put docbuf into an external pkg

Signed-off-by: Ava Affine <ava@sunnypup.io>

internal/docbuf/read_write_seek_string.go

@@ -1,100 +0,0 @@
-package docbuf
-
-import (
-	"errors"
-	"io"
-	"fmt"
-)
-
-/* WARNING:
- * This code is meant to assist with testing and mock ups
- * It is not only not designed to any rigorous standards,
- * but additionally does not offer any benefit over a static
- * in memory single layer cache.
- */
-
-type ReadWriteSeekString struct {
-	inner  string
-	cursor int
-}
-
-func NewReadWriteSeekString() ReadWriteSeekString{
-	return ReadWriteSeekString{
-		inner: "",
-		cursor: 0,
-	}
-}
-
-func (s *ReadWriteSeekString) Read(
-	buf []byte,
-) (int, error) {
-	i := 0
-	for ; i < len(buf); i++ {
-		if len(s.inner) <= s.cursor {
-			return i, nil
-		}
-		buf[i] = s.inner[s.cursor]
-		s.cursor += 1
-	}
-	return i, nil
-}
-
-func (s *ReadWriteSeekString) Write(
-	buf []byte,
-) (int, error) {
-	backfillDelta := s.cursor - (len(s.inner) - 1)
-	if backfillDelta > 0 {
-		for range backfillDelta {
-			s.inner += "\x00"
-		}
-	}
-
-	tmpBuf := ""
-	if s.cursor > 0 {
-		tmpBuf += s.inner[:s.cursor]
-	}
-	tmpBuf += string(buf)
-	if s.cursor + len(buf) < (len(s.inner) - 1) {
-		tmpBuf += s.inner[s.cursor + len(buf):]
-	}
-
-	s.inner = tmpBuf
-	s.cursor += len(buf)
-	return len(buf), nil
-}
-
-func (s *ReadWriteSeekString) Seek(
-	offset int64,
-	whence int,
-) (int64, error) {
-	var tmpCur int64
-	tmpCur = 0
-
-	switch whence {
-	case io.SeekCurrent:
-		tmpCur = int64(s.cursor)
-	case io.SeekEnd:
-		tmpCur = int64(len(s.inner))
-	case io.SeekStart:
-		tmpCur = int64(0)
-	default:
-		return int64(s.cursor),
-			errors.New("invalid whence value")
-	}
-
-	tmpCur += offset
-	if tmpCur < 0 {
-		msg := fmt.Sprintf("seek index (%d) is negative", tmpCur)
-		return int64(s.cursor), errors.New(msg)
-	}
-	s.cursor = int(tmpCur)
-	return tmpCur, nil
-}
-
-func (s *ReadWriteSeekString) Contents() string {
-	return s.inner
-}
-
-func (s *ReadWriteSeekString) Cursor() int {
-	return s.cursor
-}