100 lines
2.1 KiB
Go
100 lines
2.1 KiB
Go
package buffer
|
|
|
|
import (
|
|
"encoding/gob"
|
|
"io"
|
|
)
|
|
|
|
type swap struct {
|
|
A BufferAt
|
|
B BufferAt
|
|
}
|
|
|
|
// NewSwap creates a Buffer which writes to a until you write past a.Cap()
|
|
// then it io.Copy's from a to b and writes to b.
|
|
// Once the Buffer is empty again, it starts over writing to a.
|
|
// Note that if b.Cap() <= a.Cap() it will cause a panic, b is expected
|
|
// to be larger in order to accommodate writes past a.Cap().
|
|
func NewSwap(a, b Buffer) Buffer {
|
|
return NewSwapAt(toBufferAt(a), toBufferAt(b))
|
|
}
|
|
|
|
// NewSwapAt creates a BufferAt which writes to a until you write past a.Cap()
|
|
// then it io.Copy's from a to b and writes to b.
|
|
// Once the Buffer is empty again, it starts over writing to a.
|
|
// Note that if b.Cap() <= a.Cap() it will cause a panic, b is expected
|
|
// to be larger in order to accommodate writes past a.Cap().
|
|
func NewSwapAt(a, b BufferAt) BufferAt {
|
|
if b.Cap() <= a.Cap() {
|
|
panic("Buffer b must be larger than a.")
|
|
}
|
|
return &swap{A: a, B: b}
|
|
}
|
|
|
|
func (buf *swap) Len() int64 {
|
|
return buf.A.Len() + buf.B.Len()
|
|
}
|
|
|
|
func (buf *swap) Cap() int64 {
|
|
return buf.B.Cap()
|
|
}
|
|
|
|
func (buf *swap) Read(p []byte) (n int, err error) {
|
|
if buf.A.Len() > 0 {
|
|
return buf.A.Read(p)
|
|
}
|
|
return buf.B.Read(p)
|
|
}
|
|
|
|
func (buf *swap) ReadAt(p []byte, off int64) (n int, err error) {
|
|
if buf.A.Len() > 0 {
|
|
return buf.A.ReadAt(p, off)
|
|
}
|
|
return buf.B.ReadAt(p, off)
|
|
}
|
|
|
|
func (buf *swap) Write(p []byte) (n int, err error) {
|
|
switch {
|
|
case buf.B.Len() > 0:
|
|
n, err = buf.B.Write(p)
|
|
|
|
case buf.A.Len()+int64(len(p)) > buf.A.Cap():
|
|
_, err = io.Copy(buf.B, buf.A)
|
|
if err == nil {
|
|
n, err = buf.B.Write(p)
|
|
}
|
|
|
|
default:
|
|
n, err = buf.A.Write(p)
|
|
}
|
|
|
|
return n, err
|
|
}
|
|
|
|
func (buf *swap) WriteAt(p []byte, off int64) (n int, err error) {
|
|
switch {
|
|
case buf.B.Len() > 0:
|
|
n, err = buf.B.WriteAt(p, off)
|
|
|
|
case off+int64(len(p)) > buf.A.Cap():
|
|
_, err = io.Copy(buf.B, buf.A)
|
|
if err == nil {
|
|
n, err = buf.B.WriteAt(p, off)
|
|
}
|
|
|
|
default:
|
|
n, err = buf.A.WriteAt(p, off)
|
|
}
|
|
|
|
return n, err
|
|
}
|
|
|
|
func (buf *swap) Reset() {
|
|
buf.A.Reset()
|
|
buf.B.Reset()
|
|
}
|
|
|
|
func init() {
|
|
gob.Register(&swap{})
|
|
}
|