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/*
* Copyright 2015 Manish R Jain <manishrjain@gmail.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package commit
import (
"errors"
"io"
"io/ioutil"
"sync"
)
var E_WRITE = errors.New("Unable to write")
type Cache struct {
sync.RWMutex
buf []byte
}
func (c *Cache) Write(p []byte) (n int, err error) {
c.Lock()
defer c.Unlock()
c.buf = append(c.buf, p...)
return len(p), nil
}
func (c *Cache) ReadAt(pos int, p []byte) (n int, err error) {
c.RLock()
defer c.RUnlock()
if len(c.buf[pos:]) == 0 {
return 0, io.EOF
}
n = copy(p, c.buf[pos:])
return n, nil
}
// Reader isn't thread-safe. But multiple readers can be used to read the
// same cache.
type Reader struct {
c *Cache
pos int
}
func NewReader(c *Cache) *Reader {
r := new(Reader)
r.c = c
return r
}
func (r *Reader) Read(p []byte) (n int, err error) {
n, err = r.c.ReadAt(r.pos, p)
r.pos += n
return
}
func (r *Reader) Discard(n int) {
r.pos += n
}
func FillCache(c *Cache, path string) error {
buf, err := ioutil.ReadFile(path)
if err != nil {
return err
}
n, err := c.Write(buf)
if err != nil {
return err
}
if n < len(buf) {
return E_WRITE
}
return nil
}