/
pager.go
92 lines (80 loc) · 1.36 KB
/
pager.go
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package _se
import (
"bufio"
"errors"
"io"
)
var page [pageSize]byte
var fakeHeader = [headerSize]byte{
0xff, 0xff, 0xff,
}
type PageWriter struct {
bw *bufio.Writer
}
func NewPageWriter(w io.Writer) *PageWriter {
return &PageWriter{
bw: bufio.NewWriterSize(w, pageSize),
}
}
func (pw *PageWriter) Write(p []byte) (int, error) {
var nn int
// write header
n, err := pw.bw.Write(fakeHeader[:])
if err != nil {
return -1, err
}
nn += n
// write data
n, err = pw.bw.Write(p)
if err != nil {
return -1, err
}
nn += n
padding := pageSize - nn%pageSize
// write padding
if padding != 0 {
n, err = pw.bw.Write(page[:padding])
if err != nil {
return -1, err
}
nn += n
}
return nn, nil
}
func (pw *PageWriter) Flush() error {
err := pw.bw.Flush()
if err != nil {
return err
}
return nil
}
type PageReader struct {
br *bufio.Reader
}
func NewPageReader(r io.Reader) *PageReader {
return &PageReader{
br: bufio.NewReaderSize(r, pageSize),
}
}
var ErrBadSize = errors.New("bad size")
func (pr *PageReader) Read(p []byte) (int, error) {
if len(p)%pageSize != 0 {
return -1, ErrBadSize
}
var nn int
// read header
n, err := pr.br.Read(p[:headerSize])
if err != nil {
return -1, err
}
nn += n
// decode and err check header
//
// read data
n, err = pr.br.Read(p[nn:])
if err != nil {
return -1, err
}
nn += n
return nn, nil
}