1 files changed, 58 insertions, 0 deletions
diff --git a/fakefile.go b/fakefile.go
new file mode 100644
index 0000000..47ef529
--- /dev/null
+++ b/fakefile.go
@@ -0,0 +1,58 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"io"
+)
+
+type FakeFile struct {
+	reader *bytes.Reader
+	buffer *bytes.Buffer
+	offset int64
+}
+
+func (f *FakeFile) Read(p []byte) (n int, err error) {
+	n, err = f.reader.ReadAt(p, f.offset)
+	f.offset += int64(n)
+	return n, err
+}
+
+func (f *FakeFile) Write(p []byte) (n int, err error) {
+	n, err = f.buffer.Write(p)
+	f.offset += int64(n)
+	f.reader.Reset(f.buffer.Bytes())
+	return n, err
+}
+
+func (f *FakeFile) Seek(offset int64, whence int) (int64, error) {
+	newOffset := f.offset
+
+	switch whence {
+	case io.SeekStart:
+		newOffset = offset
+	case io.SeekCurrent:
+		newOffset += offset
+	case io.SeekEnd:
+		newOffset = int64(f.buffer.Len()) + offset
+	default:
+		return 0, errors.New("Seek: whence not at start,current or end")
+	}
+	// never can get here right?
+
+	if newOffset < 0 {
+		return 0, errors.New("Seek: offset < 0")
+	}
+
+	f.offset = newOffset
+	return f.offset, nil
+}
+
+func NewFakeFile() *FakeFile {
+	buf := &bytes.Buffer{}
+	return &FakeFile{
+		reader: bytes.NewReader(buf.Bytes()),
+		buffer: buf,
+		offset: 0,
+	}
+}