

buffer.go

@@ -8,6 +8,7 @@ import "C"
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"math"
 	"runtime"
 	"unsafe"
@@ -94,6 +95,8 @@ func (b *Buffer) Type() (Datatype, error) {
 }
 
 // Serialize returns a copy of the bytes in the buffer.
+//
+// Deprecated: Use WriteTo instead for increased performance.
 func (b *Buffer) Serialize(serializationType SerializationType) ([]byte, error) {
 	bs, err := b.dataCopy()
 	if err != nil {
@@ -103,14 +106,101 @@ func (b *Buffer) Serialize(serializationType SerializationType) ([]byte, error)
 	case TILEDB_CAPNP:
 		// The entire byte array contains Cap'nP data. Don't bother it.
 	case TILEDB_JSON:
-		// The data is a null-terminated string. Strip off the terminator.
+		// The data might be a null-terminated string. Strip off the terminator.
 		bs = bytes.TrimSuffix(bs, []byte{0})
 	default:
 		return nil, fmt.Errorf("unsupported serialization type: %v", serializationType)
 	}
 	return bs, nil
 }
 
+// ReadAt writes the contents of a Buffer at a given offset to a slice.
+func (b *Buffer) ReadAt(p []byte, off int64) (int, error) {
+	if off < 0 {
+		return 0, fmt.Errorf("offset cannot be negative")
+	}
+
+	var cbuffer unsafe.Pointer
+	var csize C.uint64_t
+
+	ret := C.tiledb_buffer_get_data(b.context.tiledbContext, b.tiledbBuffer, &cbuffer, &csize)
+	if ret != C.TILEDB_OK {
+		return 0, fmt.Errorf("error getting tiledb buffer data: %w", b.context.LastError())
+	}
+
+	if uintptr(off) > uintptr(csize) {
+		return 0, fmt.Errorf("offset cannot be greater than buffer size")
+	}
+
+	if cbuffer == nil || csize == 0 {
+		return 0, nil
+	}
+
+	availableBytes := uint64(csize) - uint64(off)
+	var sizeToRead int
+	if availableBytes > math.MaxInt {
+		sizeToRead = math.MaxInt
+	} else {
+		sizeToRead = int(availableBytes)
+	}
+
+	readSize := copy(p, unsafe.Slice((*byte)(unsafe.Pointer(uintptr(cbuffer)+uintptr(off))), sizeToRead))
+
+	var err error
+	if int64(readSize)+off == int64(csize) {
+		err = io.EOF
+	}
+
+	return readSize, err
+}
+
+// WriteTo writes the contents of a Buffer to an io.Writer.
+func (b *Buffer) WriteTo(w io.Writer) (int64, error) {
+	var cbuffer unsafe.Pointer
+	var csize C.uint64_t
+
+	ret := C.tiledb_buffer_get_data(b.context.tiledbContext, b.tiledbBuffer, &cbuffer, &csize)
+	if ret != C.TILEDB_OK {
+		return 0, fmt.Errorf("error getting tiledb buffer data: %w", b.context.LastError())
+	}
+
+	if cbuffer == nil || csize == 0 {
+		return 0, nil
+	}
+
+	remaining := int64(csize)
+
+	// Because io.Writer supports writing up to 2GB of data at a time, we have to use a loop
+	// for the bigger buffers.
+	for remaining > 0 {
+		// TODO: Use min on Go 1.21+
+		var writeSize int
+		if remaining > math.MaxInt {
+			writeSize = math.MaxInt
+		} else {
+			writeSize = int(remaining)
+		}
+
+		// Construct a slice from the buffer's data without copying it.
+		// Keep the buffer alive during the write, to prevent the GC from
+		// collecting the memory while it's being used.
+		n, err := w.Write(unsafe.Slice((*byte)(cbuffer), writeSize))
+
+		cbuffer = unsafe.Pointer(uintptr(cbuffer) + uintptr(n))
+		remaining -= int64(n)
+
+		if err != nil {
+			return int64(csize) - remaining, fmt.Errorf("error writing buffer to writer: %w", err)
+		}
+	}
+
+	return int64(csize), nil
+}
+
+// Static assert that Buffer implements io.WriterTo.
+var _ io.WriterTo = (*Buffer)(nil)
+var _ io.ReaderAt = (*Buffer)(nil)
+
 // SetBuffer sets the buffer to point at the given Go slice. The memory is now
 // Go-managed.
 func (b *Buffer) SetBuffer(buffer []byte) error {

buffer_list.go

@@ -7,6 +7,7 @@ package tiledb
 import "C"
 import (
 	"fmt"
+	"io"
 )
 
 // BufferList A list of TileDB BufferList objects
@@ -44,6 +45,36 @@ func (b *BufferList) Context() *Context {
 	return b.context
 }
 
