func NewWriter(w io.Writer) *Writer {
	return NewWriterLevelDict(w, DefaultCompression, nil)
}
NewWriter creates a new Writer with default compression options.  Writes to
the writer will be written in compressed form to w.
package zstd
import "C"
import (
	"errors"
	"fmt"
	"io"
	"unsafe"
)
var errShortRead = errors.New("short read")
type Writer struct {
	CompressionLevel int
	ctx              *C.ZSTD_CCtx
	dict             []byte
	dstBuffer        []byte
	firstError       error
	underlyingWriter io.Writer
}
func resize(in []byte, newSize int) []byte {
	if in == nil {
		return make([]byte, newSize)
	}
	if newSize <= cap(in) {
		return in[:newSize]
	}
	toAdd := newSize - len(in)
	return append(in, make([]byte, toAdd)...)
}