/
seekingbuffer.go
61 lines (54 loc) · 1.13 KB
/
seekingbuffer.go
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// 参考: https://groups.google.com/forum/#!topic/golang-nuts/mOvX0bmJoeI
package main
import (
"bytes"
"fmt"
"io"
"os"
)
type SeekingBuffer struct {
b []byte
buffer *bytes.Buffer
offset int64
size int64
}
func NewSeekingBuffer(b []byte) *SeekingBuffer {
if b == nil {
return nil
}
return &SeekingBuffer{
b: b,
buffer: bytes.NewBuffer(b),
offset: 0,
}
}
func (fb *SeekingBuffer) Read(p []byte) (n int, err error) {
n, err = fb.buffer.Read(p)
fb.offset += int64(n)
return n, err
}
func (fb *SeekingBuffer) Seek(offset int64, whence int) (ret int64, err error) {
var newoffset int64
switch whence {
case 0:
newoffset = offset
case 1:
newoffset = fb.offset+offset
case 2:
newoffset = int64(len(fb.b))-offset
}
if newoffset == fb.offset {
return newoffset, nil
}
fb.buffer = bytes.NewBuffer(fb.b[newoffset:])
fb.offset = newoffset
return fb.offset, nil
}
func main() {
fb := NewSeekingBuffer([]byte("Hello, playground"))
pos, err := fb.Seek(0, 0)
fmt.Println("pos = ", pos, ", error = ", err)
pos, err = fb.Seek(7, 0)
fmt.Println("pos = ", pos, ", error = ", err)
io.Copy(os.Stdout, fb)
}