+// WriteTo writes the contents of a BufferList to an io.Writer.
+func (b *BufferList) WriteTo(w io.Writer) (int64, error) {
+	nbuffs, err := b.NumBuffers()
+	if err != nil {
+		return 0, err
+	}
+
+	written := int64(0)
+
+	for i := uint(0); i < uint(nbuffs); i++ {
+		buff, err := b.GetBuffer(i)
+		if err != nil {
+			return 0, err
+		}
+		n, err := buff.WriteTo(w)
+		written += n
+
+		buff.Free()
+
+		if err != nil {
+			return written, err
+		}
+	}
+
+	return written, nil
+}
+
+// Static assert that BufferList implements io.WriterTo.
+var _ io.WriterTo = (*BufferList)(nil)
+
 // NumBuffers returns number of buffers in the list.
 func (b *BufferList) NumBuffers() (uint64, error) {
 	var numBuffers C.uint64_t
@@ -82,6 +113,8 @@ func (b *BufferList) TotalSize() (uint64, error) {
 }
 
 // Flatten copies and concatenates all buffers in the list into a new buffer.
+//
+// Deprecated: Use WriteTo instead for increased performance.
 func (b *BufferList) Flatten() (*Buffer, error) {
 	buffer := Buffer{context: b.context}
 	freeOnGC(&buffer)

buffer_test.go

@@ -2,6 +2,7 @@ package tiledb
 
 import (
 	"fmt"
+	"io"
 	"runtime"
 	"testing"
 
@@ -95,3 +96,60 @@ func TestBufferSafety(t *testing.T) {
 	t.Log("post gc 2")
 	verify()
 }
+
+type ByteCounter struct {
+	BytesWritten int64
+}
+
+func (b *ByteCounter) Write(x []byte) (int, error) {
+	b.BytesWritten += int64(len(x))
+	return len(x), nil
+}
+
+func TestWriteTo(t *testing.T) {
+	context, err := NewContext(nil)
+	require.NoError(t, err)
+	buffer, err := NewBuffer(context)
+	require.NoError(t, err)
+
+	testSizes := [5]int{0, 16, 256, 65536, 268435456}
+	for _, size := range testSizes {
+		err := buffer.SetBuffer(make([]byte, size))
+		require.NoError(t, err)
+
+		counter := new(ByteCounter)
+		n, err := buffer.WriteTo(counter)
+		require.NoError(t, err)
+		assert.Equal(t, size, int(n))
+	}
+}
+
+func TestReadAt(t *testing.T) {
+	context, err := NewContext(nil)
+	require.NoError(t, err)
+	buffer, err := NewBuffer(context)
+	require.NoError(t, err)
+
+	testSizes := [4]int{16, 256, 65536, 268435456}
+	for _, size := range testSizes {
+		err := buffer.SetBuffer(make([]byte, size))
+		require.NoError(t, err)
+
+		readBuffer := make([]byte, 10)
+		n, err := buffer.ReadAt(readBuffer, 0)
+		require.NoError(t, err)
+		require.Equal(t, 10, n)
+
+		n, err = buffer.ReadAt(readBuffer, int64(size-10))
+		require.Equal(t, io.EOF, err)
+		require.Equal(t, 10, n)
+
+		n, err = buffer.ReadAt(readBuffer, int64(size-5))
+		require.Equal(t, io.EOF, err)
+		require.Equal(t, 5, n)
+
+		n, err = buffer.ReadAt(readBuffer, int64(size))
+		require.Equal(t, io.EOF, err)
+		require.Equal(t, 0, n)
+	}
+}

group.go

@@ -436,38 +436,6 @@ func (g *Group) Dump(recurse bool) (string, error) {
 	return C.GoString(cOutput), nil
 }
 
-// SerializeGroupMetadata gets and serializes the group metadata
-func SerializeGroupMetadata(g *Group, serializationType SerializationType) ([]byte, error) {
-	buffer := Buffer{context: g.context}
-	freeOnGC(&buffer)
-
-	ret := C.tiledb_serialize_group_metadata(g.context.tiledbContext, g.group, C.tiledb_serialization_type_t(serializationType), &buffer.tiledbBuffer)
-	if ret != C.TILEDB_OK {
-		return nil, fmt.Errorf("Error serializing group metadata: %s", g.context.LastError())
-	}
-
-	return buffer.Serialize(serializationType)
-}
-
-// DeserializeGroupMetadata deserializes group metadata
-func DeserializeGroupMetadata(g *Group, buffer *Buffer, serializationType SerializationType) error {
-	b, err := buffer.dataCopy()
-	if err != nil {
-		return errors.New("failed to retrieve bytes from buffer")
-	}
-	// cstrings are null terminated. Go's are not, add it as a suffix
-	if err := buffer.SetBuffer(append(b, []byte("\u0000")...)); err != nil {
-		return errors.New("failed to add null terminator to buffer")
-	}
-
-	ret := C.tiledb_deserialize_group_metadata(g.context.tiledbContext, g.group, C.tiledb_serialization_type_t(serializationType), buffer.tiledbBuffer)
-	if ret != C.TILEDB_OK {
-		return fmt.Errorf("Error deserializing group metadata: %s", g.context.LastError())
-	}
-
-	return nil
-}
-
 // GetIsRelativeURIByName returns whether a named member of the group has a uri relative to the group
 func (g *Group) GetIsRelativeURIByName(name string) (bool, error) {
 	cName := C.CString(name)