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package test
import (
"encoding/hex"
"io"
)
type MemDisk struct {
data [][]byte
size int64
woff, roff int
}
func NewMemDisk() *MemDisk {
return &MemDisk{}
}
func (w *MemDisk) Write(b []byte) (int, error) {
n, err := w.WriteAt(b, int64(w.woff))
w.woff += n
return n, err
}
func (w *MemDisk) getData(off int64) []byte {
idx := int(off >> 20)
if idx >= cap(w.data) {
newdata := make([][]byte, idx+1)
copy(newdata, w.data)
w.data = newdata
}
if len(w.data[idx]) == 0 {
w.data[idx] = make([]byte, 1<<20)
}
return w.data[idx][off&((1<<20)-1):]
}
func (w *MemDisk) WriteAt(b []byte, off int64) (int, error) {
n := len(b)
for len(b) > 0 {
buf := w.getData(off)
m := copy(buf, b)
if off+int64(m) > w.size {
w.size = off + int64(m)
}
b = b[m:]
off += int64(m)
}
return n, nil
}
func (w *MemDisk) ReadAt(b []byte, off int64) (int, error) {
byteRead := 0
for byteRead < len(b) {
if off >= w.size {
return 0, io.EOF
}
buf := w.getData(off)
if int64(len(buf))+off > w.size {
buf = buf[:w.size-off]
}
if len(buf) == 0 {
return byteRead, io.EOF
}
n := copy(b[byteRead:], buf)
off += int64(n)
byteRead += n
}
return byteRead, nil
}
func (w *MemDisk) Dump() string {
return hex.Dump(w.getData(0))
}
func (w *MemDisk) SeekRead(offset int64, whence int) (ret int64) {
switch whence {
case 0:
w.roff += int(offset)
case 1:
w.roff = int(offset)
default:
}
return int64(w.roff)
}
func (w *MemDisk) SeekWrite(offset int64, whence int) (ret int64) {
switch whence {
case 0:
w.woff += int(offset)
case 1:
w.woff = int(offset)
default:
}
return int64(w.woff)
}
func (w *MemDisk) Read(b []byte) (int, error) {
n, err := w.ReadAt(b, int64(w.roff))
w.roff += n
return n, err
}
func (w *MemDisk) Close() error {
return nil
}
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