env: add skeleton of io.Reader wrapper

Signed-off-by: Alejandro Mery <amery@jpi.io>

env/reader.go

@@ -0,0 +1,55 @@
+package env
+
+import (
+	"bytes"
+	"io"
+	"os"
+)
+
+const (
+	MinimumBufferSize = 32
+	DefaultBufferSize = 4096
+)
+
+type Reader struct {
+	in  io.Reader
+	buf *bytes.Buffer
+	out *bytes.Buffer
+}
+
+func (rd *Reader) Read(b []byte) (int, error) {
+	return rd.in.Read(b)
+}
+
+//
+// Constructors
+//
+func NewReaderSize(in io.Reader, size int) *Reader {
+	if size < MinimumBufferSize {
+		size = DefaultBufferSize
+	}
+
+	return &Reader{
+		in:  in,
+		buf: bytes.NewBuffer(make([]byte, 0, size)),
+		out: bytes.NewBuffer(make([]byte, 0, size)),
+	}
+}
+
+func NewReader(in io.Reader) *Reader {
+	return NewReaderSize(in, DefaultBufferSize)
+}
+
+func NewReaderFileSize(filename string, size int) (*Reader, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	rd := NewReaderSize(f, size)
+	return rd, nil
+}
+
+func NewReaderFile(filename string) (*Reader, error) {
+	return NewReaderFileSize(filename, DefaultBufferSize)
+}