minio/pkg/objcache/capped-writer.go

51 lines
1.5 KiB
Go

/*
* Minio Cloud Storage, (C) 2016 Minio, Inc.
*
* 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 objcache implements in memory caching methods.
package objcache
// Used for adding entry to the object cache.
// Implements io.WriteCloser
type cappedWriter struct {
offset int64
cap int64
buffer []byte
onClose func() error
}
// Write implements a limited writer, returns error.
// if the writes go beyond allocated size.
func (c *cappedWriter) Write(b []byte) (n int, err error) {
if c.offset+int64(len(b)) > c.cap {
return 0, ErrExcessData
}
n = copy(c.buffer[int(c.offset):int(c.offset)+len(b)], b)
c.offset = c.offset + int64(n)
return n, nil
}
// Reset relinquishes the allocated underlying buffer.
func (c *cappedWriter) Reset() {
c.buffer = nil
}
// On close, onClose() is called which checks if all object contents
// have been written so that it can save the buffer to the cache.
func (c cappedWriter) Close() (err error) {
return c.onClose()
}